Abstract:
An electrode catheter used in an endocardial procedure to map cardiac electrical activity, heart wall position, heart wall motion and tissue viability. The electrode catheter has a flexible geometric shape for mapping any cardiac chamber and can be rotated within the chamber without being re-deployed. The electrode catheter is made from joining a tube with 4 to 256 wire leads having terminal ends and coiled electrodes. The tube either has holes or a longitudinal slit so that the coiled electrodes can protrude from the central cavity of the tube. The electrode catheter ends with a tip member that is attached to the tube by a swivel connector. The tip member has tines to allow for temporary stability when in contact with a cardiac wall. The electrode catheter is conformed to a flexible shape using a jig and heating process.

Description:
BACKGROUND OF INVENTION 
     1. Field of Invention 
     This invention relates to catheters or to electrodes arranged and constructed to be inserted into a body cavity. More specifically, the invention involves a catheter containing a large number of electrodes that can be inserted into a patient&#39;s heart to stimulate map cardiac electrical activity, heart wall position, heart wall motion and tissue viability for purposes of medical diagnosis and treatment of congestive heart failure, Bradycardia or tachyarrhythmias. The catheter may be used for other purposes as well. The invention also includes methods for manufacturing the device. 
     2. Background Art 
     Cardiovascular disease is the leading cause of death in the United States, Europe and Japan claiming more lives each year than all other diseases combined. The prevalence of this disease has prompted the development of numerous methods and devices to diagnose and treat various cardiac problems. One such device which aids in the diagnosis and treatment of heart disease is the electrode catheter. 
     In general, various types of catheters containing electrodes have been used to perform endocardial procedures for treatment and diagnosis of cardiac related problems. Examples of these devices include the stimulation catheter of Berkovits U.S. Pat. No. 3,825,015, the flow directed catheter of Blake et. al. U.S. Pat. No. 3,995,623, the multi-contact plunge electrode of Kline U.S. Pat. No. 4,172,451, the defibrillating catheter of Schulte et al. U.S. Pat. No. 5,545,205, the implantation catheter of Obino et al. U.S. Pat. No. 5,800,498 and the pacing lead delivery catheter of Bonner U.S. Pat. No. 6,055,457. 
     More specifically, in the diagnosis of cardiac conditions, electrode catheters have been used to map cardiac electrical activity. This mapping procedure is useful for the detection and treatment of conduction abnormalities and heart tissue deficiencies. Some cardiac mapping procedures are described in the article entitled: “Techniques of Intraoperative Electrophysiologic Mapping” in the American Journal of Cardiology, by John J. Gallagher, et al. which appeared in Volume 49 pages 221-240 January of 1982. 
     During a typical mapping procedure, a cardiac map is generated by recording the electric signals from the heart and depicting them spatially as a function of time. In an endocardial procedure, an electrode catheter is inserted into a chamber of the heart to measure signals directly by contact with the inside walls of the chamber. Accordingly, the number and placement of electrodes on or within the catheter is an important design consideration for maximizing effectiveness and efficiency for this internal procedure. 
     Several prior art electrode catheters have been used to generate cardiac maps. Hess U.S. Pat. No. 4,573,473 teaches a catheter with four electrode contacts on a flat planar surface. Gelinas et al. U.S. Pat. No. 4,522,212 teaches a catheter with three or more separated flexible leg electrodes. Chilson U.S. Pat. No. 4,699,147 and Edwards U.S. Pat. No. 5,471,982 define catheters with flexible electrodes that form a basket when extended. Giba et al. U.S. Pat. No. 5,997,526 discloses a shape memory catheter having electrode plates or bands. Unfortunately, such prior art devices are hard to deploy and complicated to manipulate. These difficulties often result in numerous unsuccessful treatment attempts as well as time consuming procedures. 
     OBJECTIVE AND SUMMARY OF THE INVENTION 
     In view of prior art deficiencies, an objective of the present invention is to design an improved cardiac electrode catheter for mapping cardiac electrical activity, heart wall position, heart wall motion and tissue viability. 
     It is also an objective to design an electrode catheter that is easily deployed, unobtrusive and highly maneuverable. 
     It is a further objective to provide a catheter and methods of producing the same having a large number of electrodes. 
     Additional objectives will be apparent from the following description of the invention. 
     Consistent with these objectives, a catheter constructed in accordance with this invention comprises a collection of wire leads disposed in a flexible tube. Each wire lead has a terminal end, an insulated portion and a non-insulated coiled electrode. The continuous coiled electrode preferably has at least one but no more than twenty-five turns. To prevent the coils from unraveling, each coiled electrode may be glued or fused together, for example, by a knitting or fusing procedure. Each wire lead in the collection is longitudinally staggered so that any one coiled electrode is close to but does not come in contact with the coiled electrode of any other wire lead. The tube is relatively narrow and has a proximal end and a distal end. The tube encloses the insulated portions of the collection of wire leads. Starting at the distal end of the tube, the coiled electrode of each wire lead protrudes from the tube at predetermined longitudinal positions and coils around the exterior of and is attached to the tube. The ends of the collection of wire leads protrude from the proximal end of the tube and are coupled to a suitable connector for connection to an apparatus which may be used to map the cardiac tissues, to monitor the condition of the heart, to apply appropriate therapy, etc. The electrode catheter has a tip member with flexible tines that is attached to the distal end of the tube by a swivel member. The fully assembled catheter can be shaped into various geometric configurations. In the preferred embodiment the catheter has a spiral form that correlates with the shapes of the internal chambers of the heart. 
     Several different tube configurations may be used in the catheter. In one embodiment, the tube has a longitudinal slit extending along its length, and is tapered on its distal end. The collection of wire leads is installed into the tube by opening the slit and inserting the collection of wires down the length of the tube so that the tube encompasses the insulated mid portions of the wire leads. Simultaneously, the tapered distal end of the tube is inserted through the coiled ends of the wire leads with the coiled end protruding out of the tube through the longitudinal slit. 
     In another embodiment, the tube has holes drilled through its exterior surface that are just large enough to accommodate the wire lead. The holes are drilled into the tube at an angle with respect to its longitudinal axis and may be in a generally helical pattern around the tube. The insulated portion of a wire lead is inserted into each hole starting with the terminal end. The entire wire lead is moved into the tube until only the coiled end is exposed. The installation of the wire leads may be assisted by pressurized air flow or fluid flow forced down the length of the tube from the distal end. The catheter can also be assembled by using a combination of the above listed methods. 
     A catheter made in accordance with this invention may also have a separate elongated cavity extending the length of the tubing reserved for a stylet. The stylet is used to implant the lead into the heart in the same manner as a standard pacemaker lead is implanted. The stylet is a solid metal or polymer rod small enough to fit inside the lead. 
     The stylet is long enough to extend from the insertion point on the proximal end of the lead to the distal tip. When inserted into the lead, the stylet serves to both stiffen and straighten the lead. Because the stylet straightens the lead (from it&#39;s preformed shape) the lead passes more easily through the veins. When the stylet is removed the lead deploys into the selected chamber of the heart. 
     As it will be clear from the detailed description, the catheter can be used to treat congestive heart failure or a number of conduction abnormalities of the heart such as CHF, Bradycardia, Tachycardia. For example, the catheter can be used to sequentially pace the heart of CHF patients so that a near normal contraction of the muscle takes place. This provides better contraction and increased blood flow. 
     For patients suffering from Bradycardia, the multi-electrode catheter allows the optimal location(s) within a heart chamber to be paced. Currently, leads are placed in the apex of the right ventricle and pacing from this location has detrimental long term effects on the heart muscle. The catheter of this invention will allow the doctor to select the best pacing site for each patient. 
     Fast heartbeats (tachyarrhythmias and fibrillations) can be treated with the multielectrode catheter by either preventing or terminating the event. Prevention uses the system&#39;s ability to identify and triangulate the location of a given event and pace the heart in areas that will disrupt the propagation of the arrhythmia. Termination involves delivering low voltage pulses to large areas of the heart, either simultaneously or in rapid sequence. These pulses will have the same effect as a high energy defibrillation pulse in capturing the heart and re-synchronizing the electrical activity of the heart but without the complications of a high energy shock. 
     Because this catheter is placed in the right side of the heart it allows more consistent and easier lead placement to pace the left ventricle; from the right ventricular outflow tract or the ventricular septum. The lead does not have to be threaded down the great cardiac vein with all of the associated complications and time consuming procedures. 
    
    
     DESCRIPTION OF DRAWINGS 
     FIG. 1 is depicts an elevational view of an embodiment of an electrode catheter constructed in accordance with this invention; 
     FIG. 2 depicts a single continuous wire lead for the catheter of FIG. 1; 
     FIG. 3 shows the staggering of a collection of wire leads for the catheter of FIG. 1; 
     FIG. 4 shows one embodiment of a tube used in the assembly of the electrode catheter of FIG. 1; 
     FIG. 5 shows a partially assembled electrode catheter using the tube of FIG. 4; 
     FIG. 6 shows a second embodiment of the tube for the electrode catheter of FIG. 1; 
     FIG. 7 shows a third embodiment for the tube for the catheter of FIG. 1; 
     FIG. 8 shows a cross-sectional view of the tube of FIG. 6 or  7 ; 
     FIG. 9 is a cross-sectional view of the installation of a wire lead through a hole in the tube of FIGS. 6,  7 ,  8  and an air pressure device; 
     FIG. 10 depicts a knitted coil from an electrode catheter; 
     FIG. 11 is a cross-sectional view of the tip member of the electrode catheter; 
     FIG. 12 shows one geometrically shaped embodiment of the electrode catheter within a cardiac chamber; 
     FIG. 13 is a flow chart depicting the steps in manufacturing the electrode catheter using a tube with a slit as shown in FIG. 4; 
     FIG. 14 is a flow chart depicting the steps in manufacturing the electrode catheter using a tube with holes as shown in FIGS.  6  and  7 ; 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 depicts an electrode catheter C constructed in accordance with this invention. The figure generally shows the assembled elements of the catheter C. The electrode catheter C includes a collection of wire leads  6  each having opposed terminal ends  2  and coiled electrodes  10 . The collection of wire leads  6  is encased in a tube  4 . The tube  4  has a tip member  12 . 
     FIG. 2 shows a single wire lead  6 . The wire lead  6  is made from an electrical conductor  14 . In the preferred embodiment, the electrical conductor is a MP35N, platinum or stainless steel wire with a 0.001 inch diameter. The wire lead has an insulated portion  16 . The insulating material in the preferred embodiment has a thickness of 0.001 inch or less. Such insulating materials may include ETFE, PFA, polyamide or polyurethane. Generally, the length of the wire lead must be coordinated with the length of the tube  4 . 
     The wire lead has a terminal end  18 . The terminal end  18  is attached to a connector for coupling electrically to a cardiac device so that the catheter can be used for the purposes described above. 
     The wire lead also has a coiled electrode  20  at the opposite end from the terminal end  18 . The coiled electrode  20  is formed of several helical spirals or coils of the conductor  14 . The diameter of each coil is sufficiently large to wrap around the exterior surface of the tube  4  of the catheter C. In the preferred embodiment, the coiled electrode has between one and ten coils. 
     Each catheter C requires a plurality of wire leads. FIG. 3 depicts several wire leads  24 ,  26 ,  28 , each having the same structure as wire lead  6 . The first wire lead  24 , second wire lead  26 , and third wire lead  28  are lined up in parallel fashion with the terminal ends  24 A,  26 A,  28 A on one end and the coiled electrodes  24 B,  26 B,  28 B on the other. To prevent a short or electrical interference between any two electrodes, the coiled electrodes  24 B,  26 B,  28 B are staggered or axially offset so that the first coiled electrode  24 B associated with the first wire lead  24  is adjacent to but does not overlap or come in contact with any other coiled electrode in the collection of electrodes. Similarly, the second coiled electrode  26 B of the second wire lead  26  and the third coiled electrode  26 B of the third wire lead  26  does not overlap or come in to contact with any other coiled electrode. 
     In the preferred embodiment of the electrode catheter,  128  wire leads are used. Accordingly, 128 coiled electrodes are staggered in a configuration similar to the three wire lead collection portrayed in FIG.  3 . However, the number of wire leads may be changed for example from 4 to 256, etc. 
     FIG. 4 depicts the tube used in the assembly of the electrode catheter C. The tube  4  has a proximal end  31  and a distal end  33 . The tube is a hollow cylindrical sheathing with an exterior surface  30  and defines a longitudinal central cavity  32 . The diameter of the cavity  32  of the tube must be large enough to contain the collection of wire leads  6 . The tube  4  has a longitudinal slit  34  and a taper  36  on its distal end  33 . The tube is manufactured from a material that is flexible and may have a shape memory that will force the tube  4  to return to a predefined shape after the tube is distorted. In the preferred embodiment, the tube is made from a shapeable thermoplastic polyurethane material and has an internal diameter of 0.045 inches and an external diameter of 0.060 inches. The length of the tube  4  is selected to insure that it can be used to position the electrodes in a patient&#39;s heart, or for any other desired purpose. 
     FIG. 5 depicts a portion of a partially assembled electrode catheter C using the tube  4  of FIG. 4 and a collection of wire leads  6  of FIG.  3 . The tube  4  is combined with the collection of wire leads  6  so that the insulated portion  16  of each wire lead  6  will be contained within the cavity  32  of the tube  4 . During assembly, the tapered distal end  36  extends through the coiled electrode  20  of each wire lead  6 . The coiled electrodes  20  are disposed outside the cavity  32  and extend through the longitudinal slit  34 . 
     The catheter C of FIG. 5 is assembled by positioning all the leads adjacent to each other and then pushing the tube  4  through the electrodes  20  as shown. The diameter of coils of the coiled electrodes  20  is selected to be slightly smaller than the outside diameter of tube  4  so that an interference fit is formed between the electrodes and the tube. 
     FIGS. 6 and 7 depict alternative embodiments of the tube used in the assembly of the electrode catheter C. In these figures, tubes  4 A,  4 B having a proximal end  31 , distal end  33 , exterior surface  30 , cavity  32  and generally being made from the same material and having the same internal and external diameters as the tube  4 . However, these embodiments of the tubes  4 A,  4 B have holes  44 ,  46 . The holes  44 ,  46  each extend at an angle through the exterior surface  30  and into the central cavity  32 . The holes  44 ,  46  have a diameter sufficiently large to receive one of the wire leads  6  including the insulating material  16 . 
     Due to the large number of holes  44 ,  46  needed to receive the wire leads and a need to keep the coiled electrodes closely placed, the holes  44  are disposed in patterns intended to preserve the structural integrity of the tube by increasing the separation between the holes and minimizing stress. FIG. 6 shows one such pattern. Tube  4 A has holes  44  arranged generally around the tube. In FIG. 7, sets of three or more holes  46  in tube  4 B are arranged in a generally helical pattern. Each set includes holes  46  arranged in a line parallel with the longitude axis of the tube. 
     Details of the holes  44 ,  46  are depicted in FIG.  8 . The holes  44 ,  46  are angled to reduce the resistance encountered when the wire leads are inserted through the holes  44 ,  46 . The holes  44 ,  46 , are preferably drilled through the exterior surface  30  to the central cavity  32 , each hole being angled away from the distal end  33  of the tube and towards the proximal end  31 . In the preferred embodiment, the angle  48  formed by the central axis of the hole  44  with the central longitudinal axis of the cavity  32  of the tube is about 60 degrees. This angle may vary from 15 to 90 degrees. 
     FIG. 9 depicts the installation of a wire lead  6  into a tube  4 A with holes  44 . The terminal end  18  of the wire lead  6  is inserted from the exterior surface  30  through the hole  44  into the central cavity  32  away from the distal end. Advantageously, a pipe  50  is inserted in the distal end  33  and supplies a pressurized air flow  52  in the direction of the proximal end  31  of the tube. The pressurized air flow  52  entrains the wire lead  6  into the central cavity  32  and draws the wire lead  6  down the length of the tube  4  away from the distal end  33  stopping when the coiled electrode  20  reaches the hole  44 . 
     FIG. 10 shows a coiled electrode  20  extending out through a hole  44  with the insulated portion  16  of the wire lead within the tube  4 A. In the completed assembly of the electrode catheter C, the coils  54  of the coiled electrode  20  are wrapped around the exterior surface  30  of the tube  4 A. Each coil  54  of the coiled electrode  20  are knit together or otherwise connected by a cross-bar  56  to keep the coils  54  from separating from the tube and to keep the coils  54  wrapped tightly together. In once embodiment, the coils  54  are knitted to each other or fused with a heat source such as an eximer laser. Thus, the cross-bar  56  between the coils  54  is formed by welds or a fusing of the coils  54 . In an alternative embodiment, the coils  54  are joined with an adhesive. 
     FIG. 11 depicts a cross-sectional view of the tip member  12 . The tip member serves as a cap for the end of the tube and as a surface for contact with the cardiac wall. Many possible versions of a tip member can be used. In the preferred embodiment, the tip member is comprised of a cardiac contact  60 , two or more flexible tines  62 , a mounting base  64  and a swivel connector  66 . The mounting base  64  has a cylindrical chamber  68 . The chamber  68  receives a round top portion  70  of the swivel connector  66  but is not affixed to permit the mounting base  64  to rotate around the top portion  70 . A narrow cylindrical mid-portion  72  of the swivel connector  66  extends outward from the internal chamber  68  through a central round aperture  74  in the mounting base  64 . A round bottom portion  76  of the swivel connector  66  having a diameter approximately the inside diameter of the tube is affixed within the distal end  33  of the tube with adhesive  78 , or welded thereto. 
     FIG. 12 shows a deployed electrode catheter  80 . The electrode catheter  80  is disposed within the chamber  82  and is arranged in a geometric shape appropriate for the desired purpose, such as mapping the cardiac chamber  82 . Generally the catheter  80  is shaped so that some or most of its electrodes are adjacent to or even touching the inner walls of the respective cardiac chamber. 
     FIG. 12 further shows the tip member  12  of the electrode catheter, after insertion into a cardiac chamber, engaging the cardiac wall. The flexible tines  62  provide a temporary means to stabilize the tip member on the cardiac wall. The swivel connector  66  allows the electrode catheter to be externally rotated while the tip member  12  maintains a stationary position. In this way, the electrode catheter can be used for various functions such as mapping, cardiac monitoring, pacing, and so forth. 
     FIGS. 13 and 14 summarize the steps involved in the assembly of the preferred embodiments of the electrode catheter as heretofore described. FIG. 13 defines the steps involved in making the electrode catheter using the tube  4  with a slit depicted in FIG.  4 . The assembly starts with forming the wire leads, step  90 , and forming a tube, step  94 . The wire leads are formed with the coiled electrodes by winding the wire leads into coils in step  91 . Each exposed coiled electrode  20  is separately knitted, step  100 , to join all of its coils  54 . The tube  4  formed in step  94 , is slit and tapered, step  96 , as shown in FIG.  4 . The slit and tapered tube, step  96 , is then combined, step  98 , with a staggered collection of wire leads so that the coiled electrodes  20  surround the exterior surface  30  of the tube  4  and the portion of the wire leads covered by insulated material  16  are contained within the cavity  32  of the tube  4 . Next, the tapered end is severed and the tip member is installed, step  102 . Finally, the electrode catheter is formed in a shaping process, step  104 , into a geometric configuration appropriate for a cardiac chamber by inserting the electrode catheter into a jig and then heating the assembly until the electrode catheter will generally maintain the jig&#39;s configuration. 
     The steps in the assembly of the alternative embodiment of the electrode catheter using the tube of FIG. 6 or  7  are summarized in FIG.  14 . The assembly process starts with wire leads  6 , step  106 , and a tube  4 A,  4 B, step  108 . The wire leads  6  of step  106  may be pre-made with coiled electrodes or may be coiled into coiled electrodes during the insertion step  112 . In a drilling step  110 , angled holes for each wire lead are drilled into the tube. In an insertion step  112 , each wire lead is entrained into the tube by inserting one terminal end  18  of a wire lead into each hole  44  and forcing the wire lead  6  down the length of the tube  4 A,  4 B with the assistance of a pressurized air flow  52  so that only the coiled electrode  20  extends from the hole  44 . After each wire lead  6  is separately inserted, in a knitting step  114 , each exposed coiled electrode  20  is separately knitted to join all of its coils  54 . Next, the tip member is installed, step  116 , and then the electrode catheter is given its shape, step  118 , by means of heating the electrode catheter in a jig.