Abstract:
A mapping and ablation catheter system including a radio frequency ablation source having an output, a mapping device, a catheter, and two or more capacitive components. The catheter may include two or more catheter electrodes, wherein two of the two or more catheter electrodes may be electrically coupled to the mapping device. Each of the two or more catheter electrodes may be electrically coupled to a capacitive component, wherein each capacitive component may be electrically coupled to the output of the radio frequency ablation source such that energy delivered to each catheter electrode of the two or more catheter electrodes passes through the capacitive component.

Description:
RELATED APPLICATION 
       [0001]    The present application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 61/010,519, filed on Jan. 9, 2008, titled MAPPING AND ABLATION CATHETER SYSTEM, which is hereby incorporated by reference in its entirety. 
     
    
       [0002]    The present invention relates generally to cardiac mapping and ablation catheter systems. 
         [0003]    The systems described herein may be used in the mapping and ablation of tissue associated with tachyarrhythmia. In some embodiments, the systems include a catheter that may include one or more electrodes located about the distal end of the catheter. The catheter may be manipulated within one or more cardiac chambers to obtain electrograms from the one or more electrodes. The electrograms may be used to create a map of the cardiac chamber (e.g., the map could be a real electro-anatomic map or an abstract map based on various voltages, timings, and morphologies recorded using the catheter). 
         [0004]    Once a selected site that may include arrhythmogenic tissue is identified as a result of the mapping process, radio frequency (RF) energy may be delivered to the same one or more electrodes located about the distal end of the catheter to ablate tissue at the selected site. 
         [0005]    The requirements of an ideal mapping electrode, however, are different from those of an ideal ablation electrode. For example, the ideal mapping electrode is typically smaller so as to sample electrograms from very close to the point of contact of the electrode while reducing the effect of “far-field” potentials that are a few millimeters away from the point of contact. In contrast, ablation electrodes are typically larger (in diameter and/or in length) so as to be able to deliver sufficient energy to ablate tissue effectively. 
         [0006]    When a small (e.g., short in length) electrode tip is used to ablate tissue, tissue temperature can rise very quickly, but too little power may be delivered to the tissue to effectively produce a lesion. Known non-irrigated ablation catheters have tip electrodes that are 4 millimeters (mm), 5 mm, or 8 mm long. Most commonly, the 5 mm tip is used but occasionally the 8 mm tip is needed (requiring a cumbersome and expensive catheter change) when the 5 mm tip is not sufficient. Mapping with the 8 mm tip is less precise than with the 5 mm tip because large-amplitude far-field signals may be received by the “antenna-effect” of the 8 mm tip, thereby reducing the precision of the mapping process. 
         [0007]    Mapping and ablation catheter systems have been previously been described. For example, U.S. Pat. No. 5,454,370, issued 3 Oct. 1995 to Avitall and entitled “Mapping and Ablation Electrode Configuration,” describes a mapping/ablation electrode arrangement that provides for flexible lesion size yet maintains discrete localized mapping ability and/or enables the operator to adjust the lesion size (width, length, and depth). 
       SUMMARY 
       [0008]    The present disclosure describes a variety of cardiac mapping and ablation catheter systems that may include a radio frequency ablation source, a mapping device, one or more electrodes, capacitive components located between the catheter electrodes that may be electrically coupled to the mapping device. Each of the electrodes may be electrically coupled to a capacitive component, wherein each capacitive component may be electrically coupled to the output of the radio frequency ablation source such that energy delivered to each catheter electrode of the one or more electrodes passes through the capacitive component. 
         [0009]    In some embodiments, the cardiac mapping and ablation catheter system may include a radio frequency ablation source having an output; a mapping device; a catheter having two or more catheter electrodes, wherein two of the two or more catheter electrodes are electrically coupled to the mapping device; and two or more capacitive components, wherein each of the two or more catheter electrodes is electrically coupled to a capacitive component, wherein each capacitive component is electrically coupled to the output of the radio frequency ablation source such that energy delivered to each catheter electrode of the two or more catheter electrodes passes through the capacitive component. 
         [0010]    In some embodiments, the cardiac mapping and ablation catheter system may include a radio frequency ablation source having an output; a mapping device; a catheter including a catheter electrode, wherein the catheter electrode is electrically coupled to the mapping device; and a capacitive component, wherein the catheter electrode is electrically coupled to the capacitive component, wherein the capacitive component is electrically coupled to the output of the radio frequency ablation source such that energy delivered to the catheter electrode passes through the capacitive component, and wherein the capacitive component electrically isolates the radio frequency ablation source from the catheter electrodes when the radio frequency ablation source is disabled; a sheath capable of partially surrounding the catheter and sliding along the catheter to selectively expose the catheter electrode; and a sheath electrode located on an exterior surface of the sheath, wherein the sheath electrode is electrically coupled to the mapping device. 
         [0011]    In various embodiments, one or more of the following features may be included in the systems of the present disclosure: a sheath capable of partially surrounding the catheter and sliding along the catheter to selectively expose one or more of the two or more catheter electrodes (the sheath may include one or more sheath electrodes located on an exterior surface of the sheath, wherein the one or more sheath electrodes are electrically coupled to the mapping device); a return electrode electrically coupled to the radio frequency ablation source; the capacitive components electrically may isolate the radio frequency ablation source from the two or more catheter electrodes when the radio frequency ablation source is disabled; the capacitance of each capacitive component is 0.001 microfarads to 0.1 microfarads; the radio frequency ablation source is capable of outputting electromagnetic energy at a frequency of about 300 kilohertz or higher; the mapping device is capable of sensing electromagnetic energy in the frequency of about 500 hertz or lower; each of the two or more catheter electrodes is 0.5 millimeters long to 4 millimeters long; the two or more catheter electrodes are spaced apart from each other by 0.5 millimeters to 1 millimeter; a portion of the catheter is flexible; the catheter is flexible; one of the two or more catheter electrodes is located on a distal end of the catheter; etc. 
     
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0012]    In the following detailed description of illustrative embodiments of the systems, reference is made to the accompanying figures of the drawing which form a part hereof, and in which are shown, by way of illustration, specific embodiments in which the systems may be provided. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present disclosure. 
         [0013]    The words “preferred” and “preferably” as used herein refer to embodiments that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments. 
         [0014]    As used herein, “a,” “an,” “the,” “at least one,” and “one or more” are used interchangeably. The term “and/or” (if used) means one or all of the identified elements/features or a combination of any two or more of the identified elements/features. 
         [0015]    The term “and/or” as used herein means one or all of the listed elements/features or a combination of any two or more of the listed elements/features. 
         [0016]      FIG. 1  depicts a schematic diagram of one exemplary embodiment of a mapping and ablation catheter system  50 . The system may include a catheter  10 , a mapping system  20 , a radio frequency ablation unit  30 , and switches  40 . The catheter  10 , a portion of catheter  10 , or multiple portions of catheter  10  may be flexible. 
         [0017]    The catheter  10  may include distal electrodes  12  (e.g., DD, DC, DB), distal tip electrode  14  (e.g., DA), and electrodes  16  (e.g., 4, 3, 2). Each of the electrodes may be electrically coupled to the mapping system  20  and/or radio frequency ablation unit  30 . For example, a wire may electrically couple each electrode  12 ,  14 ,  16  to the mapping system  20  and/or radio frequency unit  30 . 
         [0018]    In this embodiment, the connection between the each of the distal electrodes  12 /distal tip electrode  14  and the radio frequency ablation unit  30  includes a switch  40 . The switches  40  may allow the distal electrodes  12 ,  14  to be switched into the circuit during ablation operation while only distal electrode  14  may be used during mapping operation. The other electrodes  16  may be activated during a mapping operation also. The switches  40  may, e.g., be electronically-controlled switches. In addition, the switches may be provided using hardware, software, or combinations thereof. 
         [0019]    For example, if an operator initially begins an ablation with two distal electrodes creating, e.g., a 4 millimeter (mm) effective tip and not enough power is being delivered to obtain a desired temperature, additional electrodes (e.g., electrodes DC and DD of electrodes  12 ) may be dynamically “switched-in” to change the impedance/power transfer characteristics of the system. Further, for example, an operator could switch back-and-forth between mapping operation and ablation operation to check for efficacy of ablation. 
         [0020]      FIG. 2  depicts a partial side view of the catheter  10  as shown in  FIG. 1 . In this embodiment, the distal tip electrode  14  may have a length of, e.g., about 1.5 mm, the distal electrodes  12  may have a length of, e.g., about 2 mm, and the electrodes  12 ,  14  may be spaced apart by, e.g., about 1 mm. In other embodiments, however, the distal tip electrode  14  may have a length of, e.g., about 0.5 mm to, e.g., about 4 mm, the distal electrodes  12  may have a length of, e.g., about 0.5 mm to, e.g., about 5 mm, and the electrodes  12 ,  14 ,  16  may be spaced apart by about 0.25 mm to about 1.5 mm. Further, the distal electrodes  12  may each have a different length. 
         [0021]      FIG. 3  depicts a schematic diagram of another exemplary embodiment of a mapping and ablation catheter system  150 . The system may include a catheter  110 , a mapping system  120 , a radio frequency ablation unit  130 , and capacitive components  140 . 
         [0022]    The catheter  110  may include mapping tip electrode  114 , RF ablation electrode  116 , and mapping electrode  118 . In this embodiment, the mapping tip electrode  114  may have a length of, e.g., about 2 mm, the RF ablation electrode  116  may have a length of, e.g., about 3 mm, and the mapping electrode  118  may have a length of, e.g., about 2 mm. In other embodiments, however, the electrodes  114 ,  116 , and  118  may have lengths of, e.g., about 0.5 mm to, e.g., about 5 mm. Further, in this embodiment, the electrodes  114 ,  116 ,  118  are spaced apart by, e.g., about 0.5 mm to about 1 mm. In other embodiments, however, the electrodes  114 ,  116 ,  118  may be spaced apart by, e.g., about 0.25 mm to, e.g., about 1.5 mm. 
         [0023]    In this embodiment, the mapping tip electrode  114  and the mapping electrode  118  are electrically coupled to the mapping system  120 . The mapping tip electrode  114  and the mapping electrode  118  may be used during mapping of, e.g., a cardiac chamber. The mapping system  120  may include electronic components, e.g., amplifier  122 , to measure, amplify, etc. the signal received from the mapping electrodes  114 ,  118  to generate mapping data, e.g., an electrogram. The mapping system  120  may be capable of sensing electromagnetic energy in the frequency of, e.g., about 0.05 hertz to, e.g., about 500 hertz. 
         [0024]    Each electrode  114 ,  116 ,  118  may be electrically coupled to a capacitive component  140 . The capacitive components  140 , in turn, may be coupled to the radio frequency ablation unit  130  in parallel. As such, the electrodes  114 ,  116 ,  118  are electrically coupled to each other via the capacitive components  140 . In this embodiment, the capacitance of each capacitive component  140  may be, e.g., about 0.022 microfarads. In other embodiments, however, the capacitance of each capacitive component may be, e.g., about 0.001 microfarads to, e.g., about 0.1 microfarads. 
         [0025]    The radio frequency ablation unit  130  may include a radio frequency generator  132  and a return patch electrode  134  (or other current return mechanism). In this embodiment, the radio frequency generator  132  may be capable of outputting electromagnetic energy in the frequency of, e.g., about 500 kilohertz. In other embodiments, however, the radio frequency ablation generator may be capable of outputting electromagnetic energy in the frequency of, e.g., about 300 kilohertz to, e.g., about 3 megahertz. A return patch electrode  134  may be attached to the patient&#39;s skin during mapping and ablation. 
         [0026]    The capacitive components  140  offer a high impedance at low frequencies (e.g., below 500 hertz). The high impedance of the capacitive components  140  may effectively disconnect the electrodes  114 ,  116 ,  118  from each other and from the radio frequency ablation unit  130  at frequencies below 500 hertz. As such, when the radio frequency ablation unit is not providing RF energy at frequencies above, e.g., about 500 hertz, the electrodes  114 ,  116 ,  118  will be preferably effectively disconnected from each other and from the radio frequency ablation unit  130 . 
         [0027]    When, however, the radio frequency ablation unit  130  is outputting electromagnetic energy at a frequency of, e.g., about 300 kilohertz or higher, the capacitive components  140  may, in effect, behave like a near-short-circuit, thereby connecting the electrodes  114 ,  116 ,  118  in parallel and producing a large effective electrode with respect to the return patch  134 . 
         [0028]    For example, a capacitive component  140  with a value of, e.g., about 0.022 microfarads yields an impedance at 500 kilohertz of 15 ohms, which is sufficiently small such that it may not substantially reduce an ablation current. At 500 hertz, however, the same 0.022 microfarad capacitive component  140  presents an impedance of 15 kilo-ohms, which may constitute a small load seen by an input state of the amplifier  122  of the mapping system  120 . 
         [0029]      FIG. 4  depicts a partial side view of another embodiment of a mapping and ablation catheter  210 . In this embodiment, the catheter  210  may include a tip electrode  214 , one or more catheter electrodes  216 , and a sheath  220  adapted to move over the surface of the catheter  210 . In this embodiment, the mapping/ablation tip of the catheter  210  may have a length of, e.g., about 10 mm. In other embodiments, however, the mapping/ablation tip may have a length of, e.g., about 1 mm to, e.g., about 20 mm. 
         [0030]    The sheath  220  may preferably be a flexible, thin insulating sheath. The sheath  220  may be irrigated to minimize clot formation (e.g., keeping the end of the catheter  210  and/or sheath  220  relatively free of any clotting). Further, the sheath may include sheath electrodes  222  that may be used during mapping. 
         [0031]    The sheath  220  may preferably slide back and forth (proximally and distally) along the mapping/ablation tip of the catheter  210 . It may further be preferred that the sheath  220  can be fixed and/or locked at different intervals to expose more or less of the mapping/ablation tip of the catheter  210 . For example, during mapping, the sheath  220  may be moved forward (advanced distally) relative to the catheter  210  and locked into position to expose 2 mm of the tip  214  (e.g., to provide a precise mapping tip). To prepare for ablation, the catheter  210  may be held in place while the sheath  220  is pulled back (moved proximally) and locked into a variety of positions exposing, e.g., 5 mm, 6 mm, or 8 mm of the tip of the catheter  210 , which may produce an ablation tip of variable length. 
         [0032]    The portion of the catheter located between two of the electrodes (e.g., mapping electrodes) may be in the form of an irrigation ring that includes one or more irrigation ports. Any such irrigation ring may preferably be connected to a lumen that extends towards the proximal end of the catheter, with the lumen being used to supply irrigation fluid to the irrigation ring. Such an irrigation ring can potentially function as an insulator to distinguish the two separated electrodes during mapping, while the same two electrodes could potentially also be used for ablation in the presence of a suitable irrigation fluid. 
         [0033]    In some embodiments, the systems may further include one or more temperature sensors. For example, one or more temperature sensors may be provided in connection with two or more of the electrodes to provide temperature information during, e.g., testing and/or use of the ablation functions. Monitoring temperature during ablation may potentially assist the user in reducing the likelihood of coagulum development on, e.g., the ablation electrode or electrodes. 
         [0034]    Further, in some embodiments, it may be helpful to provide two or more temperature sensors located along the catheter, with a first temperature sensor located proximate a position on the catheter where the most ablation energy is delivered and one or more additional temperature sensors spaced apart from the first temperature sensor. Using two or more temperature sensors may provide the ability to monitor a temperature gradient between the temperature sensors during and/or after ablation. In some instances, the temperature sensors may be monitored to reduce the likelihood of coagulum formation and/or improve the likelihood of lesion creation. 
         [0035]    The complete disclosure of the patents, patent documents, and publications cited in the Background, the Summary, the Detailed Description of Exemplary Embodiments, and elsewhere herein are incorporated by reference in their entirety as if each were individually incorporated. Exemplary embodiments of some systems are described above. Those skilled in the art will recognize that many embodiments are possible within the scope of the disclosure. Other variations, modifications, and combinations of the various components and methods described herein can certainly be made and still fall within the scope of the disclosure. Thus, the invention is limited only by the following claims and equivalents thereto.