US20020143326A1 - Surgical devices and methods for use in tissue ablation procedures - Google Patents

Abstract

Devices and a method are provided to assist a surgeon in ablating conduction paths in tissue, such as a heart. A device can be configured to operate as a template that adheres to the tissue surface, and allows the surgeon to more easily sever the conduction path to form a lesion in a desired location. In particular, the template can be used to guide the surgeon's use of a surgical instrument along a desired ablation path. In some case, the template may incorporate hardware that structurally supports the instrument for travel along the ablation path. A surgical instrument such as an ablation probe, e.g., radio frequency, laser, ultrasonic, microwave, thermal, chemical, mechanical, or cryogenic ablation probe, may be used to sever the conduction paths. Measurements made substantially contemporaneously with the conduction path ablation operation may be used to evaluate whether the desired degree of ablation has been achieved. The device may also incorporate feedback to compare the desired degree of conduction path ablation with the measured degree, and may deactivate the surgical instrument when the desired degree has been achieved. In some cases, the template device can be configured to provide local stabilization of organ tissue, particularly for a moving organ such as a beating heart. In other cases, the template device may provide little or no stabilization, but provide a guide structure for placement of the ablation probe in the same frame of motion as the moving tissue. Also, for some applications, the template device may be arranged to facilitate application of other therapeutic devices, such as diagnostic probes, pacing leads, and drug delivery devices, to the surface of a moving organ.

Description

RELATED APPLICATIONS
• This application claims priority from U.S. Provisional Application Serial No. 60/217,1304, filed Jul. 11, 2000; U.S. Provisional Application Serial No. 60/206,081, filed May 22, 2000; U.S. Provisional Application Serial No. 60/190,411, filed Mar. 17, 2000; and U.S. Provisional Application Serial No. 60/181,895, filed Feb. 11, 2000, the entire content of each of which is incorporated herein by reference.[0001]
TECHNICAL FIELD
• The invention generally relates to surgical devices and, more particularly, to surgical devices and methods for use in procedures performed on moving tissue.[0002]
BACKGROUND
• Some forms of surgery involve ablation to kill tissue in an organ in order to achieve a therapeutic result. Ablation can be achieved by various techniques, including the application of radio frequency energy, lasers, cryogenic probes, and ultrasound. Thus, the term “ablation,” as used herein refers to any of a variety of methods used to kill tissue within an organ. To be successful, ablation treatment may require considerable precision. The surgeon must target a particular region, and be careful not to cause unnecessary trauma to other areas of the patient's body near the target area. Just as important, the surgeon must be confident that the procedure within the target area has been appropriately performed. For example, the surgeon may need to determine whether the tissue has been ablated to an appropriate degree. The surgery may be made more difficult if the target area is moving.[0003]
• One such surgical procedure in which a surgeon may wish to ablate moving tissue is an operation to correct an abnormal heartbeat. To function efficiently, the heart atria must contract before the heart ventricles contract. As blood returns to the heart and enters the atria, blood also flows through the atrioventricular (AV) valves and partially fills the ventricles. Following an electrical excitation by the sinoatrial (SA) node, the atria contract in unison, expelling blood into the ventricles to complete ventricular filling. The ventricles then become excited and contract in unison. Ventricular contraction ejects the blood out of the heart. Blood ejected from the right ventricle enters the pulmonary arteries for oxygenation by the lungs, and blood ejected from the left ventricle enters the main aorta and is distributed to the rest of the body. If the timing of cardiac functions is impaired, such as by the atria not contracting in unison or by the ventricles contracting prematurely, then the operation of the heart is impaired.[0004]
• The synchronization of heart functions is initiated by an excitation from the SA node, which is the heart's natural pacemaker. The excitation propagates along an interatrial pathway, extending from the SA node in the right atrium to the left atrium. The excitation then spreads across gap junctions throughout the atria, causing the atria to contract in unison. The excitation further travels down an internodal pathway to the AV node, which transmits the excitation to the ventricles along the bundle of His and across the myocardium via the Purkinje fibers. In an aging heart, the atria may stretch, and the conduction paths by which the excitations travel may become lengthened. As a result, the excitations have a longer distance to travel, and this may affect the timing of the heart contractions and may create an arrhythmia. The term “arrhythmia” is used to describe any variation from normal rhythm and sequence of excitation of the heart.[0005]
• One form of arrhythmia is atrial fibrillation. Atrial fibrillation is characterized by chaotic and asynchronized atrial cell contractions resulting in little or no effective blood pumping into the ventricle. Ventricular contractions are not synchronized with atrial contractions, and ventricular beats may come so frequently that the heart has little time to fill with blood between beats. Atrial fibrillation may occur if conduction blocks form within the tissue of the heart, causing the electrical excitations to degenerate into flurries of circular wavelets, or “reentry circuits,” which interfere with atrial activity. Initiation or maintenance of atrial fibrillation may be facilitated if atria become enlarged. Atrial enlargement increases the time required for the electrical impulse to travel across the atria. This allows sufficient time for the cells that contracted initially to repolarize and allows the re-entry circuit to be maintained.[0006]
• One surgical procedure for treating some forms of arrhythmia is to disrupt conduction paths in the heart tissue by severing the paths at selected regions of the atrial myocardium. Selective disruption of the conduction pathways permits impulses to propagate from the SA node to activate the atria and the AV node, but prevents the propagation of aberrant impulses from other anatomic sites in the atria. Severing may be accomplished, for example, by incising the full thickness of the myocardial tissue followed by closing the incision with sutures. The resultant scar permanently disrupts the conduction paths. As an alternative, permanent lesions, in which tissue is killed, can be created by ablation. The ablation process involves creating a lesion that extends from the top surface of the myocardium to the bottom surface (endocardial surface). Thus, the purpose of ablation is to create one or more lesions that sever certain paths for the excitations while keeping other paths intact. In the case of atrial fibrillation, for example, the lesions may interrupt the reentry circuit pathways while leaving other conduction pathways open. By altering the paths of conduction, the synchronization of the atrial contractions with the ventricular contractions may be restored. A plurality of lesions may be needed to achieve the desired results.[0007]
• Incision through the myocardium, referred to as the “maze procedure,” requires suturing to restore the integrity of the myocardium, and exposes the patient to considerable risk and morbidity. In contrast, thermal or other forms of ablation can create effective lesions without the need for sutures or other restorative procedures. Consequently, ablation can be performed more quickly and with far less morbidity. For these reasons, ablation is becoming a preferred method for severing conduction paths. The surgical ablation procedure may be performed during open-heart surgery. In a typical open-heart surgery, the patient is placed in the supine position. The surgeon must then obtain access to the patient's heart. One procedure for obtaining access is the median sternotomy, in which the patient's chest is incised and opened. Thereafter, the surgeon may employ a rib-spreader to spread the rib cage apart, and may incise the pericardial sac to obtain access to the cardiac muscle.[0008]
• For some forms of open-heart surgery, the patient is placed on cardiopulmonary bypass (CPB) and the patient's heart is arrested. CPB is preferred for many coronary procedures because the procedure is difficult to perform if the heart continues to beat. CPB, however, entails trauma to the patient with attendant side effects and risks.[0009]
• In some circumstances, the patient may be treated by a procedure less invasive than the procedure described above. One such less invasive procedure may be a lateral thoracotomy. The heart may be accessed through a comparatively small opening in the chest and accessed through the ribs. In such a procedure, arrest of the patient's heart may not be feasible, and if the heart cannot be arrested, the surgery must be performed while the heart continues to beat. Other procedures for access to the heart include sternotomy, thoracoscopy, transluminal, or combinations thereof.[0010]
• Once the surgeon has obtained access to the heart, ablation can be carried out with a probe that delivers ablative energy. The ablative energy may take the form of electromagnetic radiation generated by a laser or radio frequency antenna. Other techniques for achieving ablation include the application of ultrasound energy or very low temperature. For the procedure to be successful, the created lesions should sever the targeted conduction paths. Typically, the surgeon must create a lesion of a particular length to create the desired severance. The surgeon must also create a lesion of a particular depth in order to prevent the electrical impulses from crossing the lesion. In particular, when the myocardial tissue is ablated, the lesion must be transmural, i.e., the tissue must be killed in the full thickness of the myocardium to prevent conduction across the ablation line.[0011]
SUMMARY
• The present invention is directed to surgical devices and methods useful in guiding surgical instruments during procedures on internal organs such as the heart. The device may take the form of a surgical “template” device that is attached to the surface of an organ. The device can be configured to facilitate surgical procedures such as tissue ablation. For example, a surgical template can be used as a guide for travel of a surgical or ablative probe along a path to aid a surgeon in ablation of tissue to sever conduction paths in the heart and thereby alleviate arrhythmia. A surgical template device may be especially useful in operations where the organ tissue being treated is moving, e.g., for so-called beating heart surgery. The surgical template device may be effective in providing local stabilization of the tissue to which the tissue ablation procedure is directed. The devices and methods also may find use in procedures in which the pertinent organ is not moving.[0012]
• Alternatively, the device may be configured to provide little or no stabilization, but provide guide structure for placement of the ablation probe in the same frame of motion as the moving tissue. In some cases, the template may incorporate hardware that structurally supports the instrument for travel along the ablation path. The template devices and methods can be configured for application of other types of therapeutic devices, such as diagnostic probes, pacing leads, and drug delivery devices, to the surface of a moving organ. To promote adhesion, in some embodiments, the device may be equipped with a compliant, tacky material that forms a seal for contact with tissue. The device also may be equipped with one or more vacuum ports that make use of vacuum pressure to enhance the attachment to the organ tissue. Adhesion refers to the ability of the device to hold fast to an organ on a temporary basis, either with the benefit of an adhesive or vacuum pressure or both. The present invention also is directed to surgical devices and methods useful in determining the effectiveness of a tissue ablation procedure. In some embodiments, a sensor may be integrated with a surgical template device as described above to assist the surgeon by making measurements that gauge whether the surgical procedure has been satisfactorily performed. For example, the surgical device may be configured to measure the effectiveness of an ablation procedure in terms of ablation length, depth or width. For example, the sensor may measure electrical characteristics of the tissue proximate the target conduction paths, e.g., tissue impedance, tissue conduction velocity, or tissue conduction time, as an indication of the effectiveness of the procedure. The information obtained by the sensor can be used as the basis for feedback to the surgeon, e.g., in audible and/or visible form. Moreover, the sensor information can be used as feedback for the closed-loop control of the tissue ablation probe. The sensor may be employed independently of a surgical template device.[0013]
• As a further aid to the surgeon, the surgical template device may include indicators such as visible markings that show the targeted length of the ablation. The visible markings can be used as a reference by the surgeon during movement of the ablation probe within the template area provided by the device. Also, the template device may include a structure that physically restricts the length of travel of the ablation probe, as well as the shape of the path along which the probe travels. In particular, the length indicator may include a stop structure that extends into the path for travel of the ablation device and is oriented for abutment with the ablation device. In some embodiments, for example, the ablation template device may provide a linear path for travel of the ablation probe. In other embodiments, however, the template device may define a non-linear, e.g., curved, path for travel of the ablation probe.[0014]
• Further, the present invention is directed to surgical devices and methods for manipulation of the heart and local stabilization of heart tissue for a tissue ablation procedure. In this aspect, the present invention may make use of a surgical template device that provides not only a guide for a tissue ablation procedure but also a structure that provides local stabilization of heart tissue within the operative area. In some embodiments, the ablation template device may be accompanied by a surgical manipulation device that adheres to the heart tissue and enables manipulation of the heart to provide the surgeon with a desired access orientation for the procedure. The manipulation device may permit lifting, pushing, pulling, or turning of the pertinent organ to provide the surgeon with better access to a desired area. For both the template and manipulation device, to promote adhesion, a compliant, tacky interface material can be provided for contact with tissue, along with one or more vacuum ports for use of vacuum pressure.[0015]
• In addition to providing a guide for a procedure, a template device and associated methods can be arranged to provide structure that supports instruments such as ablation probes, diagnostic probes, pacing leads, and drug delivery devices, for application to the surface of a moving organ and active guidance along a path. For some surgical procedures, it is necessary to bring surgical instruments into contact with the surface of a particular organ. In addition to the ablation application described above, one example is the placement of one or more electrodes within or in contact with organ tissue to deliver electrical impulses to the organ tissue for various purposes, such as a pacing to control the beating of the heart. Another example is the placement of a syringe needle to deliver a medicament to a specific location on an organ. Although all these procedures could be performed manually by the surgeon when the body cavity is opened during surgery, each is made more difficult when performed via a small opening in the body cavity, usually through an endoscopy port. Moreover, such procedures are particularly complicated when the surface of the pertinent organ is moving, as with a beating heart.[0016]
• Recently, some types of cardiac surgery have been performed through access ports or rather small incisions in the rib cage, instead of in the open field created by cutting through the sternum (a sternotomy) and spreading open the rib cage with a mechanical device. In these situations, there are occasions when surgical devices (diagnostic, therapeutic, etc.) will need to be affixed to a particular location on the heart surface without direct contact of the human hand. This might also be done while the heart is still beating. There is an increasing frequency of coronary artery bypass surgery done on beating hearts to avoid the morbidity associated with stopping the heart and placing the patient on cardiopulmonary bypass. Some surgeries on the beating heart are also performed using the traditional sternotomy. Access procedures such as sternotomy, thoracotomy, thoracoscopy, and percutaneous transluminal are contemplated.[0017]
• To facilitate such procedures, a template device is provided to fix a particular surgical tool or diagnostic or therapeutic device within a defined operative path for the tool or device. There are some surgical procedures performed on a beating heart, or other organ, that will require the fixation of a surgical instrument, diagnostic device or therapeutic device to accomplish a specific surgical procedure, diagnostic measurement, or delivery of some therapeutic product or method. This is particularly true when such procedures, measurements, or deliveries are performed under minimally invasive conditions, such as through narrow tubes or ports that penetrate the skin and enter the abdominal or thoracic cavities. Template devices and associated methods, in accordance with the present invention, are useful in guiding surgical instruments, certain diagnostic sensors, or mechanisms for delivery of medicaments on the surface of internal organs, such as the heart.[0018]
• The template devices and methods are particularly useful in attaching such instruments to the surface of the beating heart without any additional manual assistance of the surgeon, thereby facilitating certain procedures carried out both in open and minimally invasive procedures. Notable features of the template device include conformability to the contours of the organ, such as the heart, the ability to fix the device in place using vacuum, mechanical pressure, or adhesives, and a traumatic attachment by virtue of specific soft polymeric interfaces and shapes. The template device can be configured to attach to various surfaces of the heart using a vacuum seal. This device provides two or more vacuum ports surrounded by a conformable, compressible silicone gel or elastomer. As in the ablation template, these seals contain integrated electrodes for sending and receiving an electrical signal for the purpose of measuring impedance or conductance time or velocity across tissue in a treatment area. The electrodes may be surface or interstitial. Also, the electrodes may be multipolar, e.g., bipolar. In some embodiments, a single electrode within the seal may be sufficient with a reference electrode located elsewhere. A vacuum port or other fluid removal device may be desirable to remove fluids from the chamber to avoid the effects of such fluids on the electrical performance of the electrode(s) or electrical ablation devices. The ports can be attached to a single or multiple independent vacuum lines.[0019]
• In some embodiments of the invention, ablation is performed on the interior surfaces of the tissues. For example, an ablating instrument may be directed transluminally, such as by way of a catheter, near the ostia of the pulmonary veins in the left atrium of the heart. Following the ablation and creation of a lesion, electrodes delivered by the catheter may be used to measure the efficacy of the ablation.[0020]
• For radio frequency ablation, for example, enclosed in the body of the device can be a channel in which is located a moveable cable housing a radio frequency (RF) antenna for delivery of RF energy to the myocardium. The device allows the RF antenna to be moved by a remote control unit on the distal end of the cable. The cable can be moved through its channel by the controller in response to feedback from the sensors on the vacuum seals. As a lesion becomes transmural in one location, the sensors detect either decreases in impedance or increases in conduction time. This information is processed by the controller, and the RF antenna is moved by a motor that advances the cable assembly along a track in the device. Such a device is suitable for use in both open and minimally invasive procedures for the creation of linear transmural lesions for the treatment of atrial fibrillation.[0021]
• Another embodiment is a similar device, which contains malleable metal elements that allow the device to be formed into an arc (like a shepherd's crook) whose circumference can match the outer circumference of the base of the pulmonary vein. This device is similar in construction to the embodiment described above, except that it is attached to a rod suitable for insertion into a port access device for entry into the thorax or for manual manipulation by a surgeon in an open procedure. The device is brought into contact with the base of the pulmonary vein, and vacuum is used to attach it to a portion of the basal circumference of the vein. RF energy is delivered controllably as described above. When a full thickness lesion is created on one side of the vein, the vacuum is released, and the device moved so that its arc rests over the side of the vein that has not been treated. A full thickness lesion can then be created on that side.[0022]
• For some applications, the surgeon may manually control advance of the radio frequency antenna within the template device, and control further movement with a remote control device. In particular, the surgeon can also utilize manual movement of the RF antenna assembly through a joystick or other actuation transducer that advances the RF antenna. The joystick is operated by the surgeon in response to an indicator (light, etc.) that responds to the appropriate decrease in impedance or increase in conductance time detected by the sensors mounted in the vacuum seals. As an alternative, the surgeon may simply monitor the advance of the radio frequency antenna visually, and actuate a joystick or similar device. In either case, the template device operates as both a guide and an automated actuator to translate the radio frequency antenna (or other device) along a desired path. Notably, the template device is affixed to the pertinent tissue and provides automated movement of the instrument, reducing motion problems relative to the instrument offering enhanced precision.[0023]
• In one embodiment, the present invention provides a surgical device for use in a tissue ablation procedure. The device includes a contact member that engages the tissue near a location where the tissue is to be ablated. The contact member defines a guide that indicates, upon engagement of the contact member with the tissue, the location where the tissue is to be ablated, and provides a path for travel of a tissue ablation probe. The contact member of the device may include a compliant and tacky interface element for engagement with the tissue. The device may further define an interior chamber, and may include a vacuum port in fluid communication with the interior chamber. The interior chamber may be capable of delivering vacuum pressure to the contact member, thereby promoting vacuum assisted adherence of the contact member to the tissue. In addition, the device may include a sensor that may indicate whether the desired degree of tissue ablation has been achieved.[0024]
• In another embodiment, the present invention provides an apparatus for determining whether conduction paths within heart tissue have been adequately ablated during a surgical procedure. The apparatus includes a first electrode capable of transmitting a first electrical signal adjacent the tissue to be ablated, a second electrode capable of receiving a second electrical signal adjacent the tissue to be ablated and a measuring device electrically coupled to at least the second electrode to receive the second electrical signal from the second electrode. The measuring device may determine whether the extent to which the tissue has been ablated to a sufficient degree based on the second electrical signal. The apparatus further includes an output device that provides an indication of extent, e.g., depth, to which the tissue is ablated. In order to measure impedance when using RF ablation, it may be necessary to use an energy frequency outside of the ablation energy frequency range or pulse or ablation energy and measure impedance during the quiescent period between ablation pulses.[0025]
• In another embodiment, the present invention provides a method for severing conduction paths within tissue. The method involves placing a first device near the target conduction paths to be severed, using the first device as a guide to sever the target conduction paths, and with a second device, measuring to determine whether the desired severing has been achieved. In this embodiment, the target conduction paths may be severed by tissue ablation. Measurement may involve determining whether the lesion depth is sufficient to sever the target conduction paths.[0026]
• The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects and advantages of the invention will be apparent from the description and drawings, and from the claims.[0027]
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a perspective view of an ablation template device in accordance with an embodiment of the present invention placed on a heart for purposes of illustration.[0028]
• FIG. 2 is an enlarged perspective view of an ablation template device as shown in FIG. 1, showing use of a surgical instrument.[0029]
• FIG. 3A is a top view of an ablation template device in accordance with an embodiment of the invention.[0030]
• FIG. 3B is a side view of an ablation template device in accordance with an embodiment of the invention.[0031]
• FIG. 3C is a cross-sectional side view of the device of FIGS. 3A and 3B.[0032]
• FIG. 4 is a conceptual diagram illustrating an ablation template device in accordance with an embodiment of the invention.[0033]
• FIG. 5 is another conceptual diagram illustrating an ablation template device in accordance with an embodiment of the invention.[0034]
• FIG. 6 is a perspective view of an ablation template device in accordance with an alternative embodiment of the invention placed on a heart for purposes of illustration.[0035]
• FIG. 7 is a top view of an ablation template device in accordance with an embodiment of the invention.[0036]
• FIG. 8 is a top view of an ablation template device in accordance with an embodiment of the invention.[0037]
• FIG. 9A is a perspective top view of an ablation template device in accordance with an embodiment of the invention.[0038]
• FIG. 9B is a perspective bottom view of an ablation template device as shown in FIG. 9A.[0039]
• FIG. 10 is a perspective view of an ablation template device in accordance with an embodiment of the invention.[0040]
• FIG. 11 is a perspective view of an ablation template device in accordance with an embodiment of the present invention, placed on a heart for purposes of illustration, used in cooperation with another device that permits manipulation of the heart.[0041]
• FIG. 12 is a cross-sectional side view of a cup-like manipulation device.[0042]
• FIG. 13 is a cross-section side view of another cup-like manipulation device.[0043]
• FIG. 14 is a perspective view of an ablation template device incorporating structure for accommodating an ablation probe;[0044]
• FIG. 15 is a cross-sectional view of the device of FIG. 14, taken at[0045]point145.
• FIG. 16 is a cross-sectional view of a shaft incorporated in the device of FIG. 14, taken at point B.[0046]
• FIG. 17 is a perspective view of an arcuate ablation template device incorporating structure for accommodating an ablation probe.[0047]
• FIG. 18 is a perspective view of an added ablation template device incorporating structure for accommodating an ablation probe.[0048]
• FIG. 19 is a cross-sectional view of the device of FIG. 18, taken along line[0049]210-210′.
• FIG. 20 is a bottom view of the device of FIG. 18.[0050]
• FIG. 21 is a perspective view of an ablation template device incorporating a movable carriage for support of an ablation probe.[0051]
• FIG. 22 is a cross-sectional view of the device of FIG. 21, taken along line[0052]250-250′.
• FIG. 23 is a cross-sectional view of the device of FIG. 21, taken along line[0053]244-244′.
• FIG. 24 is a cross-sectional front view of an ablation template device having an internal ablation probe.[0054]
• FIG. 25 is a cross-sectional side view of the ablation template device of FIG. 24.[0055]
• FIG. 26 is a cross-sectional side view of a catheter-mounted ablation device.[0056]
• FIG. 27 is a side view of a catheter-mounted ablation device.[0057]
• FIG. 28 is a side view of a catheter-mounted ablation device.[0058]
• FIG. 29 is a cross-sectional side view of a catheter-mounted ablation device.[0059]
• FIG. 30 is a side view of a catheter-mounted ablation device.[0060]
• In general, like reference numerals are used to refer to like components.[0061]
DETAILED DESCRIPTION
• FIG. 1 is a perspective view of an[0062]ablation template device14 in accordance with an embodiment of the present invention. In FIG. 1,ablation template device14 is shown placed on aheart10 for purposes of illustration. In particular,heart10 has been exposed by an open-chest surgical technique andablation template device14 has been affixed to theright atrium12 of the heart. In some embodiments,ablation template device14 includes acontact member17 that engages the tissue. In the example of FIG. 1,contact member17 takes the form of a substantially ovular ring. Inner andouter diameters20,21 of the ring-like contact member17 define an annular chamber for engagement with tissue on the surface ofheart10.
• [0063]Contact member17 may be affixed to thesurface15 ofatrium12 in many ways, such as by application of an adhesive at the inner andouter diameters20,21, or by application of vacuum pressure to the annular chamber. Another way to achieve adherence betweencontact member17 and thesurface tissue15 is to include aseal member23 formed from an adhesive material in the contact member. One example of an adhesive material is a coating of compliant, tacky material, such as silicone gel, at the interface between thecontact member17 and the tissue on thesurface15 ofatrium12. In this case,contact member17 may include asemi-rigid frame member25 and a compliant, tacky seal member. The compliant,tacky seal member23 provides intrinsic adhesive properties, and aids conformability and sealing to surface15, while theframe25 imparts structural integrity to contactmember17. Each offrame25 andseal member23 has a substantially annular shape. In particular,seal member23 may include inner andouter portions27,29 disposed at the inner andouter diameters20,21 ofcontact member17.
• With a silicone gel, intrinsic adherence of[0064]seal member23 may be sufficient thatablation template device14 remains affixed to theheart10 in spite of contractions ofatrium12 and in spite of the use ofdevice14 in surgical procedures described below. Nevertheless, application of vacuum pressure will be desirable in many applications to provide secure adherence. Although the adherence should be secure, the adherence preferably is not permanent. Rather, adherence betweendevice14 and the tissue may be discontinued as desired without serious trauma to the tissue, and the device repositioned and adhered anew at a different location. As an alternative,ablation template device14 can be forced againstatrium12 to provide pressure contact withheart10. In such a case,ablation template device14 may have a local stabilizing effect on the contact region ofheart10 despite continued beating of the heart.Ablation template device14 may be sized or shaped to allow it to mold to the contours of theatrium12.Ablation template device14 can be made principally of nonconductive materials, such as polyurethane, silicone, or natural or synthetic rubber. Shore A 50-80 silicone elastomer may be used, for example, to formframe25 ofdevice14. Metal such as annealed stainless steel or zinc or polymeric reinforcing members may be incorporated indevice14, e.g., embedded within the molded elastomer, to resist excessive deformation or collapse during use. Shape memory alloys, in particular, may be useful in imparting a desired shape todevice14 during use, and permit collapse and unfolding to the desired position for endoscopic deployment in minimally invasive techniques.
• An[0065]electrode16 can be affixed todevice14, e.g., withinseal member23 orframe member25, and placed in contact with thesurface15 of theheart10. Theelectrode16 may send signals across the tissue of theheart10 to be received by a second electrode (not shown in FIG. 1). These signals will traverse the tissue area being ablated. The associated circuitry for the electrodes may reachdevice14 by way of aconnective tube18. As will be described,electrode16 may form part of a sensor for determining the effectiveness of a tissue ablation procedure. In particular, the electrodes can be used to measure electrical properties (such as impedance, phase angle, conduction time, conduction velocity, capacitance) of the local tissue area being ablated, and thereby indicate whether an effective lesion has been formed in the tissue. In some embodiments,ablation template device14 may have multiple sets of electrodes situated at different positions along the major axis of the device. In this case, such electrodes may take the same types of measurements at different positions, or different types of measurements such as impedance, conduction velocity, and conduction time.
• If[0066]ablation template device14 is attached with the assistance of vacuum pressure,connective tube18 may also serve the purpose of attaching the interior chamber formed bycontact member17 to an external source of vacuum pressure (not shown).Ablation template device14 may be shaped to define an interior chamber that is enclosed upon engagement of the device with the tissue. In the example of FIG. 1, the chamber is substantially annular. Application of vacuum pressure may cause the enclosed chamber to slightly deform, creating a vacuum seal and causing thedevice14 to become more affixed to the tissue. With added compliance fromseal member23, in particular,contact member17 can conform totissue surface15 to achieve an effective seal. At the same time, thecompliant seal member23 distributes sealing force across the tissue to reduce tissue trauma.
• As shown in FIG. 1,[0067]contact member17 ofablation template device14 generally may have a somewhat annular shape, with substantially oval-shaped inner and outer diameters, and anopening31 through which the tissue ofatrium12 may be accessed. The lengths of the major and minor axes of annular-shapeddevice14 may vary to provideopening31 with varying sizes according to the characteristics of the particular procedure to be performed. In some applications, opening31 may define a narrow, linear track for travel of an ablation probe. In other applications, opening31 may be much wider or define nonlinear tracks for travel of an ablation probe. Other shapes forcontact member17 beside the annular shape may also be suitable.
• A closer perspective view of[0068]ablation template device14 appears in FIG. 2. In FIG. 2, a surgeon'sfingers24 hold a surgical instrument shown as anablation probe22 that may be used to ablate the tissue of theheart10. Even though theheart10 is beating, thesurgeon24 may position theprobe22 within theopening31 with relative ease. Thesurgeon24 may also use theprobe22 to ablate a particular area of theatrium12, even though theatrium12 is in the process of contracting and relaxing, by using theinside edge26 of thedevice14 as a guide for travel of the probe. Again, opening31 may define a substantially linear path for travel of an ablation probe. Alternatively, opening31 can be non-linear, e.g., curved, or have other shapes appropriate for given surgical applications. In either case, the surgeonman use opening31 as a guide, even resting theablation probe22 against theinside edge26 ofcontact member17 in some cases. Because significant heat may be generated by RF, laser, and ultrasonic energy, it may be desirable to provideablation probe22 with a thermally insulative sleeve that extends downward to the tip of the probe, thereby protecting theinside edge26 ofcontact member17. Also,inner edge26 ofcontact member17 can be coated with or coupled to an insulative material for contact withablation probe22.
• If[0069]ablation template device14 is fixed to a point of reference, it may provide a local stabilizing effect that holds the tissue within opening31 substantially stationary, or at least constrains the local area against excessive movement, despite continued beating ofheart10. For example,ablation template device14 may be pushed againstheart10 to apply stabilizing pressure to the local area of contact. Alternatively,ablation template device14 can make use of suction or adherence in combination with either a pushing or pulling force to provide a stabilizing effect.
• [0070]Ablation probe22 may use a number of methods to achieve ablation. Theprobe22 may, for example, use a laser to ablate tissue. As another alternative, the probe may incorporate an antenna that emits radio frequency (RF) energy to ablate tissue. The amount of power delivered by the ablation probe may vary. A typical RF probe, for example, may deliver from 5 to 50 watts. In this alternative, theprobe22 may include an electrode at its tip. An electrode can be provided withinablation template device14 to provide circuit completion for a probe using RF energy. For example, a passive electrode forming part of the sensor described above could be used as the return electrode. As a further alternative,probe22 could take the form of an ultrasound probe that emits ultrasound energy, or a cryosurgical probe that cools the tissue to ultra-low temperatures. Thermal, chemical, and mechanical probes for obtaining or incising tissue are also contemplated. In each case, opening31 ofablation template device14 provides a guide for travel ofprobe22, enabling greater precision in the ablation of conduction paths within the heart tissue.
• Other views of[0071]ablation template device14 appear in FIGS. 3A and 3B. In these views, the device is shown in a top view, FIG. 3A, and a side view, FIG. 3B. FIG. 3C is a cross-sectional side view of the device of FIGS. 3A and 3B.Inner seal member27 is indicated by dashedline33. The interior chamber ofcontact member17 is indicated byreference numeral35.Ablation template device14 may be flexible, and its relaxed shape may be curved as shown in FIG. 3B to more readily conform to the surface of the heart. The exemplary annular shape allowsfirst electrode16 andsecond electrode30 to be located opposite to each other across theopening31. The distance between theelectrodes16,30 may be a known, fixed distance. The interior edges26,32 of theopening31 preferably have sufficient rigidity to serve as a guide for travel of a probe or other surgical instrument. Althoughseal member23 may be substantially compliant and conformable, the inner edge offrame member25 may provide the degree of rigidity desirable to support the probe. In addition,ablation template device14 may include one or several length indicators in the form ofvisible markings28, to assist the surgeon in forming a lesion of a desired length.
• A surgeon desiring to make a lesion of a particular length may use the[0072]markings28 as a guide for manipulating the probe. Thus, the guide provided by opening31 is useful in guiding both the direction of travel of the probe and the extent of travel. Also, thetemplate device14 may include a structure that physically restricts the length of travel of the ablation probe, as well as the shape of the path along which the probe travels. Substantially straight ablation tracks ordinarily will be desirable. Accordingly, the guide surface on the interior of the opening may be substantially straight. In other applications, however, it may be desirable to effect a curved ablation track. Therefore, the shape of the guide withinopening31 may vary according to the application. Furthermore, because ablation typically causes a change in tissue color, themarkings28 may provide the surgeon with information as to the actual length of the lesion.
• In one aspect, the invention can be useful in determining whether the conduction path has indeed been cut. Ordinarily, a surgeon cannot visually gauge the depth of a lesion. The guide defined by[0073]ablation template device14 may provide an indication of the length of a lesion. A lesion of an insufficient depth may result in currents that pass under or over the lesion, however, and may thus be incapable of disrupting the reentry circuits or other undesirable current pathways. The myocardium consists of interlaced bundles of cardiac muscle fibers. Within the fibers, cardiac muscle cells are joined by intercalated discs, which include areas of low electrical resistance known as gap junctions. Gap junctions permit excitations or action potentials to propagate from one cell to another. A lesion created by ablation may destroy the tissue and the gap junctions, effectively interrupting electrical conduction. Thus, determination of whether the conduction paths are indeed ablated may be crucial to a successful treatment.
• As shown in FIGS. 3A and 3B,[0074]ablation template device14 may include at least two electrodes,16,30 that operate as part of a sensor. A sensor may be used to indicate to the surgeon whether a desired degree of tissue ablation has been achieved.Electrodes16,30 preferably are integrated withablation template device14 to reduce the number of instruments that need to be introduced in to the surgical field. In particular,electrodes16,30 can be molded into the material formingseal member23 orframe member25, and have conducting members that extend away from the tissue site viatube18. A tip portion of each electrode may be exposed beyond the surface ofseal member23 to enable sufficient electrical contact with the tissue to whichcontact member17 is attached.
• In other embodiments, however,[0075]electrodes16,30 may be introduced independently ofablation template device14. FIGS. 3A and 3B show an exemplary embodiment of the present invention, and other embodiments may incorporate more than two electrodes. After an ablation is performed inside theopening31, and during ablation,electrodes16 and30 may be located on opposite sides of the lesion. The distance betweenelectrodes16 and30 may be a known distance and relatively fixed. Theelectrodes16,30 may be used to determine whether the conduction path has been severed by ablation to the desired degree.
• One way to make the determination is to use the[0076]electrodes16,30 as probes for an impedance-measuring instrument.Electrodes16,30 may be electrically coupled to the impedance-measuring instrument. The impedance of the area of tissue may be measured before any ablation is made, and this measurement may be used as a baseline. The impedance may be measured again after the ablation is made and may be compared with the baseline measurement to determine whether the conduction path has been severed. Moreover, it may be desirable to measure impedance during an ablation procedure to assess progress in producing an effective lesion. During ablation, impedance measured from one side of the lesion to the other side will decrease as ablation ruptures cell membranes, permitting dissolved ions to move with less restriction. Impedance will generally decrease until impedance reaches a minimum value when the lesion becomes transmural. One way to determine whether the ablation is complete is to look for the point at which the impedance measurement levels off. For example, a baseline measurement on canine atrial myocardium may show an impedance of 240 ohms, but measurements taken during the ablation may how a steady decline in impedance, eventually leveling off at 150 ohms after about 90 seconds. It may also be possible in some circumstances to evaluate the ablation process on the basis of a percentage change of impedance or on the basis that a predetermined impedance value has been reached. Parameters such as the baseline value, the leveling off value and the time needed to produce a transmural lesion are dependent upon the patient being treated, the tissue being ablated, the distance of the electrodes, the thickness of the tissue, and other factors. In the case of the heart, for example, not all hearts have the same impedance, and different sections of a single heart may also have varying impedance. In such cases a baseline measurement may be desirable, with transmural penetration indicated by the leveling off of impedance measurements.
• In addition to measuring impedance or as an alternative to measuring impedance, alternating current (ac) phase angle may be measured. In a capacitive circuit, the voltage lags the current, and the amount of lag is often expressed in the form of a phase angle. In a purely capacitive circuit, the voltage is 90° behind the current, expressed as a phase angle of −90°. A phase angle of 0° means the circuit is purely resistive. A phase angle between 0° and −90° means the circuit is partly resistive and partly capacitive. Typically a phase angle measurement across tissue will be between 0° and −90°, indicating some capacitive nature of the tissue. As ablation proceeds, cell membranes are ruptured, making the tissue less capacitive. Accordingly, the phase angle across the ablative lesion will become more positive (i.e., will approach zero) as cells die in the lesion. One way to determine whether the ablation is complete is to look for the point at which the phase angle measurement levels off. A baseline measurement of canine myocardium, for example, may show a phase angle of −13.1°. Measurements taken during the ablation may show the phase angle becoming more positive, eventually leveling off at −12° after about 20 seconds. As with impedance measurements, phase angle measurements are dependent upon many factors.[0077]
• Another way to make the determination is to use the electrodes to measure conduction distance by measuring conduction time. A signal traveling on a conduction path propagates as an action potential and propagates via gap junctions. The length of a conduction path, the speed of conduction and the time taken for a signal to travel the path are related by the simple formula[0078]
• D=RT
• where D is the distance traveled by the signal, R is the rate of speed of the signal, and T is the time taken for the signal to travel the distance. In the case of an actual operation, a particular value of D or T may be desired. A value for R may be obtained by sending a test signal from one electrode, receiving it at the other electrode, the distance between the electrodes being known and relatively fixed, and measuring the time of conduction. In many cases, however, a relative measure of conductive velocity or time is sufficient, and therefore the distance between electrodes need not be known absolutely so long as it remains fixed. This measurement may then be used as a baseline measurement. Again, a baseline measurement may be desirable, because not all hearts have the same conduction speed, and different sections of a single heart may also have varying conduction speeds. The time of conduction may be measured again after the ablation is made and may be compared with the desired value of D or T. In general, conduction time increases and conduction velocity decreases as the ablation proceeds, and one way to determine whether the ablation is complete is to look for the point at which the measured quantity levels off. For example, a conduction time of 15 ms may be measured as a baseline. During ablation, conduction time may increase, eventually leveling off at around 30 ms. The leveling off indicates the ablation is transmural.[0079]
• In the case of measurement of conduction time, velocity, or distance,[0080]electrode30 may be a single electrode or a bipolar or multipolar electrode. Thus, in the description of this invention, it is to be understood that the transmittingelectrode16 positioned on one side of the ablation track may be unipolar, while the measurement or “recording”electrode30 positioned on the opposite side of the ablation track can be unipolar, bipolar, or multipolar, depending upon the electrical measurement that is utilized to determine if the conduction paths have been severed or ablation of the target tissue has been transmural, and desired precision. With aunipolar recording electrode16, an electrical signal transmitted into the tissue by the transmitting electrode is first sensed as an electrical signal that is then followed by a depolarization wavefront that propagates through the cells disposed betweenelectrodes16,30. It is the depolarization wavefront that is detected to measure conduction time.
• A[0081]unipolar recording electrode30 simply measures whether the depolarization wavefront exceeds a given threshold. With abipolar recording electrode30, however, the two electrodes can be used to measure current flow or a voltage potential between them. The two electrodes of thebipolar recording electrode30 can be oriented in a line substantially parallel to the ablation track, and thereby form a “T” with the transmittingelectrode16. As the depolarization wavefront propagates through the cells positioned between transmittingelectrode16 andrecording electrode30, the cells disposed between two recording electrodes ofbipolar recording electrode30 depolarize, producing a difference in current flow between the two recording electrodes. This bipolar arrangement enables measurement of an increase in the intensity of current flow between the two electrodes ofbipolar recording electrode30, and more precision in the measurement. In particular, an intensity threshold can be set. Conduction time can be measured between the time at which transmittingelectrode16 transmits the initial signal and the time at which current flow between the two electrodes ofbipolar recording electrode30 exceeds the threshold. Again, the initial signal transmitted by transmittingelectrode16 and sensed by therecording electrode30 can be ignored. Rather, the depolarization wavefront typically will be the event of interest in determining conduction time.
• A method of using measurement of impedance or conductance variables to determine the transmurality of a lesion may also be employed using bipolar radio frequency electrosurgical ablation devices. For example, separate electrodes, using an electrical frequency different from the frequency used by the ablation device, can be mounted on the device and used to form a separate measuring circuit for impedance for the purpose of measuring the distance ablated. A typical bipolar device could have two electrode surfaces, one for one side of a tissue surface and one for the other side of a planar tissue surface, such as the myocardium, or a vascular structure. One transmitting electrode, or a plurality of electrodes, can be mounted with one of the surgical electrodes, and a receiving or “recording” electrode, which could be bipolar or multipolar, or a plurality of unipolar, bipolar, or multipolar electrodes, can be mounted on the opposite surgical electrode. Impedance or conductance, such as time, distance, or velocity, can be measured as described herein and can be used to determine transmurality, and shut off power to the ablation device as described. It is envisioned that one specific application of such a bipolar device would be for deployment through a puncture hole in the myocardium. The ablation device could be equipped with “jaws” that carry the electrodes. Entry of one of the “jaws” of the surgical RF device could be either from the endocardial or epicardial surfaces. After deployment, there would be a surgical electrode on both the epicardial surface and the endocardial surface. As RF power is supplied to the surgical ablation device, the tissue between the two surgical electrodes is heated and killed, creating a lesion for the purpose of interrupting conductance pathways. The transmurality of this lesion at different points along its length can be measured simultaneously or at time intervals during ablation using measurement of impedance or conductance variables with the separate circuits defined by the transmitting and recording electrodes placed along the path of the surgical electrodes and the underlying lesion.[0082]
• FIG. 4 shows a conceptual diagram of an implementation of an aspect of the invention.[0083]Electrodes16,30 shown in FIG. 3 may serve asprobes34 for ameasurement device36. Themeasurement device36 may measure a quantity related to conduction, such as impedance or conduction time or conduction velocity. Data measured bymeasurement device36 may be fed into aprocessor38.Processor38 may be in the form of a generalized computing device, such as a personal computer. Alternatively,processor38 may be in the form of a smaller and more specialized computing device, such as a microprocessor or an application-specific integrated circuit. As a further alternative,processor38 could be realized by discrete logic circuitry configured appropriately to perform the necessary measurement control and processing functions. Accordingly,processor38 need not be embodied by integrated circuitry, so long as it capable of functioning as described herein.
• In addition,[0084]processor38 may take an active role in the measurement process and may control measurements made bymeasurement device36 throughprobes34. In particular,processor38 may control a current or voltage source to apply electrical current or voltage to one ofelectrodes16,30. Two representative instances where theprocessor38 may actively control the measurement process are in the taking of a baseline measurement, and in the taking of periodic measurements during the ablation procedure to monitor progress.Processor38 may further perform calculations as needed, and may provide output to the surgeon by way of anoutput device40 such as a display. In addition,processor38 may receive input from anadditional input device42, which may include, for example, a keyboard or a touch screen. Usinginput device42, the surgeon may, for example. input the length of a desired lesion, and theprocessor38 may be able to provide feedback to the surgeon viaoutput device40 as to whether the desired lesion has been created.Output device40 may provide audible and/or visible output such as beeps, flashing light emitting diodes (LED's), speech output, display graphics, and the like, to provide feedback to the surgeon.Output device40 can be mounted in a housing associated withprocessor38, or integrated with theablation probe22. For example, one or more LED's could be mounted on the ablation probe in view of the surgeon.
• FIG. 5 shows another conceptual block diagram of an implementation of an aspect of the invention. FIG. 5 is similar to FIG. 4, except that the[0085]processor38 is connected to theablation device44.Ablation device44 may be any device intended to sever conduction paths by killing tissue, such as the RF, laser, ultrasonic, orcryogenic probe22 depicted in FIG. 2. In each case,ablation device44 may be in the form of a powered instrument such as a laser, RF, or ultrasonic electrosurgical probe, or be coupled to a cryogenic supply.Processor38 may controlablation device44 by, for example, cutting off power or supply to the ablation device once the desired lesion has been created. In this manner, the surgeon can take advantage of closed-loop, real-time control of the output ofablation device44, ensuring ablation to a proper level of effectiveness and avoiding excessive ablation. The result may be the creation of an effective lesion in a shorter time period, reducing the time necessary for access to the patient's heart tissue. The system may be even more effective if multiple electrode pairs are mounted along opening31 to measure the effectiveness of ablation in creating a lesion along a continuous track.
• The system shown in FIG. 5 may be useful for dynamic monitoring and control of the surgical procedure. The surgeon may choose an[0086]ablation device44, such as a laser, that will not interfere with the operation of theprobes34. Alternatively, if interference is created by an RF probe, power can be intermittently turned off to enable measurement. By any combination of taking a baseline measurement or receiving input throughinput device42, theprocessor38 may determine what measurements received frommeasurement device36 will satisfy the conditions for a successful surgical procedure.Processor38 may continuously or frequently monitor the measurements received frommeasurement device36 to determine whether the criteria for a successful surgical procedure have been met. When those criteria have been met,processor38 may cut off power to, or otherwise interrupt the operation of,ablation device44. In other words,processor38 may use a feedback system as part of its control ofablation device44 for either automated control or manual control by the surgeon.
• One advantage of this system is the speed by which the surgeon may perform the ablation procedure. Speed is of a considerable advantage to the patient in several respects. First, risks attendant to surgery may be minimized if the time spent on the operating table is reduced. Second, a procedure performed on moving tissue such as a beating heart may be more efficient if done quickly.[0087]
• Once[0088]ablation template device14 is placed into position, a baseline measurement may be taken, and the surgeon may then proceed to make the ablation, usingablation template device14 as a template or a guide. Use of thedevice14 as a template or guide is one factor enhancing the speed of the procedure. The surgeon may usemarkings28 onablation template device14 to get a general idea of where to begin and end the ablation. Theprocessor38 may be used to suggest to the surgeon viaoutput device40suitable markings28 for beginning and ending the ablation pass. The surgeon may then make a pass with theablation device44. If the pass is too long, theprocessor38 may interrupt the function of theablation device44 before the pass is completed. If the pass is too short, theprocessor38 may assist the surgeon in determining the best approach for a second pass. Again, the length determination may be aided by the use of a series of electrode pairs along an ablation track. The use of dynamic processing and feedback further enhance the speed of the procedure. FIG. 6 is a perspective view of anablation template device50 in accordance with an alternative embodiment of the present invention. Likeablation template device14 in FIG. 1,ablation template device50 is shown placed on theright atrium12 of aheart10 in FIG. 6 for purposes of illustration. In particular,heart10 has been exposed andablation template device50 has been affixed to theright atrium12 of the heart.Ablation template device50 includes acontact member51 which may engage and may be affixed to thesurface15 ofatrium12 by being pushed against the heart. Becauseablation template device50 generally has a U-shaped shape,contact member51 includes two contact tines or contact “feet”53.
• Electrodes used to take the measurements described herein may take the form of discrete electrodes that operate in pairs to transmit and receive signals across the ablated tissue region. Alternatively, one or more of the electrodes may take the form of bipolar or multi-polar electrodes that are integrated in a common electrode package and positioned in very close proximity to one another. With the closer spacing available in a bipolar package, for example, the signal transmitted by one electrode and received by the other as an EMG potential can be cleaner in terms of having a reduced degree of background noise due to surrounding electrical potentials produced by the heart. Instead, the bipolar electrode is capable of more effectively measuring the local signal conduction time. Also, in some embodiments, series of electrodes on each side of the ablation track can be realized by a continuous electrode component that includes conductive electrode regions and insulating regions disposed therebetween. Again, this sort of component can permit closer electrode spacing. In this case, however, the closer spacing is not between transmitting and receiving electrodes but between adjacent transmitting electrodes and adjacent receiving electrodes extending parallel to the ablation track. The closer spacing permits a higher degree of resolution in monitoring the progress of the ablation procedure along the ablation track, and thus the length of the resulting lesion. The closer spacing permits more precise feedback and control of the ablation probe by the surgeon or by an automated controller.[0089]
• To maintain its position relative to the[0090]heart10,ablation template device50 may, in addition, have a compliant, tacky material such as silicone gel at the point of contact betweencontact member51 and thesurface15 of theatrium12, providing a compliant, tacky interface.Ablation template device50 may remain substantially affixed to theheart10 in spite of contractions ofatrium12 and in spite of the use ofablation template device50 in surgical procedures described such as those described above. By being forced against the heart,ablation template device50 may have a stabilizing effect on the contact region ofheart10 despite continued beating of the heart.Shaft52, made of a rigid material and formed in any suitable shape, may be used to pressablation template device50 againstatrium12 and hold the device in place.
• Although[0091]ablation template device50 may be more rigid thanablation template device14 in FIG. 1,ablation template device50 may be sized or shaped to allow it to mold to the contours of theatrium12. Likeablation template device14 in FIG. 1,ablation template device50 can be made (with the exception of the compliant, tacky interface) principally of substantially rigid, nonconductive materials, and may include afirst electrode56 and a second electrode (not shown in FIG. 6). The associated circuitry for the electrodes may reachablation template device50 by way ofshaft52. The general U-shape ofablation template device50 includes anopening54 through which the tissue ofatrium12 is accessible. The dimensions ofablation template device50 andopening54 may vary. Other shapes beside the U-shape may also be suitable for thedevice50, such as the annular shape, and theopening54 may be in other suitable shapes as well.
• A top view of[0092]ablation template device50 appears in FIG. 7. The exemplary U-shape allowsfirst electrode56 andsecond electrode58 to be located opposite to each other across theopening54. The distance between theelectrodes56,58 may be a known, fixed distance. The interior edges60,62 of theopening54 have sufficient rigidity to serve as a guide for travel of a probe or other surgical instrument. In addition, likeablation template device14,ablation template device50 may includeseveral length indicators64, to assist the surgeon in forming a lesion of a desired length.
• A top view of a variation of[0093]ablation template device50 appears in FIG. 8.Ablation template device50 is like the same device depicted in FIG. 7, except thefirst electrode56 andsecond electrode58 are not rigidly affixed to the body of thedevice50.Electrodes56,58 are electrically coupled toablation template device50 by way ofelectrical connectors66,68.Electrical connectors66,68 may be flexible wires, and may allow a surgeon to placeelectrodes56,58 at a desired location on the tissue or at a desired distance apart. Alternatively,electrical connectors66,68 may be spring-like connectors, that may appear somewhat like insect antennae, and which may force theelectrodes56,58 against the tissue when theablation template device50 is pressed against the tissue to enhance electrical coupling pressure and surface area. As shown in FIG. 8,electrodes56,58 may be deployed within theopening54.Electrodes56,58 may also be deployed at other locations as well.
• FIGS. 9A and 9B show an[0094]ablation template device69, which is similar to theablation template device14 shown in FIG. 1. However, FIGS. 9A and 9B illustrates aframe member75 and aseal member77 in somewhat greater detail. FIG. 9A is a perspective top view ofdevice69, while FIG. 9B is a perspective bottom view ofdevice69. FIGS. 9A and 9B differ slightly in the shape ofdevice69. Specifically,device69 of FIG. 9A is shown as having a somewhat curved contour for conformability to the surface of the tissue.
• [0095]Frame member75 can be formed from a semi-rigid material that lends structural integrity to contactmember73, whileseal member77 is formed from a more compliant material that facilitates conformance of the contact member to the tissue surface and promotes a seal that is generally atraumatic and more effective.Seal member77 includes an inner skirt-like member70 coupled to and extending around the inner edge ofcontact member73 that acts as an interface with the tissue. Skirt-like member70 may function in part as a seal gasket.Ablation template device69 also includes an outer skirt-like member72, coupled to and extending around the outer edge of thecontact member73. Skirt-like members70,72 defineannular vacuum chamber76. Inside of skirt-like member70,contact member73 defines opening81 for access to a tissue site. Skirt-like members70,72 may be composed of a material that is generally more compliant and conformable than the rest ofcontact member73.
• Use of Shore A 5-10 durometer silicone elastomer for the skirt-[0096]like member70,72 may be appropriate for some applications. Silicone gels are preferred, however, due to the intrinsic compliance and tackiness provided by such materials. Like silicone elastomers, silicone gels can be manufactured with a range of crosslink densities. Silicone gels, however, do not contain reinforcing filler and therefore have a much higher degree of malleability and conformability to desired surfaces. As a result, the compliance and tackiness of silicone gel materials can be exploited in skirt-like members70,72 to provide a more effective seal. An example of one suitable silicone gel material is MED 6340, commercially available from NUSIL Silicone Technologies, of Carpinteria, Calif. The MED 6340 silicone gel is tacky and exhibits a penetration characteristic such that a 19.5 gram shaft with a 6.35 mm diameter has been observed to penetrate the gel approximately 5 mm in approximately 5 seconds. This penetration characteristic is not a requirement, but merely representative of that exhibited by the commercially available MED 6340 material.
• Metal or polymeric reinforcing tabs can be incorporated in skirt-[0097]like members70,72 to prevent collapse, and promote structural integrity for a robust seal. Skirt-like members70,72 can be compliant, tacky silicone gel molded about the reinforcing tabs. In particular, for manufacture,frame member75 can be molded about reinforcing tabs or springs, allowing a portion of the tabs or springs to extend downward, to one or both of the inner diameter or outer diameter side of the annular contact member. Then, one or both skirt-like members70,72 can be molded ontoframe member75, encasing the exposed portions of the tabs or springs. In the example of FIG. 9, outer skirt-like member72 and the outer diameter side offrame member75 are molded about and encase a continuous spring member, shown partially in FIG. 9 and indicated byreference numeral79.Spring member79 can be shaped from a continuous length or one or more segments of spring steel, or other materials capable of exerting a spring bias oncontact member73.
• When[0098]ablation template device69 is placed in contact with tissue, skirt-like members70,72 may promote adherence between the tissue and the device. Furthermore,ablation template device69 may include avacuum port74. When vacuum pressure is supplied byconnective tube71 to vacuumport74, skirt-like members70,72 may promote the creation of a seal, further enhancing the adherence ofdevice69 to the tissue. Upon application of vacuum pressure, skirt-like members70,72 may deform slightly, conforming to the surface of the tissue and helping define a sealedvacuum chamber76 having a substantially annular shape. Skirt-like members70,72 may therefore improve adherence to the tissue in two ways: by being tacky and compliant, and by assisting the creation of a vacuum seal. Silicone gels, such as NuSil 6340, may be especially well suited for this function, providing a quality of adherence and compressibility appropriate for the intended purposes.
• FIG. 10 shows a perspective view of an[0099]ablation template device80, which is similar toablation template device50 shown in FIG. 6. Thecontact member82 of thedevice80 has been supplied with a thin layer of a compliant,tacky substance84 such as a silicone gel. Whenablation template device80 is held by pressure againsttissue using shaft86,tacky layer84 may provide added adherence between the device and the tissue, and may reduce the risk of slippage. The tacky material may be included at every point of contact between the tissue andcontact member82, or at selected sites of contact.
• FIG. 11 is a perspective view of an[0100]ablation template device100, shown placed on aheart10 for purposes of illustration.Ablation template device100 is likeablation template device69 shown in FIG. 9.Contact member102 has been placed against thesurface15 of theright atrium12. Inner skirt-like member104, extending around the inner edge ofcontact member102, and outer skirt-like member106, extending around the outer edge ofcontact member102, assist in substantially affixingdevice100 to theheart10. Vacuum pressure supplied tovacuum port108 via connectingtube110 may promote additional adherence betweencontact member102 andheart surface15.
• It may be difficult for a surgeon to obtain direct access to the tissue of the[0101]atrium12 where ablation is to be performed. It may be necessary for the surgeon to manipulate or move the heart so that access may be obtained. FIG. 11 illustrates the use of a surgical manipulatingdevice120, whereby the apex122 of theheart10 is held and manipulated, allowing the surgeon to obtain access to the desired site on theatrium12. It is known that some significant portion of the aberrant impulses responsible for atrial fibrillation can originate in myocardial cells that have migrated to the inner base of the pulmonary veins. Accordingly, it is important that ablation lines be drawn in such a way as to isolate the pulmonary veins and prevent those impulses from traveling into the atrial tissue. Accomplishing this isolation requires that the ablation lines be drawn relatively close to the base of the pulmonary veins.
• The use of surgical manipulating[0102]device120 and similar devices described herein enables the surgeon to grasp the apex122 of the beating or stoppedheart10 and access the base of the pulmonary veins, e.g., by lifting, pulling, and/or turning the beating heart to expose the pulmonary veins. Important additional benefits ofdevice120 and similar devices described herein may include the ability to lift and manipulate theheart10 without causing significant trauma to the epicardium and with minimal or no disturbance of hemodynamics, reducing the overall risk of the procedure to the patient. Therigid handle127 ondevice120 permits the surgeon to apply axial (i.e., along axis from top of heart to apex) tension to the beating heart while lifting theheart10 from the pericardial cavity. Maintaining axial tension while lifting the heart from the supine position to a position 90-110 degrees from the spine prevents distortion of valves and the decline in cardiac output that occurs when the heart is lifted by the surgeon's hand alone.
• In some embodiments, two suction devices, e.g., like surgical manipulating[0103]device120, can be used to access the posterior of the heart and the base of the pulmonary veins. One device may be applied to the apex of the heart and the second device may be applied to a suitable location on the anterior surface of the heart, such as the area between the right and left ventricles (interventricular groove). Both devices can then be manually manipulated in concert so that the heart can be raised to a vertical position, i.e., close to 90 degrees from its ordinary anatomic orientation, without distorting the axis that runs from the apex to the great vessels. In addition, manual manipulation of both devices simultaneously permits the surgeon to move the raised heart from left to right inside the thoracic cavity. The use of the second device on the anterior surface of the heart keeps the chambers and valves in the heart from being compressed or distorted, and permits elevation and rotation of the heart without compromising blood flow. No decline in blood pressure (measured just below the aortic arch with an intravascular transducer) is observed when these manipulations are performed with the two devices used in concert. The two devices (each of which may conform substantially to device120) can also be secured by a suitable clamp or frame that is anchored to the operating table or the chest retractor.
• Manipulating[0104]device120, as shown in FIG. 11, may define a cup-like chamber123 having avacuum port125 coupled to avacuum tube127.Chamber123 can be formed from acup frame121 formed with semi-rigid material and a compliant, tacky skirt-like member129.Vacuum tube127 may be coupled to an external vacuum source for delivery of vacuum pressure to the interior ofchamber123.
• Compliant, tacky skirt-[0105]like member129 can be formed, for example, from silicone gel, and can be attached to an outer wall defined bychamber123 to provide a sealing interface with tissue atapex122 ofheart10.Skirt member129 can be molded, cast, deposited or otherwise formed about the wall ofchamber123, or adhesively bonded to the chamber wall. Although the tackiness ofskirt member129 promotes adherence, adherence may be improved by application of the vacuum pressure viatube127 andport125. Upon application of vacuum pressure, at least a portion of theseal member129 deforms and substantially forms a seal against the surface.Device120, in various embodiments, may correspond substantially to similar devices described in the U.S. provisional application serial No. 60/181,925, filed Feb. 11, 2000, to Sharrow et al., entitled “DEVICES AND METHODS FOR MANIPULATION OF ORGAN TISSUE,” and bearing attorney docket no. 11031-004P01, the entire content of which is incorporated herein by reference.
• The[0106]semi-rigid chamber123 imparts structural integrity to thedevice120, while the tacky, deformable material forming the skirt-like member129 provides a seal interface with the heart tissue that is both adherent and adaptive to the contour of the heart. Moreover, as the skirt-like member129 deforms, it produces an increased surface area for contact with the heart tissue. The increased surface area provides a greater overall contact area for adherence, and distributes the coupling force of the vacuum pressure over a larger tissue area to reduce tissue trauma. In general, the structure ofdevice120 can be helpful in avoiding ischemia, hematoma or other trauma to theheart10.Device120 provides a grasping point, however, for manipulation ofheart10 to provide better access to a desired surgical site, e.g., by lifting, turning, pulling, pushing, and the like. Once the desired presentation ofheart10 is achieved usingdevice120, the heart can be held relatively stationary, e.g., by fixingvacuum tube127 to a more stationary object such as a rib spreader.Device120 and similar devices described herein can be used to stabilize the heart in a similar manner by grasping the apex and/or other suitable locations on the heart, such as the anterior interventricular groove, and attaching the device to a stationary object. In this manner, it is possible to use one or more devices such asdevice120 and similar embodiments in concert with the various embodiments of tissue ablation templates described herein placed at a variety of suitable locations on the heart to create a relatively stable epicardial surface for ablation. Such stabilization allows the surgeon to complete the manual ablation or other surgical procedures more easily and more quickly than without stabilization. For example, using afirst device120 on a suitable ventricular surface and asecond device120 on the apex permits the surgeon to elevate the heart and stabilize it to permit ablation with an ablation template on the posterior side of the heart. Addition of a flexible joint betweenvacuum tube127 andmember121 may allow the heart to maintain its normal movement resulting from contraction further reducing trauma to the heart.
• In some embodiments,[0107]device120 and an ablation template device as described herein may be appropriately miniaturized to permit deployment via port-access methods, such as small thoracotomies. An ablation template device as described herein also could be appropriately miniaturized for application on the endocardial surface of the heart, e.g., using transluminal approaches. For endocardial application, an ablation probe such as an RF antenna can be integrated with the ablation template device, which could be made substantially flexible but incorporate shape memory elements or elasticity to expand following transluminal deployment.
• In alternative embodiments, no external vacuum pressure need be applied. Instead, as shown in the cross-sectional side view of FIG. 12, a[0108]device120′ can be configured to incorporate a mechanical structure that permits variation of the volume within thechamber123′, e.g., by actuation of a piston-like member or modulation of a fluid chamber. For example, ashaft130 can be mounted withinchamber123′ substantially wherevacuum port125 andvacuum tube127 are located in FIG. 11. Adistal end131 of theshaft130 is positioned to engage aflexible membrane132 withinchamber123′. An attachment pad can be placed betweendistal end131 ofshaft130 andflexible membrane132 to permit adhesive or thermal attachment. Upon actuation of theshaft130, themembrane132 can be moved inward and outward relative to the interior ofchamber123′, and thereby change the volume and, as a result, pressure within thechamber123′.
• As an illustration, upon engagement of[0109]seal member129 withheart10,shaft130 andcup121 are pushed ontoheart surface15. Retractingshaft130 drawsmembrane132 and heart surface15 into the chamber defined bycup121. Upon release ofshaft130, elasticity ofmembrane132 biases the membrane andshaft130 back to their original positions, increasing the volume and decreasing the pressure withinchamber123′. As a result,chamber123′ produces a suction effect without application of external negative pressure that enhances the seal provided by the tacky skirt-like member129. Thus, theshaft130 andmembrane132 can be used to create a negative pressure withinchamber123′ that serves to aid adhesion of the tacky skirt-like gasket member129 to apex122 (shown in FIG. 11). FIG. 12 also illustrates internal attachment of skirt-like member129 withcup frame121. In particular, as shown in FIG. 12, skirt-like member129 can be molded about theouter lip133 ofcup frame121. Also, aninsert135 formed from a metal or polymeric material can be embedded withincup frame121 and skirt-like member129 to provide added structural integrity todevice120′.
• FIG. 13 illustrates another embodiment of a[0110]device120′ incorporating a limpet-like structure. In the example of FIG. 13, instead of ashaft130 as shown in FIG. 12,chamber123 receives afluid tube134 atport125.Fluid tube134 permits inflow and outflow offluid136 into theinternal cavity138 defined bymembrane132 and theinner wall140 ofchamber123. In this case,internal cavity138 can be normally filled with a fluid136 such as saline. When fluid is drawn fromdevice120 throughfluid tube134,membrane132 is drawn towardport125, decreasing the volume of theportion138 ofchamber123 that engagesheart10. In this manner, pressure withinchamber123 is reduced, creating a suction effect that aids the sealing pressure of skirt-like member129 atapex122. A stopping mechanism such as a valve or stopcock (not shown) may be employed to stop the flow of fluid throughfluid tube134, and thereby fixing the sealing pressure.
• FIG. 14 depicts a[0111]device141 that permits attachment of an antenna for delivery of radio frequency (RF) energy to the surface of a heart for the purpose of creating a linear lesion of dead tissue that is transmural. FIG. 15 shows a cross section atpoint145 ondevice140 of FIG. 14. Thebody147 of thedevice140 can be made of a suitable flexible polymeric material such as silicone elastomer. Ashaft142, made of either a rigid or flexible material, depending upon application, can be used to position thedevice140 in either an open or minimally invasive surgical procedure. The diameter ofshaft142 would be sized differently for each of these applications. In the example of FIGS. 14 and 15,shaft142 also contains a moveableinner catheter143 that contains the RF antenna and, if appropriate, afluid delivery lumen148. In addition to thecatheter143,shaft142 can provide a vacuum connection todevice140, which may define one or more inner chambers. Thedevice140 can be attached to the heart using twovacuum ports144,146 connected to one ormore seal members149,151. Vacuum pressure can be provided toports144,146 viatubes150,152, which are coupled to an external vacuum source and branch off fromshaft142.
• The[0112]body147 ofdevice140 can be molded to define twovacuum chambers154,156 and acentral lumen158, which opens to abase side160 of the device and forms a continuous track for accommodation ofcatheter143.Malleable metal shafts162,163,164 can be inserted into thebody147 to provide shaping capability and added structural integrity, but may not be necessary to achieve compatibility with all desired contours and positions on the heart. Vacuum pressure delivered throughvacuum chambers154,156 viavacuum ports144,146 is used to attach thedevice140 to the heart.Flexible seal members166,168, and170,172 are disposed adjacent eachvacuum chamber154,156, respectively, and conform to the surface of the heart and function asseals149,151.Seal members166,168,170,172 can be made of silicone elastomers as soft as 5 on the Shore A scale, or can be made of silicone gel. A suitable silicone elastomer material may have a durometer, for example, in the range of 5 to 30 Shore A. An example of one suitable silicone gel material is MED 6340, commercially available from NUSIL Silicone Technologies, of Carpinteria, Calif. The MED 6340 silicone gel is tacky and exhibits a penetration characteristic such that a 19.5 gram shaft with a 6.35 mm diameter has been observed to penetrate the gel approximately 5 mm in approximately 5 seconds. This penetration characteristic is not a requirement, but merely representative of that exhibited by the commercially available MED 6340 material. These materials can conform to the irregular shape of the myocardium under negative pressure created by the vacuum source and, if formed from silicone gel, may provide tackiness that aids the seal.
• The[0113]seal members166,168,170,172 can be partially shaped and stiffened, if necessary byfins174,176,178,180, respectively, placed at different intervals along the length of the seal members. These fins can be made of flexible metal or can be part of thematerial forming body147 ofdevice140 and integrally molded therewith.Seal members166,168,170,172 and associatedvacuum chambers154,156 may extend along the length ofbody147, likecentral lumen158, to define elongated tracks. Upon application of vacuum pressure to vacuumports144,146,vacuum chambers154,156 serve to holddevice140 tightly against the surface of the heart.Device140 may be sized and structured to provide a local stabilizing effect on the tissue to which the device is attached, e.g., for beating heart surgical applications. In many embodiments, however, stabilization will not be necessary. Rather, it is sufficient thatdevice140 fix a surgical instrument, e.g.,RF antenna141, in the same frame of motion as the moving tissue. In this manner, an instrument can be applied with precision to the surface of the heart without significant relative motion.
• In the[0114]central lumen158 is insertedcatheter143, which, in the example of FIGS. 14 and 15, containsRF antenna141.Antenna141 may, itself, enclosefluid delivery lumen148.RF antenna141 is shown in FIGS. 14 and 15 at the end ofcatheter143, where the antenna emerges at an angle to the catheter and protrudes through the track defined bycentral lumen158 ofdevice140. By slidingcatheter143 along the track defined bylumen158, thetip182 ofantenna141 can move along the track and deliver energy to the tissue with which it is in contact, creating a lesion that can extend the full thickness of the myocardium. An RF antenna is one example of an ablation probe suitable for use withdevice140 to ablate tissue. Other ablation instruments could be placed incatheter143, however, including laser, ultrasonic, and cryogenic probes, all, all of which could create a lesion in a similar fashion.
• In some embodiments,[0115]catheter143 can be moved throughlumen158 either manually by a surgeon by grasping the proximal end of the catheter or by a mechanical device connected to the catheter, e.g., at its distal end. For example, a variety of electrical motors could be used to drivecatheter143 alongcentral lumen158, e.g., directly via a worm gear drive or indirectly via pulley or gear arrangements. The motors can be driven either automatically, or at the direction of the surgeon using a joystick or other manual controls.Electrodes184,186 can be mounted on an inner surface of theinnermost seal members168,170 for contact with the myocardium.Electrodes184,186 are connected toconductors188,190, respectively, which extend out ofdevice body147 and continue intoshaft142.Electrode184 andconductor188 on one side of thedevice140 can be used to send an electric signal across the lesion area formed byantenna141 for detection on the other side of the device by anotherelectrode186 andconductor190.
• FIG. 16 is a cross section at point B on[0116]shaft142 of FIG. 14.Conductors188,190 can be connected via acable192 to appropriate instrumentation. Such conductor/electrode sets can be used to measure impedance across the lesion or conduction velocity across the lesion. These measurements can be used to determine if the lesion is truly transmural, that it extends the full thickness of the myocardium.Conductors188,190 can be ultimately connected to an external control unit which is capable of using impedance or conductance time or velocity measurements to generate either a signal observable by the surgeon or a signal for control of a device responsible for advancingcatheter143 alongcentral lumen158 when a transmural lesion has been created in one region. To that end, a plurality ofelectrodes184,186 can be placed on respective sides ofcentral lumen158 to take measurements at several positions along the length of the lesion track, thereby driving controlled advancement ofcatheter143 as an effective lesion is formed at each position. Again, advancement ofcatheter143 can be automated or manual. In either case the surgeon can be assured during the procedure that an effective lesion has been formed.
• As shown in FIG. 16,[0117]outer shaft142 may contain twoseparate lumens194,196, which provide vacuum pressure tochambers154,156 viatubes150,152. FIG. 16 also shows a cable with a wiringbundle including conductors188,190, for electrical communication withelectrodes184,186 (FIG. 15). The number of conductors may be dependent upon the number of electrodes placed on each side of theinner sealing members168,170. For example, eachelectrode184,186 preferably is coupled to anindividual conductor188,190, respectively. Alternatively, a single continuous electrode could be disposed on one side ofcentral lumen158 and coupled to a single conductor. In this case, a series of electrodes at various positions on one side ofcentral lumen158 would transmit signals to the continuous electrode on the other side or vice versa.Catheter143 fits in thecentral lumen158 ofshaft142 and, in this example, containsRF antenna141 andfluid lumen148. Again, other embodiments could have different types of ablation probes built intocatheter143.
• FIG. 17 shows a specialized form of a[0118]device140′ as shown in FIG. 14. In this embodiment, thedevice body147′ is shaped in a substantially semicircular form to facilitate contact around the base of the pulmonary vein or similar structure.Device body147′ is moved into position viashaft142′ and vacuum is used to affix it to its first location on the vein. In this case, a catheter is translated around the arcuate path defined by a central lumen. The catheter carries an RF antenna or other ablation probe that is exposed via opening for contact with the outer wall of the pulmonary vein. Lesion generation is carried out on the full thickness of the vein wall in one location by energization of the RF antenna or activation of other suitable probe. As shown in FIG. 17, vacuum pressure can be applied viavacuum chambers154′,156′ withseal members166′,168′,170′,172′ providing an effective seal. When vacuum pressure is released,device140′ can be moved viashaft142′ to another location to create a lesion continuous with the previous one until a circumferential lesion is created all the way around the base of the pulmonary vein. As in the example of FIGS.14-16,device140 can be fixed in the same frame of motion as the pulmonary vein, eliminating significant relative motion to enhance precision in creation of the lesion. The interior ofdevice140′ is identical to that ofdevice140 as shown in FIG. 15, with two modifications. The malleable metal inserts162,164 are replaced with shaped memory metal inserts, which cause140′ to assume an arcuate shape shown in FIG. 17.Malleable insert163 is replaced with a semi-rigid metal rod which can be withdrawn throughshaft142′ to allowelements162,164 to assume their arcuate shape andcause device140′ to also assume an arcuate shape. Insertion of the semi-rigid rod causesdevice140′ to straighten into a linear shape that would permitdevice140′ to entry into or withdraw from a tubular access port used in minimally invasive surgical procedures.
• Although[0119]device140 is depicted as having a “shepherd's crook” shape, that shape is merely an exemplary embodiment of the invention. The ablative device may take other forms such as a loop, hook, ess or snare. In any of these configurations, electrode sets may be placed on the device so as to have a one or more transmitting electrodes on one side of the lesion and one or more receiving electrodes on the opposite side of the lesion to measure the effectiveness of the ablation.
• FIGS.[0120]18-20 illustrate another embodiment of anablation template device200. FIG. 18 is a perspective side view ofdevice200. FIG. 19 is a cross-sectional side view ofdevice200 taken at line210-210′ in FIG. 18. FIG. 20 is a bottom view ofdevice200. As shown in FIGS.18-20,device200 includes a ring-like contact member202 defining an annular but generally oval-shapedchamber204.Contact member202 may include aframe204 formed from a semi-rigid material, andseal members206,208 formed at the inner and outer diameters offrame204.Seal members206,208 can be formed, for example, from a silicone gel material. Avacuum tube212 is mounted in avacuum port214 that communicates with aninterior chamber216 defined byframe204 andseal members206,208. Acover218 can be mounted within thecentral aperture220 defined byframe204, or integrally formed with the frame, e.g., by molding. Cover218 includes a slot-like track222 that extends along the major axis ofcontact member202.Track222 accommodates anablation probe224.
• [0121]Ablation probe224 may take the form of an RF, laser, ultrasonic, or cryogenic probe, and includes upper andlower flanges226,228 that hold the probe within track. In particular,upper flange226 bears on an upper surface ofcover218adjacent track222, whilelower flange228 bears on a lower surface of the cover.Ablation probe224 is slidable alongtrack222, however, to define a lesion path for an ablation procedure. In particular, a surgeon can simply slideablation probe224 alongtrack222.Electrodes230,232 on opposite sides oftrack222 can be electrically coupled to electronics that provide measurements, e.g., impedance, conduction velocity, and conduction time, to assess the effectiveness of the ablation procedure. In response to indications provided based on the electrode measurements, the surgeon advancesablation probe224 alongtrack222. Alternatively,ablation probe224 can be advanced automatically alongtrack222 in response to such indications. In some embodiments,tip234 ofablation probe224 may contact tissue.
• FIGS.[0122]21-23 illustrate anotherablation template device240. FIG. 21 is a partial perspective view ofdevice240. FIG. 22 is a partial cross-sectional side view ofdevice240 of FIG. 21 taken at line242-242′. FIG. 23 is a cross-sectional front view ofdevice240 of FIG. 21 taken at line244-244′. As shown in FIGS.21-23,device240 includes acontact member246 mounted on anelongated guide member248 that extends throughbore249.Contact member246 may be slidable alongguide member248 or fixed. The contact member includes aframe250 formed of a flexible material, and aseal member252 formed from a compliant, tacky material such as silicone gel. Theseal member252 interfaces with tissue, e.g., on the surface of the heart.Frame250 further defines one ormore rails254 that extend radially outward relative to contactmember246 and longitudinally relative to guidemember248. Acarriage256 is mounted onrails254, e.g., via inner grooves that engage the rails, and defines alateral flange258 designed to hold anablation probe260. As shown in FIGS. 21 and 23, in particular,ablation probe260 protrudes downward fromlateral flange258 for contact with organ tissue.
• [0123]Ablation probe260 can be molded into or otherwise encased inlateral flange258 ofcarriage256. A second lateral flange262 (FIG. 23) can be provided, along with acounter probe264, to contact tissue and thereby balancedevice240 on a side ofcarriage256 oppositelateral flange258.Ablation probe260 may take the form of an RF, laser, ultrasonic, or cryogenic probe designed to ablate tissue.Ablation probe260 may have electric conductors that run along the length ofguide member248 to an external power supply, in the case of an RF or ultrasonic probe. Alternatively, an optical fiber or fiber bundle may be coupled betweenablation probe260 and an external source of laser energy. As a further alternative, a fluid line may extend between ablation stylus and a cryogenic source. In each case,device240 can be sized and arranged to permit deployment by endoscopic or other minimally invasive techniques to an ablation site, e.g., on the surface of the heart. Thus, in one application,device240 can be deployed and affixed to the surface of a beating heart, and fix theablation probe260 in the same frame of motion as the heart.
• [0124]Seal member252 may define a plurality ofvacuum ports266 coincident with vacuum ports inguide member248. A vacuum tube resides within aninner lumen270 ofguide member248 and includes one or more output ports that apply vacuum pressure to vacuumports266. To perform an ablation procedure,device240 is deployed to a desired site on the surface of an organ such as the heart. Vacuum pressure is applied to affixcontact member246 to the tissue surface via the seal interface provided byseal member252. At the same time,ablation probe260 is brought in contact with the tissue surface.Ablation probe260 is then energized to ablate the local tissue area proximate the tip of the probe. A guide wire or other elongated member can be coupled tocarriage256, which preferably is slidable alongrails254 defined bycontact member252. By translating the guide wire,carriage256 can be moved relative to contactmember252 and thus relative to the tissue surface, thereby creating an ablation track. As in other embodiments, electrodes can be integrated withseal member252 to measure the extent of ablation. Again, the measurements can be used as the basis for manual or automated control of the guide wire, and resulting movement ofcarriage256.
• FIGS. 24 and 25 illustrate another[0125]ablation template device272. FIG. 24 is a cross-sectional front view ofdevice272, while FIG. 25 is a fragmentary cross-sectional side view.Device272 is somewhat similar todevice240 of FIGS.21-23. However,device272 need not incorporate a carriage. Rather,device272 provides an internaloptical waveguide274 mounted within aguide member276 that transmits laser radiation.Waveguide274 may be housed in acannula278.Waveguide274 may incorporate areflector280 at itsdistal end282 that reflects laser energy downward through a chamber defined byseal member284 to ablate tissue.Seal member284 may be substantially compliant and tacky and may be attached to asemi-rigid frame286 that is coupled to or integrated withguide member276.Cannula278 andwaveguide274 preferably are movable along the length ofguide member276, as indicated byarrow288.Optical waveguide274 can be mounted within anouter vacuum lumen290 that delivers vacuum pressure to affixdevice272 to thetissue292 viaseal member284. To form an ablation track,optical waveguide274 can be translated withinguide member276, as indicated byarrow288. Once again, electrodes can be integrated with seal member to enable manual or automated control of waveguide movement.
• Ablation, and measurement of impedance or conduction time to assess ablation lesion depth, can also be performed along the interior surfaces of a structure. For example, a linear RF electrode can be transluminally introduced via a catheter into the atria of the heart and positioned on the endocardium in appropriate locations. Ablative energy from the RF electrode can then be applied. Electrode sets used to measure impedance or conduction time or other electrical properties can be integrated into the catheter body parallel to but insulated from the active RF electrode at the distal end of the catheter. These electrode sets can be utilized as described above to both measure lesion depth (from the endocardial to the epicardial surface) and to control delivery of energy.[0126]
• Transluminal introduction, therefore, represents an additional way to create a lesion around the base of the pulmonary veins, and thereby treat atrial fibrillation. The lesion may be created on the interior surfaces of the heart or pulmonary veins, rather than the heart's or veins' exterior surfaces. The treatment entails ablating the endocardial tissue near the ostia of the pulmonary veins in the left atrium. Typically the ablation apparatus is delivered to the site on the distal end of a steerable catheter introduced into the atrium or the pulmonary veins, and is manipulated and controlled at the proximal end of the catheter.[0127]
• FIG. 26 is a side view of an apparatus that may be directed transluminally near the ostia of the pulmonary veins in the left atrium. The device of FIG. 26 may conform substantially to the device shown in U.S. Pat. No. 5,938,660 to Swartz et al. In the example of FIG. 26, however, the device has been adapted in accordance with the present invention to incorporate components for measurement of ablation depth or effectiveness. In particular, electrodes have been positioned on the device so as to come into contact with tissue on opposing sides of a lesion created by the ablative components.[0128]
• FIG. 26 depicts a distal end of a[0129]catheter body300, withballoons302,304 on thecatheter body300 shown inflated. Fluid medium introduced throughcatheter lumen306 at the proximal end emerges at the distal end throughopenings308, thus inflating theballoons302,304. Inflation causesballoons302,304 to lodge against the tissue.Catheter300 may include atip electrode310 for sensing electrical activity.Catheter300 may also includeRF electrode312, which performs the actual ablation. Afterballoons302,304 are inflated, ablation may be accomplished by introducing a conductive media throughcatheter300, which emerges at the distal end throughopenings318. Application of RF energy follows, and the tissue between theballoons302,304 is ablated.
• [0130]Electrodes314,316 are mounted on the surface of theballoons302,304 at the circumference of the balloons.Electrodes314,316 are insulatively separated fromRF electrode312 andtip electrode310.Electrodes314,316 may be uni-polar or multi-polar. Connecting leads320 and322 are coupled toelectrodes314 and316 respectively.Leads320,322 may be wires or conductors printed on the surface of balloons, or a combination of both.Leads320,322 travel fromelectrodes314,316 toward proximal end ofcatheter300, and emerge from proximal end of catheter where leads are electrically coupled to a measuring device such as an impedance meter or conduction time measuring device. Following measurements that show a successful ablation, the conductive media may be withdrawn, balloons302,304 may be deflated, and the catheter may be extracted.
• Many variations are possible. For example, a plurality of electrodes can be mounted on the surface of[0131]balloons302,304. Flexible disks or other extendable members could be used in place of balloons. The RF electrode may be extended or unfolded from the body of the catheter or otherwise steered into proximity with the tissue surface. Ultrasound energy or other energy forms may be used in place of RF. Sites other than the ostium may be treated. In each of these variations, however, electrodes can be used to measure the efficacy of the treatment.
• FIG. 27 is a side view of an additional apparatus that may be directed transluminally near the ostia of the pulmonary veins in the left atrium. The device of FIG. 27 may conform substantially to the device shown in U.S. Pat. No. 6,024,740 to Lesh et al. and to the device shown in U.S. Pat. No. 6,012,457 to Lesh. In the example of FIG. 27, however, the device has been adapted in accordance with the present invention to incorporate components for measurement of ablation depth or effectiveness. In particular, electrodes have been positioned on the device so as to come into contact with tissue on opposing sides of a lesion created by the ablation element.[0132]
• FIG. 27 depicts a distal end of a[0133]catheter330, withballoon332 on thecatheter body330 shown inflated. Fluid medium introduced throughcatheter lumen334 at the proximal end inflatesballoon332, causingballoon332 to lodge against the tissue, preferably but not necessarily at the ostia of the pulmonary veins.Catheter330 may also includeRF electrode336, which contacts the tissue.Catheter330 may further include aproximal perfusion port338 and adistal perfusion port340 connected by aperfusion lumen342.
• [0134]Electrodes344,346 are mounted on the surface ofballoon332, and contact the tissue.Electrodes344,346 are insulatively separated fromRF electrode336.Electrodes344,346 may be uni-polar or multi-polar. A plurality of such electrode pairs could be employed. Connecting leads348 and350 are coupled toelectrodes344 and346, respectively, and travel fromelectrodes344,346 toward proximal end ofcatheter330. At the proximal end of catheter, leads348,350 are electrically coupled to a measuring device such as an impedance meter or conduction time measuring device. Following measurements that show a successful ablation, theballoon332 may be deflated and the catheter may be extracted. As with the apparatus shown in FIG. 26, many variations are possible.
• FIG. 28 is a side view of a further apparatus that may be directed transluminally to various locations within either atrium. FIG. 28 depicts a distal end of a[0135]catheter body360.Catheter360 is steerable, allowing it to be positioned against the tissue. An energy delivery means such as anRF electrode362 performs the ablation.
• [0136]Electrodes364,366 may be independently controlled from the proximal end of the catheter and may be extended from or retracted intolumens368,370.Electrodes364,366 may be uni-polar or multi-polar.Electrodes364,366 extend toward proximal end ofcatheter360, where they are electrically coupled to a measuring device such as an impedance meter or conduction time measuring device.Electrode tips372,374 can be of various shapes to facilitate insertion into the tissue. For example,electrode tips372,374 may have needle-like shapes or screw-like shapes. Being independently extendable and retractable,electrodes364,366 may be directed to different sites along a lesion and may be used to make measurements at multiple locations along a lesion. There could also be a plurality of such electrodes to provide electrical measurements at various sites along a lesion.
• FIG. 29 shows another apparatus that may be used transluminally in either atrium. The device of FIG. 29 may conform substantially to the device shown in U.S. Pat. No. 5,676,662 to Fleischhacker et al. In the example of FIG. 29, however, the device has been adapted in accordance with the present invention to incorporate components for measurement of ablation depth or effectiveness. In particular, electrodes have been positioned on the device so as to come into contact with tissue on opposing sides of a lesion created by the helical ablation element.[0137]
• FIG. 29 shows a distal end of a[0138]catheter body380.Catheter380 is steerable, allowing it to be positioned against the tissue. An RF electrode382 in the form ofhelical coils384 performs the ablation.Coils384 are electrically isolated from each other by an insulatingsubstance386.
• [0139]Electrodes388,390, which may be uni-polar or multi-polar, are mounted on opposing sides ofcatheter380 and are electrically isolated fromhelical coils384.Electrodes388,390 are connected to leads392,394, which extend toward proximal end ofcatheter380. At the proximal end of catheter, leads392,394 are electrically coupled to a measuring device such as an impedance meter or conduction time measuring device.
• FIG. 30 is a side view of a further apparatus that may be directed transluminally, and may also be positioned on the atrial endocardium via thoracoscope or port access. The device of FIG. 30 may conform substantially to the device shown in U.S. Pat. No. 5,916,213 to Haissaguerre et al. In the example of FIG. 30, however, the device has been adapted in accordance with the present invention to incorporate components for measurement of ablation depth or effectiveness. In particular, electrodes have been positioned on the device so as to come into contact with tissue on opposing sides of a lesion created by the ablation elements.[0140]
• FIG. 30 depicts a distal end of a[0141]steerable catheter body400.Catheter400 includes two energy delivery surfaces402,404 such as RF electrodes, which perform the ablation. Energy delivery surfaces402,404 are mounted onmovable arms406,408 respectively.Arms406,408 can be manipulated through ayoke410, which is coupled to acable412 leading to the proximal end of the catheter. By manipulation ofcable412 andyoke410,arms406,408 can be drawn into the tip ofcatheter body400 and placed in a closed position parallel tocatheter body400.Cable412 may also be used to supply power to energy delivery surfaces402,404.Arms406,408 can be extended from the tip ofcatheter body400 and placed in an open position perpendicular tocatheter body400. Whenarms406,408 are in the open position,catheter400 can be steered to press energy delivery surfaces402,404 against the epicardium or endocardium. Once energy delivery surfaces402,404 are in place, energy may be applied to energy delivery surfaces402,404 to effect the ablation and create a lesion.
• [0142]Electrodes414 and416 are mounted on opposite sides ofarm406 andelectrodes418 and420 are mounted on opposite sides ofarm408.Electrodes414,416,418,420 may be uni-polar or multi-polar. Connecting leads422,424,426 and428 are coupled toelectrodes414,416,418 and420 respectively, and travel fromelectrodes414,416,418 and420 toward proximal end of the catheter. At the proximal end of the catheter, leads422,424,426 and428 are electrically coupled to one or more measuring devices such as an impedance meter or conduction time measuring device.Leads422 and424 carry information pertaining to the lesion created byenergy surface402, and leads426 and428 carry information pertaining to the lesion created byenergy surface404.
• Many of the devices described above, such as those depicted in FIGS. 28, 29 and[0143]30, may be used with epicardial applications as well as endocardial applications. The devices described above may also be applied to tissues other than cardiac tissues. The electrode sets may be used with or without a surgical template. Although only one set of electrodes is shown in the figures for clarity, a plurality of electrode sets can be used in any embodiment. The electrode sets may be also be deployed independently of the ablative energy delivery system, and may be used with any ablative energy delivery system. Furthermore, in the devices described above, the electrode sets may be used as probes to control the delivery of energy as outlined in FIGS. 4 and 5. The specific embodiments described above are intended to be illustrative of the general principle and are not intended to be limited to a particular device or to a particular template or to a particular ablative energy delivery system.
• A number of embodiments of the present invention have been described. Other embodiments are within the scope of the following claims.[0144]

Claims (90)

1. A surgical device for use in a tissue ablation procedure, the device comprising a contact member that engages tissue near a location where the tissue is to be ablated, the contact member defining a guide that indicates, upon engagement of the contact member with the tissue, a location where tissue is to be ablated, and provides a path for travel of a tissue ablation device.

2. The device ofclaim 1, wherein the contact member includes a substantially compliant and tacky interface element for engagement with the tissue.

3. The device ofclaim 2, wherein the contact member includes a frame formed of a material that is substantially more rigid that the interface element, the interface element being coupled to the frame.

4. The device ofclaim 1, further comprising a length indicator formed on the contact member that indicates a desired tissue ablation length along the path for travel of the tissue ablation device.

5. The device ofclaim 4, wherein the length indicator includes one or more visible markings.

6. The device ofclaim 4, wherein the length indicator includes a stop structure formed on the contact member, the stop structure extending into the path for travel of the ablation device and being oriented for abutment with the ablation device.

7. The device ofclaim 1, further comprising a length indicator along the contact member, the length indicator indicating a desired lesion length.

8. The device ofclaim 1, wherein a portion of the contact member that engages the tissue is curved to allow the contact member to conform to the shape of the tissue.

9. The device ofclaim 8, wherein a portion of the contact member that engages the heart is curved to allow the contact member to conform to the shape of the heart.

10. The device ofclaim 1, wherein the contact member defines an interior chamber and a vacuum port in fluid communication with the interior chamber, the interior chamber being capable of delivering vacuum pressure to the contact member to thereby promote vacuum-assisted adherence of the contact member to the tissue.

11. The device ofclaim 1, wherein the contact member defines an interior chamber, the device further comprising a vacuum port in fluid communication with the interior chamber, the vacuum port allowing connection to a source of vacuum pressure to provide vacuum pressure to the contact member and thereby promote vacuum-assisted adherence to the tissue.

12. The device ofclaim 1, wherein the contact member includes an adhesive material that promotes adherence of the contact member to the tissue.

13. The device ofclaim 1, wherein the contact member includes an adhesive material that promotes repositionable adherence of the contact member to the tissue.

14. The device ofclaim 1, further comprising an adhesive member that extends outward from the contact member for engagement with the tissue, the adhesive member being sufficiently compliant and tacky so as to promote adhesion of the contact member to a beating heart.

15. The device ofclaim 1, wherein the contact member is substantially annular-shaped, the device further comprising a skirt-like member that extends outward from the annular-shaped contact member for contact with the tissue, the skirt-like member being substantially compliant and tacky, thereby promoting adhesion of the contact member with the tissue.

16. The device ofclaim 15, wherein the skirt-like member is formed from a compliant, tacky silicone gel.

17. The device ofclaim 1, wherein the contact member is substantially annular-shaped.

18. The device ofclaim 1, wherein the contact member is substantially U-shaped.

19. The device ofclaim 1, wherein the contact member includes a first contact foot and a second contact foot extending outward from a common shaft, each of the first foot and the second foot including a compliant and tacky material that promotes adhesion of the contact member to the tissue.

20. The device ofclaim 1, wherein the contact member defines an opening through which the tissue may be accessed, and a port for removal of fluid proximate the tissue surface.

21. The device ofclaim 1, wherein the contact member is substantially ring-shaped and includes an annular chamber, the device further comprising a vacuum port in fluid communication with the annular chamber for delivery of vacuum pressure to the chamber, thereby promoting vacuum-assisted adherence of the contact member to the tissue.

22. The device ofclaim 21, wherein the substantially ring-shaped contact member includes an outer diameter edge and an inner diameter edge, the device further comprising an inner skirt-like member coupled to the inner diameter edge and an outer skirt-like member coupled to the outer diameter edge, the skirt-like members being substantially compliant and tacky to promote adhesion of the contact member to the tissue.

23. The device ofclaim 22, wherein the skirt-like members are formed from a compliant, tacky silicone gel.

24. The device ofclaim 1, wherein the contact member is substantially U-shaped and defines a substantially U-shaped chamber, the device further comprising a vacuum port in fluid communication with the chamber for delivery of vacuum pressure to the chamber, thereby promoting vacuum-assisted adherence of the contact member to the tissue.

25. The device ofclaim 24, further comprising a skirt-like member coupled to the contact member at a periphery of the chamber, the skirt-like member being substantially compliant and tacky to promote adhesion of the contact member to the tissue.

26. The device ofclaim 25, wherein the adhesive material is formed from a compliant, tacky silicone gel.

27. The device ofclaim 1, further comprising a sensor that indicates whether a desired degree of tissue ablation has been achieved.

28. The device ofclaim 27, wherein the sensor includes a first electrode capable of transmitting a first electrical signal and a second electrode capable of receiving a second electrical signal.

29. The device ofclaim 28, wherein the first electrode is disposed adjacent a first side of the contact member and the second electrode is disposed adjacent a second side of the contact member opposite the first side, whereby first and second electrodes are disposed on opposite sides of the location for ablation during use of the device.

30. The device ofclaim 28, wherein the distance between the first electrode and the second electrode is known.

31. The device ofclaim 28, wherein the distance between the first electrode and the second electrode is relatively fixed.

32. The device ofclaim 28, wherein the sensor includes apparatus electrically coupled to the electrodes to measure at least one of conduction time, conduction distance and conduction velocity based on the second electrical signal.

33. The device ofclaim 28, wherein the sensor includes apparatus electrically coupled to the electrodes to measure at least one of phase angle and impedance.

34. The device ofclaim 28, further comprising a processor coupled to at least the second electrode, the processor receiving signals from the second electrode and, based on the signals, determining whether the desired ablation has been achieved to a satisfactory degree.

35. The device ofclaim 34, wherein the processor includes one of a computer, microprocessor, a microcontroller, and discrete logic circuitry arranged to measure the extent of the tissue ablation procedure based on the signals received from the second electrode.

36. The device ofclaim 34, further comprising a measurement device coupled to the first electrode and the second electrode, wherein the first electrode and the second electrode serve as probes for the measurement device.

37. The device ofclaim 36, wherein the processor is electrically coupled to the measurement device, the measurement device transmitting data to the processor based on signals generated at the second electrode.

38. The device ofclaim 36, wherein the processor controls the operation of the measurement device.

39. The device ofclaim 34, wherein the processor is coupled to an input device.

40. The device ofclaim 34, wherein the processor is coupled to an output device.

41. The device ofclaim 34, wherein the processor controls the activation of a tissue ablation device that performs the ablation procedure.

42. The device ofclaim 41, wherein the processor deactivates the tissue ablation device based upon the data received from the measurement device.

43. The device ofclaim 28, further comprising a processor coupled to receive an indication of signals generated at the second electrode, the processor measuring the extent of the tissue ablation procedure based on the signals.

44. An apparatus for determining whether conduction paths within heart tissue have been adequately severed during a surgical procedure, the apparatus comprising

a first electrode capable of transmitting a first electrical signal adjacent the tissue to be severed;

a second electrode capable of receiving a second electrical signal adjacent the tissue to be severed;

a measuring device electrically coupled to at least the second electrode to receive the second electrical signal from the second electrode, the measuring device determining the extent to which the tissue has been severed; and

an output device that provides an indication of extent to which the tissue is severed.

45. The apparatus ofclaim 44, wherein the measuring device includes a measuring circuit that generates a third electrical signal indicating the degree of tissue severing, and a processor that determines whether the tissue has been adequately severed based on the third electrical signal.

46. The apparatus ofclaim 44, wherein the measuring device measures at least one of electrical conduction time, electrical conduction distance and electrical conduction velocity through the severed tissue based on the second electrical signal.

47. The apparatus ofclaim 44, wherein the measuring device measures at least one of phase angle and impedance based on the second electrical signal.

48. The apparatus ofclaim 44, wherein the first electrode is disposed on a first side of tissue to be severed and the second electrode is disposed on a second side of the tissue to be severed opposite the first side.

49. The apparatus ofclaim 44, wherein the distance between the first electrode and the second electrode is known.

50. The apparatus ofclaim 44, wherein the distance between the first electrode and the second electrode is relatively fixed.

51. The apparatus ofclaim 44, wherein the first electrode and the second electrode serve as probes for the measuring device.

52. The apparatus ofclaim 44, further comprising a processor coupled to at least the second electrode the processor receiving signals from the second electrode and, based on the signals, determining whether the desired ablation has been achieved to a satisfactory degree.

53. A method for ablation of conduction paths within tissue comprising:

placing a first device near the target conduction paths to be severed,

using the first device as a guide for an ablation probe to sever the target conduction paths, and

measuring electrical tissue characteristics proximate the target conduction paths to determine whether the desired severing has been achieved.

54. The method ofclaim 53, wherein the first device and the second device are coupled to one another.

55. The method ofclaim 53, wherein measuring comprises measuring at least one of phase angle and impedance.

56. The method ofclaim 53, wherein measuring comprises measuring at least one of conduction time, conduction distance or conduction velocity.

57. The method ofclaim 53, further comprising comparing the desired degree of ablation with the measured degree of ablation.

58. The method ofclaim 53, further comprising discontinuing ablation when the desired degree of ablation has been achieved.

59. The method ofclaim 58, further comprising automatically discontinuing ablation when the desired degree of ablation has been achieved.

60. A method for determining the effectiveness of a tissue ablation procedure in ablation conduction paths in the heart, the method comprising:

measuring at least one of electrical impedance and electrical phase angle across the ablated tissue; and

determining the effectiveness of the tissue ablation procedure based on the measurement.

61. The method ofclaim 60, further comprising prior to ablation, disposing a first electrode on a first side of tissue to be ablated and disposing a second electrode on a second side of the tissue, the second side being opposite the first side following ablation.

62. The method ofclaim 61, further comprising measuring the distance between the electrodes.

63. The method ofclaim 61, further comprising prior to ablation measuring electrical impedance between the electrodes, this measurement to serve as a baseline measurement.

64. The method ofclaim 61, further comprising prior to ablation measuring phase angle between the electrodes, this measurement to serve as a baseline measurement.

65. The method ofclaim 60, further comprising calculating an impedance value that will be measured when the tissue ablation procedure has been effectively performed.

66. The method ofclaim 60, further comprising performing tissue ablation and discontinuing tissue ablation when a predetermined impedance is measured.

67. The method ofclaim 60, further comprising calculating a phase angle value that will be measured when the tissue ablation procedure has been effectively performed.

68. The method ofclaim 60, further comprising performing tissue ablation and discontinuing tissue ablation when a predetermined phase angle is measured.

69. A method for determining the effectiveness of a tissue ablation procedure in ablation conduction paths in the heart, the method comprising:

measuring at least one of electrical conduction velocity, electrical conduction time, and electrical conduction distance across the ablated tissue as a parameter; and

determining the effectiveness of the tissue ablation procedure based on the measured parameter.

70. The method ofclaim 69, further comprising prior to ablation, disposing a first electrode on a first side of tissue to be ablated and disposing a second electrode a second side of the tissue, the second side being opposite the first side following ablation.

71. The method ofclaim 69, further comprising measuring the distance between the electrodes.

72. The method ofclaim 69, further comprising prior to ablation, measuring at least one of electrical conduction velocity, electrical conduction time, and electrical conduction distance, this measurement to serve as a baseline measurement.

73. The method ofclaim 69, further comprising calculating a value that will be measured when the tissue ablation procedure has been effectively performed, of at least one of electrical conduction velocity, electrical conduction time, and electrical conduction distance.

74. The method ofclaim 69, further comprising performing tissue ablation and discontinuing tissue ablation when a predetermined value is measured of at least one of electrical conduction velocity, electrical conduction time, and electrical conduction distance.

75. A method for ablating heart tissue to ablate conduction paths, the method comprising:

placing a guide in contact with the tissue to be ablated;

applying an ablation probe to the tissue using the guide to assist in control of movement of the ablation probe;

measuring the effectiveness of the ablation probe in ablation of the conduction paths; and

deactivating the ablation probe when the measured effectiveness meets a desired level.

76. The method ofclaim 75, wherein measuring the effectiveness of the ablation probe in ablation of the conduction paths includes measuring at least one of electrical impedance, electrical phase angle, electrical conduction velocity, electrical conduction time, and electrical conduction distance across the tissue to be ablated.

77. The method ofclaim 75, wherein measuring the effectiveness of the ablation probe in ablation of the conduction paths includes measuring impedance across the tissue to be ablated.

78. The method ofclaim 75, wherein measuring the effectiveness of the ablation probe in ablation of the conduction paths includes measuring the phase angle across the tissue to be ablated.

79. The method ofclaim 75, wherein the measurement is made using electrodes that are structurally integrated with the guide.

80. The method ofclaim 75, wherein the ablation probe is deactivated automatically when the measured effectiveness meets a desired level.

81. A tissue ablation system, the system comprising:

an ablation probe that generates energy for ablation of the tissue at an ablation site;

a contact member for engagement with the tissue adjacent the ablation site, the contact member defining a guide for movement of the ablation probe during tissue ablation;

first and second electrodes integrated with the contact member, the electrodes being disposed on opposite sides of the ablation site;

a measurement device that measures at least one of electrical impedance, electrical phase angle, electrical conduction velocity, electrical conduction time, and electrical conduction distance across the ablation site to measure an extent of the ablation procedure; and

a controller that deactivates the ablation probe when the measurement device measures an extent of the ablation procedure that meets a desired level.

82. A method for performing surgery on moving organ tissue comprising:

affixing a contact member on a moving tissue surface;

providing a surgical instrument that is attached to the contact member to place the surgical instrument in substantially the same frame of motion as the tissue surface; and

performing a surgical procedure with the surgical instrument.

83. The method ofclaim 82, wherein the moving organ tissue is beating heart tissue.

84. The method ofclaim 82, wherein the surgical instrument is an ablation probe, and performing the surgical procedure includes forming a tissue lesion with the ablation probe to sever desired conduction paths within the tissue.

85. The method ofclaim 84, wherein the ablation probe includes one of a radio frequency, laser, ultrasonic, microwave, thermal, chemical, mechanical, and cryogenic ablation probe.

86. The method ofclaim 84, further comprising moving the ablation probe along the tissue surface relative to the contact member to form the tissue lesion along a desired ablation track.

87. A surgical device for use on moving organ tissue, the device comprising:

a contact member for affixation to a tissue surface; and

a surgical instrument mounted on the contact member, thereby placing the surgical instrument in substantially the same frame of motion as the tissue surface.

88. The device ofclaim 87, wherein the surgical instrument is an ablation probe that forms a tissue lesion to sever desired conduction paths within the tissue.

89. The device ofclaim 84, wherein the ablation probe includes one of a radio frequency, laser, ultrasonic, microwave, thermal, chemical, mechanical, and cryogenic ablation probe.

90. The device ofclaim 84, further comprising moving the ablation probe along the tissue surface relative to the contact member to form the tissue lesion along a desired ablation track.

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