Active housing and subcutaneous electrode cardioversion/defibrillating system

#In addition, the present application is filed concurrently herewith U.S. patent application Ser. No. 09/940,283, filed Aug. 27, 2001 and entitled “DUCKBILL-SHAPED IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR CANISTER AND METHOD OF USE,” U.S. patent application Ser. No. 09/940,371, filed Aug. 27, 2001 and entitled “CERAMICS AND/OR OTHER MATERIAL INSULATED SHELL FOR ACTIVE AND NON-ACTIVE S-ICD CAN,” U.S. patent application Ser. No. 09/940,468, filed Aug. 27, 2001 and entitled “SUBCUTANEOUS ELECTRODE FOR TRANSTHORACIC CONDUCTION WITH IMPROVED INSTALLATION CHARACTERISTICS,” now abandoned, U.S. patent application Ser. No. 09/941,814, filed Aug. 27, 2001 and entitled “SUBCUTANEOUS ELECTRODE WITH IMPROVED CONTACT SHAPE FOR TRANSTHORACIC CONDUCTION,” now abandoned, U.S. patent application Ser. No. 09/940,356, filed Aug. 27, 2001 and entitled “SUBCUTANEOUS ELECTRODE FOR TRANSTHORACIC CONDUCTION WITH HIGHLY MANEUVERABLE INSERTION TOOL,” now abandoned, U.S. patent application Ser. No. 09/940,340, filed Aug. 27, 2001, now U.S. Pat. No. 6,937,907 and entitled “SUBCUTANEOUS ELECTRODE FOR TRANSTHORACIC CONDUCTION WITH LOW PROFILE INSTALLATION APPENDAGE AND METHOD OF DOING SAME,” U.S. patent application Ser. No. 09/940,287, filed Aug. 27, 2001 and entitled “SUBCUTANEOUS ELECTRODE FOR TRANSTHORACIC CONDUCTION WITH INSERTION TOOL,” now abandoned, U.S. patent application Ser. No. 09/940,377, filed Aug. 27, 2901, now U.S. Pat. No. 6,866,044 and entitled “METHOD OF INSERTION AND IMPLANTATION OF IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR CANISTERS,” U.S. patent application Ser. No. 09/940,599, filed Aug. 27, 2001, now U.S. Pat. No. 6,950,705 and entitled “CANISTER DESIGNS FOR IMPLANTABLE CARDIOVERTER-DEFIBRILLATORS,” U.S. patent application Ser. No. 09/940,373, filed Aug. 27, 2001, now U.S. Pat. No. 6,788,974 entitled “RADIAN CURVE SHAPED IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR CANISTER,” U.S. patent application Ser. No. 09/940,378, filed Aug. 27, 2001 and entitled “BIPHASIC WAVEFORM FOR ANTI-BRADYCARDIA PACING FOR A SUBCUTANEOUS IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR,” U.S. patent application Ser. No. 09/940,266, filed Aug. 27, 2001, now U.S. Pat. No. 6,856,835 and entitled “BIPHASIC WAVEFORM FOR ANTI-TACHYCARDIA PACING FOR A SUBCUTANEOUS IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR,” and U.S. patent application Ser. No. 09/940,471, filed Aug. 27, 2001 and entitled “POWER SUPPLY FOR AN IMPLANTABLE SUBCUTANEOUS CARDIOVERTER-DEFIBRILLATOR,” the disclosures of which applications are hereby incorporated by reference.

#Defibrillation/cardioversion is a technique employed to counter arrhythmia heart conditions including some tachycardias in the atria and/or ventricles. Typically, electrodes are employed to stimulate the heart with electrical impulses or shocks, of a magnitude substantially greater than pulses used in cardiac pacing.

#Defibrillation/cardioversion systems include body implantable electrodes and are referred to as implantable cardioverter/defibrillators (ICDs). Such electrodes can be in the form of patches applied directly to epicardial tissue, or at the distal end regions of intravascular catheters, inserted into a selected cardiac chamber. U.S. Pat. Nos. 4,603,705, 4,693,253, 4,944,300, 5,105,810, the disclosures of which are all incorporated herein by reference, disclose intravascular or transvenous electrodes, employed either alone or in combination with an epicardial patch electrode. Compliant epicardial defibrillator electrodes are disclosed in U.S. Pat. Nos. 4,567,900 and 5,618,287, the disclosures of which are incorporated herein by reference. A sensing epicardial electrode configuration is disclosed in U.S. Pat No. 5,476,503, the disclosure of which is incorporated herein by reference.

#For a better understanding of the invention, reference is now made to the drawings where like numerals represent similar objects throughout the figures where:

#FIG. 1 is a schematic view of a Subcutaneous ICD (S-ICD) of the present invention;

#FIG. 2 is a schematic view of an alternate embodiment of a subcutaneous electrode of the present invention;

#Turning now to FIG. 1, the S-ICD of the present invention is illustrated. The S-ICD consists of an electrically active canister 11 and a subcutaneous electrode 13 attached to the canister. The canister has an electrically active surface 15 that is electrically insulated from the electrode connector block 17 and the canister housing 16 via insulating area 14. The canister can be similar to numerous electrically active canisters commercially available in that the canister will contain a battery supply, capacitor and operational circuitry. Alternatively, the canister can be thin and elongated to conform to the intercostal space. The circuitry will be able to monitor cardiac rhythms for tachycardia and fibrillation, and if detected, will initiate charging the capacitor and then delivering cardioversion/defibrillation energy through the active surface of the housing and to the subcutaneous electrode. Examples of such circuitry are described in U.S. Pat. Nos. 4,693,253 and 5,105,810, the entire disclosures of which are herein incorporated by reference. The canister circuitry can provide cardioversion/defibrillation energy in different types of waveforms. In the preferred embodiment, a 100 uF biphasic waveform is used of approximately 10–20 ms total duration and with the initial phase containing approximately ⅔ of the energy, however, any type of waveform can be utilized such as monophasic, biphasic, multiphasic or alternative waveforms as is known in the art.

#In addition to providing cardioversion/defibrillation energy, the circuitry can also provide transthoracic cardiac pacing energy. The optional circuitry will be able to monitor the heart for bradycardia and/or tachycardia rhythms. Once a bradycardia or tachycardia rhythm is detected, the circuitry can then deliver appropriate pacing energy at appropriate intervals through the active surface and the subcutaneous electrode. Pacing stimuli will be biphasic in the preferred embodiment and similar in pulse amplitude to that used for conventional transthoracic pacing.

#This same circuitry can also be used to deliver low amplitude shocks on the T-wave for induction of ventricular fibrillation for testing S-ICD performance in treating V-Fib as is described in U.S. Pat. No. 5,129,392, the entire disclosure of which is hereby incorporated by reference. Also the circuitry can be provided with rapid induction of ventricular fibrillation or ventricular tachycardia using rapid ventricular pacing. Another optional way for inducing ventricular fibrillation would be to provide a continuous low voltage, i.e., about 3 volts, across the heart during the entire cardiac cycle.