ABSTRACTThe specification describes an improved cardiacpacer, and more particularly a pacer which is adapted forimplantation in a patient. The cardiac pacer apparatus hasan electrode means including at least a first electrodeadapted to stimulate the heart; control means including timingmeans which defines a sample time window and signal detectormeans including sensing means for sensing cardiac signals onthe electrode means. Filter means including a filter circuitreceive the signal sensed by the sensing means for quantizingthe sensed signal and continuously generating digital wordsrepresentative of the slope of the sensed signal over thesample time window. Parameter memory means store signalsrepresentative of predetermined selection criteria fordefining at least one component of a cardiac cycle signal.A selection circuit means including a selection circuitresponsive to the quantized output signals of the filtermeans and the stored selection criteria signals generates adetection signal if the digital slope words meet thepredetermined selection criteria. Finally generator meansgenerate a stimulating signal and couple the same to theelectrode means if the selection circuit means fails togenerate the detection signal within a predetermined time froma previous detection signal or a previous stimulating signal.
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