Abstract:
Apparatus for irrigating an electrode of a catheter are disclosed. Among other things, a catheter is disclosed that comprises a shaft portion including a fluid passage to conduct fluid, an electrode coupled to a distal end of the shaft portion, and a handle portion coupled to a proximal end of the shaft portion. A portion of the fluid passage defines an opening in the shaft portion. The opening is constructed and arranged such that when fluid is conducted through the fluid passage, at least some of the fluid will contact the electrode after passing through the opening in the shaft portion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit, under 35 U.S.C. §119(e), of the filing date of U.S. provisional application Ser. No. 60/571,731 entitled “Irrigated Catheter,” filed May 17, 2004, which is hereby incorporated herein by reference in its entirety. 
     
    
     FIELD OF INVENTION  
       [0002]    The invention relates generally to methods and apparatus for irrigating an electrode of an electrophysiology catheter. 
       BACKGROUND  
       [0003]    The human heart is a very complex organ, which relies on both muscle contraction and electrical impulses to function properly. The electrical impulses travel through the heart walls, first through the atria and then the ventricles, causing the corresponding muscle tissue in the atria and ventricles to contract. Thus, the atria contract first, followed by the ventricles. This order is essential for proper functioning of the heart. 
         [0004]    In some individuals, the electrical impulses of the heart develop an irregular propagation, disrupting the heart&#39;s normal pumping action. The abnormal heartbeat rhythm is termed a “cardiac arrhythmia.” Arrhythmias may occur when a site other than the sinoatrial node of the heart is initiating rhythms (i.e., a focal arrhythmia), or when electrical signals of the heart circulate repetitively in a closed circuit (i.e., a reentrant arrhythmia). 
         [0005]    Techniques have been developed which are used to locate cardiac regions responsible for the cardiac arrhythmia, and also to disable the short-circuit function of these areas. According to these techniques, electrical energy is applied to a portion of the heart tissue to ablate that tissue and produce scars which interrupt the reentrant conduction pathways or terminate the focal initiation. The regions to be ablated are usually first determined by endocardial mapping techniques. Mapping typically involves percutaneously introducing a catheter having one or more electrodes into the patient, passing the catheter through a blood vessel (e.g. the femoral vein or artery) and into an endocardial site (e.g., the atrium or ventricle of the heart), and deliberately inducing an arrhythmia so that a continuous, simultaneous recording can be made with a multi-channel recorder at each of several different endocardial positions. When an arrythormogenic focus or inappropriate circuit is located, as indicated in the electrocardiogram recording, it is marked by various imaging or localization means so that cardiac arrhythmias emanating from that region can be blocked by ablating tissue. An ablation catheter with one or more electrodes can then transmit electrical energy to the tissue adjacent the electrode to create a lesion in the tissue. One or more suitably positioned lesions will typically create a region of necrotic tissue which serves to disable the propagation of the errant impulse caused by the arrythromogenic focus. Ablation is carried out by applying energy to the catheter electrodes. The ablation energy can be, for example, RF, DC, ultrasound, microwave, or laser radiation. 
       SUMMARY OF THE INVENTION 
       [0006]    One embodiment of the invention is directed to an electrophysiology catheter comprising a shaft portion including a fluid passage to conduct fluid, an electrode coupled to a distal end of the shaft portion, and a handle portion coupled to a proximal end of the shaft portion. A portion of the fluid passage defines an opening in the shaft portion, and the opening is constructed and arranged such that when fluid is conducted through the fluid, at least some of the fluid will contact the electrode after passing through the opening in the shaft portion. 
         [0007]    Another embodiment of the invention is directed to an electrophysiology catheter comprising a shaft portion comprising a fluid passage, a fluid reservoir coupled to the fluid passage, and a plurality of channels coupled to the fluid reservoir. The fluid passage has a first diameter and the reservoir has a second diameter that is larger than the first diameter. The electrophysiology catheter further comprises an electrode coupled to a distal end of the shaft portion and a handle portion coupled to a proximal end of the shaft portion. Each channel of the plurality of channels coupled to the fluid reservoir defines an opening in the shaft portion configured and arranged such that fluid exiting the channel through the opening will contact the electrode. 
         [0008]    A further embodiment of the invention is directed to an electrophysiology catheter comprising a shaft portion comprising a fluid passage and a channel coupled to the fluid passage, wherein the channel defines an opening in the shaft portion. The electrophysiology catheter further comprises an electrode assembly coupled to the shaft portion and movable in a longitudinal direction along the shaft portion. The electrode assembly comprises an opening and is positionable such that fluid may flow from the channel through both the opening in the shaft portion and the opening in the electrode assembly. The electrophysiology catheter further comprises a handle portion coupled to a proximal end of the shaft portion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like reference character. For purposes of clarity, not every component may be labeled in every drawing. In the drawings: 
           [0010]      FIG. 1A  illustrates a portion of a catheter according to one embodiment of the invention; 
           [0011]      FIG. 1B  illustrates a view of the distal end of the catheter shown in  FIG. 1A ; 
           [0012]      FIG. 2A  illustrates a portion of a catheter according to another embodiment of the invention; 
           [0013]      FIG. 2B  illustrates a view of the distal end of the catheter shown in  FIG. 2A ; 
           [0014]      FIG. 3A  illustrates a portion of a catheter according to another embodiment of the invention; 
           [0015]      FIG. 3B  illustrates a view of the distal end of the catheter shown in  FIG. 3A ; 
           [0016]      FIG. 4  illustrates a portion of a catheter according to another embodiment of the invention; 
           [0017]      FIGS. 5A-C  illustrate one exemplary method for constructing a catheter in accordance with the embodiment of  FIG. 4 ; 
           [0018]      FIG. 6A  illustrates a portion of a catheter according to another embodiment of the invention; 
           [0019]      FIG. 6B  illustrates a view of the distal end of the catheter shown in  FIG. 6A ; 
           [0020]      FIG. 7A  illustrates a side view of portion of a catheter according to a further embodiment of the invention; 
           [0021]      FIG. 7B  illustrates top view of the distal end of the catheter shown in  FIG. 7A ; 
           [0022]      FIG. 8A  illustrates a side view of a portion of a catheter according to another embodiment of the invention; 
           [0023]      FIG. 8B  illustrates top view of the distal end of the catheter shown in  FIG. 8A ; 
           [0024]      FIG. 9  illustrates a portion of a catheter according to another embodiment of the invention; and 
           [0025]      FIG. 10  illustrates a portion of a catheter according to another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    To effectively treat a cardiac arrhythmia, a lesion having a sufficient size and depth must be created at a chosen location in the heart. It is known that for a given electrode size and tissue contact area, the size of a lesion created by radio frequency (RF) energy is a function of the RF power level and exposure time. At higher power levels, however, the exposure time can be limited by an increase in impedance that occurs when the temperature at the electrode-tissue interface approaches 100° C. One way of maintaining the temperature at the electrode-tissue interface below or equal to this limit is to irrigate the ablation electrode with an irrigation fluid such as saline. The saline provides convective cooling, which controls the electrode-tissue interface temperature and thereby prevents an increase in the impedance. Various embodiments of a catheter having an irrigated ablation electrode will now be described. 
         [0027]      FIGS. 1A and 1B  illustrate a first embodiment of the invention.  FIG. 1A  illustrates a catheter  2  comprising a shaft  1  having an ablation electrode  3  coupled at a distal end thereof. The shaft  1  includes an opening  5  on a distally facing surface  7  of the shaft  1 . A fluid  9 , such as saline, may be released from the shaft  1  via opening  5  and may be directed towards the electrode  3  to promote convective cooling of the electrode  3 . A groove  11  is included on a portion of electrode  3  that is adjacent to the opening  5  so as to channel fluid exiting opening  5  along the electrode  3 . The groove  11  may be configured such that the fluid  9  is directed towards portions of the electrode  3  where cooling is desired. 
         [0028]      FIG. 1B  illustrates a view of the distal end of the catheter  2 . As shown, three openings  5  are included on the distal facing surface  7  of the shaft  1 , and three corresponding grooves  11  are included on the electrode  3  adjacent openings  5 . However, it should be appreciated that the invention is not limited in this respect, and that different numbers of grooves and/or openings (e.g., two, four, five, six, or some other number of grooves/openings) may alternatively be used. Further, the number of grooves  11  and openings  5  need not be the same. For example, no grooves need be included on the electrode  3 . In addition, the illustrated configurations of openings  5  and grooves  11  are merely exemplary. Although openings  5  are shown as semicircular, these openings may alternatively be circular, linear, oval, or another suitable shape. In addition, while groove  11  is shown as having a generally semicircular cross section, the groove  11  may assume other configurations. Specifically, the groove  11  need not be uniform along the length of electrode  3 . For example, only a proximal portion of electrode  3  may include grooves, while a distal portion of the electrode  3  may include no grooves. 
         [0029]      FIGS. 2A and 2B  illustrate another embodiment of the invention. As shown in  FIG. 2A , catheter  14  comprises a shaft  13  and an electrode  15  coupled at a distal end thereof. Shaft  13  has a larger diameter than that of electrode  15 . Thus, shaft  13  includes a distal facing surface  17  at the interface of the shaft  13  and electrode  15 . An opening  19  is provided on the surface  17  from which fluid  21  may be released. The fluid  21  may be channeled by a groove  23  on the electrode  15  to direct the fluid  21  towards desired portions of the electrode  15 . 
         [0030]      FIG. 2B  illustrates a view of the distal end of the catheter  14 . As shown, three openings  19  are included on the distal facing surface  17  of the shaft  13 , and three corresponding grooves  23  are included on the electrode  15  adjacent openings  19 . As with the embodiment of  FIGS. 1A-1B , it should be appreciated that the number of grooves  23  and openings  19  illustrated in  FIGS. 2A-2B , and the configurations of such grooves and openings, is merely exemplary and that other implementations are possible. 
         [0031]      FIGS. 3A and 3B  illustrate a further embodiment of the invention. The embodiment of  FIGS. 3A and 3B  is similar to that of  FIGS. 2A and 2B , except that the openings that are provided for the release of irrigation fluid are located on the catheter shaft at a radius outside that of the ablation electrode.  FIG. 3A  illustrates a catheter  25  comprising a shaft  27  and an ablation electrode  29  coupled at a distal end thereof. A distal facing surface  31  of the catheter shaft  27  includes a plurality of openings  33  that release fluid  30  about ablation electrode  29 . Although electrode  29  is not shown as including any grooves, grooves may be included on the electrode  29  to direct the fluid released from openings  33 , if desired. 
         [0032]      FIG. 3B  illustrates a view of the distal end of the catheter  14 . As shown, four circular openings  33  are included on the distal facing surface  31  of the shaft  27 . However, the number of openings  19  and the configuration of the openings  19  shown in  FIG. 3B  is merely exemplary. For example, a different number of openings or differently shaped openings may alternatively be provided in accordance with this embodiment. 
         [0033]      FIG. 4  illustrates another embodiment of the invention. According to this embodiment, fluid openings are provided in the portion of the surface of the catheter shaft that is substantially cylindrical.  FIG. 4  illustrates a catheter  35  including a shaft  37  having an ablation electrode  39  at a distal end thereof. Electrode  39  has a diameter that is approximately equal to a diameter of the shaft  37 . Shaft  37  includes an outer surface  41  having a substantially cylindrical shape. An opening  43  is provided in the surface  41  for the release of irrigation fluid  45 . The opening  43  may be configured such that the irrigation fluid  45  is generally directed towards the distal end of catheter  35  (i.e., towards ablation electrode  39 ). If desired, grooves may also be included in the ablation electrode  39  to direct the irrigation fluid  45  as it exits opening  43 . 
         [0034]      FIGS. 5A-5C  illustrate one exemplary method for constructing a catheter in accordance with the embodiment of  FIG. 4 . The catheter  49  of  FIG. 5A  is substantially the same as the catheter  35  of  FIG. 4 , however, a distal portion  47  of the shaft  37  is formed of epoxy. As shown in  FIG. 5B , a channel  51  in the distal portion  47  of the shaft  37  is coupled between an opening  33  in the shaft and a reservoir  53  disposed within the shaft. The reservoir  53  is in turn coupled to a fluid lumen  55  disposed along a central longitudinal axis of the catheter  49 . 
         [0035]    The fluid lumen  55  may conduct irrigation fluid (e.g., saline) into reservoir  53 , and fluid may exit the shaft  37  from the reservoir  53  via the channel  51  and opening  33 . It should be appreciated that while only one channel  51  and corresponding opening  33  is shown in catheter  49 , a plurality of channels  51  and corresponding openings  33  may be provided. For example, a plurality of channels  51  may be coupled to the reservoir  53  and may be associated with corresponding openings  33  in the outer surface  41  of the shaft  37 . Although not illustrated, it should be appreciated that a catheter handle may be provided at a proximal end of the shaft  37 . Fluid may be introduced into the fluid lumen  55 , for example, via a port provided on or near the handle. In addition, while only a single fluid lumen  55  is illustrated, a plurality of fluid lumens may be used to conduct fluid to openings  33 . For example, each opening  33  may be associated with a corresponding fluid lumen that runs the length of the shaft  37 , and reservoir  53  may be eliminated. 
         [0036]    The distal portion  47  of shaft  37  may function to attach the electrode  39  to the remainder of the shaft  37 . In addition, the distal portion  47  may be moldable such that channels  51  may be formed therein. It should be appreciated that while the distal portion  47  is described as being formed of epoxy, other adhesive materials through which channels may be formed may also be suitable.  FIG. 5C  illustrates a method of forming the channel  51  in the distal portion  47  of shaft  37 . In particular,  FIG. 5C  illustrates a cylindrical rod  57  that may be used to form channels in the epoxy of distal portion  47 . The rod  57  may be disposed within distal portion  47 , between the reservoir  53  and the exterior of the shaft  37 , during hardening of the epoxy used to form the distal portion  47 . It should be appreciated that the rod  57  may be solid or have a tubular shape or have any other configuration that enables channels  51  to be formed. 
         [0037]      FIGS. 6A and 6B  illustrate a further embodiment of the invention. According to this embodiment, the ablation electrodes includes protrusions, each having a fluid channel therein.  FIG. 6A  illustrates a catheter  59  comprising a shaft  61  and an ablation electrode  63  coupled at a distal end thereof. The electrode  63  includes a plurality of protrusions  65 , each having an irrigation channel  67  therein. Each irrigation channel  67  defines an opening  69  at a surface of the electrode  63 . The openings  69  release fluid  71  about the ablation electrode  63 . Although electrode  63  is not shown as including any grooves, grooves may be included on the electrode  63  to direct the fluid released from the openings  69 , if desired. Each irrigation channel  67  in electrode  63  may be coupled to a fluid lumen  73  in shaft  61  (as shown for one fluid lumen  73  in  FIG. 6A ). Fluid lumen  73  conducts fluid along the length of the catheter shaft  61  to the ablation electrode  63 . 
         [0038]      FIG. 6B  illustrates a view of the distal end of the catheter  59 . As shown, three protrusions  65  and three corresponding openings  69  are included on the ablation electrode  63 . However, the number of openings  63  and protrusions  65  shown is merely exemplary. Moreover, the configuration of the openings  63  and protrusions  65  shown in  FIG. 6B  is merely exemplary. For example, a different number of openings and/or protrusions and differently shaped openings and/or protrusions may alternatively be provided in accordance with this embodiment. 
         [0039]      FIGS. 7-10  illustrate embodiments of the invention that include an irrigated movable electrode.  FIGS. 7A and 7B  illustrate a side view and top view of a catheter  77  comprising a shaft  79  and an ablation electrode  81  movably coupled to the shaft  79 . For example, the electrode  81  may be slid longitudinally along the shaft  79 . Exemplary mechanisms for moving the electrode are described in U.S. Pat. No. 6,178,354 to Gibson, U.S. Pat. No. 6,461,356 to Patterson, and U.S. Pat. No. 6,464,698 to Falwell, each of which is assigned to C.R. Bard Inc. and incorporated herein by reference. The shaft  79  includes a fluid lumen  87  that conducts fluid along the length of the catheter shaft  79 . The shaft  79  further includes a plurality of irrigation channels  85  coupled to the fluid lumen  87 . Each irrigation channel  85  defines an opening  83  at a surface of the shaft  79 . The openings  83  release fluid  89  along the shaft  79  and about the ablation electrode  81 . Electrode  81  may be solid such that the openings  83   a  obscured by electrode  81  at a given position of the electrode do not release fluid. Alternatively, electrode may be hollow such that the openings  83   a  obscured by electrode  81  at a given position of the electrode release fluid into the electrode to cool the electrode from within. The fluid may also be withdrawn from the electrode (e.g., via a movable lumen coupled thereto) as in “closed circuit” cooled electrode configurations. 
         [0040]      FIGS. 8A and 8B  illustrate an embodiment of the invention that is similar to the embodiment of  FIGS. 7A and 7B , but wherein the movable electrode includes openings for the release of irrigation fluid. Catheter  91  comprises a shaft  79  and an ablation electrode  93  movably coupled to the shaft  79  in the manner discussed in connection with  FIGS. 7A-7B . The shaft  79  includes a fluid lumen  87  that conducts fluid along the length of the catheter shaft  79 , and a plurality of irrigation channels  85  coupled to the fluid lumen  87 . Each irrigation channel  85  defines an opening  83  at a surface of the shaft  79 . The openings  83  release fluid  97  along the shaft  79  and about the ablation electrode  93 . Electrode  93  also includes openings  95  that release fluid  97  about the ablation electrode. Electrode  93  may be hollow such that fluid  97  passes through openings  83  in the shaft into the electrode  93  and then exits through openings  95  in the electrode  93 . Alternatively, channels in the electrode  93  may correspond with channels in the shaft  79  such that when the electrode  93  is properly positioned, fluid flows from the channels  85  in the shaft into channels in the electrode  93  that are coupled to openings  95 . The openings  95  in the electrode  93  may assume a number of different configurations. The openings  95  may be included about the circumference of the electrode  93  or on one side of the electrode  93 . The openings  95  may also be in any pattern or number on the electrode  93 . 
         [0041]      FIGS. 9 and 10  illustrate further embodiments of a catheter comprising a movable electrode. The catheters of  FIGS. 9 and 10  are operable in substantially the same manner as the catheter of  FIGS. 8A and 8B , but include electrodes having different configurations than that of  FIGS. 8A and 8B . The catheter  99  of  FIG. 9  comprises a shaft  79  and an ablation electrode  101  movably coupled to the shaft  79  in the manner discussed in connection with  FIGS. 7A-7B . Electrode  101  has a dumbbell shape such that the diameters of the electrode at the longitudinal ends of the electrode are greater than the diameter at the center of the electrode. The shaft  79  includes a plurality of openings  83  that release fluid  103  along the shaft  79  and about the ablation electrode  101 . Electrode  101  also includes openings  105  that release fluid  103  about the ablation electrode  101 . Electrode  101  may be hollow such that fluid  103  passes through openings  83  in the shaft  79  into the electrode  101  and then exits through openings  105  in the electrode  101 . Alternatively, channels in the electrode  101  may correspond with channels in the shaft  79  such that when the electrode  101  is properly positioned, fluid flows from the channels in the shaft into channels in the electrode  101  that are coupled to openings  105 . The openings  105  in the electrode  101  may assume a number of different configurations. The openings  105  may be included about the circumference of the electrode  101  or on one side of the electrode  101 . The openings  105  may also be in any pattern or number on the electrode  101 . 
         [0042]    The catheter  107  of  FIG. 10  comprises a shaft  79  and an electrode assembly  109  movably coupled to the shaft  79  in the manner discussed in connection with  FIGS. 7A-7B . Electrode assembly  109  comprises electrodes  111  and  113  coupled to a sleeve  115 . One or both of electrodes  111  and  113  may be ablation electrodes. At least one electrode may be a mapping electrode. The sleeve  115  includes openings  117  between electrodes  111  and  113  that release fluid between the electrodes. The shaft  79  includes a plurality of openings  83  that release fluid  103  along the shaft  79  and about the electrode assembly  109 . A portion of sleeve  115  may form a reservoir about the shaft  79  such that fluid  119  passes through openings  83  in the shaft  79  into the reservoir then exits through the openings  117  in the sleeve  115 . Alternatively, channels in the sleeve  115  may correspond with channels in the shaft  79  such that when the sleeve  115  is properly positioned, fluid flows from the channels in the shaft into channels in the sleeve  115  that are coupled to openings  117 . The openings  117  in the sleeve  115  may assume a number of different configurations. The openings  117  may be included about the circumference of the sleeve  115  or on one side of the sleeve  115 . The openings  117  may also be in any pattern or number on the sleeve  115 . 
         [0043]    Having thus described several aspects of at least one embodiment of this invention, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description and drawings are by way of example only.