Positive fixation device

Abstract: An implantable defibrillation electrode (110) including a conductive distal end portion and a non-conductive proximal end portion is provided with at least a major portion of the length of the distal end portion having a pre-configured shape and being resiliently deformable into a generally straight condition. The distal end portion includes distal and proximal ends and at least one (119) of those ends is hollow and has hook structure (133) shiftably supported therein for movement longitudinally thereof from a retracted position at least substantially contained within the hollow end (119) and an extended position at least substantially fully outwardly projected from the hollow end. Spring structure is provided for yieldingly biasing the hook structure from the extended position toward the retracted position and axial thrust developing structure is slidingly telescoped through the proximal end portion and operatively associated with the hook structure for exerting an axial thrust thereon from the terminal end of the proximal end portion in order to effect shifting of the hook structure from the retracted position to the extended position.

Description: The invention relates to an implantable defibrillation electrode according to the preamble of the main claim. Lately, deployable defibrillation leads have been developed which are implanted without the currently practised thoracotomy procedures. The implantation of these leads requires making a small incision in the chest to gain access to the pericardial space. The defibrillation leads are then threaded through the incision and into the pericardial space either alone or through the lumen of a thin walled guiding catheter. Once initially placed in his fashion, a deployment action is performed to expand the surface area of the lead. At this point, the lead is generally held against the myocardial surface by the pericardium. Because of the lubricious conditions which exist within that space, and the need to more precisely position the leads for defibrillation, lead fixation is required. Fixation to the pericardial sack is the safest approach since it completely avoids accidental laceration of the myocardial circulation. An implantable defibrillation electrode as mentioned in the preamble of the main claim, is known from the DE 27 36 275 A1. This known electrode comprises a flexible hollow cable and at least two fixing hooks used opposed to each other at an end of the electrode device. The hooks are biased by spring action into the opening position and are biased by a retraction spring into the interior of a hollow housing. The hooks may be moved by means of a mandrine out of the opening of the tubular housing. When in the retracted position, the hooks are completely enclosed in the tubular housing. U.S. Patent No. 3,814,104 describes a pacemaker lead which attaches to endocardial tissue by means of two gently curved hooks advanced from the lead by means of axial force applied by an internal stylet. The essentially straight hooks provide some degree of fixation but can allow the lead to be simply pulled from the tissue. Also, a special separate flexible catheter is required to force the hooks together if the device needs to be repositioned. U.S. Patent No. 4,858,623 also describes a pacemaker lead with an extendable hook retracted by a coil spring. It is felt that the violent contraction of the heart which results from a defibrillation shock may cause the dislodgement of this or any easily removable lead. The need for additional, special hardware for repositioning is also unattractive. In view of the above, it is an object of the present invention to provide an implantable defibrillation electrode, the fixation structure of which is effective to hook engage adjacent tissue and to draw the adjacent tissue laterally into engagement with that portion of the electro-catheter from which the hook is supported, whereby the fixation structure is carried by the distal end of the electro-catheter. The electrode according to the invention is specially designed for use as an internal defibrillator electrode, but also may be used as a pacing lead. The fixation device of the electrode according to the invention utilizes hooks that penetrate through the pericardium and return to the interior of the hollow housing of the electrode. Therefore, sharp and pointed objects embedded in the tissues are not left over. Furthermore, the fixation means are used in order to remain effective through the violent contractions experienced by the heart during initial defibrillation testing. Also the present invention is mainly described in connection with pericardial fixation, the invention with the fixing means can also be applied to myocardial tissue if knowledge of the local circulation is accurate. The electro-catheter of the invention may be positioned using routine implant techniques including the use of an internal stylet or an outer tubular catheter, each of which being withdrawable to effect deployment of a resilient deformable distal end electrode of predetermined shape. It is also an advantage of the implantable and internally deployable defibrillation electrode that it may be used to effect fixation of the electrode prior or subsequently to internal deployment of the electrode. Another advantage of the implantable and internally deployable defibrillation electrode of the invention is that the biasing action of the biasing means accomplishes the fixation action and is more readily operable to release and subsequently reestablish fixation in the event it is desired to shift the positioning of a deployed defibrillation electrode subsequent to initial fixation thereof. Advantagous embodiments of the invention are defined in the subclaim. Embodiments of the invention are now described in connection with the drawings in which: Figure 1 is a schematic fragmentary enlarged longitudinal vertical sectional view of the distal end of a deployable implantable defibrillation electrode and with the fixation structure thereof in a spring biased retracted position in solid lines and a partially extended position in phantom lines; This fixation structure is not part of the invention. Figure 2 is a schematic plan view of a first form of the deployed defibrillation electrode utilizing the fixation structure of Figure 1; Figure 3 is a schematic plan view of a second form implantable defibrillation electrode in a deployed condition and wherein the fixation structure of Figure 1 is incorporated in an intermediate length portion of the electrode at the proximal end of the deployable distal end; This fixation structure is not part of the invention. Figure 4 is a side elevational view of the implantable defibrillation electrode fixation structure according to the invention with portions of the tubular body of the electrode broken away and illustrated in section, the fixation hook thereof being in a retracted, shielded condition; Figure 4A is a distal end view of the structure illustrated in Figure 4 with alternate positions of the fixation hook shown in phantom lines; Figure 4B is a fragmentary elevational view similar to Figure 4 with the fixation hook being disposed in a fully extended position; Referring now more specifically to Figures 1 and 2 of the drawings, there may be seen an internally deployable electro-catheter referred to in general by the reference numeral 10 employing a deployable distal end portion 12 and a proximal end portion 14. The distal end portion 12, in Figure 2, is illustrated in its deployed pre-configured flat zig-zag shape, the entire length of the electro-catheter being flexible and the distal end portion 12 being capable of being straightened either through the use of an internal straightening stylet inserted thereinto from the proximal end portion 14 or an external flexible tubular catheter (not shown) of greater stiffness than the distal end portion 12. The precise electrical construction of the deployable end portion 12 may be of any suitable well known type. Suffice it to say that through leads extending the length of the electro-catheter, electrical energy is delivered from a pulse generator to the cardiac tissue of the patient via the conductive distal end portion 12 of the structure. The terminal distal end 16 comprises a dielectric (biocompatible polymer) tubular housing 19 and defines an endwise outwardly opening cylindrical cavity 18 into which the distal end 20 of a helical tubular spring 22 extending through the distal end portion 12 projects, the proximal end (not shown) of the spring 22 being anchored relative to the proximal end portion 14 in any convenient manner. The distal end 20 includes a stretchable diametrically enlarged portion 24 disposed within the cavity 18 terminating in a diametrically reduced terminal end 26 also disposed within the cavity 18. The portion 24 comprises axial thrust developing means for yieldingly biasing the terminal end 26 in one direction. The base end 28 of a reverse turned spring hook 30 is anchored to the terminal end 26 of the spring 22 and includes a reversed turned hook 30 on its free end 32 substantially fully contained within the cavity 18. After the electro-catheter has been inserted and positioned generally as desired for example the electro-catheter being inserted through the utilization of a tubular catheter, a fixation stylet (see Figure 4B) is associated with the proximal end portion 14 and inserted through the electro-catheter 10 for engagement with the interior of the terminal end 26 of the spring 22 in which the base end 28 of the spring hook 30 is anchored. The fixation stylet thereafter is actuated against the terminal end 26 in a fashion similar to a camera cable release to force the latter toward the open end of the cavity 18 to and past the phantom line position thereof illustrated in Figure 1 thus expanding the large diameter end portion 24 of the spring 22. Displacement of the terminal end 26 past the phantom line position of Figure 1 projects the bend 23 of the reversed turned hook 32 from the open end of the cavity 18 for lateral displacement therefrom and engagement of the free end 32 thereof with the tissue to which the terminal distal end 16 is to be fixed. Then, the fixation stylet is released to enable retraction of the hook 30 from the phantom line position thereof to the solid line position thereof to thereby draw the exterior of the terminal distal end 16 laterally into tight contact with the tissue engaged by the hook 30. Thereafter, the fixation stylet may be removed and the tubular catheter may be withdrawn from about the deployable end portion 12 to thereby enable the latter to deploy and assume the pre-configured shape thereof illustrated in Figure 2. With attention now invited more specifically to Figure 3, a modified form of electro-catheter is referred to in general by the reference 10' incorporating a deployable distal end portion 12' and a proximal end portion 14'. The electro-catheter 10' is of a design to be inserted through the utilization of a tubular catheter and the deployable distal end portion 12' thereof is in the form of a flat spiral coil. The electro-catheter 10' incorporates a tubular housing 19' corresponding to the tubular housing 19 defining the cavity 18. The housing 19' is serially disposed within the electro-catheter 10' between the proximal end portion 14' thereof and the deployable distal end portion 12' thereof. The internal structure of the housing 19' is substantially identical to the internal structure of the housing 19 in that a helical tubular spring 22' corresponding to the spring 22 has its distal end 20' projecting into the cavity 18' of the housing 19' and the base end 28' of a spring hook 30' corresponding to the spring hook 30 is anchored in the terminal end 26' of the distal end 20', the distal end 20' including an enlarged diameter end portion 24' corresponding to the end portion 24. The distal end portion 12' is, however, provided with a slot 29 through which the free end 32' of the spring hook 30' may be extended upon utilization of a fixation stylet, for example, of the camera shutter cable release type herein above referred to. Accordingly, the housing 19' of the electro-catheter 10' may be laterally anchored to suitable internal tissues through the utilization of a fixation stylet. In this manner, an intermediate portion of the electro-catheter 10' can be affixed to body tissue after the distal active end of the electrode is permitted to deploy into the pre-configured shape illustrated in Figure 3. With attention now invited to Figures 4, 4A and 4B, there may be seen a terminal distal end 16'' of an electro-catheter 10'' according to the invention which may be considered as substantially identical to the electro-catheter 10, except for the terminal distal end 16'' thereof. The electro-catheter 10'' includes an internal coil spring 22'' corresponding to the spring 20 equipped with a distal end 20'' incorporating an enlarged diameter end portion 24'' and a terminal end 26'', all of which are enclosed with a housing 19'', the distal terminal end of the housing 19'' being hollow and frusto conical as at 21 and provided with a partial spiral slot 23. The terminal distal end of housing 19'' is open as at 25 on its minor diameter end and the terminal end 26'' is projectable through the open end 25 and includes an end enlargement 27 which is retractable only partly into the open end 25. The terminal end 26'' has the base end of a curved hook 33 anchored thereto and the hook 33 projects outwardly through and is slidably received within the slot 23, the slot 23 extending less than 180 degrees about the terminal distal end 21. The housing 19'' comprises the terminal distal end of an electro-catheter such as the electro-catheter 10 in lieu of the terminal distal end 19 thereof. The electro-catheter 10'' would be designed for insertion in the same manner as the electro-catheter 10 and fixed in the desired position prior to deployment of the deployable distal end portion 12'' of the electro-catheter 10'' corresponding to the deployable distal end portion 12. In order to affix the terminal distal end 16'', after the electro-catheter 10'' has been positioned utilizing routine implant techniques such as a tubular delivery catheter, a fixation stylet 17, is inserted into the electro-catheter 10'' and associated with the proximal end portion thereof. Then, the fixation stylet is operated in a fashion similar to a camera cable release to lengthwise elongate the enlarged diameter end portion 24'' from the condition thereof illustrated in Figure 4 to the expanded condition thereof illustrated in Figure 4B, which movement causes the hook 33 to move from the end 37 of the slot 23 in which the hook 33 is retracted to the end 39 of the slot 23, in which position the hook 33 is fully extended, the terminal end 26'' being projected through the open end 25 of the terminal distal end 21. Thereafter, the fixation stylet may be released so that the spring biasing action of the enlarged diameter end portion 24'' may retract the hook 33 back through the slot 23 from the end 39 thereof to the end 37 thereof, during which movement the hook 33 engages adjacent tissue and laterally draws the terminal distal end 21 toward and against that tissue and simultaneously draws the sharp point 33' into the outwardly opening recess 45 shown in Figure 4. After fixation of the electro-catheter 10'', the tubular delivery catheter (not shown) may be withdrawn to thereby allow the distal end portion 12'' to deploy and assume the pre-configured shape of the-distal end portion 12 illustrated in Figure 2. The housings 19, 19' and 19'' are insulated from the electrical conductors (not shown) which bring electrical energy to conductive outer surface portions of the distal end portions 12, 12' and 12''. Further, the phantom lines 41 and 41' indicate the structure of the distal end portions 12 and 12', respectively, which comprise the spiral conductors disposed thereabout and which bring electrical energy to the outer surface portions of the end portions 12 and 12' (the electricity being supplied thereto through proximal lumen tubing or possible bilumen tubing with one lumen incorporating the electrical conductor leading to the conductors and the second lumen dedicated to operation of the fixation device). When the hook 33 is disposed in the end 37 of the slot 23 (subsequent to release of engagement of the hook 33 with organ tissue), it is positioned immediately forward of the shield 45 to thereby facilitate repositioning or removal of the electro-catheter 10'' subsequent to its usage.

Claims: An implantable defibrillation electrode, including a conductive distal end portion (12'') and a non-conductive proximal end portion (14), said distal end portion (12'') including distal and proximal ends, at least one of said ends being hollow and having hook means (33), shiftably supported therein for movement longitudinally thereof from a retracted position at least substantially entirely contained within said hollow end to an extended position at least substantially fully outwardly projected from said hollow end, means (22'') yieldingly biasing said hook means (33) from said extended position toward said retracted position, said proximal end portion being hollow, and axial thrust developing means (17), slidingly telescoped through said proximal end portion and operatively associated with said hook means (33) for exerting an axial thrust thereon from the terminal end of said proximal end portion , characterised in that at least a major portion (12) of the length of said distal end portion has a pre-configured shape and is resiliently deformable into a generally straight condition, and that said one end comprises said distal end and includes a tubular end housing (19'') whose terminal end is tapered (21), said tapered distal end (21) including a partial spiral slot (23) formed therein, said hook means (33) projecting at least slightly from the end of said slot (23) adjacent the major dimension end of said tapered distal terminal end (21) when said hook means (33) is in said retracted position and being slidable along said slot (23) toward the end of said slot (23) adjacent the minor dimension end (25) of said tapered distal terminal end (21) as said hook means (33) is shifted toward said extended position. The electrode of claim 1, characterised in that the minor dimension end (25) of said tapered distal terminal end (21) is open, that the means yieldingly biasing said hook means (33) from said extended position toward said retracted position is a coil spring (22''), equipped with a distal end (20''), incorporating an enlarged diameter end portion (24''), and a terminal end (26''), which is projectable through the open end (25) and includes and end enlargement (27), which is retractable only partly into the open end (25), that the terminal end (26'') has the base end of the curved hook (33) anchored thereto, that the slot (23) extends less than 180 degrees about the terminal distal end (21), that the hook (33) has a sharp point (33'), and that an outwardly opening recess (45) is provided for receiving the sharp point (33'), when the hook (33) is retracted through the slot (23) from one end (39) thereof to the other end (37) thereof by the spring biasing force of the enlarged diameter end portion (24'') of spring (22'').

Inventors: HEIL RONALD W JR, KENKNIGHT BRUCE H, WICKHAM ROBERT W JR, HEIL, RONALD W., JR., KENKNIGHT, BRUCE H., WICKHAM, ROBERT W., JR.
Applicants: CARDIAC PACEMAKERS INC, CARDIAC PACEMAKERS, INC.
Application year: 1993
Main classification: A61N1
IPC codes: A61N1