Abstract: A unitary intravascular defibrillating catheter includes distal and proximal spring electrodes, displaced to such distance from one another that defibrillating shock is effected through a field including the interventricular septum and left ventricular free wall. In one embodiment of this catheter, the proximal electrode is placed in the region of the subclavian vein. Alternatively, it may be placed in the region of the third through seventh intercostal space. A unitary catheter is also described which includes an intermediate electrode, placed between distal and proximal electrodes. Selection of placement of electrodes either in the superior vena cava or in the region of the subclavian vein is medically indicated by physiological conditions of the individual patient. The cardioversion system further includes a unipolar or bipolar sensing circuit with at least one sensing electrode, and a cardioversion/defibrillation circuit with either two or three spaced apart spring electrodes.

Abstract: A unitary intravascular defibrillating catheter includes distal and proximal spring electrodes, displaced to such distance from one another that defibrillating shock is effected through a field including the interventricular septum and left ventricular free wall. In one embodiment of this catheter, the proximal electrode is placed in the region of the subclavian vein. Alternatively, it may be placed in the region of the third through seventh intercostal space. A unitary catheter is also described which includes an intermediate electrode, placed between distal and proximal electrodes. Selection of placement of electrodes either in the superior vena cava or in the region of the subclavian vein is medically indicated by physiological conditions of the individual patient.The cardioversion system further includes a unipolar or bipolar sensing circuit with at least one sensing electrode, and a cardioversion/defibrillation circuit with either two or three spaced apart spring electrodes.

Abstract: A system for determining the defibrillation threshold energy of a defibrillation lead arrangement by shocking the heart during the T wave of the ECG at decreasing energy levels until the heart is placed in fibrillation. The lowest energy level tested which fails to place the heart in fibrillation correlates to the defibrillation threshold energy of the lead arrangement.

Abstract: A cardioversion system includes a bipolar sensing circuit with two sensing electrodes, and a cardioversion circuit with two spaced apart spring electrodes. The sensing electrodes are spaced apart from one another but kept sufficiently close to one another for isolated, localized R-wave sensing. The sensing electrodes further are positioned remotely of the cardioversion electrodes, to avoid post-shock abnormalities which otherwise would interfere with a timely R-wave sensing, to substantially prevent the discharge of an unnecessary cardioversion pulse after return of the heart to normal cardiac rhythm. One preferred version of the system is a unitary catheter including a distal tip electrode and ring electrode as the sensing electrodes, and to substantially larger, more proximal spring electrodes for defibrillation. Alternatively, the defibrillation electrodes and the sensing electrodes can be provided on two separate catheters.

Abstract: A switch for placement in the lead line connecting a pacing pulse generator to an implanted pacing tip electrode in a combined implantable pacing-defibrillation system. The switch is triggered by switch control circuitry to open during defibrillation and to close during pacing. When the switch is open, the implantable unit is electrically isolated from the high voltage defibrillation pulse delivered to the heart. When the switch is closed, a low resistance conduction path is provided in the pacing lead to the pacing tip electrode.

Abstract: An apparatus for stimulating and sensing evoked response to stimulus in the heart. First and second electrodes are in electrical contact with the heart, a third indifferent electrode is also in electrical contact with the heart. A pacemaker provides stimulus signals through the electrodes in the stimulating mode of operation. The first and second electrodes are switched through switching apparatus wherein in the first mode the first and second electrodes are maintained at equal electrical potentials, and in a second, sensing mode, the switch operates between the first and second electrodes so as to allow the first and second electrodes to act as bipolar sensing leads. Evoked response is sensed by a differential amplifier having a first differential input connected to the first electrode and a second differential input connected to the second electrode. The differential amplifier provides a differential signal which is proportional to the evoked cardiac response.

Abstract: An output bridge circuit comprising four independently controlled transistors connected between first and second electrode terminals and a defibrillation capacitor. Two of the four transistors are driven by push-pull driver circuits and connected between the capacitor and the first and second electrode terminals. The remaining two transistors are connected between the first and second electrode terminals and ground terminals. By triggering one of the transistors connected to the push-pull driver circuits and one of the transistors connected between the electrode terminals and the ground terminal, a mono-phasic, multi-phasic, or sequential defibrillation pulse can be generated by activating the appropriate transistors.

Abstract: An implantable defibrillation/cardioversion system and method comprising an electrode having a plurality of discrete electrically conductive segments. The conductive segments are electrically isolated from each other and electrically connected to a defibrillation/cardioversion unit. An electrical pulse block is generated and chopped into a plurality of discrete pulse segments by the defibrillation/cardioversion unit and applied to the electrode so that each conductive segment receives a particular electrical pulse assigned from the series of pulses. In this way, the concentration of gas generated from ionic current produced by a high energy defibrillation pulse is reduces and more energy is delivered to the heart, thus reducing the required energy input to the electrode. The electrode may be planar or in a catheter electrode configuration.

Abstract: A circuit for generating a biphasic voltage pulse to restore rhythm to a fibrillating heart, the circuit utilizing a capacitor for providing the voltage pulse. The circuit further comprises first and second thyristors to regulate the voltage and first and second electrodes to apply the regulated voltage to the fibrillating heart. The circuit further comprises an output sensing circuit that senses the exponential decay of the capacitor and signals a control circuit to switch the thyristors such that after one thyristor applies the voltage pulse to the heart in a first polarity, the other thyristor applies the voltage pulse in the opposite polarity. Therefore, substantially all energy in the capacitor is provided to the heart.

Abstract: Disclosed are an electrode configuration and a method for its use with an automatic implantable cardioverter/defibrillator. The electrode configuration includes a catheter electrode intravenously positioned within the heart of a patient wherein one electrode, defined by the catheter, is within the right ventricle and a second electrode, also defined by the catheter and spaced from the first electrode, is within the superior vena cava region. A third electrode, in the form of a flexible, substantially planar patch, is subcutaneously positioned outside the thoracic cavity in the region of the left ventricle. At the time of electrical discharge, or permanently, the first and second electrodes of the catheter are connected together. The electrode arrangement can be implanted without opening of the thoracic cavity by intravenously placing the catheter electrode within the heart of a patient and subcutaneously implanting the patch electrode between the skin and the thoracic cavity.

Abstract: A novel electrode apparatus and method for use with an automatic implantable cardioverter/defibrillator. The electrode apparatus includes a catheter electrode intravenously positioned within the heart of a patient wherein one electrode, defined by the catheter, is within the right ventricle and a second electrode, defined by the catheter, spaced from the first electrode, is within the superior vena cava. A third electrode, in the form of a flexible, substantially planar patch, is subcutaneously positioned outside the thoracic cavity proximate to the apex of the left ventricle. The third electrode is electrically connected with the second electrode of the catheter. The electrode arrangement can be implanted without opening of the thoracic cavity by intravenously placing the catheter electrode within the heart of a patient and subcutaneously implanting the patch electrode between the skin and the thoracic cavity.

Abstract: An implantable cardioversion system employing a bipolar electrode for R-wave sensing, the system utilizing heart rate averaging and probability density function techniques in determining whether or not the heart of a patient is to be automatically cardioverted. An improved bipolar electrode facilitates acquisition of a highly accurate R-wave. The implantable system is further provided with the capabilities of (1) providing, upon magnet-type interrogation, an audible indication of proper placement of the bipolar electrode in the body of a patient, (2) providing an audible indication to verify the status of the implanted device (activated or deactivated), (3) the capability of providing, upon request, a transmitted signal modulated with stored information corresponding to the number of times cardioversion of the patient has taken place, (4) the capability of preventing external cardioversion shock from being shunted across the electrodes, and (5) the capability of detecting average heart rate.

Abstract: A multiple electrode unitary intravascular cardiac catheter comprising a distal electrode for sensing and pacing, an intermediate electrode for sensing, pacing and cardioverting, and a proximal electrode for sensing and cardioverting. The catheter may also be employed in combination with an external patch electrode.

Abstract: An output bridge circuit comprising four independently controlled transistors connected between first and second electrode terminals and a defibrillation capacitor. Two of the four transistors are driven by push-pull driver circuits and connected between the capacitor and the first and second electrode terminals. The remaining two transistors are connected between the first and second electrode terminals and ground terminals. By triggering one of the transistors connected to the push-pull driver circuits and one of the transistors connected between the electrode terminals and the ground terminal, a mono-phasic, multi-phasic, or sequential defibrillation pulse can be generated by activating the appropriate transistors.