Adaptive and morphological system for discriminating p-waves and r-waves

Abstract

The present invention is a method and apparatus for processing a sensed atrial electrogram in conjunction with a sensed ventricular electrogram. The present invention permits accurate discrimination of atrial P-waves from far field ventricular events such as far field R-waves and avoids oversensing such far field ventricular events as atrial sense events and undersensing atrial events occurring within a fusion beat masked by a far field ventricular event in the atrial electrogram. Atrial channel trigger signals are generated in response to sensed P-waves and far field R-waves in the atrial electrogram, and ventricular trigger signals are generated in response to sensed R-waves in the ventricular electrogram. In response to each ventricular channel trigger signal, the sensed atrial electrogram signal is adaptively filtered for an adaptive filter time window only to remove the far field R-wave signal from the sensed atrial electrogram signal while avoiding adaptive filtering of the sensed atrial electrogram signal at other times. In response to each atrial channel trigger signal, the adaptively filtered, sensed atrial electrogram signal is subjected to morphological analysis in respect of a morphological model of a P-wave only during a morphology time window. In this manner, P-waves in the sensed atrial electrogram signal are detected and far field R-waves in the sensed atrial electrogram signal are not mistakenly detected as P-waves, while morphological analysis of the sensed atrial electrogram at other times is avoided.