Abstract: An implantable defibrillator derives a rectangular current waveform from a capacitor discharge by using a current limiter. This pulse-shaping method is equally applicable to single-path and multiple-path situations. A rectangular pulse delivers a maximum of energy for a given peak-field value with a particular electrode combination and pulse duration. Peak field is a measure of the tissue-damage potentiality of a particular discharge.

Abstract: An implantable defibrillator derives a rectangular current waveform from a capacitor discharge by using a current limiter. This pulse-shaping method is equally applicable to single-path and multiple-path situations. A rectangular pulse delivers a maximum of energy for a given peak-field value with a particular electrode combination and pulse duration. Peak field is a measure of the tissue-damage potentiality of a particular discharge.

Abstract: A defibrillator pulse generator for pectoral implant utilizing the metal case as an electrode and operative to supply unique patterns of monophasic, biphasic, or pairs of electrical pulses to the connected electrodes.

Abstract: An implantable multichamber cardioversion and defibrillation system is provided with multiple independently controllable and programmable switched electrode discharge pathways. This independently controlled switching arrangement provides for control over the polarity, phase, direction and timing of all cardioversion and defibrillation countershocks, and allows for the varying of subsequent countershocks after an initial countershock. The switching arrangement is, preferably, both programmable prior to implantation of the system and re-programmable after implantation of the system.

Abstract: The first embodiment of the present invention repositions the shunt thyristor used in the monophasic-waveform generator of the prior art so that it discharges the main capacitor through a series thyristor, thus increasing current through it briefly, rather than reducing current through it. The result of this arrangement is that the node between the series thyristor and the heart is pulled rapidly to a low voltage, causing the shunt switch to discharge the cardiac capacitance, as well as the main capacitance. The consequence is that discharging the cardiac capacitance requires a reversal of current in the heart, which enhances the heart-stimulating effect of the defibrillating waveform. The resulting true-voltage-pulse waveform has an efficacy approximating that of a biphasic waveform and is achieved with a circuit no more complex than that used to generate a monophasic waveform.

Abstract: A defibrillator pulse generator for pectoral implant utilizing the metal case as an electrode and operative to supply unique patterns of monophasic, biphasic, or pairs of electrical pulses to the connected electrodes.

Abstract: An improved dual battery power system uses two separate battery power sources for an implantable cardioverter defibrillator, each having optimized characteristics for monitoring functions and for output energy delivery functions, respectively. The monitoring functions are supplied electrical power by a first battery source, such as a conventional pacemaker power source in the form of a lithium iodide battery which is optimized for long life at very low current levels. The output energy delivery functions are supplied by a separate second battery source, such as a pair of lithium vanadium pentoxide batteries, which is optimized for high current drain capability and low self-discharge for long shelf life. The first battery source provides electrical power only to the monitoring functions of the implantable cardioverter defibrillator, and the second battery source provides all of the electrical power for the output energy delivery functions.

Abstract: A major shortcoming in the prior art for detecting cardiac arrhythmias for the purpose of making an electrical intervention decision has been that each variable sensed was given in effect a "veto" over intervention on the basis of its own particular predetermined threshold value, and irrespective of the values of companion variables. The present invention overcomes this prior art problem by generating a function of relevant variables, and assigning a threshold value to the function. As a result, an individual variable can range widely for a positive intervention decision, depending upon the values of the companion variables. Thus, the intervention exploits features often described as those associated with fuzzy logic. The functions chosen for this purpose can be as one desires, with the choice depending upon the current state of advancing knowledge.

Abstract: Epicardial-patch electrodes for defibrillation are efficient in deliverying electrical energy accurately to the necessary tissue and in minimizing electrical losses, but they are risky and costly because their implantation requires major surgery. Intravenous implantation of endocardial-coil electrodes, such as right-ventricular-apex (RVA) and superior-vena-cava (SVC) electrodes, by means of cardiac catheters, on the other hand, involves simpler procedures. Also, implantation of a subcutaneous-patch (SUB) electrode or of a pulse-generator housing (CAN, subject to co-pending application) electrode requires comparatively minor surgery. Using these last four electrodes, however, involves accepting electrical losses in intervening tissue, relatively inefficient current directions in some cases, and unfavorable energy distributions among paralleled paths.

Abstract: An improved dual battery power system uses two separate battery power sources for an implantable cardioverter defibrillator, each having optimized characteristics for monitoring functions and for output energy delivery functions, respectively. The monitoring functions are supplied electrical power by a first battery source, such as a conventional pacemaker power source in the form of a lithium iodide battery which is optimized for long life at very low current levels. The output energy delivery functions are supplied by a separate second battery source, such as a pair of lithium vanadium pentoxide batteries, which is optimized for high current drain capability and low self-discharge for long shelf life. The first battery source provides electrical power only to the monitoring functions of the implantable cardioverter defibrillator, and the second battery source provides all of the electrical power for the output energy delivery functions.