Electrode device

Abstract: The invention relates to an electrode device, for intracardiac stimulation and/or defibrillation of heart tissue and/or sensing heart signals in a patient, with a soft, flexible electrode cable with an outer coating of insulation containing at least one elongate conductor connected to an electrode arranged on the electrode cable. In order to attain an electrode device of this kind, which is constructively very simple and in which all the electrodes on the electrode cable can be applied to the heart wall in a very simple manner so the entire electrode surface faces the wall and firmly presses against same, it is proposed according to the invention that the electrode cable (4, 20, 22) be at least partially band-shaped.

Description: The device relates to an electrode device, for intracardiac stimulation and/or defibrillation of heart tissue and/or sensing heart signals in a patient, with a soft, flexible electrode cable with an outer coating of insulation containing at least one elongate conductor connected to an electrode arranged on the electrode cable. With the aid of e.g. a bipolar pacemaker electrode device, the heart can be stimulated and its activity sensed with the electrodes arranged on the electrode cable. For good sensing of heart activity and desired stimulation of the heart, it would be very advantageous if the electrodes pressed against the heart wall. This electrode application is possible with the use of fixation means which, virtually without exception, are arranged only near the electrode located at the distal end of the electrode cable. The other electrodes on the electrode cable are floatingly arranged in the heart. A fixation means of the said kind, which consists of backward pointing flukes, is known from US patent document 4 409 994. The flukes are to become embedded in the heart's trabeculae and will accordingly keep the electrode pressed against the heart wall. Flukes of this kind could penetrate into heart tissue, thereby damaging the myocardium. Another way to have the electrode press against the heart wall and which is non-traumatic is to use a relatively heavy electrode head, as is described in US patent document 3 911 928. Another electrode device using non-traumatic, a basket-shaped fixation means is known through US patent document 3 935 864. The basket-shaped means, which also serves as the electrode head, ultimately becomes coated with tissue and therefore affixed to the wall. The electrode cable for both these electrodes has a round cross-section. As a result of this shape, the distal electrode head also has a round shape, for the most part, so the arranged conductive surface is usually equally distributed on the electrode head, or the entire surface is conductive. This distribution of the conductive surface is because the cable can rotate on its longitudinal axis. The physician can therefore place the electrode head against the heart wall during implantation, so at least some conductive surface presses against that wall. Since parts of the conductive surface are not in contact with heart wall for stimulation, energy consumption could be needlessly heavy. As a rule, other electrodes arranged on the electrode cable also extend around the electrode cable, leading to the same problem, especially if these electrodes are used for stimulation. As previously noted, the shape of the electrode cable does not generally allow the electrode(s) arranged behind the distally located electrode to press against the heart wall but is/are floatingly arranged in the heart. One example of this is shown in the DE patent document 3 152 963. EP patent application 0 009 732 describes an additional pacemaker electrode device. For the atrial electrodes to press against surrounding heart wall, one section of the electrode cable is provided with branches forming a basket, said branches being equipped with electrodes. As a result of this construction, such an electrode device is complex and accordingly relatively expensive. It may also be hard to implant. The object of the invention is to achieve an electrode device of the above-described kind whose structure is very simple and in which all the electrodes on the electrode cable can be made to press against the heart wall in a very simple manner, so the entire surface of the electrode can face that wall and press firmly against it. This problem is solved when the electrode cable is band-shaped over at least part of its length. This shape gives the electrode cable sufficient torsional strength along the band-shaped sections to prevent the cable from twisting after implantation, and the flat shape is also easy to bend in the cable's longitudinal direction. This means that the experienced implanter can, after the distal end of the electrode cable has been placed in the ventricle, push the electrode cable a little further in, causing the electrode cable e.g. to bend in the atrium and/or the ventricle and pressing its electrodes against surrounding heart wall. It would be advantageous if the electrode were band-shaped along its entire length. The band shape would give the cable torsional strength preventing the electrodes from being twisted away from the wall. DE patent document 3 912 377, disclosing the features of the preamble of claim 1, describes a defibrillation electrode device consisting of an elongate electrode cable with a round cross-section which is pre-shaped in such a way that it helical in the unstretched position, thereby forming a patch-type electrode device. The electrode cable is equipped with a plurality of adjacent, outward-pointing, wing-like, electrically conductive parts to facilitate the positioning of the defibrillation electrode, in its helical configuration, on the round electrode cable against the external wall of a patient's heart. As a result of the said parts, this defibrillation electrode device has a relatively complex structure and is therefore expensive to make. According to one embodiment of the invention, it is proposed that the electrode cable be band-shaped in the area in which the electrode is arranged. The electrode cable can also be advantageously band-shaped elsewhere than in the area in which the electrode is arranged. The torsional strength conveyed by the electrode cable's band-shape in both these embodiments is relatively great, so the electrode does not twist out of the desired position after implantation. In one advantageous embodiment of the invention, it is proposed that the conductor be arranged with a wavy shape in the band-shaped part of the electrode cable. The electrode cable can then be stretched without damaging the conductor. In one embodiment, in which the electrode cable is equipped with at least two conductors, it is proposed according to the invention that the conductors be braided, at least in the band-shaped part of the electrode cable. In this manner, the torsional strength of the electrode cable can be further enhanced. According to the invention, the electrode can also be arranged on one side of the band-shaped part of the electrode cable. This would ensure that the entire electrode surface faces in the desired direction and presses against heart wall. According to one preferred embodiment of the invention, it is proposed that at least one longitudinal side of the band-shaped part of the electrode cable has an irregular shape, e.g. a zig-zag-shape, preferably along a section in the electrode area. During implantation, the irregularly shaped longitudinal side would become entangled in the heart's trabeculae and then serve as a fixation means. The band-shaped part of the electrode cable can also be advantageously provided with holes and/or pits, preferably in the electrode area. Tissue would grow into the holes or pits of this embodiment after the implantation, thereby achieving good fixation of the electrode cable. In one advantageous embodiment of the invention, it is proposed that the electrode cable be equipped along the band-shaped sections with channels, preferably arranged along the electrode cable's longitudinal sides, with wires, running in the said channels, which are attached to the distal end of the electrode cable and extend beyond the proximal end of the electrode cable. When one of the wires is pulled, or two are pulled simultaneously, the electrode cable can be maneuvered longitudinally and laterally. Additional advantages and details are set forth in the dependent claims. The invention will be now be described in greater detail, referring to the FIGURES in the attached drawings in which: FIG. 1 is a section through a heart with an electrode device implanted in it according to the invention; and FIGS. 2-10 are important parts of electrode devices which elucidate the invention in different embodiments. FIG. 1 shows a pacemaker electrode device 1 connected to a pacemaker 2 and applied in a patient's heart 3. The electrode device consists of a soft, flexible electrode cable 4 which, in this embodiment, is band-shaped along its entire length. The electrode cable 4 is provided with an external layer of insulation 5, and conductors (described below), running from the electrode cable's 4 proximal end and connected to separate electrodes arranged on the electrode cable 4, are embedded in the layer of insulation 5. In this embodiment, the electrode device 1 is equipped with four electrodes 6, 7, 8, 9, two of the electrodes 6, 7 being placed in such a way that they are arrayed in the atrium after the electrode device has been implanted. The other two electrodes 8, 9 are arranged at the distal end of the electrode cable 4 and placed in the ventricle. In FIG. 2 the proximal end of the electrode device 1 is shown with the electrode cable 4 and a pin 10 which is connectable to the pacemaker 2. The conductors 11 - 14 are clearly shown in this FIGURE, even though they are actually embedded in the electrode cable's 4 layer of insulation 5. The conductors 11 - 14, which are insulated from each other, run parallel to each other and are arranged in a wavy shape in the band-shaped electrode cable 4. This ensures that the conductors only straighten out when the electrode cable 4 stretches in its longitudinal direction, thereby preventing broken conductors. FIGS. 3 and 4 show that each conductor 11 - 14 is connected tc a separate electrode, the conductor 11 being connected to electrode 6, the conductor 12 to electrode 7, the conductor 13 to electrode 8 and the conductor 14 to the distal electrode 9. The electrode device's 1 electrode cable 4 can advantageously be implanted in the heart 3 via a vein using a known (and therefore not shown) catheter into which the electrode cable 4 is inserted. The catheter is removed after the electrode cable 4 has been introduced into the heart. In order to control the movements of an implanted electrode cable 4 in the heart 3, the electrode cable is equipped with channels 15, 16, preferably arranged along the longitudinal sides of the electrode cable 4. Wires 17, 18 running in the channels 15, 16 are connected to the distal end of the electrode cable 4 and extend beyond the proximal end of the electrode cable 4, as shown in FIG. 2. When one of the wires 17, 18 is pulled, or both are pulled simultaneously while the electrode cable 4 is kept from moving, the electrode cable 4 can be maneuvered laterally but especially longitudinally, causing the electrode cable to bend and assume a shape such as the one shown in FIG. 1. Since the electrode cable 4 is band-shaped, the cable can assume a curved shape in which it presses against the heart wall, and because the electrode cable resists twisting, the entire surface of the electrodes 6 - 9, if arranged on one side of the band-shaped electrode cable, will press against heart wall, even in the atrium. In the extended position, the wires 17, 18 can be affixed to the proximal end so the electrode cable remains in the described position. The operator can also make the electrode cable assume other shapes. An example of one such shape is the one shown with the dash-dotted line in FIG. 1, the described electrodes 6 - 9 being arranged at some other suitable location on the electrode cable 4. If the electrode device is intended for defibrillation of the heart, the defibrillation electrode is preferably arranged on the side of the band-shaped electrode cable facing away from the heart wall in order to prevent burn damage. FIG. 5 shows the distal end of a band-shaped electrode cable 4 according to the invention. This electrode cable 4 differs from the above-described cable by having irregularly shaped, e.g. zig-zag-shaped, longitudinal sides 19. These irregularly shaped longitudinal sides 19 are preferably arranged along a section in the area for the electrodes 8, 9 and serve as a fixation means for making contact with the heart's trabeculae. The electrode cable 4 can also be provided with irregularly shaped longitudinal sides along other sections of the electrode cable, preferably along a section in the area for some other electrode than the above-mentioned electrodes. The band-shaped electrode cable 4 can also be provided with holes and/or pits, preferably in the area for the electrodes 8, 9, as shown in FIG. 6. After heart tissue grows into them, these holes and/or pits serve to affix the electrode cable 4. In order to further ensure good fixation of the band-shaped electrode cable 4, a combination of irregularly shaped longitudinal sides 19 and holes and/or pits 26 is also conceivable. FIG. 7 shows that another electrode cable 20 according to the invention can be band-shaped only in the section(s) in which an electrode 21/electrodes (not shown) is/are arranged. This electrode cable can have a conventional, round cross-section with helical conductors, whereas conductors in the band-shaped section can be wavy. FIG. 8 shows that an additional electrode cable 22 according to the invention can be band-shaped elsewhere than in the section in which the electrodes are arranged. Only one electrode 23, ring-shaped in this embodiment, is shown in the FIGURE. This ring shape can be replaced with a conductive surface facing the heart after the electrode has been implanted. FIG. 9 shows a lateral view of the electrode cable 22 which clearly shows that parts of the electrode are band-shaped. Within the scope of the invention, an electrode cable (not shown here) can be devised so the cable's distal end with the electrodes has a round cross-sectional configuration, and the electrode cable is band-shaped along the section(s) in which the electrode(s) is/are arranged. FIG. 10 shows that the conductors 11 - 14 for electrodes, e.g. 6 and 7, in the band-shaped part of the electrode cable 4, 20, 22, can even be braided. In this embodiment, the conductors, each connected to a separate electrode, are naturally insulated against each other. The advantage of this embodiment is that the design increases the electrode cable's torsional strength. The electrode cables 20, 22 described in conjunction with FIGS. 7 - 9 can be equipped with channels, arranged along the longitudinal sides of the band-shaped sections, holding wires attached at the distal end of the electrode cables 20, 22 and extending beyond the proximal end of the electrode cables 20, 22. These electrode cables 20, 22 can accordingly be maneuvered in the same way as was described in conjunction with FIGS. 1 -4. With a band shape over at least part of its length, the electrode cable acquires torsional strength ensuring that the electrode always assumes a stable position after implantation. Moreover, the electrode cable can be devised in such a way that electrodes arranged behind the distal electrodes, e.g. in the atrium, can press against heart wall with the electrode facing towards or away from the wall.

Claims: An electrode device (1), for intracardiac stimulation and/or defibrillation of heart tissue and/or sensing heart signals in a patient with a soft, flexible electrode cable (4, 20, 22) with an outer coating of insulation (5) containing at least one elongate conductor (11 to 14) connected to an electrode (6, 7, 8, 9) arranged on the electrode cable, characterized in that the electrode cable (4, 20, 22) is band-shaped over at least part of its length. An electrode device according to claim 1, characterized in that the electrode cable (4) is band-shaped along its entire length. An electrode device according to claim 1, characterized in that the electrode cable (20) is band-shaped in the section in which the electrode (21) is arranged. An electrode device according to claim 1, characterized in that the electrode cable (22) is band-shaped elsewhere than in the section in which the electrode (23) is arranged. An electrode device according to any of claims 1 - 4, characterized in that the at least one conductor (11 - 14) is arranged with a wavy shape in the part of the electrode cable (4, 20, 22) which is band-shaped. An electrode cable according to any of claims 1 - 4, in which the electrode cable is provided with at least two conductors, characterized in that the conductors (11 - 14) are braided, at least in the part of the electrode cable (4, 20, 22) which is band-shaped. An electrode device according to claim 5, characterized in that the conductors (11 - 14) are individually insulated and connected to separate electrodes (6 - 9, 21, 23). An electrode device according to any of claims 1 - 3, 5 - 7, characterized in that the electrode (6 - 9, 21) is arranged on one side of the band-shaped part of the electrode cable (4, 20). An electrode device according to any of claims 1 - 6, characterized in that at least one longitudinal side (19) of the band-shaped part of the electrode cable (4) is irregularly shaped, e.g. zig-zag shaped, preferably along a section in the area in which the electrode (8, 9) is arranged. An electrode device according to any of claims 1 - 9, characterized in that the band-shaped part of the electrode cable (4) is provided with holes and/or pits (26), preferably in the area in which the electrode (8, 9) is arranged. An electrode device according to any of claims 1 - 10, characterized in that the electrode cable (4, 20, 22) is provided in the band-shaped sections with channels (15, 16), preferably arranged along the longitudinal sides of the electrode cable (4, 20, 22), and wires (17, 18), attached to the electrode cable's (4, 20, 22) distal end and extending beyond the electrode cable's (4, 20, 22) proximal end, run in the channels (15, 16).

Inventors: EKWALL CHRISTER, HIRSCHBERG JAKUB, HOEGNELID KURT, EKWALL, CHRISTER, HIRSCHBERG, JAKUB, HOEGNELID, KURT, Högnelid, Kurt
Applicants: ST JUDE MEDICAL, ST. JUDE MEDICAL AB
Application year: 1995
Main classification: A61N1
IPC codes: A61B5, A61N1