Automatic sensing level adjustment for implantable cardiac rhythm management devices

摘要

An implantable cardiac rhythm management device 10 includes a microprocessor-based controller 28 adapted to receive digitized electrogram signals from leads 14 placed on or in the heart and incorporates an autosense algorithm which is called into play when an electrogram is detected that exceeds an event detect threshold ET and capable of adjusting a sensing threshold ST to improve detection of cardiac depolarization signals in the presence of noise. The sensing threshold is automatically set on a beat-to-beat basis at a level that is dependent on a predetermined percentage of the peak amplitude of a current and an immediately preceding sensed or paced beat. The event threshold ET, which is always set at 50% of the sensing threshold, provides noise discrimination. The predetermined percentage value applied to the average peak value in arriving at the sensing threshold ST is dependent upon relative amplitudes of electrogram excursions and the signal-to-noise ratio encountered.