Abstract:
A method and system capable of identifying ectopic foci, rotors, or conduction pathways involved in reentrant arrhythmias within cardiac tissue, and then treating identified ectopic foci, rotors, and/or pathways with either lethal or sub-lethal temperatures. The system includes a medical device having one or more mapping elements and one or more treatment elements, and a computer programmable to identify ectopic foci and rotors based at least in part on signals received from the one or more mapping elements at one or more locations.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a divisional of patent application Ser. No. 13/749,298, filed Jan. 24, 2013, entitled CATHETERS AND METHODS FOR INTRACARDIAC ELECTRICAL MAPPING and is related to and claims priority to U.S. Provisional Patent Application Ser. No. 61/684,380, filed Aug. 17, 2012, entitled CATHETERS AND METHODS FOR INTRACARDIAC ELECTRICAL MAPPING, the entirety of which is incorporated herein by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    n/a 
       TECHNICAL FIELD 
       [0003]    The present invention relates to a method and system for cardiac mapping and ablation. 
       BACKGROUND 
       [0004]    A cardiac arrhythmia is a condition in which the heart&#39;s normal rhythm is disrupted. There are many types of cardiac arrhythmias, including supraventricular arrhythmias that begin above the ventricles (such as premature atrial contractions (PACs), atrial flutter, accessory pathway tachycardias, atrial fibrillation, and AV nodal reentrant tachycardia (AVNRT)), ventricular arrhythmias that begin in the lower chambers of the heart (such as premature ventricular contractions (PVCs), ventricular tachycardia (VT), ventricular fibrillation, and long QT syndrome), and bradyarrhythmias that involve slow heart rhythms and may arise from disease in the heart&#39;s conduction system. Further, cardiac arrhythmias may be classified as reentrant or non-reentrant arrhythmias. In reentrant arrhythmias, the propagating wave of bioelectricity that normally spreads systematically throughout the four chambers of the heart instead circulates along a myocardial pathway and around an obstacle (reentry point) or circulates freely in the tissue as a scroll wave or spiral (referred to herein as “rotors”). In non-reentrant arrhythmias, propagation of the normal bioelectricity wave may be blocked or initiated at abnormal (ectopic) locations. 
         [0005]    Certain types of cardiac arrhythmias, including ventricular tachycardia and atrial fibrillation, may be treated by ablation (for example, radiofrequency (RF) ablation, cryoablation, ultrasound ablation, laser ablation, and the like), either endocardially or epicardially. However, a physician must first locate the point of reentry, ectopic focus, or regions of abnormal conduction to effectively treat the arrhythmia. Unfortunately, locating the best site for ablation has proven to be very difficult, even for the most skilled physicians. 
         [0006]    Cardiac electrical mapping (mapping the electrical activity of the heart that is associated with depolarization and/or repolarization of the myocardial tissues) is frequently used to locate an optimal site for ablation, for instance, a reentry point, ectopic focus, or a site of abnormal myocardium. However, the source of an arrhythmia may be difficult to determine based upon the sensed electrogram morphology. In addition to signals emanating from the local myocardium, the electrogram morphology may include fractionation due to poor electrode contact, electrode design, or complex electrical activity in the vicinity of the electrodes. The signals may also include “far-field” content from distant tissues (such as detection of ventricular activity on atrial electrodes) or the signal may be attenuated due to disease, ischemia, or tissue necrosis. Further, ablation of one or more identified sites may also be problematic. To date, such ablations require either substantial trial and error (for example, ablation of all sources of complex fractionated electrograms) or the use of separate mapping and ablation devices (complex mapping systems utilizing multielectrode arrays or baskets may be used to identify an ablation site, but cannot also be used to ablate the tissue). Therefore, a system and method are desired that not only streamline the site identification and ablation processes, but also combine mapping and ablation functionality. 
       SUMMARY 
       [0007]    The system and method of the present application provides a non-ambiguous representation of the electrical activity of the myocardium at each particular site within or on the heart, improved means for searching for and testing potential ablation sites including both ectopic foci and rotors, and both mapping and treatment functionality. The non-ambiguous representation of local myocardial depolarization, repolarization timing, and action potential duration is enabled through the use of electrodes that are able to record local monophasic action potentials (MAPs). 
         [0008]    The system may generally include a medical device defining a distal end including a plurality of mapping elements and a treatment element, and a control unit in communication with the medical device and programmable to identify a source of electrical conduction of interest within cardiac tissue based at least in part on signals received from the plurality of mapping elements at one or more tissue locations and programmable to treat the source of electrical conduction of interest by activating the treatment element. The treatment element may be an expandable element, such as a balloon defining an anterior face, the plurality of mapping elements being affixed to the anterior face of the balloon. The plurality of mapping elements may be arranged in a radially symmetrical pattern. Further, the balloon may have a substantially concentric spiral configuration when expanded. Alternatively, the distal end of the device may include one or more array arms, and each of which may include a first portion and a second portion, the first portion being in a plane that is substantially orthogonal to the longitudinal axis of the device. The one or more tissue areas are composed of cells, and the plurality of mapping elements may selectively transmit energy capable of ablation and/or electroporation of the cells. Further, the treatment element may selectively transmit energy capable of adjusting the temperature of the one or more tissue areas to a sub-lethal temperature, ablating the one or more tissue areas, and/or electroporating the cells of the one or more tissue areas. The device may further comprise a plurality of treatment elements, with each treatment element selectively transmitting energy capable of ablation and/or electroporation of cells. Each of the plurality of mapping elements may record monophasic action potentials, such that at least one of depolarization timing, repolarization timing, action potential morphology, and action potential duration is unambiguously determined. 
         [0009]    The method of locating and treating a source of electrical conduction within cardiac tissue may generally include the following steps: (a) positioning one or more mapping elements affixed to a distal end of medical device in contact with cardiac tissue at a first position, the medical device being in communication with a control system including a computer having a display and programmable to execute algorithms, the cardiac tissue being composed of cells; (b) executing computer algorithms to determine directional and morphological features of the electrical conduction of interest based at least in part on signals received by the computer from the one or more mapping elements at the first position; (c) displaying on the computer display a suggested second position at which the one or more mapping elements should be placed in contact with the cardiac tissue; (d) repositioning the one or more mapping elements at the second position; (e) executing computer algorithms to determine directional and morphological features of the electrical conduction of interest based at least in part on signals received by the computer from the one or more mapping elements at the second position; (f) repeating steps (a)-(e) until a source or pathway of the electrical conduction of interest is located; and (g) activating one or more treatment elements in contact with the cardiac tissue cells to treat the cells at a non-lethal temperature and disrupt the source or pathway of the electrical conduction of interest. Treating the cells may include cooling or heating the cardiac cells at the source or pathway of electrical conduction of interest to a non-lethal temperature. The method may further include treating the cardiac cells at the source or pathway of the electrical conduction of interest at a lethal temperature, which may include cryoablation, tissue cooling, applying radiofrequency energy, applying laser energy, applying microwave energy, applying laser energy, and/or applying ultrasound energy. Additionally or alternatively, the method may further include electroporating the cardiac cells at source or pathway of the electrical conduction of interest with pulses of high voltage energy. Electroporation may be followed by delivering to the cardiac cells at the source or pathway of the electrical conduction of interest genes, proteins, drug therapy substances, agents that modify the behavior of the cells, and combinations thereof. The cardiac cells at the source or pathway of the electrical conduction of interest may be treated at a lethal temperature only after treating the cardiac cells at the source or pathway of the electrical conduction of interest at a non-lethal temperature. Furthermore, treating the cardiac cells at the source or pathway of electrical conduction of interest at a lethal temperature may terminate the electrical conduction of interest. 
         [0010]    Alternatively, the method may include: (a) positioning one or more mapping elements affixed to a distal end of a medical device in contact with cardiac tissue at a first position, the medical device being in communication with a control system including a computer having a display, the cardiac tissue being composed of cells; (b) executing computer algorithms to determine directional and morphological features of the electrical conduction of interest based at least in part on signals received by the computer from the one or more mapping elements at the first position; (c) displaying on the computer display a suggested second position at which the one or more mapping elements should be placed in contact with the cardiac tissue; (d) repositioning the one or more mapping elements at the second position; (e) executing computer algorithms to determine directional and morphological features of the electrical conduction of interest based at least in part on signals received by the computer from the one or more mapping elements at the second position; (f) repeating steps (a)-(e) until a the source of the electrical conduction of interest is located; (g) activating one or more treatment elements in contact with the cardiac tissue cells to treat the cells at a non-lethal temperature; and (h) if (g) disrupts the source or pathway of the electrical conduction of interest, activating the one or more treatment elements in contact with the cardiac tissue cells to perform at least one of treating the cells with a lethal temperature and electroporating the cells. 
         [0011]    The present invention advantageously provides a method and system for, with a single device, obtaining a non-ambiguous representation of depolarization and repolarization at each particular site within or on the heart, searching for and testing potential ablation sites that include ectopic foci, rotors, or conduction pathways involved in reentrant arrhythmias and ablating identified ectopic foci, rotors, and/or pathways. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 
           [0013]      FIG. 1  shows a system in accordance with the present invention; 
           [0014]      FIG. 2  shows a stylized representation of a distal end of a medical device placed substantially centered on an ectopic focus; 
           [0015]      FIG. 3  shows a stylized representation of a distal end of a medical device placed substantially centered on a rotor; 
           [0016]      FIG. 4  shows a stylized representation of a distal end of a medical device placed substantially on a reentrant pathway; 
           [0017]      FIG. 5  shows a stylized representation of a distal end of a medical device placed a distance from an ectopic focus; 
           [0018]      FIG. 6  shows a stylized representation of a distal end of a medical device placed a distance from a rotor; 
           [0019]      FIG. 7  shows a first embodiment of a distal end of a medical device with mapping and treatment functionality; 
           [0020]      FIG. 8  shows a second embodiment of a distal end of a medical device with mapping and treatment functionality; 
           [0021]      FIG. 9  shows a third embodiment of a distal end of a medical device with mapping and treatment functionality; 
           [0022]      FIG. 10  shows a fourth embodiment of a distal end of a medical device with mapping and treatment functionality; 
           [0023]      FIG. 11  shows a cross section of a first embodiment of a mapping element such as in  FIG. 7, 8 , or  9 ; 
           [0024]      FIG. 12  shows a cross section of a second embodiment of a mapping element such as in  FIG. 7, 8 , or  9 ; 
           [0025]      FIG. 13  shows a perspective view of a third embodiment of a mapping element such as in  FIG. 10 ; and 
           [0026]      FIG. 14  shows a fifth embodiment of a distal end of a medical device with mapping and treatment functionality. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    Now referring to  FIG. 1 , a system  10  in accordance with the present invention is shown. The system  10  generally includes a medical device  12  for mapping and/or treating an area of tissue and a console  14  that houses various system  10  controls. The system  10  may be adapted for radiofrequency (RF) ablation and/or phased radiofrequency (PRF) ablation, cryoablation, ultrasound ablation, laser ablation, microwave ablation, or other ablation methods or combinations thereof. 
         [0028]    The device  12  may be a catheter with mapping and treatment functionality generally including a handle  16 , an elongate body  18  having a distal portion  20  and a proximal portion  22 , one or more mapping elements or sensors  24 , and one or more treatment elements  26 . The device  12  may have a longitudinal axis  28 . The distal portion  20  of the device  12  may include an expandable element (such as a balloon or wire mesh), a deformable coil or concentric spiral (as shown in  FIG. 7 ), or other array on which mapping  24  and treatment elements  26  may be disposed (for example, as shown in  FIG. 8 ). Alternatively, the distal portion  20  of device  12  may be straight, such as a focal catheter that may be bendable to an approximately 90-degree angle (as shown in  FIG. 9 ). The mapping  24  elements may be sensors or electrodes capable of sensing electrical activity within the myocardial cells as the cells polarize and depolarize, such as monophasic action potential (MAP) electrodes. The device  12  may also include one or more reference electrodes  30 . The treatment elements  26  may be electrodes capable of transmitting thermal energy, and may be larger (that is, have more surface area) than the mapping  24  electrodes. Additionally or alternatively, the treatment elements  26  may include an expandable treatment element  26  such as a cryoballoon. Further, the device  12  may include one or more thermoelectric cooling elements. 
         [0029]    The elongate body  18  of the device  12  may include one or more lumens  32 . If the device  12  is a cryoablation catheter, for example, the elongate body  18  may include a main lumen, a fluid injection lumen in fluid communication with the coolant reservoir  34 , and a fluid return lumen in fluid communication with the coolant return reservoir  36 . In some embodiments, one or more other lumens may be disposed within the main lumen, and/or the main lumen may function as the fluid injection lumen or the fluid return lumen. If the ablation catheter includes thermoelectric cooling elements or electrodes capable of transmitting radiofrequency (RF), ultrasound, microwave, electroporation energy, or the like, the elongate body  18  may include a lumen in electrical communication with an energy generator  38  and/or a power source  40 . 
         [0030]    The console  14  may be in electrical and fluid communication with the medical device  12  and include one or more fluid (such as coolant or saline) reservoirs  34 , fluid return reservoirs  36 , energy generators  38  (for example, an RF or electroporation energy generator), and computers  42  with displays  44 , and may further include various other displays, screens, user input controls, keyboards, buttons, valves, conduits, connectors, power sources, and computers for adjusting and monitoring system  10  parameters. The computer  42  may be in electrical communication with the one or more mapping elements  24  and/or the one or more treatment elements  26  and programmable to execute an algorithm for locating one or more optimal treatment areas. For example, the computer may assess arrhythmia morphology and directionality using activation timing signals from the one or more mapping elements  24 . Based on the calculated morphology and directionality, the computer may then determine one or more optimal treatment sites (for example, as shown in  FIGS. 5 and 6 ) and communicate those sites, via one or more displays or screens, to the user. 
         [0031]    Once an optimal treatment site is located, and the medical device  12  positioned in contact with this site, the one or more treatment elements  26  may be activated to treat the site. As a non-limiting example, the system  10  may be configured for use in cryoablation procedures. For example, the device  12  may include a cryoballoon as the treatment element  26 . Once an optimal treatment site is located, the medical device  12  may be placed in contact with the treatment site and the treatment element  26  activated to cool the treatment site to a sub-lethal temperature (or heated to a sub-lethal temperature, if non-cryogenic energy modalities are used). If the application of the sub-lethal temperature abates, disrupts, or temporarily terminates the arrhythmia, the user may then choose to increase the cooling effect, or lower the temperature, of the one or more treatment elements  26  in order to permanently ablate the tissue of the treatment site (or raise the temperature to a lethal temperature, if non-cryogenic energy modalities are used). Thus, alternatively, the user may choose to ablate the treatment site once it has been located and confirmed as an accurate target. Additionally or alternatively, once an optimal treatment site is located, the medical device  12  may be placed in contact with the treatment site and activated to transmit short pulses of high voltage in order to electroporate the cells of the treatment site. This electroporation may be used to disable cells, ablate cells, or prepare cells for subsequent therapies such as gene delivery, protein delivery, or other therapeutic agent or substance intended to modify the behavior of the cells. 
         [0032]    Now referring to  FIGS. 2 and 3 , stylized representations of a distal portion  20  of a medical device  12  (depicted as a rectangle) placed substantially centered on an ectopic focus and a rotor are shown, respectively, on cardiac tissue  50 . In  FIG. 2 , the small black circle represents the center of the focus  46 A. Likewise, in  FIG. 3 , the small black circle represents the position of rotation of the rotor  48 A (which, for simplicity, will be referred to as the “center”  48 A of the rotor  48 ). Referring to  FIG. 4 , a stylized representation of a distal portion  20  of a medical device  12  placed substantially within a reentrant pathway  52  is shown. The stylized distal portion  20  shown in  FIGS. 2-4  may represent any configuration, such as a coil or concentric spiral (for example, as shown in  FIG. 7 ), a crossed-arm array (for example, as shown in  FIG. 8 ), or a linear distal portion  20  (for example, as shown in  FIG. 9 ). For simplicity, the distal portion  20  is depicted as a rectangle in  FIGS. 2-4 . 
         [0033]    In  FIG. 2 , a small black circle is shown within the rectangle, representing a distal portion  20  of a medical device  12  being substantially centered above the center  46 A of an ectopic focus  46 . The dashed arrows represent propagating waves of bioelectricity emanating from the center  46 A of the ectopic focus  46  in an outward direction through cardiac tissue  50 . In  FIG. 3 , a small black circle is shown within the rectangle, representing a distal portion  20  of a medical device  12  being substantially centered above the center  48 A of the rotor  48 . The arrows represent a pattern of propagating waves of bioelectricity from the center (position of rotation  48 A), with smaller arrows representing a higher frequency and larger arrows representing a lower frequency. The direction of the arrow indicates the direction of the wave. In  FIG. 4 , the rectangle represents the distal portion  20  of a medical device  12  being positioned substantially on a reentrant loop  52 . The pattern of propagating waves in the rotor  48  may be a spiral, scroll wave, or other nonlinear pattern, and the location of the center  48 A of the rotor may change. The propagating waves may move outward from the center  46 A of an ectopic focus  46  in any direction or in any pattern away from the center  48 A in a rotor  48 . For reentrant loops  52 , the electrical conduction may be in a repeating circuit with or without the involvement of the tissue in the center of the circuit. In contrast, a rotor  48  (or spiral wave reentry) may involve the center  48 A of the circuit, and the circuit can be continuously varying and not following a uniquely defined pathway. For rotors  48  and ectopic foci  46 , the frequency of a wave will generally decrease as it moves farther from the center of the ectopic focus  46 A or rotor center  48 A. That is, a mapping element  24  positioned proximal the center  46 A of an ectopic focus  46  or rotor center  48 A will record a greater depolarization frequency than a mapping element  24  positioned a greater distance from the center  46 A of the ectopic focus  46  or rotor center  48 A. Further, the one or more mapping elements  24  may each record a direction of a curved propagating wave, which data is used by the computer  42  to calculate the rotor pattern. For reentrant loops  52 , the circuit may define a discrete pathway having a width. Particularly if the width is narrow, small relocations of the device distal portion  20  may detect the pathway, which will have a frequency that is independent of neighboring tissue. An optimal ablation site for a reentrant loop  52  is anywhere within the loop  52  that will disrupt the conduction loop or pathway. Thus,  FIG. 4  the center of the reentrant loop  52  is not represented by a small black circle as in  FIGS. 2 and 3 , because the center of the reentrant loop  52  may not be the optimal ablation site. 
         [0034]    Now referring to  FIGS. 5 and 6 , stylized representation of a distal portion  20  of a medical device  12  (depicted as a rectangle) placed a distance from the center  46 A of an ectopic focus  46  and a rotor center  48 A are shown, respectively. The representations in  FIGS. 5 and 6  (such as arrows, rectangles, and black circles) are the same as in  FIGS. 2-4 . The propagating waves may move outward from the center  46 A of the ectopic focus  46  in any direction or in any pattern away from the central point in a rotor, but the frequency of a wave will generally decrease as it moves farther from the center  46 A of the ectopic focus  46  or rotor center  48 A. Using the morphological and directional characteristics of one or more propagating waves sensed by the one or more mapping elements  24  and communicated to the computer  42 , the computer  42  may communicate to the user (via one or more screens or other displays  44 ) suggested treatment sites, or at a minimum a general distance and direction that might allow the user to move closer to the origin of the ectopic focus  46  or rotor  48 . Using the algorithm discussed above, the computer  42  may continue to suggest treatment sites until an optimal treatment site, a site substantially at the center  46 A of an ectopic focus  46 , rotor center  48 A, or reentrant loop  52 , is located. 
         [0035]    Now referring to  FIG. 7 , a first embodiment of a distal portion  20  of a medical device  12  with mapping and ablation functionality is shown. The distal portion  20  may have a coil or concentric spiral configuration  54  with a plurality of turns. The coil or concentric spiral  54  may lie in a plane that is substantially orthogonal to the longitudinal axis  28  of the device  12 . Each turn includes an anterior face  56 , on which is positioned one or more mapping elements  24  and/or one or more treatment elements  26 . If the spiral  54  is the treatment element  26 , then the face  56  of the spiral  54  may only contain mapping elements  24 . To enhance surface area and tissue contact, the one or more mapping  24  and/or treatment elements  26  may have a curved or semi-circular profile that extends from the anterior face  56  of each turn of the spiral  54  (for example, as shown in  FIG. 11 ). As a non-limiting example, as shown in  FIG. 7 , the spiral  54  is the treatment element  26  on which a plurality of mapping elements  24  are borne. The mapping elements  24  may have a curved or semi-circular profile that extends from the anterior face  56  of each turn of the spiral  54 . Alternatively, the one or more mapping  24  and/or treatment elements  26  may be set within and flush with the anterior face  56  of each turn (for example, as shown in  FIG. 12 ). The distal portion  20  may be affixed to a shaft  58  that is slidably movable within the elongate body  18  of the device  12 , or the distal portion  20  may be continuous with the elongate body  18  of the device  12 . For example, the distal portion  20  may include a cryoballoon coupled to the elongate body  18  that may be inflated with coolant to assume the coiled configuration shown in  FIG. 7 . Alternatively, the distal portion  20  may be composed of a resilient and deformable material, and may assume a first position for allowing passage through the vasculature to the region of interest and a second extended position for mapping and/or treatment. Further, the resilient and deformable material may be biased toward either the first or second position and may be steerable by one or more pull wires, guide wires, rods, or other steering mechanisms controllable at or proximal to the handle  16  of the device  12 . Similarly, the distal portion  20  may be an elongated cryoablation element that can assume a coiled configuration. For example, the distal portion  20  may include an inflatable element or balloon that, when inflated, assumes the coiled configuration. Further, the balloon may bear one or more mapping  24  and/or treatment  26  elements on an outer surface (used, for example, for RF ablation, microwave ablation, ultrasound ablation, electroporation, or other treatment method), or may enclose a coolant so the balloon may be used to cool and/or ablate a target tissue area. The one or more treatment elements  26  may be in fluid communication with a coolant reservoir  34  and/or may be cooled using a thermoelectric cooler or cryogenic fluid. Additionally or alternatively, the one or more treatment elements  26  may be capable of transmitting RF, laser, ultrasound, or microwave energy, or the like. 
         [0036]    Now referring to  FIG. 8 , a second embodiment of a distal portion  20  of a medical device  12  with mapping  24  and ablation functionality is shown. The distal portion  20  may include a crossed-arm array  60  that includes a plurality of arms  62 , each of which bearing one or more mapping  24  and/or treatment elements  26  at an anterior face  64  of the array  60 . Each arm  62  may include a first portion  66  at the anterior face  64  of the array  60  on which the one or more mapping  24  and/or treatment elements  26  are borne, and a second portion  68  that is coupled to the device  12 . Each electrode may serve a mapping and/or ablation function, and it is conceived that mapping elements  24  may protrude from underlying ablative structures (as shown and described in  FIGS. 11 and 13 ). The point at which the first  66  and second  68  portion of each arm  62  meet may form an acute angle. The second portion  68  of each arm  62  may be affixed to a shaft  58  that is slidably movable within the elongate body  18  of the device  12 , or affixed directly to the elongate body  18 . To enhance surface area and tissue contact, the one or more mapping  24  and/or treatment elements  26  may have a curved or semi-circular profile that extends from the first portion  66  of each arm  62  (for example, as shown in  FIG. 10 ). Alternatively, the one or more mapping  24  and/or treatment elements  26  may be set within and flush with the first portion  66  of each arm  62  (for example, as shown in  FIG. 11 ). Each element may be capable of both mapping and ablation. Alternatively, for example, the mapping element  24  may protrude farther from the center point  69  of the cross-arm array  60  to enhance tissue contact and signal quality, whereas the treatment elements  26  may cover a larger “footprint” for ablation of larger areas of tissue. Further, the distal portion  20  may be composed of a resilient and deformable material, and may assume a first position for delivery (not shown) and a second position for mapping and/or treatment (as shown in  FIG. 8 ). When in the second expanded position, the first portion  66  of each arm  62  may lie in a plane that is substantially orthogonal to the longitudinal axis  28  of the device  12 . Still further, the resilient and deformable material may be biased toward either the first or second position and may be steerable by one or more pull wires, guide wires, rods, or other steering mechanisms controllable at or proximal to the handle  16  of the device  12 . The one or more treatment elements  26  may be in fluid communication with a coolant reservoir  34  and/or may be cooled using a thermoelectric cooler or cryogenic fluid. Alternatively, the one or more treatment elements  26  may be capable of transmitting RF, laser, ultrasound, microwave, electroporation energy, or the like. 
         [0037]    Now referring to  FIG. 9 , a third embodiment of a distal portion  20  of a medical device  12  with mapping and ablation functionality is shown. The device  12  may be a focal catheter or similar device, without a distal array or configuration and the one or more mapping  24  and/or treatment elements  26  (referred to in  FIG. 9  as “ 24 / 26 ”) being borne along the distal portion  20  of the elongate body  18 . Alternatively, the distal portion  20  of the device  12  may be composed of a material different than that of the elongate body  18 , may have a different diameter or rigidity, or the like. To enhance surface area and tissue contact, the one or more mapping  24  and/or treatment elements  26  may have a curved or semi-circular profile that extends from the distal portion  20  (for example, as shown in  FIG. 10 ). Alternatively, the one or more mapping  24  and/or treatment elements  26  may be set within and flush with the distal portion  20  (for example, as shown in  FIG. 11 ). Additionally, the distal portion  20  may be composed of a resilient and deformable material that permits bending of the distal portion  20 , such as into a right-angle (or other acute or obtuse angle) bend, as depicted in dashed lines in  FIG. 9 . The one or more mapping  24  and/or treatment elements  26  may be disposed longitudinally along the distal portion  20 . The one or more treatment elements  26  may be in fluid communication with a coolant reservoir and/or may be cooled using a thermoelectric cooler or cryogenic fluid. Additionally or alternatively, the one or more treatment elements  26  may be capable of transmitting RF, laser, ultrasound, microwave, electroporation energy, or the like. When mapping cardiac tissue, the distal portion  20  may either be oriented or bent to position one or more mapping elements  24  in contact with the tissue (for example, in a linear pattern). When treating cardiac tissue (either with lethal or sub-lethal temperatures), the device  12  may be used like a focal catheter to create a substantially circular focal lesion (such as when only the distal tip is placed in contact with the treatment site) or bent to create a substantially linear lesion (such as when a longitudinal surface of the distal portion  20  including two or more treatment elements  26  is placed in contact with the treatment site). 
         [0038]    Now referring to  FIG. 10 , a fourth embodiment of a distal portion  20  of a medical device  12  with mapping and ablation functionality is shown. The distal portion  20  may include an array  70  that includes one or more arms  72  bearing one or more mapping  24  and/or treatment elements  26 . Each arm  72  may include a first portion  76  at the anterior face  74  of the array  70  on which the one or more mapping  24  and/or treatment elements  26  are borne, and a second portion  78  that is coupled to the device  12 . The array  70  may further include one or more reference electrodes  30 . As shown in  FIG. 10 , the one or more treatment elements  26  may each include a mapping element  24 , which may protrude from the corresponding treatment element  26 . The point at which the first  76  and second  78  portion of each arm  72  meet may form an acute angle. The second portion  78  of each arm  72  may be affixed to a shaft  58  that is slidably movable within the elongate body  18  of the device  12 , or affixed directly to the elongate body  18 . The cross-section of each treatment element  26 /mapping element  28  combination may be as shown in detail in  FIG. 13 . Further, the distal portion  20  may be composed of a resilient and deformable material, and may assume a first position for delivery (not shown) and a second position for mapping and/or treatment (as shown in  FIG. 10 ). When in the second expanded position, the first portion  76  of each arm  72  may lie in a plane that is substantially orthogonal to the longitudinal axis  28  of the device  12 . Still further, the resilient and deformable material may be biased toward either the first or second position and may be steerable by one or more pull wires, guide wires, rods, or other steering mechanisms controllable at or proximal to the handle  16  of the device  12 . The one or more treatment elements  26  may be in fluid communication with a coolant reservoir  34  and/or may be cooled using a thermoelectric cooler or cryogenic fluid. Additionally or alternatively, the one or more treatment elements  26  may be capable of transmitting RF, laser, ultrasound, or microwave energy, or the like. 
         [0039]    Now referring to  FIGS. 11 and 12 , cross sections of a first embodiment and a second embodiment of a mapping element  24  such as in  FIGS. 7, 8, and 9  are shown. The cross section is taken along line A-A of  FIGS. 7-9 . As described above, the one or more mapping  24  and/or treatment elements  26  (referred to as “ 24 / 26 ” in  FIGS. 11 and 12 ) may have a curved or semi-circular profile that protrudes from the device  12  or portion thereof (for example, array arm, elongate body, or the like) in order to enhance surface area and tissue contact (as shown in  FIG. 11 ). Alternatively, the one or more mapping  24  and/or treatment elements  26  may be set within and flush with the device  12  (as shown in  FIG. 12 ). 
         [0040]    Now referring to  FIG. 13 , a perspective view of a third embodiment of a mapping element  24  such as in  FIG. 10  is shown. The one or more treatment elements  26  may each include a mapping element  24  protruding therefrom. Further, an insulative layer  80  may be included that surrounds each mapping element  24  to electrically isolate it relative to the treatment element  26  and thus reduce the region of tissue from which electrical activity is sensed. The insulative layer  80  may also act to at least partially shield the one or more mapping elements  24  from energy transmitted by the one or more treatment elements  26 . 
         [0041]    Now referring to  FIG. 14 , a fifth embodiment of a distal portion  20  of a medical device  12  with mapping and ablation functionality is shown. The distal portion  20  may include an inflatable element or balloon  82  on which a plurality of electrodes  84  are borne. For example, the electrodes  84  may be small button electrodes that are affixed to the outer surface of the balloon  82 . The electrodes  84  may be affixed to an anterior face  86  of the balloon  82 , and they may be affixed in a radially symmetrical pattern. The electrodes  84  may be used to map and ablate an area of target tissue. Additionally or alternatively, the electrodes  84  may be used to map tissue, whereas ablation of the tissue is accomplished through the use of a coolant that is circulated within the balloon lumen  88 . 
         [0042]    It will be understood that any of the above devices may be used to apply electroporation energy to the cells of the area of target tissue. Electroporation utilizes high electric field amplitude electrical pulses to effectuate a physiological modification (i.e. permeabilization) of the cells to which the energy is applied. Such pulses may preferably be short (for example, having a nanosecond, microsecond, or millisecond pulse width) in order to allow application of high voltage without a large flow of electrical current that would result in significant tissue heating. In particular, the pulsed energy induces the formation of microscopic pores or openings in the cell membrane. Depending on the characteristics of the electroporation pulses, an electroporated cell can survive electroporation (referred to as “reversible electroporation”) or be killed by electroporation (referred to as “irreversible electroporation” or “IEP”). Reversible electroporation may be used to transfer agents, including large molecules, into targeted cells for various purposes. Thus, electroporation may be used to disable tissue cells, ablate tissue cells, or prepare tissue cells for subsequent therapies, such as gene delivery, protein delivery, or delivery of other therapeutic agents or substances intended to modify the behavior of the target tissue cells. 
         [0043]    It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the invention, which is limited only by the following claims.