US20060009756A1 - Method and devices for treating atrial fibrillation by mass ablation - Google Patents

Abstract

Apparatus and method for ablating target tissue including a non-linear area of tissue in the left atrium of a patient. The method can include selecting an ablation apparatus having an ablator with a tissue engagement section, penetrating a chest cavity of the patient, and identifying the target tissue. The method can also include positioning the ablation apparatus adjacent to the target tissue so that the tissue engagement section can transfer ablation energy to the target tissue. The method can further include energizing the tissue engagement section with ablation energy in order to create a footprint on the non-linear area of tissue in the left atrium and to reduce an overall mass of excitable tissue in the left atrium.

Description

RELATED APPLICATIONS
• This application claims the benefit of the filing date of U.S. Provisional Patent Application No. 60/571,182 filed on May 14, 2004, which is incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
• The present invention relates to tools and procedures generally and relates more particularly to the use of ablation to reduce the mass of excitable tissue of the left atrium to prevent and treat atrial fibrillation or other medical conditions.
BACKGROUND
• Focal triggers initiating atrial fibrillation are thought to frequently arise from the pulmonary veins and their ostia. Surgeons have used the technique of modifying the substrate of the heart in these areas to prevent the propagation of the arrhythmia. In some patients with chronic atrial fibrillation, the Cox/MAZE III procedure has been employed. This procedure controls propagation of the depolarization wavefronts in the right and left atria by means of surgical incisions through the walls of the right and left atria. The incisions create blind or dead end conduction pathways, which prevent re-entrant atrial tachycardias from occurring.
• While the Cox/MAZE procedure is successful in treating atrial fibrillation, the procedure is quite complex and is currently practiced by only a few very skilled cardiac surgeons in conjunction with other open-heart procedures. The procedure also is quite traumatic to the heart, as in essence, the right and left atria are cut into pieces and sewed back together, to define lines of lesion across which the depolarization wavefronts will not propagate. Still today, the Cox/MAZE procedure is done with traditional cut and sew techniques.
• The market is demanding quicker, safer and less invasive approaches. As a result, there has been much recent research and evaluation of mechanisms to encircle and isolate the pulmonary veins and replicate the incisions of the MAE operation. Companies are developing ablation techniques that heat (or cool) or chemically destroy the underlying tissue along these lines.
• It has been suggested that procedures similar to the MAZE procedure could be instead, performed by means of electrosurgical ablation, for example, by applying radio frequency energy to internal or external surfaces of the atria to create lesions across which the depolarization wavefronts will not propagate. Such procedures are disclosed in U.S. Pat. No. 5,895,417, issued to Pomeranz, et al. (“the Pomeranz '417 patent”); U.S. Pat. No. 5,575,766, issued to Swartz, et al. (“the Swartz '766 patent”); U.S. Pat. No. 6,032,077, issued to Pomeranz (“the Pomeranz '077 patent”); U.S. Pat. No. 6,142,994, issued to Swanson, et al. (“the Swanson '994 patent”); and U.S. Pat. No. 5,871,523, issued to Fleischman, et al. (“the Fleischman '523 patent”), all incorporated herein by reference in their entireties.
• The Pomeranz '417 patent discloses an apparatus for ablating tissue by making linear lesions within the chamber of a patient's heart by application of a plurality of spaced electrodes along an elongate member. The Schwartz '766 patent discloses a process for treating atrial arrhythmia by creating discrete ablation tracks within both the left and right atrium. The Pomeranz '077 patent discloses an ablation catheter that is electrically connected to tissue to be ablated by a foam on the electrodes that is soaked in saline. The foam in the Pomeranz '077 patent acts as a conductive fluid to allow energy from the electrode to ablate the contacted tissue. The Swanson '994 patent discloses a surgical method and apparatus for positioning an element in the body of a patient for diagnosis or therapy. The apparatus in the Swanson '994 patent may be a catheter or a probe having a shaft with a lumen extending there through. The Fleischman '523 patent discloses a helically-wound emitter on an element with a insulating sheath movable over the emitter.
• Various types of electrophysiology devices are used for ablating tissue. Typically, such devices include a conductive tip or blade that serves as one electrode in an electrical circuit that is completed via a grounding electrode coupled to the patient. The contact point is small or linear to create lesions to form linear tracks of ablated tissue. A power source creates high levels of electrical energy between the two electrodes causing the tissue to heat to a sufficient level to denature proteins within the tissue and cause cell death. In order for such procedures to be effective, it is desirable that the electrosurgically-created lesions are continuous along their length and extend completely through the tissue of the heart.
• Manufacturers have developed catheters that have a linear array of electrodes along a long axis (e.g., the Amazr, MECCA, and Revelation catheters). The surgeon positions the catheter and electrodes in contact with the tissue and either individually or sequentially applies energy to each electrode. Additionally, catheters that incorporate an electrode that is energized and moves along its length have been proposed, such as the Flex-10 from AFx, Inc., of 47929 Fremont Aye, Fremont, Calif. 94538.
• Surgeons have also been able to create linear lesions on the heart using applications of the same techniques. For example, Kottkamp, et. al. in an article entitled “Intraoperative Radio Frequency Ablation of Chronic Atrial Fibrillation: A Left Atrial Curative Approach by Elimination of Anatomic ‘Anchor’ Reentrant Circuits,”Journal of Cardiovascular Electrophysiology,10:772-780 (1999), describe a hand-held device that creates as series of spot or short (less than 1 cm) linear lesions. Other investigators have used long, linear unipolar probes to create somewhat longer lesions. Still others have used multi-electrode linear catheters, similar to those described above to create a series of ablations that net a linear lesion.
• The focus of most investigators has been to isolate the pulmonary veins. There is growing research that suggests this may not be necessary in the prevention and cure of atrial fibrillation, as discussed in the article by G. Stabile, P. Turco, V. La Rocca, P. Nocerino, E. Stabile, and A. Dc Simone entitled “Is Pulmonary Vein Isolation Necessary for Curing Atrial Fibrillation?,”Circulation,108:657-660 (2003). Rather than focusing on only isolating the pulmonary veins, reduction in the overall volume of excitable tissue in the left atrium is sufficient to prevent atrial fibrillation. The general concept is to ablate a large enough nonlinear area of the left atrium to prevent re-entrant waves and the propagation of atrial fibrillation.
SUMMARY OF THE INVENTION
• Some embodiments of the invention provide a method of ablating target tissue including a non-linear area of tissue in the left atrium of a patient. The method can include selecting an ablation apparatus having an ablator or ablation member with a tissue engagement section, penetrating a chest cavity of the patient, and identifying the target tissue. The method can also include positioning the ablation apparatus adjacent to the target tissue so that the tissue engagement section can transfer ablation energy to the target tissue. The method can further include energizing the tissue engagement section with ablation energy in order to create a footprint on the non-linear area of tissue in the left atrium and to reduce an overall mass of excitable tissue in the left atrium.
• In some embodiments, an ablation apparatus can include an insertion tool having a proximal end, a distal end, and a lumen. The ablation apparatus can include an ablator or ablation member having a conductor and a tissue engagement portion. The conductor can include a source end extending from the proximal end of the insertion tool and a delivery end coupled to the tissue engagement portion. The ablator can be removably inserted in the lumen. The ablation apparatus can also include an energy source connected to the conductor. The insertion tool can be inserted into a patient so that the distal end is adjacent the target tissue. The conductor can urge the ablator out of the lumen to engage the target tissue. Energy can be conducted from the energy source to the ablator to create a footprint on the target tissue to reduce an overall mass of excitable tissue.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is an illustration of a posteroinferior view of the human heart removed from the chest cavity.
• FIG. 2 is an illustration of a cross-section of the human heart showing the left atrium and the ostia leading to the pulmonary veins.
• FIG. 3 is a schematic illustration of an ablation apparatus according to one embodiment of the invention shown being applied to a patient.
• FIG. 4 is a top view of an ablation apparatus according to another embodiment of the invention with an ablator on an insulated balloon.
• FIG. 4A is a cross-sectional view along theline4A-4A ofFIG. 4.
• FIG. 4B is a partial perspective view of a distal end of an insertion tool having the ablator ofFIG. 4 removably inserted therein.
• FIG. 5 is a top view of an ablation apparatus according to another embodiment of the invention with an ablator as a patch.
• FIG. 5A is a cross-sectional view of the ablation apparatus alongline5A-5A ofFIG. 5.
• FIG. 6 is a top view of an ablation apparatus according to another embodiment of the invention with an ablator as a contoured patch.
• FIG. 7 is a perspective view of an ablation apparatus according to another embodiment of the invention with an ablator as a bipolar electrode.
• FIG. 8 is a perspective view of an ablation apparatus according to another embodiment of the invention with a suction tent having a wiper.
• FIG. 9 is a perspective view of an ablation apparatus according to another embodiment of the invention with an ablator as an adhesive tongue electrode.
• FIG. 10 is a perspective view of an ablation apparatus according to another embodiment of the invention with a head having a cauterizing chemical applicator.
• FIG. 11 is a top view and an end view of an ablation apparatus according to another embodiment of the invention with a rolled electrode for insertion in a catheter or other delivery tool.
• FIG. 12 is a side view of an ablation apparatus according to another embodiment of the invention with a web ablator.
• FIGS. 13A and 13B are perspective views of an ablation apparatus according to another embodiment of the invention having an expandable mesh with electrodes.
• FIG. 14 is a side view of an ablation apparatus according to another embodiment of the invention with a contoured ablator for ablating adjacent to the pulmonary veins.
• FIG. 15 is a top view of an ablation apparatus according to another embodiment of the invention with an ablator as a contoured patch.
• FIG. 16 is a top view of an ablation apparatus according to another embodiment of the invention with a rolled electrode for insertion in a catheter or other delivery tool.
DETAILED DESCRIPTION
• Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limited. The use of “including,” “comprising” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms “mounted,” “connected” and “coupled” are used broadly and encompass both direct and indirect mounting, connecting and coupling. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings, and can include electrical connections or couplings, whether direct or indirect.
• Some embodiments of the invention provide a method and apparatus for reducing the mass of the viable tissue (e.g., by rendering the mass of tissue non-contractile, non-viable, or unable to propagate an action potential) in the left atrium of the heart to prevent or cure atrial fibrillation. Some embodiments of the invention can include preventing reentry of depolarizing wavefront signals by ablating a large area of the left atrium. Furthermore, some embodiments of the invention can substantially prevent the sustenance of atrial fibrillation.
• Embodiments of the invention can provide an ablation apparatus used to conduct ablating energy to a locale of contacted or non-contacted and possibly surrounding tissue with the intent to ablate an entire area, while not harming neighboring tissue. The ablation apparatus can include an electrode having a footprint of a dimension designed to cover a predetermined region of tissue in the left atrium.
• According to some embodiments of the invention, an ablation apparatus can be used to ablate a non-linear area of the tissue in the left atrium en masse. This method can be performed by endocardial positioning of an ablation device in the left atrium either via a trans-atrial septal puncture or retrograde through the arterial system. Alternatively, embodiments of the invention can provide a method of ablating tissue in the left atrium in a predefined area by inserting an ablating apparatus using an epicardial approach with access to the posterior left atrium through the pericardial space, either by a sub-xiphoid or inter-costal incision.
• Some embodiments of the invention provide a method of ablating tissue using a large footprint ablation electrode for the control, prevention, and cure of atrial fibrillation. The method can include ablating a predefined area of tissue in the left atrium, while protecting other areas of the heart, lungs, and esophagus using directional energy delivery, insulation, or standoffs to space the ablation apparatus from protected areas. The method of ablating the heart tissue can include using a trans-venous catheter from the inside of the heart to deliver the ablation apparatus. Location and imaging techniques such as echogram, sonogram, magnetic resonance imaging, ultrasound, X-ray, sensors or transmitters on the ablation device, or other mapping technology can allow for proper placement to minimize damage to surrounding tissue.
• Some embodiments of the invention include a locatable ablation apparatus having a predefined footprint that can be delivered through an incision in the chest wall in order to ablate by trans-myocardial engagement with a bipolar electrode. The ablation apparatus can use any of suitable method and/or procedure with electro-surgical devices or other types of ablation devices (e.g., thermal ablation, micro-wave ablation, cryogenic ablation, ultrasound ablation, etc.) to ablate tissue in the left atrium to reduce the mass of excitable tissue therein.
• The apparatuses and methods of some embodiments of the invention are designed to reduce the overall excitable mass of the left atrium and to reduce or cure atrial fibrillation (AF). Some embodiments of the invention use radio frequency energy to create heat and ablate an area of tissue. However, other embodiments of the invention may include additional or alternative energy sources, such as microwave, cryogenic, ultrasound, laser, thermal, etc. Also, some embodiments of the invention can be used for creating ablation lesions in other areas of the heart, such as the ventricles.
• FIG. 1 illustrates thehuman heart10 from a posteroinferior view. Theleft atrium12 includes anexternal surface14 of anarea target tissue15, which includes the area of tissue to be ablated. In some embodiments, thetarget tissue15 can be defined as the entire left atrial posterior wall tissue extending around, but not including, the pulmonary veins. As shown inFIG. 1, thetarget tissue15 can be generally spaced from thepulmonary veins16 to prevent damage to thepulmonary veins16.
• As shown inFIG. 2, aninner chamber22 of theleft atrium12 includes aninternal surface24 of thetarget tissue15. Thepulmonary veins16 themselves are generally not included in thetarget tissue15 due to concern over vein stenosis. Theinternal surface24 of thetarget tissue15 may be defined as the entire left atrial posterior wall tissue extending into the ostial regions surrounding thepulmonary veins16, but not extending over into the lumen of the pulmonary veins, extending to near the mitral valve annulus. There is interest in creating conduction block in the area between one or both of the right inferior pulmonary vein and the mitral valve annulus. Tissue to be protected can include all tissue in the patient not defined as thetarget tissue15. Tissue to be protected can be isolated to prevent damage. Thetarget tissue15 can be spaced from the ostia of thepulmonary veins16, but may extend to areas surrounding the pulmonary vein ostia as well.
• FIG. 3 illustrates anablation apparatus30 according to one embodiment of the invention for ablating thetarget tissue15. Theablation apparatus30 can include or be used in conjunction with aninsertion tool32, such as a trocar, an endoscopy port, a catheter, etc. Theinsertion tool32 can include adistal end34 and aproximal end36. Theablation apparatus30 can also include alumen38 that can extend through theinsertion tool32 and can open at thedistal end34 and/or theproximal end36 of theinsertion tool32. Theablation apparatus30 can further include anablator43 that can extend from thedistal end34 of theinsertion tool32. Theablator43 can be inserted in thelumen38 for delivery through anincision40 in thepatient42. Aconductor44 can extend through thelumen38 to connect theablator43 to apower source46. Thepower source46 can be a source of ablation energy, such as radio frequency energy. Other forms of ablative methods and energy sources can be used with theablator43. Other forms of ablation techniques include, but are not limited to, microwave, ultrasound, heat, cyrogenic, radiation, and chemical ablation.
• Proper positioning of theablator43 on the targetedtissue15 can be performed by any suitable means, such as direct visualization, fluoroscopic X-ray visualization, ultrasound positron emission tomography, fluoroscopy, intra-cardiac echo, trans-esophageal echo, magnetic resonance imaging, computerized tomography, or by endoscopic imaging. As shown inFIG. 3, amapping tool48 can include asensor50 connected to adisplay52 to represent or visualize the position of theablator43 with respect to thetarget tissue15. An input device, such as atoggle stick54 or apointer pen56, can be used to identify thetarget tissue15 on theheart10.
• Theablator34 can include a tissue engagement section60 (as shown inFIGS. 4-6), which can include a footprint that allows thetissue engagement section60 to ablate a predefined area with each energization.
• As shown inFIG. 4, theablator43 can include aballoon58 having atissue engagement section60 with a footprint for endocardial or epicardial application. The footprint can be of a size and shape to conform to the individual patient requirements. Theballoon58 may include aninflator tube62 positioned in theinsertion tool32. Theinflator tube62 can be connected to aninflation source64 for inflating theballoon58 with air, CO², saline, etc. Aninsulator66 on theballoon58 can protect adjacent tissue from the energy in theablator43, while ablating thetarget tissue15 bearing against the footprint of thetissue engagement section60. Additional insulation can be achieved by the saline or gas in theballoon58. Theinsertion tool32 can be flexible or rigid to help the surgeon manipulate the position of theballoon58 to bring thetissue engagement section60 in contact with thetarget tissue15. Theinflation source64 can direct liquid or gas through theinflator tube62 to inflate theballoon58. Theballoon58 can expand to cause thetissue engagement section60 to bear against thetarget tissue15. In some embodiments, as shown inFIG. 4, bowing struts67 can be deployed within theleft atrium12 to push theablator43 into contact with the left atrial posterior wall. When deployed in the pericardial space, theballoon58 may be inflated to force contact of thetissue engagement section60 with theepicardial target tissue15.
• In some embodiments, theballoon58 can include a conducting surface that acts as atissue engagement section60. Acollapsed balloon58 can be inserted into theleft atrium12 or into the pericardial space surrounding the epicardial surface of thetarget tissue15. In one embodiment, theballoon58 can then be inflated with saline from theinflation source64 and oriented such that a thermally-transmissive,tissue engagement section60 of theballoon58 can be positioned against the posterior left atrium and an insulated portion of theballoon58 can be positioned against the anterior left atrium. The saline can be heated by electrical current supplied bypower source46 to a temperature between 50 degrees Celsius and 85 degrees Celsius, and in some embodiments, between 55 degrees Celsius and 65 degrees Celsius. At these temperatures, the cells in thetarget area15 generally die without collagen shrinkage. Alternatively, theballoon58 can be cooled with cryogenic technology to freeze the atrial tissue and ablate thetarget tissue15. Generally, temperatures for cryogenic therapy must be less than negative 20 degrees Celsius to negative 40 degrees Celsius.
• FIG. 4 illustrates a cross section of theballoon58 with theinsulator66 surrounding theablator43. Theablator43 can include one ormore ablating elements68 on thetissue engagement section60 for transferring the energy of thepower source46 to thetarget tissue15.Ablating elements68 may comprise one or more electrodes, ultrasound transducers, microwave antennae, cryogenic elements, chemical elements and/or radioactive elements, for example. Insertion of theballoon58 into theleft atrium12 allows theballoon58 to be manipulated during inflation to bring theablating elements68 of thetissue engagement section60 to bear against thetarget tissue15 and to space theablating elements68 from the tissue to be protected. Theinsulator66 can protect adjacent tissue not within the area of thetarget tissue15.
• Theablator43 can be delivered to the desired location in the patient using theinsertion tool32, such as acatheter70, as shown inFIG. 4B. The footprint of theablator43 can be configured for any patient anatomy and/or any ablation pattern desired. Thecollapsed balloon58 of theablator43 can be removably inserted through thedistal end34 of thecatheter70, so that theconductor44 extends through theinsertion tool32, as shown inFIG. 4B. Thecatheter70 can be inserted into the patient42 (as described with respect toFIG. 3) to position thedistal end34 adjacent thetarget tissue15. Theconductor44 can be used to push theablator43 out of thelumen38 to a position extending from thedistal end34, as shown inFIG. 4.
• FIGS. 5 and 5A illustrate an embodiment of acircular ablator43. In other embodiments, theablator43 can be elliptical, oval, etc. Thecircular ablator43 can include atissue engagement surface60 and anoutside skirt72. Theoutside skirt72 can be used as a stand-off to space thetissue engagement surface60 from delicate tissue, such as thepulmonary veins16. Thecircular ablator43 can include one ormore ablating elements68 on thetissue engagement surface60 and aninsulation layer66 on the opposite surface, as shown inFIG. 5A. Theablating elements68 can be positioned in a helical or circular pattern. Theoutside skirt72 can be constructed of a soft, heat-insulating material, such as silicone or other elastomeric material. Theoutside skirt72 can include anouter edge74 constructed of a resilient material to positively space theablating elements68 from the tissue to be protected.
• Thecircular ablator43 can be used epicardially by insertion within the pericardial space adjacent the posterior left atrium. In one embodiment, thecircular ablator43 can alternatively include an uncoiling spiral configuration. The uncoiling spiral can be positioned through asheath32, and when advanced beyond thesheath32, can uncoil to take the desired shape. Pre-formed shape memory or superelastic alloys, such as NiTi, can be used to ensure that the spiral uncoils into the desired shape.
• In another embodiment, twocircular ablators43 can be used in a bipolar arrangement. Oneablator43 can be on theexternal surface14 of thetarget tissue15 and anotherablator43 can be positioned on theinternal surface24 of thetarget tissue15 in theleft atrium12. The bipolarcircular ablator43 can also be positioned using an uncoiling spiral configuration. The uncoiling spiral can be positioned through asheath32, and when advanced beyond thesheath32, can uncoil to take the desired shape. Pre-formed shape memory or superelastic alloys, such as NiTi, can be used to ensure that the spiral uncoils into the desired shape.
• FIGS. 6 and 15 illustrate two embodiments of a contouredpatch ablator43 having a predefined shape with contourededges76. The contoured edges76 can bear against structures in the heart, such as thepulmonary veins16, to position thetissue engagement surface60 against thetarget tissue15. As shown inFIG. 6, ablatingelements68 can be connected to apower source46 by theconductor44 extending through aninsertion tool32 for either epicardial or endocardial use.
• FIG. 7 illustrates anablator43 having two ablating elements, afirst ablating element80 and asecond ablating element82. Aconductor44 may be used to connect the first andsecond ablating elements80,82 together or separately for individual control. In one embodiment, ablatingelements80,82 may comprise electrodes, which can be energized using radio frequency energy.Ablating elements80,82 may be held in contact with tissue by a vacuum applied toports83. Alternatively, thefirst ablating element80 may be a high intensity focused ultrasound (HIFU) crystal transmitter or transducer and thesecond ablating element82 can be another HIFU crystal transmitter or transducer, both of which can focus ultrasound energy on thetarget tissue15. Alternatively, the first andsecond ablating elements80,82 may be microwave antennae, which can deliver microwave ablation energy to thetarget tissue15. Theablator43 may be used, in some embodiments, from a location within the esophagus to focus ablation energy on the posterior left atrium of the heart.
• FIG. 8 illustrates anablator43 having askirt73 and adeployable wiper86 that can be placed in the patient to surround thetarget tissue15. Theskirt73 can be held to thetarget tissue15 by a vacuum applied to asuction chamber84. Thedeployable wiper86 can be connected to aconductor44 and can move within theskirt73 of theablator43 to rotate in an arc around a pivot point (e.g., a motor88). Thedeployable wiper86 may include one or more ablating elements. Thedeployable wiper86 can sweep from side to side and/or can rotate 360 degrees and can apply energy to ablate during all or during a portion of the rotation. Theskirt73 can be collapsible to be removably inserted in acatheter70. A resilientouter edge74 can releasably seal onto thetarget tissue15 when the vacuum is applied. An air gap between theskirt73 and thedeployable wiper86 can protect adjacent tissue from harm by the ablation energy. Also, to aid in guiding the ablations within theskirt73, a lumen can be provided adjacent to theconductor44 to allow passage of a fiber optic or endoscopic catheter, which can provide visual confirmation of proper positioning of theskirt73 and of the selected region for ablation.
• FIG. 9 illustrates anablator43 including anadhesive tongue90 having a footprint extending from acatheter70. Askirt72 can be used to ablate tissue within anouter edge74. Theadhesive tongue90 can be removably attached to thetarget tissue15 for directed ablation by a vacuum applied through aconductor44. In other embodiments, contact may be facilitated with a biological compatible glue or adhesive91 on atissue engagement surface60. Aconductive fluid92 can be used in achamber84 of theskirt72 to translate the ablating energy to all tissue within theouter edge74. Alternatively, epicardial application of theadhesive tongue90 with slow release ablation chemicals can be used to ablate tissue. Theadhesive tongue90 can also include, in some embodiments, anti-arrhythmia medications or other medications.
• FIG. 10 illustrates anablator43 designed to deliver one or more ablation agents, e.g., chemical ablation agents and/or radioactive ablation agents. A conductor orconduit44 can transfer an ablative agent through a tip96 to come in contact with tissue within anouter edge74 of askirt72. The tip96 can be removably inserted into acatheter70 to be positioned in the left atrium. Thecatheter70 can be manipulated and rotated to cause theskirt72 to cover thetarget tissue15. An ablation agent can be introduced into achamber84 within theshirt72 to ablate thetarget tissue15. Following the ablation procedure, any remaining ablation agent may be removed back through tip96. In some embodiments, tip96 may be designed for mechanical injection and/or needle-less injection of an ablation agent into tissue. In one embodiment, the ablation agent diffuses into the tissue to be treated. Alternatively, the ablation agent is delivered via controlled slow-release delivery and/or iontophoresis techniques.
• FIG. 11 illustrates anablator43 including a rolled ablatingelement98 that can be rolled into a single roll or parallel rolls and can be removably inserted in aninsertion tool32. S-shapedmemory wires100 can unroll the rolled ablatingelement98 when aconductor44 urges the rolled ablatingelement98 out of alumen38. The rolled ablatingelement98 can be rolled for placement between theheart10 and pericardium for epicardial ablation onto theexternal surface14 of thetarget tissue15. The rolled ablatingelement98 can be similar to the circular and contoured embodiments shown inFIGS. 5 and 6, respectively.
• FIG. 12 illustrates anablator43 including awebbed fan102 havingablating elements68aand68bpositioned in an apex104 of eachfold106. Theablating elements68awhen positioned adjacent thetarget tissue15 can be energized and theablating elements68bspaced from thetarget tissue15 can remain non-energized to protect tissue outside the area oftarget tissue15. Thewebbed fan102 can include an insulation layer on one side. Thewebbed fan102 can be unfolded into a flat sheet to energize all or a portion of theablating elements68a,68b. Thewebbed fan102 may be compressed to be removably inserted in alumen38 of acatheter70.
• FIGS. 13A and 13B illustrate anablator43 with an expandable mesh with numerousablating elements68. Theablator43 can be positioned in the left atrium using aninsertion tool32. Each ablatingelement68 can be individually represented using amapping tool48 and displayed on adisplay52. Aconductor44 can allowindividual electrodes68 in contact with thetarget tissue15 to be energized by apower source46 to ablate tissue. One ormore sensors50 can be positioned inside the expandable mesh to locate thetarget tissue15. Theablating elements68 on the expandable mesh that are contacting the posterior left atrium can be selected. Selection can be facilitated by electrophysiological mapping, computerized complex algorithms, imaging, individual addressing ofsmart ablating elements68, or other suitable methods. Theappropriate ablating elements68 can be are energized either individually or collectively to create an area of ablated tissue on the posterior.
• FIG. 14 illustrates a contouredablator43 with a predefined shape defined by contourededges76. The contoured edges76 can bear against structures on the heart, such as thepulmonary veins16 to position atissue engagement surface60 against thetarget tissue15. One or moreablating elements68 can be connected to a power source (not shown) by aconductor44.
• FIG. 16 illustrates a coiledlinear ablator43 with one or more coiled ablating elements that can be deployed out of an insertion tool32 (e.g., a sheath) to create an area for ablation. In some embodiments, the coiledlinear ablator43 can deliver energy in one direction (e.g., toward the epicardial surface of the posterior left atrium).
• In some embodiments, the ablator43 (e.g., an ablation energy transmitting member having one or more ablating elements) may be remote from thetarget tissue15. For example, ultrasound energy may be focused remotely on thetarget tissue15, causing ablation of thetarget tissue15, while passing without ablating through non-targeted tissue located between the targeted tissue andablator43. The location of the energy focus on thetarget tissue15 can be moved throughout the region to be ablated by steering a focal point about a non-linear area to be ablated. A steering mechanism can be manual (e.g., by physically moving an ultrasound transducer relative to the tissue) or electrical (e.g., by using phased arrays of ultrasound transducers or by otherwise modifying the ultrasound focal zone).
• Some embodiments of the invention are effective at terminating atrial fibrillation, yet can be performed more safely than some conventional methods. Some embodiments of the invention can perform ablations more quickly than some conventional methods. Some embodiments of the invention can also be used to amputate, ligate, staple, etc. the left atrial appendage (LAA) of the heart—a major source of clots and strokes in the population. Some embodiments of the invention result in less trauma to the patient and less chance of accidentally damaging the heart and surrounding structures. Some embodiments of the invention can minimize the size of the incision required to insert theablation apparatus30 and/or theablator43 through the chest wall. Some embodiments of the invention can eliminate the need for contiguous, linear lesions to treat atrial fibrillation. Some embodiments of the invention can allow the surgeon to create lesions in the heart from the epicardial surface of the beating heart. Some embodiments of the invention can be practiced via transvenous catheters from the inside of the heart.
• Various additional features and advantages of the invention are set forth in the following claims.

Claims (28)

1. A method of ablating target tissue including a non-linear area of tissue in a left atrium of a patient, the method comprising:

selecting an ablation apparatus having an ablator with a tissue engagement section;

penetrating a chest cavity of the patient;

identifying the target tissue;

positioning the ablation apparatus adjacent to the target tissue so that the tissue engagement section can transfer ablation energy to the target tissue; and

energizing the tissue engagement section with ablation energy in order to create a footprint on the non-linear area of tissue in the left atrium and to reduce an overall mass of excitable tissue in the left atrium.

2. The method ofclaim 1 and further comprising choosing an ablation apparatus using at least one of radio frequency energy, thermal energy, cryogenic energy, chemical energy, pharmacological energy, ultrasound energy, microwave energy, laser energy, and radiation energy.

3. The method ofclaim 1 and further comprising choosing an ablation apparatus including at least one of a balloon, a mesh, a patch, a rolled electrode, a fan, a bipolar electrode, a wiper, and a crystal transmitter.

4. The method ofclaim 1 and further comprising penetrating the chest cavity by entering through at least one of a sub-xiphoid incision, a sub-costal incision, a sternotomy, a thoracotomy, and a trans-venous puncture.

5. The method ofclaim 1 and further comprising identifying the target tissue using at least one of direct visualization, X-ray, ultrasound, magnetic resonance imaging, positron emission tomography, computerized tomography, fluoroscopy, endoscopic observation, intra cardiac echo, and transesophageal echo.

6. The method ofclaim 1 and further comprising placing the ablation apparatus adjacent the outside of the left atrium by an epicardial approach.

7. The method ofclaim 1 and further comprising placing the ablation apparatus adjacent the inside of the left atrium by an endocardial approach.

8. The method ofclaim 1 and further comprising placing the ablation apparatus adjacent the left atrium by a transesophageal approach.

9. The method ofclaim 8 and further comprising energizing the tissue engagement section with ultrasound energy.

10. The method ofclaim 9 and further comprising focusing the ultrasound energy on the target tissue.

11. The method ofclaim 1 and further comprising transferring energy to a portion of the ablation apparatus at the tissue engagement section.

12. The method ofclaim 1 and further comprising:

removably placing the ablation apparatus in a delivery end of an insertion tool;

positioning the insertion tool into the patient through an incision;

directing the delivery end to a location adjacent the target tissue;

removing the ablation apparatus from the insertion tool; and

adjusting the ablation apparatus to bring the tissue engagement section in contact with the target tissue.

13. The method ofclaim 1 and further comprising affixing the tissue engagement section to the target tissue by at least one of a bio-adhesive, a vacuum, an inflatable balloon, a mechanical deflection, a magnetic field, a shape memory alloy, and a superelastic alloy.

14. The method ofclaim 1 and further comprising providing an insulator in the ablation apparatus to prevent damage to tissue adjacent the target tissue.

15. An ablation apparatus for ablating target tissue of a patient, the ablation apparatus comprising:

an insertion tool having a proximal end, a distal end, and a lumen;

an ablator including a conductor and a tissue engagement portion, the conductor having a source end extending from the proximal end of the insertion tool and a delivery end coupled to the tissue engagement portion, the ablator removably inserted in the lumen; and

an energy source connected to the conductor;

the insertion tool being inserted into a patient so that the distal end is adjacent the target tissue, the conductor urging the ablator out of the lumen to engage the target tissue;

energy being conducted from the energy source to the ablator to create a footprint on the target tissue to reduce an overall mass of excitable tissue.

16. The ablation apparatus ofclaim 15 and further comprising a sensor connected to the ablator to sense the target tissue.

17. The ablation apparatus ofclaim 15 and further comprising a mapping tool to visualize the tissue engagement portion of the ablator.

18. The ablation apparatus ofclaim 15 wherein the insertion tool includes a catheter.

19. The ablation apparatus ofclaim 15 wherein the ablator includes a patch removably attachable to the target tissue, the patch including at least one of an adhesive patch, a tongue patch, a circular patch, a balloon patch, a suction patch, a chemical release patch, a rolled patch, a carbon patch, and a webbed patch.

20. The ablation apparatus ofclaim 15 wherein the ablator includes a skirt that can suction to the target tissue, the skirt receiving fluid for conducting the energy to the target tissue.

21. The ablation apparatus ofclaim 20 wherein the fluid is electrically conductive.

22. The ablation apparatus ofclaim 20 wherein the fluid is caustic.

23. The ablation apparatus ofclaim 20 wherein the fluid is thermally conductive.

24. The ablation apparatus ofclaim 15 wherein the ablator includes a balloon, the balloon being inflatable to occupy a cavity in the patient adjacent to the target tissue, the balloon being removably stored in the distal end of the insertion tool wherein the balloon is inflated causing the balloon to emerge from the insertion tool, and the balloon being positionable to cause the tissue engagement portion to bear against the target tissue.

25. The ablation apparatus ofclaim 15 wherein the ablator includes a chemical delivery system.

26. The ablation apparatus ofclaim 25 wherein the chemical delivery system includes a delivery method of at least one of diffusion, iontophoresis, mechanical injection, needle-less injection, and controlled slow-release delivery.

27. The ablation apparatus ofclaim 15 wherein the ablator includes a skirt and an adhesive tongue inside the skirt, the tongue moveable within the skirt to engage the target tissue, the skirt affixing the ablator to the target tissue by a vacuum.

28. The ablation apparatus ofclaim 15 wherein the tissue engagement portion includes a first bipolar tissue electrode and a second bipolar tissue electrode, wherein the first bipolar tissue electrode is applied to the interior of the left atrium endocardially, wherein the second bipolar tissue electrode is applied to the exterior of the left atrium epicardially, each of the first and second bipolar tissue electrodes connected to the energy source, energy being applied from the energy source to conduct from the first bipolar tissue electrode to the second bipolar tissue electrode to render a mass of left atrium tissue located between the first and second bipolar tissue electrodes at least one of non-contractile, non-viable, and unable to propagate an action potential.

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