Abstract: The subject apparatus integrates a two-channel defibrillator with a programmable stimulator to provide a means for assessing lethal ventricular tachyarrhythmias and determining defibrillation thresholds during implantable defibrillator procedures. The subject apparatus includes a number of features to aid doctors as well as improve patient care at substantially decreased patient risk. These features include an automatic charging circuit, as well as dual channel high voltage capacitor circuits to reduce the time in which a rescue shock can be delivered to a patient after an initial test defibrillation shock. Parameter storage is provided to allow the unit to be preprogrammed prior to the initiation of an electrophysiologic procedure. A microprocessor controlled display system provides the physician with information parameters regarding defibrillation shocks. This displayed information includes the energy delivered and the resistance in the patient.

Abstract: A method is disclosed for combined cardiac pacing and defibrillating with an implanted pacer/defibrillator having sensing and pacing leads connected to the atrium and the ventricle. P-waves and R-waves are sensed, and a V-V timer and a V-A timer are reset if an R-wave is sensed. If an R-wave is sensed during the V-V timer interval, a pacing stimulus to the ventricle is inhibited. If a P-wave is sensed during the V-A timer interval, a pacing stimulus to the atrium is inhibited. If an R-wave is sensed during the V-V timer interval, arrhythmia therapy is provided if an arrhythmia is determined to be present. If the sensed ventricular rate is greater than a selected tachycardia rate but is less than a selected fibrillation rate, than a determination is made whether the sensed atrial rate is greater than a selected fibrillation rate, and if so, the V-V and V-A timers are reset, but if the sensed atrial rate is not greater than a selected fibrillation rate, then arrhythmia therapy is provided.

Abstract: The subject invention integrates a two-channel defibrillator with a programmable stimulator to provide a means for assessing lethal ventricular tachyarrhythmias and determining defibrillation thresholds during implantable defibrillator procedures. The subject apparatus includes a number of features to aid doctors as well as improve patient care at substantially decreased patient risk. These features include an automatic charging circuit, as well as dual channel high voltage capacitor circuits to reduce the time in which a rescue shock can be delivered to a patient after an initial test defibrillation shock. Parameter storage is provided to allow the unit to be preprogrammed prior to the initiation of an electrophysiologic procedure. A microprocessor controlled display system provides the physician with information parameters regarding defibrillation shocks. This displayed information includes the energy delivered and the resistance in the patient.

Abstract: A method is disclosed for combined cardiac pacing and defibrillating with an implanted pacer/defibrillator having sensing and pacing leads connected to the atrium and the ventricle. P-waves and R-waves are sensed, and V--V timer and a V--A timer are reset if an R-wave is sensed. If an R-wave is sensed during the V--V timer interval, a pacing stimulus to the ventricle is inhibited. If a P-wave is sensed during the V--A timer interval, a pacing stimulus to the atrium is inhibited. In an R-wave is sensed during the V--V timer interval, arrhythmia therapy is provided if an arrhythmia is determined to be present. If the sensed ventricular rate is greater than a selected tachycardia rate but is less than a selected fibrillation rate, then a determination is made whether the sensed atrial rate is greater than a selected fibrillation rate, and if so, the V--V and V--A timers are reset, but if the sensed atrial rate is not greater than a selected fibrillation rate, then arrhythmia therapy is provided.

Abstract: A combination two-channel defibrillator and programmable pacing stimulator for assesses lethal ventricular tachyarrhythmias and determine defibrillation thresholds during implantable defibrillator procedures. A pair of switching transistors are provided to protect the pacing circuit when a defibrillation shock is delivered. These switching transistors provide symmetric voltage protection and prevent the defibrillation energy from being shunted back to the patient through the pacing leads.