US20030236455A1 - Probe assembly for mapping and ablating pulmonary vein tissue and method of using same - Google Patents

Abstract

The present invention relates to a probe assembly for mapping and ablating pulmonary vein tissue and method of using the same. The probe assembly includes an expandable and collapsible basket assembly having multiple splines. One or more of the splines carry one or more electrodes adapted to sense electrical activity in the pulmonary vein tissue. The basket assembly defines an interior, and a microporous expandable and collapsible body is disposed in the interior of the basket assembly and defines an interior adapted to receive a medium containing ions. An internal electrode is disposed within the interior of the body and is adapted to transmit electrical energy to the medium containing ions. The body includes at least one microporous region having a plurality of micropores therein sized to passions contained in the medium without substantial medium perfusion therethrough, enabling ionic transport of electrical energy from the internal electrode, through ion-containing medium to an exterior of the body to ablate pulmonary vein tissue. In other aspects of the invention, the microporous body may be replaced by a non-porous expandable and collapsible body that receives a fluid medium for expanding the nonporous body to exclude blood from the electrodes on the splines, or the probe assembly may not include any expandable and collapsible body in the basket assembly interior (one or more electrodes on splines sense electrical activity in the pulmonary vein tissue and ablate the pulmonary vein tissue).

Description

FIELD OF THE INVENTION
• The present invention relates, in general, to electrode probe assemblies and methods for mapping and/or ablating body tissue, and, in particular, to electrode probe assemblies and methods for mapping and/or ablating pulmonary vein tissue.[0001]
BACKGROUND OF THE INVENTION
• Aberrant conductive pathways can develop in heart tissue and the surrounding tissue, disrupting the normal path of the heart's electrical impulses. For example, anatomical obstacles, called “conduction blocks,” can cause the electrical impulse to degenerate into several circular wavelets that circulate about the obstacles. These wavelets disrupt the normal activation of the atria or ventricles. The aberrant conductive pathways create abnormal, irregular, and sometimes life-threatening heart rhythms called arrhythmias. An arrhythmia can take place in the atria, for example, as in atrial tachycardia (“AT”) or atrial fibrillation (“AF”). The arrhythmia can also take place in the ventricle, for example, as in ventricular tachycardia (“VT”).[0002]
• In treating arrhythmias, it is sometimes essential that the location of the sources of the aberrant pathways (called focal arrhythmia substrates) be located. Once located, the focal arrhythmia substrate can be destroyed, or ablated, e.g., by surgical cutting or the application of heat. In particular, ablation can remove the aberrant conductive pathway, thereby restoring normal myocardial contraction. An example of such an ablation procedure is described in U.S. Pat. No. 5,471,982 issued to Edwards et al.[0003]
• Alternatively, arrhythmias may be treated by actively interrupting all of the potential pathways for atrial reentry circuits by creating complex lesion patterns on the myocardial tissue. An example of such a procedure is described in U.S. Pat. No. 5,575,810, issued to Swanson et al.[0004]
• Frequently, an arrhythmia aberration resides at the base, or within one or more pulmonary veins, wherein the atrial tissue extends. To treat such an aberration, physicians use multiple catheters to gain access into interior regions of the pulmonary vein tissue for mapping and ablating targeted tissue areas. A physician must carefully and precisely control the ablation procedure, especially during procedures that map and ablate tissue within the pulmonary vein. During such a procedure, the physician may introduce a mapping catheter to map the aberrant conductive pathway within the pulmonary vein. The physician introduces the mapping catheter through a main vein, typically the femoral vein, and into the interior region of the pulmonary vein that is to be treated.[0005]
• Placement of the mapping catheter within the vasculature of the patient is typically facilitated with the aid of an introducer guide sheath or guide wire. The introducer guide sheath is introduced into the left atrium of the heart using a conventional retrograde approach, i.e., through the respective aortic and mitral valves of the heart. Alternatively, the introducer guide sheath may be introduced into the left atrium using a transeptal approach, i.e., through the atrial septum. In either method, the catheter is introduced through the introducer guide sheath until a probe assembly at a distal portion of the catheter resides within the left atrium. A detailed description of methods for introducing a catheter into the left atrium via a transeptal approach is disclosed in U.S. Pat. No. 5,575,810, issued to Swanson et al., which is fully and expressly incorporated herein by reference. Once inside the left atrium, the physician may deliver the probe assembly into a desired pulmonary vein by employing a steering mechanism on the catheter handle. The physician situates the probe assembly within a selected tissue region in the interior of the pulmonary vein, adjacent to the opening into the left atrium, and maps electrical activity in the pulmonary vein tissue using one or more electrodes of the probe assembly.[0006]
• After mapping, the physician introduces a second catheter to ablate the aberrant pulmonary vein tissue. The physician further manipulates a steering mechanism to place an ablation electrode carried on the distal tip of the ablation catheter within the selected tissue region in the interior of the pulmonary vein. The ablation electrode is placed in direct contact with the tissue that is to be ablated. The physician directs radio frequency energy from the ablation electrode through tissue to an electrode to ablate the tissue and form a lesion.[0007]
• Problems with this approach include the possibility of misdirecting or misplacing the ablation electrode and inadvertently ablating non-aberrant, i.e., healthy, pulmonary vein tissue. Further, this approach is time-consuming because the physician has to introduce and remove two catheters. This leads to more patient discomfort and room for physician error. Poorly controlled ablation in the pulmonary vein can result in pulmonary vein stenosis. The pulmonary vein stenosis can lead to pulmonary hypertension, pulmonary edema, necrosis of lung tissue, and even complete pulmonary failure of a lung or lung lobe. In severe and rare cases, the only treatment may be a lung transplant.[0008]
SUMMARY OF THE INVENTION
• The present invention includes the following three main aspects that solve the problems with separate mapping catheters and ablation catheters for mapping electrical activity in pulmonary vein tissue and ablating the pulmonary vein tissue: 1) a probe assembly with a microporous ablation body used with a basket assembly for mapping and ablating pulmonary vein tissue; 2) a probe assembly with a basket assembly for mapping and ablating pulmonary vein tissue; and 3) a probe assembly with an expandable body used with a basket assembly for mapping and ablating pulmonary vein tissue. Each of these aspects is summarized in turn below.[0009]
• 1. Probe Assembly with an Expandable Body used with a Basket Assembly for Mapping and Ablating Pulmonary Vein Tissue:[0010]
• A first aspect of the invention includes a probe assembly for mapping and ablating pulmonary vein tissue. The probe assembly includes an expandable and collapsible basket assembly including multiple splines, one or more of the splines carrying one or more electrodes adapted to sense electrical activity in the pulmonary vein tissue, the basket assembly defining an interior, a microporous expandable and collapsible body disposed in the interior of the basket assembly and defining an interior adapted to receive a medium containing ions, an internal electrode disposed within the interior of the body and adapted to transmit electrical energy to the medium containing ions, the body including at least one microporous region having a plurality of micropores therein sized to pass ions contained in the medium without substantial medium perfusion therethrough, to thereby enable ionic transport of electrical energy from the internal electrode, through the ion-containing medium to an exterior of the body to ablate pulmonary vein tissue. In an exemplary implementation of the first aspect, the microporous expandable and collapsible body is adapted to be maintained in an expanded condition at a substantially constant pressure by a continuous flow of the medium through the body, providing a cooling effect in the microporous body and the pulmonary vein tissue.[0011]
• 2. Probe Assembly with a Basket Assembly for Mapping and Ablating Pulmonary Vein Tissue:[0012]
• A second aspect of the invention involves a probe assembly for mapping and ablating pulmonary vein tissue. The probe assembly includes an expandable and collapsible basket assembly including multiple splines, one or more of the splines carrying one or more electrodes, and at least one of the one or more electrodes adapted to sense electrical activity in the pulmonary vein tissue and ablate the pulmonary vein tissue.[0013]
• 3. Probe Assembly with an Expandable Body used with a Basket Assembly for Mapping and Ablating Pulmonary Vein Tissue:[0014]
• A third aspect of the invention includes a probe assembly for mapping and ablating pulmonary vein tissue. The probe assembly includes an expandable and collapsible basket assembly including multiple splines, one or more of the splines carrying one or more electrodes adapted to sense electrical activity in the pulmonary vein tissue, the basket assembly defining an interior, and a non-porous expandable and collapsible body disposed in the interior of the basket assembly and defining an interior adapted to receive a fluid medium for expanding the expandable and collapsible body to exclude blood from the electrodes. In an exemplary implementation of the third aspect, the non-porous expandable and collapsible body is adapted to be maintained in an expanded condition at a substantially constant pressure by a continuous flow of the medium through the body, providing a cooling effect in the body and the pulmonary vein tissue.[0015]
• Other and further objects, features, aspects, and advantages of the present inventions will become better understood with the following detailed description of the accompanying drawings.[0016]
BRIEF DESCRIPTION OF DRAWINGS
• The drawings illustrate both the design and utility of preferred embodiments of the present invention, in which like elements are referred to with common reference numerals.[0017]
• FIG. 1 is a schematic illustration of a RF mapping and ablation catheter system including a probe assembly constructed in accordance with a first aspect of the invention.[0018]
• FIG. 2 is an enlarged elevational view of the probe assembly illustrated in FIG. 1, taken in the region of[0019]2-2 of FIG. 1.
• FIG. 3A is an enlarged side view of an alternative embodiment of a probe assembly with a fewer number of splines than that depicted in FIGS. 1 and 3.[0020]
• FIG. 3B is an enlarged cross sectional view of one of the splines of FIG. 3A taken along line[0021]3B-3B.
• FIG. 4 is an enlarged side elevational view of a portion of the catheter, taken in the region of[0022]4-4 of FIG. 2.
• FIG. 5 is an enlarged cross sectional view of the probe assembly, taken along line[0023]5-5 of FIG. 2.
• FIG. 6 is an enlarged side elevational view of a distal portion of the catheter illustrated in FIG. 1, with a portion of the catheter body removed to show the probe assembly in a collapsed condition.[0024]
• FIG. 7 is an enlarged side elevational view of an alternate embodiment of the probe assembly.[0025]
• FIG. 8 is an enlarged side elevational view of a further embodiment of the probe assembly.[0026]
• FIG. 9 is an enlarged side elevational view of a probe assembly constructed in accordance with a second aspect of the invention.[0027]
• FIGS.[0028]10A-10C are cross sectional views of the probe assembly illustrated in FIG. 9, and depict alternative embodiments of lesion creating techniques.
• FIG. 11 is an enlarged side elevational view of the probe assembly illustrated in FIG. 9 placed at the ostium of a pulmonary vein.[0029]
• FIG. 12 is an enlarged side elevational view of a probe assembly constructed in accordance with a third aspect of the invention.[0030]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• The present invention involves a mapping and ablation probe assembly for a catheter that solves the problems described above associated with a separate mapping catheter for mapping electrical activity in pulmonary vein tissue and ablation catheter for ablating the pulmonary vein tissue. Three main aspects of the probe assembly are described below. The first aspect is a probe assembly with a microporous ablation body used with a basket assembly for mapping and ablating pulmonary vein tissue. Along with a description of this aspect of the probe assembly, an exemplary catheter system that is applicable to all three main aspects will also be described. The second aspect is a probe assembly with a basket assembly for mapping and ablating pulmonary vein tissue. The third aspect is a probe assembly with an expandable body used with a basket assembly for mapping and ablating pulmonary vein tissue. Each of these aspects will now be described in turn.[0031]
• 1. Probe Assembly with an Expandable Body used with a Basket Assembly for Mapping and Ablating Pulmonary Vein Tissue:[0032]
• With reference to FIGS. 1 and 2, a[0033]catheter10 including aprobe assembly14 for mapping and ablating pulmonary vein tissue and constructed in accordance with a first aspect of the invention will now be described. Although theprobe assembly14 and alternative probe assembly embodiments described further below are described in conjunction with mapping and ablating pulmonary vein tissue, it will be readily apparent to those skilled in the art that the probe assemblies may be used to map and ablate other body tissues such as, but not by way of limitation, myocardial tissue. Further, it should be noted, theprobe assembly14 andcatheter10 illustrated in drawings are not necessarily drawn to scale. Theprobe assembly14 will first be described, followed by a description of the rest of the catheter system and a method of using the probe assembly.
• A. Probe Assembly:[0034]
• With reference to FIG. 2, the[0035]probe assembly14 may include an expandable andcollapsible basket18 and amicroporous body22 located in aninterior region26 of thebasket18.
• The geometry of the[0036]microporous body22 may be altered between a collapsed geometry (FIG. 6) and enlarged expanded geometry (FIGS. 2, 5) by injecting and removing a pressurized andconductive inflation medium30 into and from an interior36 of themicroporous body22. Thepressurized inflation medium30 also maintains themicroporous body22 in the expanded geometry. Theinflation medium30 is composed of an electrically conductive liquid that establishes an electrically conductive path from aring electrode40 to the surface of themicroporous body22. Preferably, the electrically conductive medium30 possesses a low resistivity to decrease ohmic losses and, thus, ohmic heating effects, within themicroporous body22. The composition of the electrically conductive medium30 can vary. In the illustrated embodiment, the electrically conductive medium30 comprises a hypertonic saline solution having a sodium chloride concentration at or about 100% weight by volume. The medium may include a 70:30 mixture of 10% saline and radio-opaque solution. An exemplary radio-opaque solution that may be used is sold as Omnipaque® by Nycomed Amersham Imaging of Princeton, N.J. A medium30 with a radio-opaque solution allows thebody22 to be visualized using fluoroscopy.
• The[0037]ring electrode40 is located within theinterior region36 of themicroporous body22. Thering electrode40 transmits RF energy that is delivered to pulmonary vein tissue via ionic transport through theconductive inflation medium30 and micropores in themicroporous body22. In this regard, thering electrode40 is composed of a material having both a relatively high electrical conductivity and a relatively high thermal conductivity, e.g., gold, platinum, or platinum/iridium.
• It should be noted that the ring-like structure of the[0038]electrode40 provides a relatively large circumferential exterior surface in communication with theinflation medium30 in theinterior region36 of themicroporous body22, providing an efficient means of energizing theinflation medium30. Although theelectrode40 is described as a ring, theelectrode40 can take the form of any suitable structure that can contact theinflation medium30. The length of theelectrode40 can be accordingly varied to increase or decrease the amount of RF energy delivered to theinflation medium30. The location of theelectrode40 can also be varied.
• Although in the embodiment shown and described, the operative ablative element is a[0039]RF electrode40 and tissue is ablated through the delivery of RF energy, in alternative embodiments, the ablative element may be adapted to ablate body tissue using an ultrasound transmitter, a laser, a cryogenic mechanism, or other similar means. For example, thebody22 may be adapted to receive a cryogenic medium to thereby enable cryogenic ablation of pulmonary vein tissue via said cryogenic medium and saidbody22.
• The[0040]microporous body22 is preferably made of an electrically nonconductive material including micropores in at least a portion of thebody22. The micropores are preferably 0.0001 to about 0.1 microns in diameter. The microporous structure of themicroporous body22 acts as the energy-emitting surface, establishing ionic transport of RF energy from theRF electrode40, through theinflation medium30, and into the tissue outside of themicroporous body22, thereby creating a lesion.
• The geometry of the energy-emitting surface of the[0041]microporous body22 can be customized to more efficiently produce the desired lesion characteristics. In particular, the delivery of RF energy from theelectrode40 to themicroporous body22 can be concentrated in certain regions of themicroporous body22. For example, themicroporous body22 may include amicroporous region32 that runs around a central circumferential portion of themicroporous body22. Additionally or alternatively, themicroporous region32 may run along another portion of thebody22 such as adjacent to a proximal base of thebody22 or adjacent to a distal tip of thebody22. One way to concentrate the delivery of RF energy from one or more regions of themicroporous body22 is by masking the micropores of themicroporous body22 in the regions where RF energy delivery is not desired.
• The electrical resistivity of the[0042]microporous body22 has a significant influence on the tissue lesion geometry and controllability. Ablation with a low-resistivity microporous body22 enables more RF power to be transmitted to the tissue and results in deeper lesions. On the other hand, ablation with a high-resistivity microporous body22 generates more uniform heating, therefore improving the controllability of the lesion. Generally speaking, lower resistivity values for the microporous body22 (below about 500 ohm-cm) result in deeper lesion geometries, while higher resistivity values for the microporous body22 (above about 500 ohm-cm) result in shallower lesion geometries.
• The electrical resistivity of the[0043]microporous body22 can be controlled by specifying the pore size of the material, the porosity of the material (space on the body that does not contain material), and the water absorption characteristics (hydrophilic versus hydrophobic) of the material. In general, the greater the pore size and porosity, the lower the resistivity of themicroporous body22. In contrast, the lesser the pore size and porosity, the greater the resistivity of themicroporous body22. The size of the pores is selected such that little or no liquid perfusion through the pores results, assuming a maximum liquid pressure within the interior region of themicroporous body22. Thus, the pores are sized to pass ions contained in the medium without substantial medium perfusion therethrough to thereby enable ionic transport of electrical energy from the ion-containingmedium30 to an exterior of thebody22 to ablate pulmonary vein tissue.
• In general, hydrophilic materials possess a greater capacity to provide ionic transfer of radio frequency energy without significant perfusion of liquid through the[0044]microporous body22 than do hydrophobic materials. Additionally, hydrophilic materials generally have lower coefficients of friction with body tissues than have hydrophobic materials, facilitating routing of the catheter through the vasculature of the patient. Exemplary materials that can be used to make themicroporous body22 include, but not by way of limitation, regenerated cellulose, nylon, nylon 6, nylon 6/6, polycarbonate, polyethersulfone, modified acrylic polymers, cellulose acetate, poly(vinylidene fluoride), poly(vinylpyrrolidone), and a poly(vinylidene fluoride) and poly(vinylpyrrolidone) combination. A microporous body made of a poly(vinylidene fluoride) and poly(vinylpyrrolidone) combination is disclosed in Hegde, et al., U.S. Application No. ______ (Unknown) entitled “POROUS MEMBRANES”, filed on May 22, 2000, the specification of which is fully and expressly incorporated herein by reference. Also, further details concerning the manufacture of themicroporous body22, including the specification of the material, pore size, porosity, and water absorption characteristics of the material, are disclosed in Swanson, et al., U.S. Pat. No. 5,797,903, the specification of which is fully and expressly incorporated herein by reference.
• The[0045]basket18 includes multipleflexible splines44. Each of thesplines44 is preferably made of a resilient inert material such as Nitinol metal or silicone rubber; however, other materials may be used.Multiple electrodes48 are located on eachsphine44. Connected to eachmapping electrode48 aresignal wires52 made from a highly conductive metal such as copper. Thesignal wires52 preferably extend through eachsphine44 and intocatheter body80. Thesplines44 are connected to abase member56 and anend member60. Thesphines44 extend circumferentially between thebase member56 and theend member60 when in the expanded geometry. Plastic tubing may be used to cover thesplines44 and contain thesignal wires52 running from theelectrodes48.
• Although the[0046]electrodes48 are described below as mapping electrodes, in alternative embodiments, theelectrodes48 may be multi-functional electrodes used for mapping, pacing, and/or ablating body tissue. In a further embodiment, thesplines44 may not include any electrodes. Any or all of the embodiments described below may also includesplines44 havingmulti-functional electrodes48 or no electrodes.
• The[0047]basket18 is shown with specific number ofsplines44 andelectrodes48 for eachspline44, i.e.,8; however, it will be readily apparent to those skilled in the art that the number ofsplines44 and/or the number ofelectrodes48 perspline44 may vary. For example, FIG. 3A depicts a basket structure with six splines44 (twosplines44 are hidden from view), with some of thesplines44 having nineelectrodes48 andother splines44 having tenelectrodes48. Further, the shape of thesplines44 andelectrodes48 may vary.
• Because the[0048]electrodes48 in this embodiment are mounted onflexible splines44, when thebasket18 is expanded in the vasculature of a patient, thesplines44 conform to a large range of different vein sizes and shapes. The flexibility and resiliency of thesplines44 also allows for the basket structure to push outward on the tissue. This increases the friction between theelectrodes48 and the vein and thereby anchors theprobe assembly14 in position, yielding a more precise ablation location.
• The[0049]splines44 may carry one ormore temperature sensors50 that may take the form of thermistors, thermocouples, or the equivalent, and are in thermal conductive contact with the exterior of theprobe assembly14 to sense conditions in tissue outside theprobe assembly14 during ablation. Thetemperature sensors50 may be located on thesplines44 such that when thesplines44 are expanded, thetemperature sensors50 are located at or near the largest diameter of theprobe assembly14. Although thebasket18 in FIG. 2 is shown with twotemperature sensors50 for eachspline44, it will be readily apparent to those skilled in the art that the number oftemperature sensors50 perspline44 may vary.
• With reference to FIGS. 3A and 3B, in an alternative embodiment, the[0050]electrodes48 may comprise rings that surround thetemperature sensors50, splines44, andsignal wires52.
• With reference to FIG. 5, the[0051]microporous body22 may include a construction that, when inflated, has a larger volume than the volume V defined by the expandedbasket18, causing thebody22 to extend or bulge between and beyond the circumferential region or volume V defined by thebasket assembly18 when thebasket assembly18 and thebody22 are in an expanded state. This may help put themicroporous body22 in more direct contact with the targeted pulmonary vein tissue, improving ablation treatment of the tissue. This may also cause the delivery of RF energy from themicroporous body22 to be concentrated in the bulging regions of themicroporous body22, which may be desirable depending on the targeted tissue that needs ablating. Additionally, themicroporous body22 restricts blood flow to the ablation area, which reduces the possibility of coagulated blood embolus. Finally, restricting blood flow renders the relationship between ablation parameters (power, time, and temperature) and lesion characteristics more predictable, since the important lesion parameters of energy loss attributable to the convective losses and to energy delivery are more predictable.
• B. Catheter System:[0052]
• With reference generally to FIGS.[0053]1-4 and6, the remaining components of the catheter system will now be described.
• The[0054]catheter10 can be functionally divided into four regions: the operative distalprobe assembly region64, adeflectable catheter region68, amain catheter region72, and a proximalcatheter handle region76. Ahandle assembly77 including ahandle78 is attached to the proximalcatheter handle region76 of thecatheter10. With reference to FIG. 6, thecatheter10 also includes acatheter body80 that may include first and secondtubular elements84 and86, which form, in conjunction, the structure of the distalprobe assembly region64; a thirdtubular element90, which forms the structure of thedeflectable catheter region68; and a fourthtubular element94, which forms the structure of themain catheter region72. It should be noted, however, that thecatheter body80 may include any number of tubular elements required to provide the desired functionality to the catheter. The addition of metal in the form of a braided mesh layer sandwiched in between layers of the plastic tubing may be used, greatly increasing the rotational stiffness of the catheter. This may be beneficial to practice one or more lesion creation techniques described in more detail below.
• With reference to FIG. 2, the operative distal[0055]probe assembly region64 includes theprobe assembly14. Thecatheter10 may also include asheath98 that, when moved distally over thebasket18, collapses the basket18 (FIG. 6). In a preferred embodiment, themicroporous body22 is collapsed (by the removal of theinflation medium30 therefrom) before thebasket18 is collapsed; however, in an alternative embodiment, collapsing thebasket18 may cause fluid to be removed from themicroporous body22 and, thus, themicroporous body22 to collapse. Conversely, retracting thesheath98 or moving thesheath98 proximally away from theprobe assembly14 may deploy thebasket18. This removes the compression force causing thebasket18 to open to a prescribed three-dimensional shape. Moving thesheath98 distally in the direction indicated by arrow106 causes thesheath98 to apply a compressive force, thus, collapsing thebasket18. Moving thesheath98 proximally in the direction indicated by the arrow110 removes the compressive force of thesheath98, thus, allowing thebasket18 to expand.
• With reference to FIGS. 1, 2 and[0056]6, thedeflectable catheter region68 is the steerable portion of thecatheter10, which allows theprobe assembly14 to be accurately placed adjacent the targeted tissue region. A steering wire (not shown) may be slidably disposed within thecatheter body80 and may include a distal end attached between the secondtubular element86 and the thirdtubular element90 and a proximal end suitably mounted within thehandle78. Thehandle assembly77 may include a steering member such as arotating steering knob114 that is rotatably mounted to thehandle78. Rotational movement of thesteering knob114 counter clockwise relative to thehandle78, in the direction indicated by the arrow118, may cause a steering wire to move proximally relative to thecatheter body80 which, in turn, tensions the steering wire, thus pulling and bending thecatheter deflectable region68 into an arc (shown by broken lines in FIG. 1). On the contrary, rotational movement of thesteering knob114 clockwise relative to thehandle78, in the direction indicated by the arrow122, may cause the steering wire to move distally relative to thecatheter body80 which, in turn, relaxes the steering wire, thus allowing the resiliency of the thirdtubular element90 to place thecatheter deflectable region68 of the catheter back into a rectilinear configuration. To assist in the deflection of the catheter, thedeflectable catheter region68 is preferably made of a lower durometer plastic than themain catheter region72.
• The[0057]catheter10 may be coupled to aRF generator126 such as that described in Jackson et al., U.S. Pat. No. 5,383,874, the specification of which is fully and expressly incorporated herein by reference. TheRF generator126 provides thecatheter10 with a source of RF ablation energy. TheRF generator126 includes aRF source130 for generating the RF energy and acontroller134 that controls the amplitude of, and time during, which theRF source130 outputs RF energy. TheRF generator126 is electrically coupled to thecatheter10 via acable138. One ormore signal wires140 are routed through an ablation wire tubular member142 (FIG. 2, 4) in thecatheter body80 and couple thering electrode40 to thecable138. Operation of theRF generator126 provides RF energy to thering electrode40, which in turn is ionically transferred through theinflation medium30, and out through the pores of themicroporous body22, into the targeted tissue region. Thus, when operated, theRF generator126 allows the physician to ablate body tissue such as pulmonary vein tissue in a controlled manner, resulting in a tissue lesion with the desired characteristics.
• A[0058]mapping signal processor146 may also be coupled to thecatheter10, allowing a physician to map the electrical activity in the target tissue site before, during and/or subsequent to the ablation process. Themapping processor146 may be part of thecontroller134. Themapping processor146 is in electrical communication with themapping electrodes48 via amapping cable150 and thesignal wires52. Thesignal wires52 are preferably routed through a mapping wire tubular member156 (FIG. 2, 4) in thecatheter body80.
• An inflation medium reservoir and pump[0059]160 may be coupled to thecatheter10 for supplying themicroporous body22 with theinflation medium30. The reservoir and pump160 may supply ionic fluid at room temperature or may include a chiller for supplying cool ionic fluid. A constant flow of ionic cooling fluid such as a 10% saline solution may be circulated through themicroporous body22 to cool themicroporous body22 and supply the ionic fluid necessary to allow ionic transfer through the body for ablation. Aninlet lumen354 and anoutlet lumen356 are adapted to communicate at proximal ends,inlet port355 andoutlet port357, with the reservoir and pump160 and at distal ends with the mouth or interior of themicroporous body22. Preferably, thefluid lumens354,356 have the same length and internal diameters, resulting in a microporous body pressure that is approximately half of that at theinlet port355. The pressures at theinlet port355 andoutlet port357 may be measured with respective inlet and outlet pressure sensors,358,360. Thus, the microporous body pressure may be estimated/controlled using the pressure measured at theinlet sensor358.
• The fluid is preferably circulated at a rate and pressure that maintains the fluid pressure in the[0060]microporous body22 at a predetermined pressure. Alternatively, the microporous body pressure may be controlled by injecting the fluid into theinlet port355 at a known, controlled rate.
• The[0061]pump160 may impart the pressure necessary to circulate the fluid through themicroporous body22 and the fluid may passively flow out of theoutlet port357. Alternatively, thepump160 may apply a vacuum pressure to theoutlet port357 to increase the allowable flow rate through themicroporous body22.
• An inlet control valve[0062]362, e.g., pop-off valve, and/oroutlet control valve364 at theinlet355 and/oroutlet357 may be used to prevent themicroporous body22 from being inflated above the body's burst pressure or a lower predefined pressure to prevent over-inflation or bursting, ensuring patient safety. A control valve set to a low pressure value may also be used to ensure that thebody22 remains inflated even when flow to thebody22 is stopped, if the pressure value exceeds that required to maintain body inflation.
• A continuous flow of ionic fluid maintains the[0063]microporous body22 and ablation site at a cooler temperature, allowing for more power delivery to the target tissue to make deeper lesions. The continuous flow also enables the use of a smaller RF electrode within themicroporous body22 because heat generated near the electrode can be convected away from that electrode. Finally, the continuous flow reduces the possibility that non-targeted adjacent tissue will be damaged, thereby increasing patient safety.
• An[0064]auxiliary member172 may be coupled to thecatheter10 via anexternal connector176 and further coupled to theprobe assembly14 via an internal connector or carrier180 (FIG. 4) in thecatheter body80. The one ormore temperature sensors50 on one or more of thesplines44 of thebasket18 may be connected to one or more temperature sensor wires guided through the internal connector orcarrier180 of thecatheter body80. Theauxiliary member172 may be a controller that is coupled to the one or more temperature sensor wires via theexternal connector176. If theauxiliary member172 is a controller, it is preferably the same as thecontroller134 of theRF generator126.
• Temperatures sensed by the[0065]temperature sensors50 are processed by thecontroller172. Based upon temperature input, thecontroller172 adjusts the time and power level of radio frequency energy transmissions by theRF generator126, and consequently thering electrode40, to achieve the desired lesion patterns and other ablation objectives and to avoid undesired tissue necrosis caused by overheating.
• Temperature sensing and controlling using the one or[0066]more temperature sensors50 of thesplines44 will now be described in more detail. Thecontroller172 may include aninput182 for receiving from the physician a desired therapeutic result in terms of (i) the extent to which the desired lesion should extend beneath the tissue-electrode interface to a boundary depth between viable and nonviable tissue and/or (ii) a maximum tissue temperature developed within the lesion between the tissue-electrode interface and the boundary depth. Thecontroller172 may also include aprocessing element184 that retains a function that correlates an observed relationship among lesion boundary depth, ablation power level, ablation time, actual sub-surface tissue temperature, and electrode temperature. Theprocessing element184 compares the desired therapeutic result to the function and selects an operating condition based upon the comparison to achieve the desired therapeutic result without exceeding a prescribed actual or predicted sub-surface tissue temperature.
• The operating condition selected by the[0067]processing element184 can control various aspects of the ablation procedure such as controlling the ablation power level, limiting the ablation time to a selected targeted ablation time, limiting the ablation power level subject to a prescribed maximum ablation power level, and/or the orientation of themicroporous region32 of thebody22, including prescribing a desired percentage contact between theregion32 and tissue.
• If the ablating electrode(s) is the[0068]microporous body22 or conventional metal electrode(s) where an expandable body is used to restrict blood flow around the electrode(s), theprocessing element184 may rely upon thetemperature sensors50 to sense actual maximum tissue temperature because thebody22 restricts blood flow to the ablation site, minimizing convective cooling of the tissue-electrode interface by the surrounding blood flow. As a result, the region of maximum temperature is located at or close to the interface between the tissue and themicroporous body22. The temperature conditions sensed by thetemperature sensors50 closely reflect actual maximum tissue temperature.
• If the ablating electrode(s) is a conventional metal electrode(s) and blood is free to flow over the electrode(s), the[0069]processing element302 may predict maximum tissue temperature based upon the temperature sensed by thetemperature sensors50 at the tissue-electrode interface. When using a conventional metal electrode(s) to ablate tissue, the tissue-electrode interface is convectively cooled by surrounding blood flow. Due to these convective cooling effects, the region of maximum tissue temperature is located deeper in the tissue. As a result, the temperature conditions sensed by thetemperature sensors50 associated with metal electrode elements do not directly reflect actual maximum tissue temperature. In this situation, maximum tissue temperature conditions must be inferred or predicted by theprocessor184 from actual sensed temperatures.
• In a preferred embodiment, the one or[0070]more temperature sensors50 are used to sense instantaneous localized temperatures (Ti) of the thermal mass corresponding to theregion32. The temperature Ti at any given time is a function of the power supplied to theelectrode40 by thegenerator126.
• The characteristic of a lesion can be expressed in terms of the depth below the tissue surface of the 50 degree C. isothermal region, which will be called D.sub.50C. The depth D.sub.50C is a function of the physical characteristics of the microporous region[0071]32 (that is, its electrical and thermal conductivities, resistivities, and size); the percentage of contact between the tissue and themicroporous region32; the localized temperature Ti of the thermal mass of theregion32; the magnitude of RF power (P) transmitted by theinterior electrode40, and the time (t) the tissue is exposed to the RF power.
• For a desired lesion depth D.sub.50C, additional considerations of safety constrain the selection of an optimal operating condition among the operating conditions listed above. The principal safety constraints are the maximum tissue temperature TMAX and maximum power level PMAX.[0072]
• The maximum temperature condition TMAX lies within a range of temperatures that are high enough to provide deep and wide lesions (typically between about 50 degree C. and 60 degree C.), but are safely below about 65 degree C., the temperature at which pulmonary stenosis is known to occur. It is recognized that TMAX will occur somewhere between the electrode-tissue interface and D.sub.50C. As discussed above, if the ablating electrode is the[0073]microporous body22 or a conventional electrode(s) and an expandable body is used to restrict blood flow at the ablation site, TMAX will be closer to the interface because of the lack of convective cooling by the blood flow. If the ablating electrode is a conventional metal electrode(s) and nothing restricts blood flow to the ablation site, TMAX will be deeper in the tissue because of the convective cooling of the electrode(s) by the blood flow.
• The maximum power level PMAX takes into account the physical characteristics of the[0074]interior electrode40 and the power generation capacity of theRF generator126. The D.sub.50C function for a givenporous region32 can be expressed in terms of a matrix listing all or some of the foregoing values and their relationship derived from empirical data and/or computer modeling. Theprocessing element184 includes in memory this matrix of operating conditions defining the D.sub.50C temperature boundary function for multiple arrays of operating conditions.
• The physician also uses the[0075]input182 to identify the characteristics of thestructure22, using a prescribed identification code; set a desired maximum RF power level PMAX; a desired time t; and a desired maximum tissue temperature TMAX.
• Based upon these inputs, the[0076]processing element184 compares the desired therapeutic result to the function defined in the matrix, and selects an operating condition to achieve the desired therapeutic result without exceeding the prescribed TMAX by controlling the function variables.
• Using the[0077]microporous body22, typical ablation conditions are to control to sensed temperatures of 65 degree C. and apply RF power for one minute.
• With reference back to FIG. 4, the internal carrier[0078]180 (or an internal carrier similar to the internal carrier18) may be used as a transport lumen for drug delivery via the body22 (if the pores were large enough and/or the drug molecules small enough) or other means. Theinternal carrier180 may terminate in thehandle assembly77, where a physician may inject the medicine into theinternal carrier180 or the medicine may be supplied by theauxiliary member172. The medicine may travel through theinternal carrier180 to thebody22. Additional or fewer auxiliary components may be used depending on the application.
• C. Method of Use[0079]
• With reference to FIGS.[0080]1-6, a method of using thecatheter10 andprobe assembly14 will now be described. Before thecatheter10 can be introduced into a patient's body, theprobe assembly14 must be in a collapsed condition (FIG. 6). If thecatheter10 is not already in this condition, theprobe assembly14 can be collapsed by moving thesheath98 forward, towards the distal end of the catheter10 (in the direction indicated by the arrow106).
• Placement of the[0081]catheter10 within the vasculature of the patient is typically facilitated with the aid of an introducer guide sheath or guide wire, which was previously inserted into the patient's vasculature, e.g., femoral vein. The introducer guide sheath is introduced into the left atrium of the heart using a conventional retrograde approach, i.e., through the respective aortic and mitral valves of the heart. One or more well-known visualization devices and techniques, e.g., ultrasound, fluoroscopy, etc., may be used to assist in navigating and directing thecatheter10 to and from the targeted region. Alternatively, the introducer guide sheath may be introduced into the left atrium using a conventional transeptal approach, i.e., through the vena cava and atrial septum of the heart. A detailed description of methods for introducing a catheter into the left atrium via a transeptal approach is disclosed in U.S. Pat. No. 5,575,810, issued to Swanson et al., which is fully and expressly incorporated herein by reference.
• In either method (conventional retrograde approach or transeptal approach), the[0082]catheter10 is introduced through the introducer guide sheath until theprobe assembly14 resides within the left atrium. Once inside the left atrium, the physician may deliver theprobe assembly14 into a desired pulmonary vein through rotational movement of thesteering knob114 on thecatheter handle78.
• The physician situates the[0083]probe assembly14 within a selected tissue region in the interior of the pulmonary vein, adjacent to the opening into the left atrium. Thebasket18 is deployed by moving thesheath98 proximally in the direction indicated by the arrow110, causing thesheath98 to slide away from thebasket18 and removing the compression force thereon. Thebasket18 then expands, allowing one or more of themapping electrodes48 to contact the pulmonary vein tissue.
• The[0084]mapping electrodes48 are used to sense electrical activity in the pulmonary vein tissue, and may be used to pace pulmonary vein tissue as well.
• Mapping data received and interpreted by the[0085]mapping signal processor146 is displayed for use by the physician to locate aberrant pulmonary vein tissue. Theprobe assembly14 may be moved one or more times which may require collapsing and deploying theprobe assembly14 one or more times, in an effort to locate aberrant pulmonary vein tissue.
• When the physician has determined that the aberrant pulmonary vein tissue has been located ([0086]basket18 is deployed), the physician may then expand themicroporous body22 by filling themicroporous body22 with theinflation medium30 to contact the targeted pulmonary vein tissue. Thepump160 may be activated to introduce the ionic fluid through theinlet lumen354 and into themicroporous body22 at a constant pressure, inflating thebody22. The ionic fluid circulated may be cool or at room temperature. The ionic fluid exits themicroporous body22 and flows through theoutlet lumen356 to theoutlet357. The fluid may passively drip or flow out of theoutlet lumen356, or may be drawn out of theoutlet lumen356 with vacuum pressure from thepump160. Inflating or maintaining themicroporous body22 at less than full pressure is desirable because a non-turgidmicroporous body22 better conforms to the tissue surface.
• Once the physician has determined that the[0087]microporous body22 is effectively inflated and in contact with the pulmonary vein tissue, the physician may begin ablating the targeted tissue. RF energy is preferably supplied to thering electrode40, which is located within themicroporous body22 and surrounded byinflation medium30. Through ionic transport, the electrical energy from theelectrode40 is transported through theinflation medium30 and through the pores of themicroporous body22, to the exterior of themicroporous body22, into and through at least a portion of the pulmonary vein tissue so as to ablate the targeted pulmonary vein tissue, and to a return electrode.
• If the[0088]electrodes48 are also (or alternatively) used to ablate the pulmonary vein tissue and saline or a fluid having similar heat transfer characteristics is used to deploy thebody22, thermal transfer within the body may enable contiguous lesion formation between theelectrodes48 to be created more consistently.
• Throughout this process the physician may monitor the temperatures of the tissue region using the[0089]temperature sensors50 to more accurately ablate the target tissue.
• Once ablation is completed, or in between ablation treatments, electrical activity in the pulmonary vein tissue may be mapped using the[0090]mapping electrodes48 to confirm effective ablation treatment.
• To collapse the[0091]probe assembly14, theinflation medium30 in microporous body106 is removed, but no longer supplied, causing the microporous body106 to deflate. Thebasket18 is also collapsed by moving thesheath98 forward, towards the distal end of the catheter10 (in the direction indicated by the arrow106). Thecatheter10 is then removed from the patient's body or moved to a different location for additional diagnosis and/or treatment.
• Thus, the[0092]probe assembly14 and method described above are advantageous because they allow the physician to map and ablate the targeted pulmonary vein region with a single probe assembly positioning. Prior to the present invention, the physician would introduce the mapping electrode and map the aberrant region of the pulmonary vein, then remove that mapping electrode, and follow with the ablation electrode to ablate the aberrant region. Problems with the prior approach include the possibility of misdirecting or misplacing the ablating electrode and inadvertently ablating non-aberrant, i.e., healthy, pulmonary vein tissue, and the excessive time-consumption because the physician had to introduce and remove two catheters. This leads to more patient discomfort and room for physician error. Further, the apparatuses and methods of the present invention incorporate all the advantages of an expandable and collapsible microporous body with those of a mapping basket assembly.
• With reference to FIG. 7, in an alternative embodiment, a[0093]probe assembly201 is comprised of elements from separate catheters, namely, amicroporous body22 from anablation catheter202 and abasket18 from amain catheter203. Thebasket18 may includeelectrodes48 that are adapted to map, pace, and/or ablate pulmonary vein tissue.
• The[0094]ablation catheter202 is slidably removable with respect to themain catheter203 for positioning themicroporous body22 within or removing it from thebasket18. Thecatheter body203 may include an additional lumen200 through which theablation catheter202 may be slidably disposed.
• Both the distal portions of the[0095]ablation catheter202 and themain catheter203 are preferably steerably controllable in a manner similar to that described above with respect to thecatheter10.
• The[0096]microporous body22 may range in size in the expanded state from the size of one of theelectrodes48 to just larger than the diameter of thebasket18. Theactive band32 of thebody22 is preferably relatively large to better ensure lesion creation. In one embodiment, thebody22, when expanded, is large enough to create a circumferential lesion in the vein or around the ostium.
• However, placement of lesion around the entire circumference is often not required to electrically isolate the pulmonary veins in atrial fibrillation patients. Therefore, in another exemplary embodiment, the expanded[0097]microporous body22 is smaller than the pulmonary vein diameter or vein orifice to create one or more ablation sectors of the pulmonary vein, decreasing the probability of creating clinically significant pulmonary stenosis compared to a complete circumferential lesion. Additionally, asmaller microporous body22 enables blood flow in pulmonary veins to continue during ablation.
• A method of using the[0098]probe assembly201 is similar to that described above with respect to theprobe assembly14, except themain catheter203 andablation catheter202 may be introduced separately to the targeted site. Theablation catheter202 may be introduced into the lumen200 of themain catheter203 via thehandle78 and snaked through the lumen200 until the collapsedmicroporous body22 is located within thebasket18. The physician may then inflate themicroporous body22 and steer thebody22 so that it contacts the targeted pulmonary vein tissue. As discussed above, inflation of themicroporous body22 at a pressure corresponding to a less than fully expanded state may be desirable because anon-turgid body22 better conforms to the tissue surface than aturgid body22. Themicroporous body22 may be maintained in an expanded state by continuously circulating a fluid medium through thebody22 as described above or by inflating thebody22 with the medium and preventing the medium from exiting the catheter.
• For sectional ablation (i.e., non-circumferential ablation), a relative small, expanded[0099]microporous body22 such as that illustrated in FIG. 7 may be used to ablate one or more targeted areas. Additionally or alternatively, theelectrodes48 may be used to ablate one or more targeted areas. If theelectrodes48 are used to ablate tissue, thebody22 may be used to restrict blood flow from the ablation area.
• For circumferential ablation, a larger, expanded[0100]microporous body22 such as that illustrated in FIGS. 2 and 5 may be used. A larger, expandedmicroporous body22 restricts blood flow to the ablation site, increasing the efficiency of the ablation since RF currents flow substantially into the tissue only, and not into the blood. Restricting blood flow also reduces the possibility of coagulated blood embolus and renders the relationship between ablation parameters (power, time and temperature) and lesion characteristics more predictable since fewer uncontrolled variables exists (mostly attributable to convective losses and to energy delivery to tissue). Further, if theelectrodes48 are also used to ablate the pulmonary vein tissue and saline or a fluid having similar heat transfer characteristics is used to deploy thebody22, thermal transfer within thebody22 may enable contiguous lesion formation between theelectrodes48 to be created more consistently. Also, themicroporous body22 may create a lossy electrical connection between theelectrodes48 that may enable contiguous lesion formation between theelectrodes48 to be created more consistently.
• With reference to FIG. 8, in a further embodiment, a[0101]probe assembly310 includes abasket18 located at a distal end of acatheter312 and amicroporous body22 integrated with thebasket18. Themicroporous body22 may be located at the distal end of asteerable member314 that is steerable in a manner similar to that described above with respect tocatheter10. Theprobe assembly310 is similar to theprobe assembly201 described above with respect to FIG. 7, except themicroporous body22 andsteerable member314 are not removable from thecatheter202. Thecatheter312 is also steerable in a manner similar to that described with respect tocatheter10. Themicroporous body22, when expanded, can range in size from the size of asingle spline electrode48 to a large body that will be large enough to fill the entire inner cavity of thebasket18.
• The method of using the[0102]probe assembly310 is similar to that described above with respect to probeassembly201, except a separate ablation catheter is not snaked through a main catheter or removed therefrom because themicroporous body22 andsteerable member314 are integrated with thebasket18.
• 2. Probe Assembly with a Basket Assembly for Mapping and Ablating Pulmonary Vein Tissue:[0103]
• With reference to FIGS. 9 and 10A-[0104]10D, a second aspect of aprobe assembly300 of a mapping andablation catheter302 will now be described. Unlike the prior embodiments, theprobe assembly300 does not include a microporous body. Instead, theprobe assembly300 includes abasket18 with a plurality ofmulti-functional electrodes48 adapted to map and ablate body tissue. Thecatheter302 is preferably steerable in a manner similar to that described above with respect tocatheter10.
• The number of[0105]electrodes48 that eachspline44 carries, the spacing between theelectrodes48, and the length of theelectrodes48 may vary according to the particular objectives of the ablating procedure: These structural features influence the characteristics of the lesion patterns formed.
• [0106]Segmented electrodes48 may be well suited for creating continuous, elongated lesion patterns provided that theelectrodes48 are adjacently spaced close enough together to create additive heating effects when ablating energy is transmitted simultaneously to theadjacent electrodes48. The additive heating effects between close,adjacent electrodes48 intensify the desired therapeutic heating of tissue contacted by theelectrodes48. The additive effects heat the tissue at and between theadjacent electrode48 to higher temperatures than theelectrode48 would otherwise heat the tissue, if conditioned to individually emit energy to the tissue. The additive heating effects occur when theelectrodes48 are operated simultaneously in a bipolar mode between electrodes. Furthermore, the additive heating effects also arise when the electrodes are operated simultaneously in a unipolar mode, transmitting energy to an indifferent electrode.
• Conversely, when the[0107]electrodes48 are spaced sufficiently far apart from each other, theelectrodes48 create elongated lesion segments.
• The length of each[0108]electrode48 may also be varied. If theelectrode48 is too long, the ability of thesplines44 to conform to the anatomy of the pulmonary vein may be compromised. Also, long electrodes may be subject to “hot spots” during ablation caused by differences in current density along the electrode. Another approach is to use multipleshort electrodes48 on eachspline44 to cover a large effective ablating length and avoid hot spots. An electrode approximately 3 mm in length or less makes an adequate lesion without hot spots, although other lengths may also work.
• Ablating energy can be selectively applied individually to just one or a selected group of electrodes, when desired, to further vary the size and characteristics of the lesion pattern.[0109]
• A[0110]basket18 including eightsplines44 should be adequate for ablating in pulmonary veins of 10 to 15 mm in diameter; however, thebasket18 may have a greater or lesser number ofsplines44, depending on the size of the target anatomy. A small vein may requirefewer splines44 than a larger vein to form a continuous circular lesion around the circumference of the vein.
• The method of using the[0111]probe assembly300 is similar to that described above for theprobe assembly14, except once thebasket18 is at the appropriate location, the physician may begin ablation using thesame electrodes48 that were used to map electrical activity in the pulmonary vein tissue. Should the physician decide that only one section or certain sections of thevein304 needs ablation, the physician may activate RF energy to selectelectrodes44 corresponding to the section or sections of thevein304.
• With reference additionally to FIG. 10A, if the physician decides that the entire circumference of the[0112]pulmonary vein304 needs treatment and thevein304 is relatively small relative to the number ofsplines44 of theprobe assembly300, the physician may simply activate RF energy once to all theelectrodes48 or to certaincircumferential electrodes44.
• With reference to FIG. 10B, in an alternate lesion-making technique, where a single ablation step such as that described above with respect to FIG. 10A proves insufficient to form an unbroken tesion line in[0113]larger veins304, thecatheter302 may be rotated slightly, and a second ablation may be performed. One or more successive rotations and ablations with theprobe assembly300 may be necessary in order to make acontiguous lesion305.
• With reference to FIG. 10C, in a further lesion-making technique, the[0114]catheter302 may be rotated while simultaneously ablating thepulmonary vein304. The handle76 (FIG. 1) of thecatheter302 may be rotated slowly until thelesion305 made by onespline44 begins to overlap thelesion305 started by anadjacent spline44.
• After a first round of ablation, the physician may then take[0115]further electrode44 readings, retract thebasket18, and reposition thecatheter302 for further ablation procedures or, if done, remove thecatheter302 from the patient's vasculature.
• With reference to FIG. 11, an advantage to this aspect of the invention is that the[0116]probe assembly300 does not include a structure likely to blocksignificant blood flow306 or otherwise occlude thevein304. Sufficient blockage can cause hemodynamic compromise in some patients. In addition,blood flow306 has a beneficial cooling effect that allows theprobe assembly300 to create deeper lesions at lower temperatures and inhibit damaging non-target adjacent tissue. Finally, this embodiment containsseparate electrodes48 that can create lesions at selected sections of thevein304 or around the entire circumference by one of the lesion-creating techniques described above.
• 3. Probe Assembly with an Expandable Body used with a Basket Assembly for Mapping and Ablating Pulmonary Vein Tissue:[0117]
• With reference to FIG. 12, a[0118]probe assembly400 constructed in accordance with a further aspect of the invention will now be described. Theprobe assembly400 is located at a distal end of acatheter402 that is preferably steerably controlled in a manner similar to that described above with respect tocatheter10.
• The[0119]probe assembly400 is similar to probe assembly300 described above with respect to FIG. 9, i.e., includesmulti-functional electrodes48 that may map, pace and/or ablate, except theprobe assembly400 further includes a non-porous, non-electrically conducting expandable balloon404. The nonporous, non-electrically conducting balloon404 includes the following two primary functions: (1) to assist in maintaining the position of thebasket structure18 by placing some force against the vein walls, and (2) to restrict blood flow to the ablation area.
• A method of using the[0120]probe assembly400 will now be described. A physician may guide thecatheter402 to the appropriate location and deploy thebasket18. Electrical activity in the pulmonary vein may be mapped using themulti-function electrodes48 on thesplines44. The physician may interpret the resulting electrical activity data, and determine the proper position of theprobe assembly400 for ablation.
• Once satisfied that the position is accurate, the physician may inflate the non-electrically conducting body[0121]404 with a fluid such as saline or CO₂and perform ablation of the targeted tissue with theelectrodes48. As described above with respect tobody22, the fluid may be constantly circulated though the body404.
• The expanded body[0122]404 restricts blood flow to the ablation site, increasing the efficiency of the ablation since RF currents flow substantially into the tissue only, and not into the blood. Restricting blood flow also reduces the possibility of coagulated blood embolus and renders the relationship between ablation parameters (power, time and temperature) and lesion characteristics more predictable since fewer uncontrolled variables exist (mostly attributable to convective losses and to energy delivery to tissue). If saline or a fluid having similar heat transfer characteristics is used to deploy the body404, thermal transfer within the body404 may enable contiguous lesion formation between theelectrodes48 to be created more consistently.
• While preferred methods and embodiments have been shown and described, it will be apparent to one of ordinary skill in the art that numerous alterations may be made without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited except in accordance with the following claims.[0123]

Claims (52)

We claim:

1. A probe assembly for mapping and ablating pulmonary vein tissue, comprising an expandable and collapsible basket assembly including multiple splines, one or more of said splines carrying one or more electrodes adapted to sense electrical activity in said pulmonary vein tissue, said basket assembly defining an interior; and

an expandable and collapsible body disposed in the interior of said basket assembly and defining an interior adapted to receive a fluid medium for expanding said expandable and collapsible body.

2. The assembly ofclaim 1, wherein said expandable and collapsible body is a microporous expandable and collapsible body defining an interior adapted to receive a medium containing ions, an internal electrode disposed within said interior of said body and adapted to transmit electrical energy to said medium containing ions, said body including at least one microporous region having a plurality of micropores therein sized to pass ions contained in the medium without substantial medium perfusion therethrough, to thereby enable ionic transport of electrical energy from the internal electrode, through the ion-containing medium to an exterior of the body to ablate pulmonary vein tissue.

3. The assembly ofclaim 2, wherein the body is made of a poly(vinylidene fluoride) and poly(vinylpyrrolidone) combination.

4. The assembly ofclaim 2, wherein said body includes at least one customized microporous region with a predetermined geometry to more efficiently produce a desired lesion characteristics.

5. The assembly ofclaim 2, wherein said body is adapted to extend between and beyond the circumferential region defined by said basket assembly when said basket assembly and said body are in an expanded state.

6. The assembly ofclaim 2, wherein said body when expanded is sized to create a circumferential lesion in the pulmonary vein or around the ostium.

7. The assembly ofclaim 2, wherein said body when expanded is smaller in size than the vein orifice so as to allow blood flow thereby, and said body is adapted to sectionally ablate the pulmonary vein or vein ostium.

8. The assembly ofclaim 2, wherein said microporous body is integrated with said basket assembly.

9. The assembly ofclaim 2, wherein said microporous body is removable from said basket assembly.

10. The assembly2, wherein said microporous body and basket assembly are separately steerable.

11. The assembly ofclaim 2, wherein said one or more electrodes are adapted to also ablate pulmonary vein tissue.

12. The assembly ofclaim 11, wherein said microporous body when expanded is adapted to exclude blood from said electrodes.

13. The assembly ofclaim 2, wherein said microporous body is adapted to be maintained in an expanded condition at a substantially constant pressure by a continuous flow of said medium therethrough, providing a cooling effect in said microporous body and pulmonary vein tissue.

14. The assembly ofclaim 13, further including an inlet lumen adapted to continuously deliver said medium to said microporous body and an outlet lumen adapted to continuously withdraw said medium from said microporous body.

15. The assembly ofclaim 1, wherein said body is a non-porous expandable and collapsible body.

16. The assembly ofclaim 15, wherein said one or more electrodes are adapted to also ablate pulmonary vein tissue.

17. The assembly ofclaim 16, wherein said microporous body when expanded is adapted to exclude blood from said electrodes.

18. The assembly ofclaim 15, wherein said non-porous expandable and collapsible body is adapted to be maintained in an expanded condition at a substantially constant pressure by a continuous flow of said medium therethrough, providing a cooling effect in said microporous body and pulmonary vein tissue.

19. The assembly ofclaim 18, further including an inlet lumen adapted to continuously deliver said medium to said microporous body and an outlet lumen adapted to continuously withdraw said medium from said microporous body.

20. The assembly ofclaim 1, wherein said expandable and collapsible body includes an interior adapted to receive a cryogenic medium to thereby enable cryogenic ablation of pulmonary vein tissue via said cryogenic medium and said body.

21. The assembly ofclaim 1, wherein said probe assembly includes a drug delivery mechanism adapted to deliver one or more drugs to pulmonary vein tissue or adjacent tissue.

22. A probe assembly for mapping and ablating pulmonary vein tissue, comprising an expandable and collapsible basket assembly including multiple splines, one or more of said splines carrying one or more electrodes, at least one of said one or more electrodes adapted to sense electrical activity in said pulmonary vein tissue and ablate said pulmonary vein tissue.

23. The probe assembly ofclaim 22, wherein each of said one or more electrodes at least partially surround a temperature sensor.

24. A probe assembly for mapping and ablating pulmonary vein tissue, comprising an expandable and collapsible basket assembly including multiple splines, one or more of said splines carrying one or more electrodes, at least one of said one or more electrodes adapted to sense electrical activity in said pulmonary vein tissue, and said probe assembly further including an ablating element adapted to ablate said pulmonary vein tissue.

25. The assembly ofclaim 24, wherein said ablating element is an electrode adapted to ablate pulmonary vein tissue by the transmission of RF energy through the pulmonary vein tissue.

26. The assembly ofclaim 24, wherein the probe assembly includes a body having an interior adapted to receive a cryogenic medium to thereby enable cryogenic ablation of pulmonary vein tissue via said cryogenic medium and said body.

27. The assembly ofclaim 24, wherein said probe assembly includes a laser adapted to deliver laser light to ablate pulmonary vein tissue.

28. The assembly ofclaim 24, wherein said probe assembly includes an ultrasound transmitter adapted to deliver ultrasonic energy to ablate pulmonary vein tissue.

29. The assembly ofclaim 24, wherein said probe assembly includes a drug delivery mechanism adapted to deliver one or more drugs to pulmonary vein tissue or adjacent tissue.

30. A method of mapping and ablating pulmonary vein tissue, comprising:

providing an integrated probe assembly in a target region of a pulmonary vein, the integrated probe assembly including:

an expandable and collapsible basket assembly including multiple splines, one or more of said splines carrying one or more electrodes adapted to sense electrical activity in said pulmonary vein tissue and transmit electrical energy to ablate the pulmonary vein tissue;

expanding said basket assembly of said probe assembly so that one or more of said electrodes contact said pulmonary vein tissue;

mapping electrical activity in said pulmonary vein tissue with said one or more electrodes; and

without removing the basket assembly and one or more electrodes, ablating one or more targeted regions of pulmonary vein tissue determined by said mapping step by transmitting electrical energy to the electrodes, ablating the pulmonary vein tissue.

31. The method ofclaim 30, further comprising rotating the probe assembly one or more times and ablating the pulmonary vein tissue so that a contiguous lesion lesion is created in the pulmonary vein tissue.

32. The method ofclaim 30, wherein the basket assembly includes an interior, a microporous expandable and collapsible body located in said interior, said microporous expandable and collapsible body defining an interior adapted to receive a medium containing ions, an internal electrode disposed within said interior of said body and adapted to transmit electrical energy to said medium containing ions, said body including at least one microporous region having a plurality of micropores therein sized to pass ions contained in the medium without substantial medium perfusion therethrough, to thereby enable ionic transport of electrical energy from the internal electrode, through the ion-containing medium to an exterior of the body to ablate pulmonary vein tissue, the method further including expanding the microporous porous expandable and collapsible body and excluding blood from said electrodes, and ablating one or more targeted regions of pulmonary vein tissue by ionic transport of electrical energy from the internal electrode, through the ionic-containing medium, and into the pulmonary vein tissue.

33. The method ofclaim 30, wherein the basket assembly includes an interior, a non-porous expandable and collapsible body located in said interior, the method further including expanding the non-porous expandable and collapsible body and excluding blood from said electrodes.

34. A method of mapping and ablating pulmonary vein tissue, comprising:

providing a probe assembly in a target region of a pulmonary vein, the probe assembly including:

an expandable and collapsible basket assembly including multiple splines, one or more of said splines carrying one or more electrodes adapted to sense electrical activity in said pulmonary vein tissue, said basket assembly defining an interior; and

a microporous expandable and collapsible body defining an interior adapted to receive a medium containing ions, an internal electrode disposed within said interior of said body and adapted to transmit electrical energy to said medium containing ions, said body including at least one microporous region having a plurality of micropores therein sized to pass ions contained in the medium without substantial medium perfusion therethrough, to thereby enable ionic transport of electrical energy from the internal electrode, through the ion-containing medium to an exterior of the body to ablate pulmonary vein tissue

expanding said basket assembly of said probe assembly so that one or more of said mapping electrodes contact said pulmonary vein tissue;

mapping electrical activity in said pulmonary vein tissue with said one or more electrodes; and

without removing the basket assembly and one or more electrodes, ablating one or more targeted regions of pulmonary vein tissue determined by said mapping step by ionic transport of electrical energy from the internal electrode, through the ionic-containing medium, and into the pulmonary vein tissue.

35. The method ofclaim 34, wherein said body is adapted to extend between and beyond the circumferential region defined by said basket assembly when said basket assembly and said body are in an expanded state, and the method further including ablating said pulmonary vein tissue with a microporous portion of said body extending between and beyond the circumferential region defined by said basket assembly.

36. The method ofclaim 34, further including expanding said body and ablating said tissue to create a circumferential lesion in the pulmonary vein or around the ostium.

37. The method ofclaim 34, further including expanding said body to a size smaller than the vein orifice so as to allow blood flow thereby, and ablating one or more sectors of the pulmonary vein or vein ostium.

38. The method ofclaim 34, wherein providing a probe assembly in a target region of a pulmonary vein includes providing an integrated microporous body and basket assembly simultaneously in a target region of a pulmonary vein.

39. The method ofclaim 34, wherein providing a probe assembly in a target region of a pulmonary vein includes providing a basket assembly in a target region of a pulmonary vein, and separately introducing the microporous body in the basket assembly.

40. The method ofclaim 34, further including separately steering said microporous body and basket assembly to a target region of a pulmonary vein.

41. The method ofclaim 34, further including ablating said pulmonary vein tissue with said one or more electrodes.

42. The method ofclaim 34, further including expanding said microporous body and excluding blood from said electrodes.

43. The method ofclaim 34, further including constantly circulating said medium through said microporous body so as to maintain said microporous body in an expanded condition at a substantially constant pressure.

44. The method ofclaim 43, wherein said probe assembly includes an inlet lumen for supplying the medium to the microporous body and an outlet lumen to withdraw the medium from the microporous body.

45. The method ofclaim 44, further including applying a vacuum pressure to said outlet lumen.

46. The method ofclaim 44, wherein said inlet lumen includes a pressure control valve adapted to release pressure in said inlet lumen when the pressure exceeds a predetermined pressure limit.

47. A method of mapping and ablating pulmonary vein tissue, comprising:

providing an integrated probe assembly in a target region of a pulmonary vein, the integrated probe assembly including:

an expandable and collapsible basket assembly including multiple splines, one or more of said splines carrying one or more electrodes adapted to sense electrical activity in said pulmonary vein tissue;

expanding said basket assembly of said probe assembly so that one or more of said electrodes contact said pulmonary vein tissue;

mapping electrical activity in said pulmonary vein tissue with said one or more electrodes; and

without removing the basket assembly and one or more electrodes, ablating one or more targeted regions of pulmonary vein tissue determined by said mapping step with an ablating element.

48. The method ofclaim 47, wherein said ablating element is an electrode and ablating one or more targeted regions of pulmonary vein tissue includes ablating pulmonary vein tissue by the transmission of RF energy through the pulmonary vein tissue.

49. The method ofclaim 47, wherein said ablating element is an electrode body having an interior adapted to receive a cryogenic medium and ablating one or more targeted regions of pulmonary vein tissue includes cryogenically ablating pulmonary vein tissue via said cryogenic medium and said body.

50. The method ofclaim 47, wherein said ablating element is a laser and ablating one or more targeted regions of pulmonary vein tissue includes delivering laser light to the pulmonary vein tissue to ablate the pulmonary vein tissue.

51. The method ofclaim 47, wherein said ablating element is an ultrasound transmitter and ablating one or more targeted regions includes delivering ultrasonic energy to the pulmonary vein tissue to ablate the pulmonary vein tissue.

52. The method ofclaim 47, further including the step delivering one or more drugs to pulmonary vein tissue or adjacent tissue with a drug delivery mechanism.

Images