Siemens Aktiengesellschaft

Hans Andersen

Hans G Strandberg

Martin Obel

Lars Wallen

An implantable defibrillator has a capacitor which, through a controllable switch arrangement, can either be connected to a voltage source for charging the capacitor, or connected across electrodes placed at the heart for delivering a defibrillation pulse. To calculate the minimum pulse energy required for successful defibrillation, ventricular fibrillation is first induced, so that a plurality of defibrillation attempts, with energy increasing from attempt-to-attempt can be undertaken until successful defibrillation occurs. For inducing ventricular fibrillation, the capacitor of the implantable defibrillator is connected to the voltage source until a prescribed charging voltage, which is significantly below the voltage necessary for defibrillation, is reached, and subsequently, the capacitor is disconnected from the voltage source during brief time spans at intervals within the framework of a sequence and is connected during those time spans to the electrodes. Between the time spans, the capacitor is again charged.

Implantable defibrillator with fibrillation-inducing capability and

A method and apparatus for detecting a sequence of abnormal events in an electrical signal, such as the depolarization signal of the heart, compares a selective signal parameter to a defined threshold, and measures the maximum value of the signal parameter for each event which exceeds the threshold. The characteristic quantity corresponding to the statistical distribution of the respective maximum values for a defined number of most recently, successively occurring events is calculated, with each newly measured maximum value causing the characteristic quality to be updated. The characteristic quality is compared in a comparator to a defined rated value, and a signal indicating the presence of a sequence of abnormal events in the electrical signal is generated if the characteristic quality differs from the rated value by more than a selected amount.

Method and apparatus for detecting a sequence of abnormal events in an

To make it possible to suppress spurious signals of any type without having a negative effect on the stimulation or detection characteristics of a cardiac pacemaker, a signal processing unit is provided which prevents control signals from being applied to the device for controlling the heart stimulation pulses when signals from the two unipolar pacemaker electrodes are received at substantially the same time.

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Voellingby, Sweden

Hans Andersen