Implantable intravenous cardiac stimulation system with pulse generator housing serving as optional additional electrode

Abstract: A pulse generator housing (10,10') for enclosing and containing pulse generator defibrillation circuitry (18). At least one surface (14,14') is electrically conductive and connected to the pulse generator circuitry for delivering defibrillating energy to the heart. The pulse generator housing is implanted in the pectoral region proximate the heart with the conductive surface facing the heart.

Description: BACKGROUND OF THE INVENTION This invention relates to an implantable heart treatment system according to the preamble of claim 1 for applying electrical energy to an abnormally functioning heart. Electrodes implanted in the body for electrical stimulation of muscle or body organs are well known. More specifically, electrodes implanted on or about the heart have been used to reverse certain abnormal and life-threatening arrhythmias. Electrical energy is applied to the heart via the electrodes to return the heart to normal sinus rhythm. Common abnormal cardiac arrhythmias include bradycardia (slower than normal heartbeat rhythm), ventricular tachycardia (faster than normal heartbeat rhythm), and ventricular fibrillation (sporadic and uncoordinated beating of the heart). The latter two arrhythmias generally are fatal if left untreated. To control the heartbeat rhythm and prevent fatalities from ventricular tachycardia and fibrillation, several devices have been designed having the ability to stimulate the heart according to a sensed cardiac signal such as a sensed ECG signal. See for example U.S. Patent No. 4,603,705 to Speicher et al. The Speicher et al. patent discloses a multiple electrode unitary intravascular cardiac catheter having a distal electrode for sensing and pacing, an intermediate electrode for sensing, pacing and cardioverting, and a proximal electrode for sensing and cardioverting. This multiple electrode catheter maintains the ability for heart rate sensing and low threshold pacing immediately following cardioversion. From CH-667 395 A5 a heart treatment system according to the preamble of claim 1 is known. However the known system has the disadvantage of allowing only a twofold combination of the electrodes. The need therefore exists for implantable cardiac heart treatment system capable of performing standard pacing, such as anti-bradycardia pacing, anti-tachycardia pacing, low-energy cardioversion, and high-energy defibrillation. SUMMARY OF THE INVENTION : It is a primary object of this invention to provide an implantable heart treatment system having pacemaking, cardioversion and higher energy defibrillation capabilities. It is an additional object of this invention to provide an implantable heart treatment system having pacemaking, cardioversion and defibrillation capabilities via a selectable electrode configuration. It is yet a further object of this invention to provide an implantable heart treatment system utilizing a relatively small number of implantable parts. Briefly, the implantable heart treatment system comprises a transvenous myocardial, or pericardial lead having a plurality of electrodes. Typically, the lead electrodes are capable of sensing and performing standard anti-bradycardia pacing, anti-tachycardia pacing, cardioversion and defibrillation. The transvenous lead is connected to a pulse generator having full-function pacing capabilities as well as cardioversion and defibrillation capabilities. The housing of the pulse generator is conductive and is connected to the pulse generator circuitry so that it may selectively serve as a discharge electrode. The outer surface of the pulse generator could be of a special configuration to facilitate its discharge capabilities. Typically, the pulse generator is implanted in the pectoral or abdominal region of the body proximate the heart. A programmable switch is provided to select the electrode configuration which may include or exclude the pulse generator housing electrode. As a result, different electrode configurations can be obtained for specific types of cardiac stimulations. The above objects and advantages of the present invention can be further understood when reference is made to the following description, taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS : Figure 1 is a perspective view illustrating the pulse generator housing serving as a cardiac electrode in accordance with a first embodiment of the present invention. Figure 2 is a cross-sectional view taken through line 2-2 of Figure 1. Figure 3 is a perspective view illustrating the pulse generator housing having conductive mesh on a face thereof for serving as a cardiac electrode in accordance with the second embodiment of the present invention. Figure 4 is a cross-sectional view taken through line 4-4 of Figure 3. Figure 5 is a side view of a transvenous electrode and lead used in conjunction with the pulse generator illustrated in Figure 1 or Figure 3. Figure 6 is a diagram illustrating the placement of the pulse generator housing adjacent the heart and connected to the implanted transvenous electrode and lead. DETAILED DESCRIPTION OF THE DRAWINGS Referring to Figures 1 and 2, the pulse generator housing of the present invention is generally shown at 10. Typically, housing 10 is of a rectangular box shape having four side walls, a top wall, and a bottom wall. In one embodiment, at least one of the side walls is highly conductive. To this end, housing 10 includes side wall 12 having an outer discharge surface 14 formed of highly electrically conductive material. The conductive surface 14 is connected to the pulse generator circuitry 18 via a programmable switch 16. The pulse generator circuitry 18 is also electrically connected to electrode lead plug receptacle 20. As previously mentioned, the number of side walls of housing 10 having conductive discharged surfaces may vary. However, it is envisioned that as many as four side walls may be made electrically conductive. Referring now to Figures 3 and 4, a pulse generator housing of a second embodiment is illustrated at 10'. Housing 10' is similar to housing 10 of Figures 1 and 2 except the side wall 12' includes a conductive mesh surface 14'. It is to be understood that, hereinafter, the term "mesh" includes that as illustrated as well as any other high surface area conductive materials. As shown in Figure 6, conductive mesh surface 14' is electrically connected via switch 16 to pulse generator circuitry 18 contained within housing 10'. In addition a separate conductive patch (not shown) could be added and connected to the bottom of the pulse generator housing to increase the conductive surface area. This patch could attach by a snap or other similar means to the housing. Pulse generator circuitry 18 has full-function pacing capabilities including pacing for bradycardia and tachycardia both to inhibit an intrinsic beat or to adapt the rate to a higher or lower rate. In addition, circuitry 18 has cardioversion and defibrillation capabilities and includes cardiac detection circuitry capable of distinguishing when the heart is in normal sinus rhythm, should be paced, or requires higher energy cardioversion, or defibrillation. The switch 16 is selectively activated to include or exclude the conductive surface of side wall 12 from the discharge sequence. Pulse generator housing 10 or 10' is typically used in conjunction with other cardiac electrodes implanted on or about a human heart. One such lead is illustrated in Figure 5. Lead 30 is provided having a catheter portion 31 supporting electrode 28 on the distal end as well as electrode 29 on a proximate end of catheter portion 31. Lead 30 includes plug connectors 32 and 34 at its proximal end. In addition, a sensing tip electrode 36 may be provided at the distal tip of catheter portion 31 for sensing cardiac activity. Electrodes 28 and 29 could also have sensing capabilities. Referring to Figure 6, in operation, lead 30 is implanted transvenously in the human heart 38 with electrode 28 in the right ventricle 40 and electrode 29 proximate the right atrium or the superior vena cava 42. Alternatively, a single catheter electrode may be used for placing the electrode in the right ventricle. Pulse generator housing 10 or 10' is implanted in the pectoral region proximate but not in contact with the heart, just under the skin, with its conductive side wall(s) facing the heart. Alternatively, the housing 10 or 10' could be implanted in the abdominal region. Plug connectors 32 and 34 are inserted into receptacle assembly 20. When an arrhythmia is sensed where it is appropriate for an electrical shock to be delivered to the heart 38, the programmable switch 16 determines which electrodes are energized under control of circuitry 18. If the heart activity is slower or faster (bradycardia or tachycardia) than normal, the switch 16 is triggered so that the pulse generator circuitry 18 selects only electrode 28. On the other hand, if the sensed activity is indicative of rapid ventricular tachycardia or fibrillation requiring higher energy stimulation, the switch 16 is triggered so that the pulse generator circuitry 18 selects both distal and proximal electrodes 28 and 29, respectively, as well as the electrode discharge surface 14 to discharge energy from the conductive wall(s) of housing 10 or 10' for delivering electrical energy to the heart 38 for generating a defibrillating electric field across the heart. Alternatively, prior to applying a high energy defibrillating shock to the heart, a lower energy cardioverting shock can be applied between electrodes 28 and 29 against the conductive wall(s) of the pulse generator housing 10 or 10'. Thereafter, if the heart does not revert back to normal sinus rhythm, the higher energy defibrillation pulse is applied across the same electrodes. In yet another alternate form, the programmable switch 16 may be programmed to select one of the electrodes 28 and 29, and the electrode discharge surface 14 of the pulse generator housing 10 or 10'. In this way, the electrode discharge surface 14 of the pulse generator housing 10 or 10' will be discharged against only one of the electrodes 28 and 29. Further, the choice between the electrodes 28 and 29 may be based on certain cardiac conditions. It is considered that the above description is intended by way of example only, and is not intended to limit the present invention in any way except as set forth in the following claims.

Claims: An implantable heart treatment system having anti-arrhythmia pacemaking, cardioversion, and defibrillation capabilities for maintaining proper function of the heart, said system comprising: an implantable pulse generator means (18) for producing an anti-arrhythmia waveform; a pulse generator housing (10, 10') enclosing and containing said pulse generator means (18), said pulse generator housing (10, 10') including a conductive surface (14, 14') electrically connected to said pulse generator means (18) for delivering electrical energy to the heart, said housing (10, 10') being implantable proximate the heart with said conductive surface facing the heart; a first electrode (28) being implantable in or about the heart and being electrically connected to said pulse generator (18); a second electrode (29) being implantable in or about the heart and being electrically connected to said pulse generator (18); characterized in that programmable switching means (16) are provided for directing said anti-arrhythmia waveform upon a first condition of said heart, to at least one of said first (28) and second (29) electrodes and to said conductive surface (14, 14') of said pulse generator housing (10, 10'); upon a second condition of the heart directing said anti-arrhythmia waveform to said first (28) and second (29) electrodes and to said conductive surface (14, 14') of said pulse generator housing (10, 10'); and upon a third condition of the heart to said first and second electrodes. The implantable heart treatment system of claim 1, in which at least one of said first and second electrodes (28, 29) additionally has sensing capability (36) electrically connected to the pulse generator (18) for use by said programmable switching means (16). The implantable heart treatment system of any of claims 1 to 2, further comprising a sensing electrode (36) electrically connected to the pulse generator (18) for use by the switching means (16). The implantable heart treatment system according to any preceding claim, in which at least one electrode (28, 29) is located on a transvenous lead (30). The implantable heart treatment system of claim 4, in which at least one electrode (29) is arranged on a proximal portion of the transvenous lead (30) so as to be located in the atrium or vena cava region of the heart. The implantable heart treatment system of claim 4, in which at least one electrode (28) is arranged on a distal portion of the transvenous lead (30) so as to be located in the right ventricle of the heart. The implantable heart treatment system of claim 4, in which the transvenous lead (30) comprises first and second electrodes (28,29) arranged on the lead (30) such that the first electrode (28) is located at a distal position so as to be located in the right ventricle of the heart and the second electrode (29) is located at a proximal position so as to be located in the atrium or vena cava region of the heart. The implantable heart treatment system according to any preceding claim, in which the pulse generator housing (10) comprises a plurality of walls (12), and further characterized in that said conductive surface (14, 14') comprises more than one wall (12). The implantable heart treatment system according to any preceding claim, in which the conductive surface (14, 14') is comprised of electrically conductive mesh. The implatable heart treatment system according to any preceding claim, further comprising a separate conductiv patch electrode connected to said conductive surface (14, 14') of said pulse generator housing (10, 10').

Inventors: HAUSER ROBERT G, HAUSER, ROBERT G.
Applicants: CARDIAC PACEMAKERS INC, CARDIAC PACEMAKERS, INC.
Application year: 1991
Main classification: A61N1
IPC codes: A61N1