Monolithic pericardial pacemakers

Abstract

Pacemakers and pacemaker delivery systems and methods are disclosed which use a modified cylindrical pacemaker body having a downward facing side which includes the anode / cathode and mechanical features that stabilize the pacemaker in place on the epicardial surface of the heart.

Description

MONOLITHIC PERICARDIAL PACEMAKERS

[0001] This Patent Application claims priority to U.S. Provisional PatentApplication Serial No. 63 / 525,632, filed July 7, 2023, the content of which is hereby incorporated by reference herein in its entirety into this disclosure.TECHNICAL FIELD

[0002] The present subject disclosure relates generally to cardiac pacemakers.More specifically, the present subject disclosure relates to monolithic pericardial pacemakers.BACKGROUND OF THE SUBJECT DISCLOSURE

[0003] The heart is a hollow muscular structure that resides inside a baglike membrane called the pericardium. There are many medical conditions in which the heart does not beat at a reliable rate or at a sufficiently high rate to sustain healthy life. Since their introduction in the 1950s, cardiac pacemakers have generally taken the form of a surgically implanted electrical pulse generator powered by a primary cell and connected to one or more flexible, endovascular leads that pass through the major veins into the interior of the right atrium and / or right ventricle, where they are anchored to the myocardial muscle. One of themost common forms of failure is stress fatigue of the leads from constant bending with each heartbeat.

[0004] For patients who are too small to accommodate such endovascular leads, have cardiac anatomic abnormalities that preclude transvenous lead placement or have infections or blood clotting or other disorders that contraindicate such endovascular leads, epicardial leads may be sutured to the outer surface of the myocardium. This requires major surgery to open the chest and pericardium to gain access to the epicardial surface.

[0005] It is generally desirable to eliminate the need for open surgical implantation of any medical device and to eliminate the need for repeat implantation procedures when the primary power source is depleted. Any open surgery entails risks from anesthesia and wound-healing and generally results in substantial pain, discomfort, and limited motor function for days to weeks after surgery. Making the implant small enough to enable minimally invasive implantation techniques necessarily compromises the amount of energy that can be stored in the implant. It is now possible to use one or more rechargeable cells to power the implant and to recharge those cells from outside the body by inductive or other transcutaneous transmission of electrical power. Nevertheless, it is important to conserve electrical energy by minimizing the strength of the electrical pulses required to capture the heart rate so to minimize battery drain.

[0006] More recently, "leadless pacemakers" have been developed which are intended to be intravenously attached to the endocardial wall of the right ventricle as a single, free-standing module. Nevertheless, such leadless pacemakers stillresult in inflammation, fibrosis, and can get dislodged from their positions by exposure to repeated cardiac motion. Such events tend to increase the strength of the electrical pulses required to capture the heart rate, thereby shortening the life of the power supply.SUMMARY OF THE SUBJECT DISCLOSURE

[0007] In the present subject disclosure, Applicants have developed a pacemaker with a unique shape and configuration which is low profile, can be implanted using minimally invasive techniques, and is structurally designed to fit within the pericardium while minimizing inflammation and the formation of scar tissue. Further, the pacemaker’s unique shape and structure prevent or minimize rolling or planar movement by fitting within the pericardium, which secures it therein.

[0008] In one exemplary embodiment, the present subject disclosure is a pacemaker device. The pacemaker includes an elongated, cylindrical shell having a leading end with features that facilitate anchoring of the pacemaker at the desired location on an epicardial surface of the heart and a trailing end with features for controlling the release of the pacemaker within the pericardial space. The pacemaker has a flat electrode surface positioned on the flattened side that functions as a cathode to the pacemaker device.

[0009] In another exemplary embodiment, the present subject disclosure is a pacemaker delivery assembly. The assembly includes an elongated cannula; an insertion tool positionable within the cannula and having a proximal end and a distal end; and a pacemaker positionable within the cannula, adapted to engagewith the insertion tool, and comprising: an elongated, cylindrical shell having a leading end with features that facilitate anchoring of the pacemaker at the desired location on the surface of the heart and a trailing end with features for controlling the release of the pacemaker within the pericardial space.

[0010] In another exemplary embodiment, the present subject disclosure is a method of inserting a pacemaker. The method includes threading a string around a pulley on one end of the pacemaker; mounting the pacemaker on a distal end of an insertion tool; reversibly attaching both ends of the string to a proximal end of the insertion tool; and inserting the insertion tool and pacemaker within a cannula to deliver to a target location on an epicardial surface.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the subject disclosure and technical data supporting those embodiments, and together with the written description, serve to explain certain principles of the subject disclosure.

[0012] FIG. 1 A shows an oblique view of a pacemaker delivery assembly, according to an exemplary embodiment of the present subject disclosure.

[0013] FIG. 1 B shows a detailed view of a pacemaker delivery assembly disposed within a cannula, according to an exemplary embodiment of the present subject disclosure.

[0014] FIG. 1 C shows a detailed view of a pacemaker delivery assembly as the pacemaker is being released from the insertion tool, according to an exemplary embodiment of the present subject disclosure.

[0015] FIG. 2A shows a side cross-sectional view of a pacemaker, according to an exemplary embodiment of the present subject disclosure.

[0016] FIG. 2B shows an end cross-sectional view of the pacemaker of FIG. 2A through the leading end, according to an exemplary embodiment of the present subject disclosure.

[0017] FIG. 2C shows a top cross-sectional view of the pacemaker of FIG. 2A, according to an exemplary embodiment of the present subject disclosure.

[0018] FIG. 3A shows a side cross-sectional view of an alternative design for the leading end of the pacemaker as it would sit on the epicardial surface of the heart, according to an exemplary embodiment of the present subject disclosure.

[0019] FIG. 3B shows a side cross-sectional view of an alternative design for the leading end of the pacemaker while contained within the sleeve of the insertion tool, according to an exemplary embodiment of the present subject disclosure.

[0020] FIG. 30 shows a top cross-sectional view of an alternative design for the leading end of the pacemaker while contained within the sleeve of the insertion tool, according to an exemplary embodiment of the present subject disclosure.

[0021] FIG. 4A shows a detailed top view of an articulated and steerable pacemaker delivery assembly before release of the pacemaker, according to an exemplary embodiment of the present subject disclosure.

[0022] FIG. 4B shows a detailed side view of an articulated and steerable pacemaker delivery assembly contained within the insertion cannula, according to an exemplary embodiment of the present subject disclosure.DETAILED DESCRIPTION OF THE SUBJECT DISCLOSURE

[0023] The following detailed description references specific embodiments of the subject disclosure and accompanying figures, including the respective best modes for carrying out each embodiment. It shall be understood that these illustrations are by way of example and not by way of limitation.

[0024] The present subject disclosure describes highly effective and simple to use devices, assemblies, and methods which comprise a monolithic pacemaker implanted through a percutaneous pericardial approach and placed at the epicardial surface without pacing leads. The pacemaker will remain in place while minimizing any potential inflammation at the electrode. Repositioning / removal is possible using the devices and techniques presented herein.

[0025] The pacemaker described herein has a unique shape in that it is substantially a cylinder with specialized extensions at either end to control its location and orientation. The cathodal electrode may be located on the side of the cylinder facing the epicardial surface. The extension at the leading end may include an anodal electrode, wings that deploy laterally onto the epicardial surface to inhibit axial roll, and / or downward projecting spikes to prevent sliding. The device may be deployed from a sleeve on a specially designed insertion tool that may be steerable at its distal end.

[0026] The device is also leadless without being on the inside of the heart, eliminating the risk of embolization. It is possible to place multiple devices either initially or at different times. Devices may be implanted on any part of the heart and may coordinate their monitoring and pacing functions as is well-known in the art. With this device, it is possible to pace the left ventricle directly. Its insertion entails minimally invasive procedures.

[0027] FIGS. 1 A, 1 B, and 1 C show various views of a pacemaker delivery assembly 100, according to the present subject disclosure. In these and other figures, proximal end 171 refers to the end of the pacemaker insertion tool 170 that is outside the body and controlled by the operator, while distal end 172 refers to the end of the pacemaker insertion tool 170 that is positioned inside the pericardial membrane and delivers the pacemaker 120 into the pericardial space. FIG. 1 A shows an overall, oblique view of pacemaker delivery assembly, which has a pacemaker 120 mounted at distal end 172 of an insertion tool 170. Proximal end 171 of insertion tool 170 includes a handle 173 for the operator and other components whose function will be described below, including one or more tubes 176 attached to handle 173, pull rod 177 attached to slide 174 and removable spacer 175 that maintains the distance between handle 173 and slide 174. Handle 173 also includes stanchion 189 and string 188 that passes through tubes 176 and may be tied or otherwise attached to stanchion 189.

[0028] Insertion tool 170 is depicted as straight in FIG. 1 but could be made to be flexible and deflectable and potentially covered with a protective membrane in the middle section where it includes the tubes 176 and pull rod 177. Materialsand means for such function are well-known in the art of minimally invasive medical devices, as appreciated by one having ordinary skill in the art.

[0029] As depicted in FIG. 1 B, the pacemaker delivery assembly 100 includes a cannula 101 , which may include a deployable retention feature 105 to keep it from falling out of the pericardium during positioning and release of the pacemaker 120. An example of retention feature 105 in the form of retractable hoops is shown and presented in Applicant’s co-pending application, U.S. Patent Application Serial Number 15 / 552,250, which is incorporated by reference herein in its entirety into this disclosure. In the first part of the implantation procedure, the operator uses standard components and techniques such as are well-known in the art to pass cannula 101 from outside the body so that distal end 102 is within the pericardial space.

[0030] An endoscope (not shown) may be included and passed through cannula 101 to visualize potential implanting sites for the pacemaker 120.

[0031] A pacemaker 120 takes up a substantial cross-sectional area of the cannula 101 . The pacemaker 120 has a unique shape which will be described herein as “modified cylindrical.” As used herein and throughout this disclosure, “modified cylindrical” is defined as having an overall cylindrical outer surface with extensions on each end, as shown in FIG. 1 C / 2A / 2C and others. The cross section of the pacemaker 120 must provide sufficient internal volume to the pacemaker to house electronics that power and control pacing function. Further, although shown as substantially round (circular), the cross section of the pacemaker 120 and / or cannula may be other shapes, such as oval.

[0032] Most of the internal volume of a pacemaker 120 is advantageously occupied by its power source to provide as much stored energy as possible. This is often a lithium cell, which is typically manufactured in layers using a “jelly roll” construction that produces a cylindrical component. For biomedical applications, such lithium cells usually have an outer shell made from titanium which connects to the negative electrode of the cell and may be used to provide or connect to the cathodal electrode of the pair of electrodes through which pacing pulses are delivered to the heart. Given the small size and limited power storage capabilities of lithium primary cells, it may be useful to employ a rechargeable lithium cell along with electronic circuit means to receive externally transmitted energy and convert it to a form suitable for recharging the lithium cell as needed. Throughout this narrative, we refer to “lithium cell” as the power source, but other energy storage technology may be employed in the subject disclosure described and claimed herein.

[0033] As shown in FIG. 2A-2C, the cylindrical portion of the pacemaker 120 may be comprised of the lithium cell 210 itself, whose titanium shell is covered over most of its surface by a dielectric jacket 221. The dielectric jacket 221 may have one or more fenestrations 212 that expose the titanium shell where a pacing electrode is desired. Advantageously, the exposed portion 212 of the titanium shell may be coated with a thin layer of another material that provides a lower impedance interface such as a sputtered-on coating of iridium or iridium oxide, as is well known in the art.

[0034] Alternatively, the pacing electrode may be electrically separate from the shell of the lithium cell 210 while still located on the downward facing side of the cylindrical portion of the pacemaker 120. That may be accomplished by incorporating a conventional hermetic feedthrough into the housing of the electronic circuit and attaching it to a flexible circuit consisting of an insulated thin-film or foil lead with exposed electrode contact. This may be affixed to the desired location on the downward facing side of the cylindrical lithium cell. Such flexible circuit and multiple hermetic feedthroughs may be used to provide additional electrode contacts suitable for recording bioelectric signals from the heart for advanced pacing and monitoring functions, as is well known in the art. Some or all of the remaining portions of the lithium cell shell may be exposed to function as a counter-electrode for pacing or recording functions. These techniques permit the design of bipolar electrode configurations that may be desirable for efficient pacing of or reliable recording of bioelectric signals from the heart.

[0035] It is generally desirable to reduce the amount of inflammatory response around the pacemaker 120. This may be achieved by coating some or all of the external surface of the pacemaker 120 with a material that slowly elutes an antiinflammatory drug such as a corticosteroid, as is well known in the art.

[0036] As shown in FIGS. 2A-2C, hollow extension 240 at leading end 201 of the pacemaker 120 may provide a housing for the electronic circuit for generating the pacing pulse output and / or receiving externally transmitted energy for recharging the lithium cell and / or communicating with an external programmer. Such hollowextension 240 is advantageously made from hermetic materials such as metal, ceramic or glass that can be sealed in such a manner as to exclude the entry of water or water vapor into the electronic circuit area. One common method of transmitting energy from outside to inside the human body is inductive coupling of an oscillating magnetic field, in which case the hollow extension 240 is advantageously made from a dielectric material such as ceramic that will not shield or dissipate the magnetic field. Biocompatible ceramics such as alumina and zirconia may be hermetically sealed to the titanium shell of the lithium cell by brazing or welding directly or through intermediate rings of a suitable metal such as niobium and / or gold, as is well known in the art. The leading extension 240 may also include a metallic cap 202 that functions as the counter-electrode for the pacing pulse output.

[0037] The leading extension 240 may support one or more features to control the location and orientation of the pacemaker 120 after release into the pericardial space. These may include wings 129, which prevent axial roll of the pacemaker 120 on the epicardial surface of the heart. Wings 129 are illustrated as wire loops that project laterally and parallel to the downward facing side of the leading extension 240. Insertion tool 170 includes a sleeve 186 that projects over pacemaker 120 so that wings 129 are compressed into sleeve 186 so that the pacemaker delivery assembly 100 can be slid freely through cannula 101 , as shown in FIG. 1 B. When pacemaker 120 is extruded from sleeve 186, wings 129 deploy laterally, as shown in FIG. 1 C. Wings may be made of any shape or material to provide this functionality. In a preferred embodiment, the wings aremade from nitinol alloy wire approximately 0.15 mm in diameter. When deployed, the wings may provide the operator with a sense of the orientation of the epicardial surface.

[0038] One or more spikes 132 that may or may not be connected as electrodes may be incorporated to reduce the possibility of pacemaker 120 migrating on the epicardial surface after it is originally deployed. The spikes 132 may be in the shape of protruding, sharp metal contacts that act as an effective anode. The pacing electrode and / or the spikes 132 may be composed of a metal which minimizes impedance, such as, for example, iridium. The spikes 132 may be slender, tapered and highly sharpened to facilitate penetration of the epicardial surface of the heart. The spikes 132 may incorporate barbs along the shaft to increase retention in the myocardium.

[0039] If not being used as active electrodes, the spikes 132 and / or wings 129 are needed only for temporary fixation of the pacemaker 120 at the time of implantation until connective tissue forms around the pacemaker 120 to hold it in place. The spikes and / or wings may be made from a material that dissolves gradually and safely in the body such as alloys of zinc as described in Liu et al., 2019 (Liu, Y., Zheng, Y., Chen, X. H., Yang, J. A., Pan, H., Chen, D., . . . Wu, S., Fundamental theory of biodegradable metals — definition, criteria, and design. Advanced Functional Materials, 29(18), 1805402). This may minimize damage to the heart muscle that may occur as a result of its regular contractions against the spikes and could facilitate later removal of the device.

[0040] In the embodiment illustrated in FIG. 2A, the one or more spikes 132 normally protrude beyond the cylindrical profile of the sleeve into which pacemaker 120 is loaded for passage down the cannula and into the pericardium. The spikes 132 may be fabricated from a springy material that can be folded into the sleeve in a manner similar to the above-described folding of the wings. The external shape of the hollow extension may include features that provide a recess into which the spikes may fold as well as features for mounting the above-described wings.

[0041] FIG. 2A and 2C shows a metallic cap 202 at the leading end 201 of the hollow extension 240 of the pacemaker 120. This may be incorporated to provide a large surface-area counter-electrode with a low interface impedance in the output circuit for the pacing pulses. The metallic cap 202 may be made from or coated with a material such as activated iridium to further reduce its interface impedance.

[0042] FIG. 3A shows an alternative embodiment for the hollow extension 240 of the pacemaker 120 as it would lie on the epicardial surface of the heart and under the pericardial membrane. Spike 132 is illustrated penetrating the myocardium under the epicardial surface. A cathode electrode 223 is illustrated projecting away from the cylindrical surface of the pacemaker 120 and deforming the epicardial surface, a configuration that may displace some of the connective tissue that tends to surround any foreign body and thereby reduce the threshold electrical energy required to achieve pacing capture. In this particular embodiment, spikes 132 are mechanically and electrically connected to ametallic cap 202 that serves as the anode for pacing and the cathode electrode 223 is mechanically and electrically connected to the casing of the lithium cell 210, which is otherwise insulated from contact with the body by a dielectric jacket 221 that may also be coated with a steroid eluting material. Other electrical and mechanical configurations of either or both electrodes are well-known in pacemaker design and are within the scope of this subject disclosure.

[0043] FIGS. 3B and 3C show the same alternative embodiment as FIG. 3A but at an earlier time during the implantation procedure when the pacemaker 120 is still contained within the sleeve of the insertion tool 170. The flexible shafts of spikes 132, the flexible stem of the cathode electrode 223 and the flexible wings 129 are all held by the sleeve 186 in retracted positions so that the pacemaker 120 can pass smoothly through the cannula 101 into the pericardial membrane.

[0044] FIG. 4A shows a detailed top view of the distal end 102 of a pacemaker delivery assembly 100 that incorporates an articulated and steerable linkage 190. Control wires that originate at the exterior handle of the insertion tool 170 connect to the distal articulated segment that holds the pacemaker 120. By applying tension to one or the other of the control wires, the distal articulated segment may be directed away from the axis of the cannula, facilitating the delivery of the pacemaker 120 to various parts of the epicardial surface of the heart. More than one such articulation in series may be used to provide more flexible positioning. Pacemaker 120 is contained within sleeve 186, which initially holds wings 129 and foldable spikes 132 in a furled and protected position but is here shown partially retracted with wings 129 and sharpened spikes 132 unfurledso that they may start to engage with the epicardial surface of the heart. Retraction of sleeve 186 may be controlled by pulling on pull wire 177 after removing spacer 175 in handle 173 as illustrated in FIG. 1A. Pacemaker 120 may be pulled against the face of holder 180 by string 188 which passes through tubes 176 and around pulley 127 (better visualized in FIG. 4A). String 188 may be tied or otherwise affixed to stanchion 189 as illustrated in FIG. 1A. After complete retraction of sleeve 186, untying or cutting string 188 may allow pacemaker 120 to float freely on the epicardial surface of the heart so that the efficacy and efficiency of cardiac pacing may be assessed. If pacing is deemed satisfactory, string 188 may be withdrawn by pulling on one end, allowing pacemaker 120 to be released completely from pacemaker delivery assembly 100. If pacing is unsatisfactory, the operator may pull on both ends of string 188, which is still looped through pulley 127, while withdrawing pacemaker delivery assembly 100 back through cannula 101 , thereby retrieving pacemaker 120. Release of pacemaker 120 from the epicardial surface of the heart and withdrawal into cannula 101 may be facilitated by protracting sleeve 186 so as to capture previously unfurled pacemaker elements such as spikes 132 and / or wings 129. Alternative embodiments not illustrated replace the string 188 with other attachment mechanism that allows relatively free motion of the pacemaker 120 on the surface of the beating heart during assessment of pacing.

[0045] FIG. 4B illustrates a side-view detail of the steerable linkage 190 of pacemaker delivery assembly 100 within cannula 101. It includes sleeve 186, pull wire 177, tube 176, and string 188. All of these elements might advantageouslybe built from flexible materials that allow lateral deformations of cannula 101 and the pacemaker delivery assembly 100 along its path from entry through the skin to entry into the pericardial membrane. These lateral deformations would allow the implantation equipment to be maneuvered in the pericardial space without compression of the heart and its pumping chambers.

[0046] Procedures for Use

[0047] The distal end of the cannula 101 is introduced into the pericardial space under fluoroscopic guidance. This is accomplished according to the conventional clinical procedure of first introducing a wire through a hypodermic needle and then dilating the passageway (often with graded dilators - not illustrated). The cannula may be prevented from accidental dislodgement from within the pericardial sac by deploying retractable retention features 105 from the distal end 102 of the cannula 101 as illustrated in FIG.1 B. An example of retractable loops is shown and presented in Applicant’s co-pending application, U.S. Patent Application Serial Number 15 / 552,250, which is incorporated by reference herein in its entirety into this disclosure.

[0048] The insertion tool 170 with the pacemaker 120 loaded into the sleeve 186 and withdrawal string 188 attached through the pulley 127 is passed through the cannula 101 and into the pericardial space.

[0049] When the pacemaker 120 is in the desired location, the sleeve 186 of the insertion tool 170 may be retracted sufficiently to allow the wings 129 on the pacemaker 120 to deploy. By rotating the insertion tool 170 axially, the operator may feel the wings 129 pushing against the epicardial surface or identify a properorientation of the wings 129 via fluoroscopy to position the pacemaker 120 so that its flattened surface is parallel to the epicardial surface. The withdrawal string 188 may be loosened from the handle on the insertion tool 170 and the sleeve 186 may be fully retracted so that the pacemaker 120 is free to engage with the epicardial surface into which the spikes 132 are intended to penetrate. The pacing threshold is determined by introducing stimulus pulses with variable amplitude until capture is determined by a physiological monitor such as electrocardiography (ECG).

[0050] If the pacing threshold is acceptable, the string 188 is pulled out through the pulley 127. It is beneficial to make the string 188 from a fine, flexible material that will slide freely past itself and through the tubes and pulley loop. Mercerized cotton-polyester thread is one suitable material, for example. The tubes of the insertion tool 170 provide smooth passages for string 188 to prevent its two sides from entangling. The insertion tool 170 may be removed after the string 188 has been removed from the pulley 127 of the pacemaker 120. The retention features 105 on the cannula 101 are retracted and the cannula 101 is removed, leaving the pacemaker 120 in place.

[0051] If the pacing threshold is not acceptable, both ends of the string 188 are pulled to drag the trailing end 125 of the pacemaker 120 into the sleeve 186 of the insertion tool 170 or into the cannula 101 . The whole pacemaker delivery assembly 100 may then be removed from the cannula 101 and the pacemaker 120 may be refitted to the insertion tool 170 for another attempt at implantation.

[0052] Novel Features

[0053] The pacemaker 120 body has a number of advantageous individual and combination features. The spikes 132 are intended to dig into the surface of the epicardium as the sleeve 186 is pulled back from the pacemaker 120, reducing the possibility that the pacemaker 120 will be dislodged when the withdrawal string 188 is removed. These spikes are advantageously made from a high tensile strength and springy metal such as, for example, pure iridium or various alloys of iridium with platinum or alloys of zinc with magnesium. Wire stock may be electrolytically etched and the tip sharpened by ion-beam milling, both processes well-known to practitioners of the art.

[0054] Pure iridium may be electrochemically activated with a conductive surface oxide that provides a low impedance interface for charge injection, as described by (Robblee LS, Lefko JL and Brummer SB (1983) Activated lr: An electrode suitable for reversible charge injection in saline solution. Journal Electrochemical Society 130: 731-733.). Lowering the impedance in the circuit consisting of the two stimulating electrodes and the intervening tissue reduces the voltage required to push the necessary stimulating current through the tissue.

[0055] The arrangement of the electrodes is intended to provide stable, low- threshold pacing capture. The location of the cathodal electrode 223 on the downward facing, dielectric surface of the pacemaker 120 and anodal returnelectrode as the metallic cap 202 on the leading end 125 of the pacemaker 120 may establish a bipolar stimulation configuration that encourages the applied current of the pacing pulse to stay mostly within the small volume of excitable myocardial tissue immediately beneath and between the electrodes. The one ormore spikes 132 may be connected electrically to pacemaker circuitry such as recharging coil 241 and circuit board 242 to serve as the functional anodal electrode for the pacing pulses (also known as an indifferent or return electrode). Gradual release of an anti-inflammatory steroid such as, for example, dexamethasone from a coating on some or all of the pacemaker 120 reduces the deposition of connective tissue associated with the normal foreign body response of the body to an implanted artificial material. One objective is to allow the pericardium to slide over the pacemaker 120, which will become encapsulated and anchored to the beating epicardial surface. Another objective is to minimize the connective tissue that forms under the cathodal electrode 223, which tends to displace the electrode from healthy, excitable myocytes, thereby increasing strength of the electrical pulses required to capture the heartbeat.

[0056] Reducing the stimulus charge and the required voltage may each or both be used to minimize the electrical energy consumed from the power supply, extending the life of that power supply. Experiments in animals have demonstrated that the pacemaker 120 illustrated in Figure 2 can capture the ventricular rate using electrical pulses with a charge of 0.05 - 0.5 microcoulombs and voltages of 0.2 - 1 .5 V. This compares favorably to conventional endovascular pacing, which typically requires a charge of 0.1 - 1.0 microcoulombs and voltages of 0.5 - 3.0 V.

[0057] The monolithic, leadless design of the present pacemaker 120 eliminates a major source of long-term failure in conventional cardiac pacemakers arising from stress fatigue of flexible components, such as leads and electrodes. In orderto fit into the pericardial space and accommodate the pumping motion of the heart, the present pacemaker 120 is advantageously limited in size to a diameter of 4-12 mm and a length of 10-40 mm, depending on the size of the patient. The relatively small internal volume of the present monolithic pacemaker 120 suggests that the amount of energy that can be stored in a primary cell such as lithium may not be sufficient to pace over the remaining life of the patient. Advantageously, the pacing circuitry’s power can be provided by a rechargeable cell. Circuitry in the pacemaker 120 to receive externally transmitted power and data such as via an inductive link can be used to recharge the pacemaker 120 whenever indicated. FIG. 2A, 2B, and 2C show an ovoid, flat inductive coil 241 disposed horizontally above the electronic circuit board 242 within the hollow extension 240. This arrangement optimizes the size and orientation of the inductive coil 241 to capture magnetic flux from an external transmitting coil so as to provide efficient transfer of energy for recharging such a rechargeable cell 210. The construction of the leveling wings 129 on the pacemaker 120 addresses a trade-off of desirable properties. The wings 129 need to be positioned near the bottom surface of the pacemaker 120 and extend some distance laterally to provide a useful feel for and anchoring to the epicardial surface, but they will not fit into the cannula in this orientation. Advantageously they can be made from a highly springy wire so that they will fold up alongside hollow extension 240 when pacemaker 120 is within the sleeve 186 of the insertion tool 170 as it passes through the cannula 101 . Wings 129 may then spring into the desired lateral extension when the pacemaker 120 emerges from the distal end 172 of sleeve186. One suitable material for this wire is nitinol with a diameter of 0.1-0.25 mm.The detailed shape of the distal extension 240 illustrated in FIGS. 2A-2C provides for attaching wings 129 to the pacemaker 120 and facilitates smooth folding up as the wings 129 enter the sleeve and cannula and full deployment when they exit, as indicated by the dashed lines on either side of hollow extension 240 in Figure 2B.

[0058] The insertion tool 170 incorporates various features that facilitate accurate, stable placement of the pacemaker 120 by the operator. It is designed to slip smoothly through the lumen of a cannula that provides percutaneous access to the pericardial space. The pacemaker 120 has a smooth top surface and deployable wings 129 that are designed so as to hold the bottom of the pacemaker 120 flat against the epicardial surface despite the movement of the beating heart within the pericardial membrane. The sleeve 186 at the distal end 102 of the insertion tool 170 holds the pacemaker wings 129 in a folded, retracted position within the sleeve 186 until the sleeve is withdrawn. When the wings 129 are deployed in their lateral orientation, they may provide the operator with haptic feedback about the orientation of the epicardial surface with respect to the axial rotation of the insertion tool 170. One or more spikes 132 toward the leading end of the pacemaker 120 may be folded within and protected by the sleeve 186 until the sleeve is withdrawn. The insertion tool 170 allows the operator to retract the sleeve 186 while pushing on the trailing end of the pacemaker 120 so as to release the pacemaker 120 onto the surface of the heart in the desired location. Upon such release the spikes 132 may engage with andpenetrate the epicardial surface to prevent sliding of the pacemaker 120. The string 188 allows the pacemaker 120 to float freely on the surface of the heart while the threshold for pacing in that location is measured. The string 188 may then be used to pull the pacemaker 120 back partially or completely into the sleeve 186 of the insertion tool 170 for repositioning elsewhere on the heart if deemed necessary by the operator. The arrangement of the withdrawal string 188 within the tubes 176 of the insertion tool 170 and through the pulley 127 is intended to minimize sliding friction of the string 188 and traction force applied to the pacemaker 120 as the string 188 is withdrawn. Experiments in animals have confirmed that the above steps can be performed reliably and rapidly by an operator using fluoroscopic visualization of the cannula, insertion tool 170 and pacemaker 120 during the implantation process.

[0059] The pacemaker 120 that is the subject of this subject disclosure may include multiple, physically separate devices located on the epicardial surface of different chambers of the heart (including the atria), where they may generate output pacing pulses and / or record bioelectric signals. This enables more sophisticated control of pacing, for example to synchronize the various chambers or to pace only as needed physiologically, as is well-known in the art. Physically separate modules may transmit information between them by various techniques that are well-known in the art, including radio waves, electrical fields, ultrasound, infrared light, etc. The articulated and / or flexible portions of the insertion tool 170 are intended to facilitate positioning of one or more modules on the epicardialsurface of one or more different chambers of the heart via a single placement of the percutaneous cannula into the pericardial space.

[0060] The pacemaker 120 that is the subject of this subject disclosure may be suitable for direct implantation onto a surgically exposed heart and fixation onto the epicardial surface of the heart without the use of the insertion tool 170 described herein. This may be advantageous, for example, if the patient receiving the pacemaker 120 has an adherent or incomplete pericardial sac that makes it difficult or impossible to use the minimally invasive insertion techniques described herein. It may also be advantageous if multiple, separate devices are required in critical locations on the surface of the heart as described above or if previously implanted devices need to be surgically removed. In addition, this may be advantageous in very small patients where there is a desire to avoid placing the implantation equipment percutaneously. During direct surgical implantation, the wings 129 of the pacemaker 120 (or alternative attachment mechanisms) may be sewn directly into the epicardial tissue using conventional sutures, staples or other surgical fixation technique. In such a case, the spikes 132 may be unnecessary or contra-indicated and may be omitted or removed prior to implantation.

[0061] The foregoing disclosure of the exemplary embodiments of the present subject disclosure has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the subject disclosure to the precise forms disclosed. Many variations and modifications of the embodiments described herein will be apparent to one of ordinary skill in the artin light of the above disclosure. The scope of the subject disclosure is to be defined only by the claims appended hereto, and by their equivalents.

[0062] Further, in describing representative embodiments of the present subject disclosure, the specification may have presented the method and / or process of the present subject disclosure as a particular sequence of steps. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps set forth in the specification should not be construed as limitations on the claims. In addition, the claims directed to the method and / or process of the present subject disclosure should not be limited to the performance of their steps in the order written, and one skilled in the art can readily appreciate that the sequences may be varied and still remain within the spirit and scope of the present subject disclosure.

Claims

WHAT IS CLAIMED IS:1 . A pacemaker device, comprising: an elongated modified cylindrical shell having an extension at a leading end that carries wings that project laterally; and; an electrode positioned on an epicardially-facing side, and functioning as a cathodal pacing electrode.

2. The pacemaker device of claim 1 , wherein the wings may be folded alongside the extension at the leading end so as to fit within a cylindrical insertion tool.

3. The pacemaker device of claim 1 , further comprising one or more elongated spikes protruding from the extension at the leading end, which provide an anti-sliding resistance force between the pacemaker device and an epicardial surface.

4. The pacemaker device of claim 3, wherein the one or more of the elongated spikes functions as an anode for the pacemaker device.

5. The pacemaker device of claim 3, wherein the one or more elongated spikes may be folded alongside or ahead of the extension at the leading end so as to fit within a cylindrical insertion tool.

6. The pacemaker device of claim 1 , wherein an anti-inflammatory drug elutes from some or all of a surface on the cylindrical shell.

7. The pacemaker device of claim 1 , wherein a part of a surface of the extension at the leading end functions as an anodal counter-electrode.

8. The pacemaker device of claim 1 , wherein the cathodal pacing electrode is located on an exposed portion of the cylindrical shell.

9. The pacemaker device of claim 1 , wherein the cathodal pacing electrode is located on a flexible stem that allows it to protrude from the epicardially-facing side.

10. The pacemaker device of claim 1 , further comprising a pulley on an extension on a trailing end of the shell to accommodate a removable string whereby the pacemaker device may be withdrawn during an insertion procedure.11 . The pacemaker device of claim 1 , further comprising a rechargeable power supply.

12. A pacemaker delivery assembly, comprising: an elongated cannula; an insertion tool positionable within the cannula and having a sleeve at its distal end; and a pacemaker positionable within the cannula, adapted to engage with the sleeve of the insertion tool, and comprising: an elongated modified cylindrical shell having an extension at a leading end that carries wings that project laterally; and; an electrode surface positioned on an epicardially-facing side of the pacemaker, and functioning as a cathodal pacing electrode.

13. The pacemaker delivery assembly of claim 12, wherein a holder portion of the insertion tool has one or more articulations that allows it to be deflected away from a longitudinal axis of the elongated cannula through which it is inserted.

14. The pacemaker delivery assembly of claim 13, wherein the holder portion of the insertion tool includes a flexible material such that the insertion tool can freely bend within pericardial space.

15. The pacemaker delivery assembly of claim 12, wherein the pacemaker includes a pulley in a trailing end of the pacemaker to accommodate a removable string whereby the pacemaker may be withdrawn during an insertion procedure.

16. The pacemaker delivery system of claim 15, wherein the insertion tool includes a stanchion and at least one tube through which the removable string may pass from the stanchion to the pulley.

17. The pacemaker delivery assembly of claim 12, wherein the pacemaker includes one or more elongated spikes protruding from its epicardially-facing side.

18. The pacemaker delivery system of claim 17, wherein the one or more of the elongated spikes functions as an electrode for the pacemaker.

19. The pacemaker delivery system of claim 12, wherein the wings that project laterally may be folded into the sleeve when the pacemaker is engaged with a holder portion of the insertion tool.

20. The pacemaker delivery system of claim 12, wherein a portion of the insertion tool is flexible and may be deflected as desired.21 . The pacemaker delivery system of claim 12, wherein an anti-inflammatory drug elutes from one or more external surfaces.

22. The pacemaker delivery system of claim 12, wherein the insertion tool includes a mechanism whereby the operator may pull the sleeve away from the pacemaker so as to release the pacemaker into pericardial space.

23. A method of inserting a pacemaker, comprising: threading a string around a pulley on a trailing end of the pacemaker; mounting the pacemaker on a distal end of an insertion tool; reversibly attaching both ends of the string to a proximal end of the insertion tool; and inserting the insertion tool and pacemaker within a cannula to deliver to a target location on an epicardial surface.

24. The method of inserting a pacemaker of claim 23, further comprising using an insertion tool sleeve to protect the cannula and body tissues from spikes protruding from an epicardially-facing surface of the pacemaker.

25. The method of inserting a pacemaker of claim 23, wherein the pacemaker has deployable wings.

26. The method of inserting a pacemaker of claim 23, further comprising loosening the string to detach the pacemaker from the insertion tool and separating the insertion tool from the inserted pacemaker.

27. The method of inserting a pacemaker of claim 26, further comprising withdrawing the pacemaker into the cannula by pulling on the string if a pacing function is unsatisfactory.

28. The method of inserting a pacemaker of claim 26, further comprising withdrawing the string by pulling on one end, then withdrawing the insertion tool and the cannula and leaving the pacemaker on the epicardial surface.

29. The method of inserting a pacemaker of claim 23, further comprising deflecting the insertion tool to reach the desired location for the pacemaker.

30. A pacemaker device, comprising: an elongated modified cylindrical shell having wings or other attachment mechanisms that project laterally and can be sewed on to the epicardial surface; and; an electrode positioned on an epicardially-facing side, and functioning as a cathodal pacing electrode.31 . A pacemaker device, comprising: an elongated modified cylindrical shell having an extension at either a proximal end or more centrally on the shell that carries wings that project laterally; and; an electrode positioned on an epicardially-facing side, and functioning as a cathodal pacing electrode.

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