Demand heart pacer with dual time bases

Abstract

A heart pacer providing heart stimulating electrical impulses in the absence of naturally occurring heartbeats, including two electrical impulse generating time bases each capable of emitting heartbeat stimulating impulses. A sensed signal, accepted against criteria preceding it in time, as a valid heartbeat signal rather than an interference signal, serves to reset one time base while a second time base continues its cycle on the assumption that the sensed signal is an invalid or interference signal. If further signals are sensed, within criteria indicating that the original sensed signal was, in fact, invalid, the second time base continues its cycle until it emits a heart stimulating impulse at which time the first time base timing cycle is cancelled. If, however, the original sensed signal is not shown to be invalid the output of the second time base is suppressed and the reset timing cycle of the first time base continues. The pacer allows the validity of the sensed signal to be judged against both preceding and succeeding criteria.