Unitary intravascular defibrillating catheter with separate bipolar sensing

Abstract: A cardioversion system includes a bipolar sensing circuit (80) with two sensing electrodes (20, 22), and a cardioversion circuit (72) with two spaced apart spring electrodes (24, 26). The sensing electrodes (20, 22) are spaced apart from one another but kept sufficiently close to one another for isolated, localized R-wave sensing. The sensing electrodes (20, 22) further are positioned remotely of the cardioversion electrodes (24, 26), to avoid post-shock abnormalities which otherwise would interfere with a timely R-wave sensing, to substantially prevent the discharge of an unnecessary cardioversion pulse after return of the heart to normal cardiac rhythm. One preferred version of the system is a unitary catheter (16) including a distal tip electrode (20) and ring electrode (22) as the sensing electrodes (24, 26), and two substantially larger, more proximal spring electrodes (24, 26) for defibrillation. Alternatively, the defibrillation electrodes (24, 26) and the sensing electrodes (20, 22) can be provided on two separate catheters. Yet another alternative involves providing one or more patch electrodes as defibrillation electrodes.

Description: BACKGROUND OF THE INVENTION This invention relates to body implantable medical devices, and more particularly to defibrillating catheters employing bipolar sensing. Heart disease is a major cause of deaths in the United States and in other industrial nations. Tachyarrythmias (rapid disturbances in cardiac electrical activity), in particular the conditions of ventricular tachycardia, ventricular flutter and ventricular fibrillation, are widely believed to be the primary cause of sudden deaths associated with heart disease. Atrial tachyarrythmic conditions, on the other hand, are not considered life threatening unless they lead to rapid ventricular disturbance. Recent experience confirms that tachyarrythmic conditions frequently can be corrected by applying relatively high energy electrical shocks to the heart, a technique often referred to as cardioversion. Cardioversion devices include implantable electronic stand-by defibrillators which, in response to the detection of an abnormally rapid cardiac rhythm, discharge sufficient energy through electrodes connected to the heart to de-polarize and restore the heart to normal cardiac rhythm. Cardioverting or defibrillation devices typically include means for monitoring heart activity as well as delivery of cardioversion energy. For example, U. S. Patent No. 3,942,536 (Mirowski et al) discloses an intravascular catheter with a cap electrode at the distal tip, a distal electrode including a plurality of rings near the tip, and a proximal electrode also consisting of a plurality of rings. The tip and distal electrodes are used to provide pacing pulses, while defibrillation pulses are provided using the distal and proximal electrodes. A probe is provided to sense pressure in the right ventricle, to initiate cardioversion upon sensing a pressure that does not exceed a predetermined threshold. U. S. Patent No. 4,355,646 (Kallok et al) is directed to a transvenous defibrillating lead with one tip electrode and three additional, annular electrodes. The tip electrode and the most distal of the annular electrodes are placed in the right ventricle and used to measure impedance changes in the ventricle. Defibrillating pulses are delivered across all four of the electrodes. A key factor in successful defibrillation by implantable devices is the timely and accurate detection of the R-waves, the relatively weak electrical signals produced by ventricular contraction. In particular, the sensing means (one or more electrodes) of the defibrillating device must be capable of quickly detecting abnormally high cardiac rhythm in order to trigger the defibrillation pulse. Perhaps more importantly, the sensing means preferably is able to confirm a successful defibrillation, i.e. a return to normal cardiac rhythm, as soon as possible after each defibrillation pulse. Otherwise, there is the danger of the device delivering an unnecessary and possibly harmful defibrillation pulse. The advantage of preventing unnecessary or undue defibrillation pulses is recognized in U. S. Patent No. 4,614,192 (Imran et al). Imran teaches an implantable cardiac defibrillator employing bipolar sensing, in particular a bipolar sensing electrode assembly including a distal tip electrode and a nearby ring electrode, along with two sensing and high voltage delivery electrodes, one in the superior vena cava and another in the form of a patch over the myocardium, near the apex of the heart. This system contemplates three separately implanted electrodes or groups of electrodes. A unitary intravascular multiple electrode catheter according to the preambles of claims 1 and 4 is disclosed in U. S. Patent No. 4,603,705 & GB-A-2 157 954 (Speicher et al). The catheter includes three electrodes: a distal tip electrode, an intermediate spring electrode and a proximal spring electrode. The tip and intermediate electrodes are used in pacing and sensing, while the intermediate and proximal spring electrodes are used to deliver defibrillation pulses. Use of a common lead for sensing and delivering defibrillation pulses, however, interferes with the timely sensing of R-waves. In particular, tissue proximate the cardioversion discharge electrodes temporarily loses much of its ability to conduct electrical impulses immediately after discharge, resulting in an effective suppression of the R-wave immediately following a defibrillation pulse. Thus, post-shock sensing abnormalities prevent an immediate sensing that the heart has returned to normal sinus rhythm in response to the defibrillation pulse, presenting the risk that another, unneeded defibrillation pulse will be delivered. Therefore, it is an object of the present invention to provide a unitary intravascular implantable device in which post-defibrillation pulse sensing abnormalities are substantially reduced or eliminated. Another object is to provide a unitary defibrillation catheter with sensing circuitry independent of the defibrillation circuitry and with increased spacing of sensing electrodes from the nearest defibrillation electrode, for more discrete and localized electrograms. Another object of the invention is to provide an implantable defibrillation device with a defibrillation pulse delivery system with electrodes and conductors suited for relatively high energy defibrillation, along with independent sensing circuitry including electrodes and conductors suited to sensing. Yet another object is to provide a unitary defibrillation catheter which simultaneously affords optimum spacing between bipolar sensing electrodes, between a pair of defibrillation electrodes, and between the most adjacent sensing and defibrillation electrodes. SUMMARY OF THE INVENTION To achieve these and other objects, there is provided a unitary intravascular cardioversion device as defined in the appended claims. In an embodiment the device includes an elongate, flexible and dielectric catheter body having a proximal end region, a distal end region and a lumen means formed in the body from the proximal end region to the distal end region. The device has a cardioversion circuit including a cardioversion electrode means mounted on the catheter body proximally of the distal region, and a flexible conductor means connected to the cardioversion electrode means, for conducting electrical pulses between the cardioversion electrode means and the proximal end region, and a cardioversion connector means near the proximal end region for electrically coupling the conductor means with a cardioversion pulse generating means, thereby to deliver cardioversion pulses to the cardioversion electrode means. The device further includes a cardiac sensing circuit including a first sensing electrode mounted on the catheter body at the distal end region, a first sensing conductor means connected to the first sensing electrode for detecting electrical pulses between the first sensing electrode and the proximal end region, a second sensing electrode mounted on the catheter body at the distal end region proximally of the first sensing electrode and spaced apart from the first sensing electrode by a predetermined first distance, a second flexible sensing conductor means connected to the second sensing electrode for detecting electrical pulses between the second sensing electrode and the proximal end region, and a sensing connector means near the proximal end region for electrically coupling the first and second sensing conductor means with a pulse sensing means, thereby to utilize the first and second sensing electrodes as a bipolar pulse sensing pair independent of the cardioversion circuit. Preferably, the first sensing electrode is a distal tip electrode at the distal end of the catheter body, and the second sensing electrode is a ring electrode surrounding the catheter body and spaced apart from the tip electrode a distance in the range of from one to twenty millimeters, preferably ten millimeters. The cardioversion means advantageously includes distal and proximal cardioversion electrodes in the form of flexible, electrically conductive coils. In this event, the conductor means includes a first cardioversion conductor coupled to the distal conversion electrode and a second cardioversion conductor coupled to the proximal electrode. Both cardioversion conductors are flexible and contained in the lumen means, with the cardioversion connector means then coupling both cardioversion conductors to the pulse generating means. Each of the proximal and distal cardioversion coils can have a length in the range of from 1 to 7.5 centimeters. The preferred spacing between the proximal sensing electrode or ring electrode, and the distal defibrillating electrode, is at least one centimeter. This ensures that heart tissue proximate and between the sensing electrodes is effectively isolated from the tissue subject to the defibrillation pulse. As a result the device affords accurate R-wave sensing immediately after applying a defibrillation pulse, substantially eliminating the possibility of charging for and delivering unnecessary defibrillation pulses after the heart has returned to normal sinus rhythm. A further advantage of the present invention is that it permits selection of the distance between the defibrillating electrodes for a preferred positioning of the distal defibrillating electrode, e.g. in the right ventricle near the apex, and of the proximal defibrillating electrode, e.g. high in the right atrium or within the superior vena cava. Total electrical independence of the sensing system from the defibrillation circuit permits simultaneous optimum separation of the tip and ring electrodes, the ring electrode and distal defibrillating electrode, and the two defibrillating electrodes, an advantage not attainable when a single electrode is utilized for defibrillation pulsing and sensing. A further advantage of the present invention resides in the ability to tailor electrodes and conductors specifically for the sensing system, and to tailor other electrodes and conductors specifically for the defibrillation circuit. The relatively high currents and voltages involved in the defibrillation circuit require relatively large surface area electrodes to reduce impedance, and conductors formed of drawn brazed strand (DBS) wires or other highly conductive material. The sensing system does not impose these requirements. A unitary catheter with independent sensing and cardioversion systems, in accordance with the present invention, permits a better impedance matching of the two sensing electrodes. Such catheter further allows selection of materials and component sizes customized to either sensing or cardioversion, for example multi-conductor tube (MCT) construction involving coaxial windings for defibrillation conductors, in combination with sensing conductors contained within a central lumen of the catheter. Another aspect of the present invention is a cardioversion and sensing system in which sensing electrodes are mounted on a sensing catheter for use in conjunction with a pair of cardioversion electrodes provided, possibly as coils, on a separate cardioversion catheter. The electrodes are placed in the heart, encompassing ventricular and atrial endocardial placement, intraparacardial placement and vascular positioning. Thus, in accordance with the present invention, a catheter system provides sensing electrodes in complete isolation from a defibrillation pulse delivery system, for substantially immediate R-wave sensing following the application of each defibrillation pulse. IN THE DRAWINGS For a further understanding of the above and other features and advantages, reference is made to the following detailed description and the drawings, in which: Figure 1 is a plan view of a unitary intravascular defibrillating catheter constructed in accordance with the present invention; Figure 2 is a sectional view of a portion of the catheter of Figure 1; Figure 3 is a sectional view illustrating the positioning of the catheter of Figure 1 within the heart; Figure 4 is a sectional view of a portion of an alternative embodiment catheter constructed in accordance with the present invention; Figure 5 is a plan view of another alternative embodiment of the invention comprising two leads separately implanted in the heart; and Figure 6 is a schematic view of another alternative example not according to the invention using patch electrodes for defibrillation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to the drawings, there is shown in Figure 1 a unitary intravascular defibrillation catheter 16 including an elongate and flexible catheter body 18 constructed of a dielectric material, for example silastic or polyurethane. Four electrodes are mounted to the catheter body, including a distal tip electrode 20 at the distal end of the body, a bipolar ring electrode 22, a distal spring electrode 24 and a proximal spring electrode 26. A plurality of tines 28 near the distal end of the catheter, formed of the dielectric material comprising the body, assist in the positioning and securing of the catheter during implant. Catheter body 18 further includes a reduced diameter distal tubing portion 30 which supports the tip and ring electrodes, a proximal reduced diameter tubing portion 32 between spring electrodes 24 and 26, and a sheath portion 34 encompassing the majority of the catheter length. A reinforcing member 36 provides a junction for sheath 34 and three lengths of electrically insulative tubing 38, 40 and 42. Tubing 38 contains a conductor 44 provided for transmitting electrical signals from distal spring electrode 24 to a pin 46. An electrically insulative boot 48 surrounds pin 46 and tubing 44. A conductor 50, contained within insulative tubing 42 and sheath 34, electrically couples proximal spring electrode 26 and a pin 52, with pin 52 and tubing 42 being surrounded by an electrically insulative boot 54. Similarly, a conductor 56 electrically couples ring electrode 22 with a pin 58, and a conductor 60 similarly couples tip electrode 20 with a pin 62. Pins 58 and 62 and conductors 56 and 60 are surrounded by an insulative plug 64 with boot portions 66 and 68. In use, catheter 16, particularly at plug 64 and boots 48 and 54, is electrically and mechanically coupled to a defibrillation control unit 70 including defibrillation pulse generating circuitry 72, represented schematically in Figure 1. Unit 70 includes a pair of receptacles 76 and 78 for receiving pin 46 and boot 48, and pin 52 and boot 54, respectively, thus to electrically couple spring electrodes 24 and 26 with defibrillation pulse generating circuitry 72. Boots 48 and 54 fit tightly within their respective receptacles to provide a positive fluid seal. Defibrillation unit 70 further includes pulse or heart rate sensing circuitry represented schematically at 80. A pair of sensing receptacles 82 and 84 receive plug 64, to electrically couple distal tip electrode 20 and ring electrode 22 with the sensing circuitry, with the boot portions of the plug member again providing a fluid seal. Further details of defibrillation control unit 70 are not discussed herein as they are known in the art and not particularly germane to the present invention. In short, the connection of pins 46, 52, 58 and 62 as described creates two independent electrical circuits: a sensing circuit including tip electrode 20 and ring electrode 22, and a defibrillation circuit including spring electrodes 24 and 26. The sensing circuit monitors heart electrical activity, in particular to sense tachyarrythmias. In response to such sensing, the pulse generating circuit delivers a defibrillating pulse to the heart across spring electrodes 24 and 26. As seen in Figure 2, tip electrode 20 is constructed of one or more filaments, preferably a thin wire 86 of platinum or a platinum iridium alloy. The wire is stretched, then crumpled and packed against the distal end of catheter body 18. A screen 88, also of platinum or a platinum alloy, is fastened to the periphery of the catheter body distal end and maintains the crumpled wire in place. For further information regarding this type of electrode, reference is made to U.S. Patent No. 4,156,429 (Amundson). So constructed, electrode 20 is highly porous, for example consisting of approximately twenty percent platinum alloy by volume, the remaining eighty percent being open to permit passage of bodily fluids through the tip electrode and to admit ingrowth of tissue, which assists in anchoring the tip electrode after implant. Tip electrode performance may be further enhanced by surface treatment to micro texturize the tip, as disclosed in U.S. Patent application Serial No. 325,764 filed March 20, 1989 and assigned to the assignee of this application published as US-A-5 074 313. This treatment substantially increases the reactive surface area of the tip. Conductor 60 includes a single wound coil 90 formed of a nickel alloy or other electrically conductive material permitting flexure. The exposed distal end of coil 90 is electrically and mechanically coupled to distal tip electrode 20. The remainder of the coil is surrounded by a flexible, dielectric sheath 92. The remaining conductors are similarly constructed. Conductor 56 includes a single wound coil 94 surrounded by a sheath 96 and with its exposed distal end coupled to ring electrode 22. The ring electrode is constructed of platinum, a platinum iridium alloy or other appropriate electrically conductive and body compatible material. The outer surface area of the ring electrode exposed to bodily tissue and fluids is in the range of from ten to fifty square millimeters, and more preferably is about the same in effective surface area as the tip. If desired, ring electrode 22 can be subject to sputtering or other surface treatment to impart microporosity. For accurate R-wave sensing, ring electrode 22 must be spaced apart from tip electrode 20 in the range of from one to twenty millimeters, with a particularly preferred spacing between these electrodes being about ten millimeters. Proximally of ring electrode 22 is a fitting 98 which surrounds distal tubing portion 30. Fitting 98 is joined to the distal end of spring electrode 24, and cooperates with a fitting 100 at the proximal end of spring electrode 24 to support the electrode. Distal spring electrode 24 can have a length of from 1 to 7.5 centimeters, and up to 15 centimeters if especially smooth. Preferably electrode 24 is 6 centimeters long, to provide a relatively large exposed surface area necessary for effective delivery of defibrillation pulses. Spring electrode 24 is spaced apart from ring electrode 22 a distance in the range of five to twenty millimeters, although generally a spacing of at least one centimeter is recommended to ensure that heart tissue used in sensing pulse rate, particularly tissue near ring electrode 22, is sufficiently distant from tissue affected by the defibrillation pulse to ensure a localized, isolated and therefore more accurate R-wave sensing. Proximally of spring electrode 24, a pair of fittings, one of which is shown at 102, support proximal spring electrode 26. Like spring electrode 24, spring electrode 26 is constructed of an electrically conductive and bodily compatible material such as titanium or platinum. Proximal spring electrode 26 can have a length in the range of 1 to 7.5 centimeters, and is preferably 3.8 centimeters long. The spacing between proximal and distal spring electrodes 24 and 26 preferably is about eleven centimeters, although a spacing of from six to fourteen centimeters has been found satisfactory. Tubing sections 30 and 32, spring electrodes 24 and 26 and sheath 34 cooperate to define a central lumen 104 running the length of the catheter from the distal tip to reinforcing member 36. Conductors 44, 50, 56 and 60 all are contained within lumen 104. Proximally of reinforcing member 36, each of the conductors is contained within its corresponding one of tubing sections 38, 40 and 42. Thus, the proximal tubing sections sheath, spring electrodes, and distal tubing sections form a lumen means in which the conductors are contained and thus isolated from bodily fluids. Catheter 16 is inserted intravenously, for example into the subclavian vein or the cephalic vein, and progressively moved toward the heart until the distal end reaches a selected cardiac chamber. As illustrated in Figure 3, catheter 16 preferably is inserted to position distal tip electrode 20 and ring electrode 22 in a right ventricle 106 of the heart 108, near the apex 110. Within the ranges for spacing and lengths discussed above, spring electrode 24 preferably is within the right ventricle when tip electrode 20 is positioned as described, with proximal spring electrode 26 located high in the right atrium 112 or in the superior vena cava 114. With the distal tip positioned as shown, the lead proximal end, still outside the body, is maneuvered to implant the distal tip into the endocardium. Once implanted, distal tip electrode 20, ring electrode 22, conductors 56 and 60 and sensing circuitry 80, cooperate to monitor electrical activity in the heart, in particular R-wave activity. Figure 4 shows an alternative design catheter 120 with a solid platinum or titanium tip electrode 122 and an annular electrode 124 near the tip electrode for bipolar R-wave sensing. A central lumen 126 of catheter 120 contains a pair of conductors 128 and 130 connected to tip electrode 122 and annular electrode 124, respectively. Conductor 128 includes a conductive single coil winding 132 surrounded by an insulative sheath 134 and exposed at its distal end for connection to the tip electrode. Similarly, conductor 130 includes a coil winding 136 surrounded by an insulative sheath 138 and exposed for its connection to the annular electrode. Electrodes 122 and 124 are mounted on a dielectric and flexible distal tubing section 140 of catheter 120. Defibrillation pulses are applied through a pair of spring electrodes, a distal spring electrode 142 and a proximal spring electrode 144. The distal spring electrode is supported between a pair of fittings 146 and 148 at its opposite ends. Spring electrode 144 is similarly supported between a pair of fittings, one of which is shown at 150. For transmission of cardioversion pulses between spring electrodes 142 and 144, multi-filament conductors 152 and 154 are connected to electrodes 142 and 144, respectively, and also are electrically coupled to a pulse generator, not shown. Each of conductors 152 and 154 includes a plurality of individual electrically conductive filaments arranged in parallel, helical paths about the center of catheter 120. More particularly, conductor 152 includes filaments 152a, 152b and 152c, embedded in a length of insulative tubing 156 and thus electrically isolated from one another. At their distal ends, however, filaments 152a-c are exposed for electrical coupling to distal spring electrode 142. Similarly, conductor 154 includes filaments 154a, 154b and 154c. Through the majority of the length of conductor 154, the filaments are embedded in tubing 156 and thus are electrically isolated. The distal ends of the filaments are exposed near electrically conductive fitting 150, for electrical coupling to this fitting, illustrated as an alternative to a coupling of these filaments to spring electrode 144. Conductors 152 and 154 are laterally offset from one another over the entire length of tubing 156 and thus are electrically isolated from one another. The multi-filament construction of these conductors affords the desired flexibility in catheter 120 and the increased cross-sectional conductive area desired for handling high energy cardioversion pulses, while permitting the catheter diameter to remain relatively small. For a further explanation of the helically wound and isolated filament technique, reference is made to U. S. Patent No. 4,559,951 (Dahl et al). Figure 5 discloses yet another approach to separate sensing and defibrillating, employing a sensing catheter 160 and a defibrillation catheter 162, separately implantable within the right ventricle 164 of the heart 166. Sensing catheter 160 includes a tip electrode 168 and a ring electrode 170 near the distal tip but separated from the tube electrode by one to ten millimeters as previously explained. A pair of conductors, contained within insulative tubing 172, connect tip and ring electrodes 168 and 170 with pulse sensing circuitry near the proximal end of sensing catheter 160. Defibrillation catheter 162 includes a distal tip with tines 174 to assist in positioning the catheter upon implant. Proximal and distal spring electrodes 176 and 178 are mounted to catheter tubing 180 as explained in connection with Figures 2 and 4. A pair of conductors, one associated with each of spring electrodes 176 and 178, transmit defibrillation pulses to the spring electrodes. The conductors may be contained in a central lumen of the catheter, or alternatively helically wound as explained in connection with Figure 4. The sensing and defibrillating conductors are coupled to pulse generating and heart rate sensing circuitry by plugs 184 and 182, respectively. If desired, a patch electrode 186, at least equal to spring electrodes 176 and 178 in surface area, is secured to myocardial tissue and used in combination with the spring electrodes. As compared to the embodiments in Figures 2 and 4, the two-catheter system in Figure 5 of course requires a greater degree of skill and effort for implantation. On the other hand, it affords the added advantage of lateral or transverse orientation of the sensing electrodes from the defibrillation spring electrodes, to assure localized R-wave sensing remote from tissue subject to defibrillation, and further to permit optimum positioning of the sensing system and the defibrillation system, each fully independently of the other. Figure 6 schematically illustrates a an example not according to the invention employing a sensing catheter 190 having a tip electrode 192 and a ring electrode 194 spaced apart from the tip electrode by one to ten millimeters. A pair of conductors in the catheter are connected at their distal ends to electrodes 192 and 194, respectively, and at their proximal ends to pins 196 and 198. The pins are plugged into a defibrillation control unit 200 similar to unit 70 described in connection with Figure 1, to electrically couple the sensing electrodes to sensing circuitry in the control unit. The system further includes a pair of defibrillation electrodes in the form of patch electrodes 202 and 204, each of which is subcutaneously implanted in the thoracic region, e.g. secured to myocardial tissue. A conductor electrically couples patch electrode 202 with a proximal pin 206, and another conductor likewise couples patch electrode 204 to a proximal terminal pin 208. Pins 206 and 208 are plugged into control unit 200 to electrically couple the patch electrodes with a pulse generating circuit contained in the control unit. In this system, catheter 190 is provided solely for sensing and defibrillation is accomplished solely through the patch electrodes. Accordingly, this system is particularly useful in applications calling for maximum flexibility in the positioning of defibrillation electrodes, and in which a single catheter is preferred. Figures 7 and 8 illustrate another alternative, namely a bifurcated catheter 191 having a proximal spring cardioversion electrode 193 and a distal spring cardioversion electrode 195. Separate conductors are connected to spring electrodes 193 and 195 respectively, for transmitting cardioversion pulses between these electrodes. Near the distal end of catheter 191, an insulative boot forms a junction 197. A first extension 199, distally of the junction, supports a helical coil 201 used in a known manner to secure extension 199, and thus the remainder of the lead, to endocardial tissue. A second extension 203 of the catheter is directed generally proximally of junction 197 but inclined relative to the remainder of the catheter. Two sensing electrodes including a tip electrode 205 and a ring electrode 207, are supported on extension 203 and constructed as previously described. Separate conductors are connected to tip electrode 205 and ring electrode 207 respectively, each for transmitting electrical pulses between its associated sensing electrode and the proximal end region of catheter 191. As seen in Figure 8, catheter 191 preferably is inserted to position the distal tip of extension 199 in the right ventricle 208 of the heart 210, at the apex 212. Coil 201 is secured to endocardial tissue at the apex and thus maintains catheter 191 in the desired position. As noted previously in connection with other embodiments, distal spring electrode 195 preferably is within the right ventricle and proximal spring electrode 193 is in either the right atrium 214 or the superior vena cava 216. Extension 203 of the catheter is inclined away from the remainder of catheter 191 toward the septum 218, preferably to position tip electrode 205 and ring electrode 207 against the septum along the outflow tract, again resulting in sensing remotely of the area subject to cardioversion pulses. In view of the reverse bend in the conductors from the sensing electrodes at junction 197, it is recommended that these conductors be coils, with a known reverse winding technique used to negotiate the relatively sharp bend. In other respects, the electrodes and conductors can be constructed as previously described. Thus, in accordance with the present invention the R-wave sensing system is configured in complete electrical isolation from the cardioversion system, with a bipolar sensing electrode means interacting with endocardial tissue remote from tissue subject to the immediate electrical affects of cardioversion. Consequently post-shock sensing abnormalities encountered in connection with previous devices, particularly unitary catheters, are substantially eliminated. A more timely and accurate R-wave sensing is achieved, to substantially reduce the risk of generating unnecessary and possibly harmful cardioversion pulses after a return to normal sinus rhythm.

Claims: An intravascular cardioversion apparatus comprising an elongate flexible, dielectric catheter body (18; 120; 191); first and second sensing electrodes (20, 22; 122, 124; 205, 207) mounted at a distal end region of the catheter body, said second sensing electrode being spaced apart proximally of the first sensing electrode by a predetermined first distance; first and second flexible conductors (56, 60; 128, 130) connected to the first and second sensing electrodes respectively, for transmitting electrical pulses between said first and second sensing electrodes respectively and a pulse-sensing means (80) near a proximal end region of the catheter body; a first stimulating electrode (24; 142, 195) mounted on the catheter body at said distal end region; a second stimulating electrode (26; 144; 193) mounted on said catheter body proximally of said first stimulating electrode and spaced apart from the first stimulating electrode; a said sensing electrodes (20, 22; 122, 124; 205, 207), first and second conductors (56, 60; 128, 130) and sensing connector means (46, 52, 54, 62) forming part of a cardiac sensing circuit, a third (44; 152) flexible conductor connected to the first stimulating electrode for conducting electrical pulses between the stimulating electrodes and a cardioversion pulse generating means (72) proximate said proximal end of the catheter body; characterised in that a fourth flexible conductor (50, 154) is connected to the second stimulating electrode for conducting electrical pulses between the stimulating electrodes and a cardioversion pulse generating means (72) proximate said proximal end of the catheter body and said stimulating electrodes (24, 26; 142, 144; 193, 195) third and fourth conductors (44, 50; 152, 154) and cardioversion pulse generating means (72) form part of a cardioversion circuit electrically isolated from said sensing circuit, and in which the first and second stimulating electrodes (24, 26; 142, 144; 193, 195) are utilized as a cardioversion electrode pair; in that each of said first and second stimulating electrodes (24, 26; 142, 144; 193, 195) has a surface area at least three times the surface area of each of the first and second sensing electrodes (20, 22; 122, 124; 205, 207); and in that each of the sensing electrodes is spaced apart from each of the stimulating electrodes by a selected second distance so as to isolate tissue proximate and between the stimulating electrodes from tissue adjacent the sensing electrodes. Apparatus according to Claim 1, wherein the catheter body comprises a lumen means (104; 126) running substantially the length of the body. Apparatus according to Claim 2, wherein: said third conductor (44; 152); and said fourth conductor (50; 154) are each multi-filament conductors (152, 154); including a plurality of electrically conductive filaments wound about the centre of said catheter body (120) in parallel, helical paths; and wherein each of the filaments of said third and fourth conductors is embedded in said catheter body substantially over its entire length, and includes an exposed distal portion for electrical coupling with its associated one of said stimulating electrodes. An intravascular cardioversion apparatus comprising an elongate, flexible and dielectric sensing catheter body (160); first and second sensing electrodes (168, 170) mounted at a distal end region of the sensing catheter body and the second sensing electrode spaced apart proximally from the first sensing electrode by a first predetermined distance; first and second flexible conductors connected to the first and second sensing electrodes respectively, for transmitting electrical pulses between the sensing electrodes and a pulse-sensing means electrically coupled by a sensing connector means near a proximal end region of the sensing catheter body, said sensing electrodes, first and second conductors, sensing connector means and pulse-sensing means forming part of a cardiac-sensing circuit; a first stimulating electrode (178); a second stimulating electrode (176) disposed proximally of and spaced apart from the first stimulating electrode; a flexible third conductor connected to the first stimulating electrode; characterised in that a fourth conductor is connected to the second stimulating electrode, the third and fourth conductors being for transmitting electrical pulses between the stimulating electrodes (178, 176) and a cardioversion pulse-generating means; said stimulating electrodes, said third and fourth conductors and cardioversion pulse generating means forming part of a cardioversion circuit utilizing the first and second stimulating electrodes as a cardioversion electrode pair; and in that the cardioversion apparatus further comprises an elongate, flexible and dielectric cardioversion catheter body (162) having a proximal end region and a distal end region, said first and second stimulating electrodes being mounted to said cardioversion catheter body with said first stimulating electrode being mounted near the distal end region; and in that the cardioversion apparatus includes means for mounting said sensing catheter body and stimulating catheter body with their respective sensing electrodes (168, 170) and stimulating electrodes (178, 176) in spaced relationship to each other, with each of the sensing electrodes separated from each of the stimulating electrodes by a selected second distance so as to isolate tissue proximate and between the stimulating electrodes from tissue adjacent the sensing electrodes. Apparatus according to any one of the preceding claims wherein: said pulse sensing means (80) and said cardioversion pulse generating means (72) are contained within a body implantable defibrillation unit (70; 200). Apparatus according to Claim 4 wherein said stimulating electrodes (176,178) have surface areas at least three times the surface areas of said sensing electrodes (168,170). Apparatus according to any of Claims 1 to 3, wherein: said sensing electrodes (20, 22; 122, 124) are mounted on said catheter body (18; 120) distally of said first stimulating electrode (24; 142). Apparatus as in any of Claim 1 respectively Claims 4 to 7 further including: a lumen means (104; 126) formed in said catheter body (18; 120) respectively in said sensing catheter body and/or in said stimulating catheter body from said proximal end region to said distal end region. Apparatus as in any one of the preceding claims wherein: said first sensing electrode (20; 122; 168; 205) is mounted at the distal end of said catheter body respectively of said sensing catheter body and comprises a distal tip electrode (20, 122; 168; 205). Apparatus of Claim 9, wherein: said distal tip electrode (20; 122; 168; 205) includes a platinum alloy wire (86), and a platinum alloy screen (88) secured with respect to the distal end of said catheter body (18) respectively of said sensing catheter body, for maintaining the wire crumpled and packed against the catheter body (18). Apparatus of Claim 10, wherein: said distal tip electrode (20; 122; 168; 205) is microtexturised. Apparatus as in any of Claims 1 or 2, wherein: said second sensing electrode (22; 124; 207) has an outer exposed surface area in the range of from ten to fifty square millimetres. Apparatus of Claim 1, wherein: said first distance is within the range of from one to twenty millimetres. Apparatus of Claim 1, wherein: said first distance is from about 5 to about 10 millimetres. Apparatus of Claim 12, wherein: said stimulating electrodes (24, 26; 142, 144; 176, 178; 193, 195) respectively comprise distal and proximal electrically conductive coils. Apparatus of Claim 15, wherein: each of said proximal and distal coils (24, 26; 142, 144; 176, 178; 193, 195) has a length in the range of from 1 to 7.5 centimetres. Apparatus of Claim 16, wherein: said distal coil (24; 142) and said second sensing electrode (22) are separated from one another by said second distance in the range from five to twenty millimetres. Apparatus of Claim 17, wherein: said second distance between said second sensing electrode and said distal coil is approximately one centimetre. Apparatus as in any of Claims 1 or 2, wherein: each of said first, second, third and fourth conductor means (44, 50, 56, 60; 128, 130, 152, 154) comprises an electrically conductive coil winding (90, 94; 132, 136; 152 a-c, 154 a-c) housed in a dielectric sheath (92, 96; 134, 138, 156). Apparatus as in Claim 2 wherein: said lumen means (104; 126) includes a single lumen (104; 126) centrally of said catheter body (18; 120) Apparatus of Claim 20, wherein: said first, second, third and fourth conductor means (44, 50, 56, 60) are contained within said central lumen (104). Apparatus of Claim 20, wherein: said first and second conductor means (128, 130) are contained in said central lumen (126), and said third and fourth flexible conductor means (152, 154) comprise a plurality of filaments embedded in said catheter body (156). The apparatus as in any one of the preceding claims wherein: said sensing electrodes (20, 22; 122, 124; 205, 207) are substantially equal to one another in surface area, and said stimulating electrodes (24, 26; 142. 144; 193, 195) are substantially equal to one another in surface area. Apparatus as in Claim 1, wherein: said catheter body (191) is bifurcated to form first (199) and second (203) extensions, with said first extension (199) including a fixation means (201) for securing the catheter body (191) to endocardial tissue, and the sensing electrodes (205, 207) are mounted on said second extension (203). Apparatus of Claim 24, wherein: said stimulating electrodes (195, 193) are disposed proximally of a junction (197) of the first and second extensions (199, 203). Apparatus of Claim 24 wherein: said stimulating electrodes (195, 193) are disposed proximally of a junction (197) of the first and second distal extensions (199, 203) and said first sensing electrode (205) and said second sensing electrode (207) are mounted on said second distal extension (203).

Inventors: BACH STANLY M JR, DAHL ROGER W, LANG DOUGLAS J, SHAPLAND EDWARD J, BACH, STANLY M., JR., DAHL, ROGER W., LANG, DOUGLAS J., SHAPLAND, EDWARD J.
Applicants: CARDIAC PACEMAKERS INC, CARDIAC PACEMAKERS, INC.
Application year: 1991
Main classification: A61N1
IPC codes: A61N1