Forced atrioventricular synchrony dual chamber pacemaker

A dual chamber cardiac pacemaker is adapted to operate in a forced synchrony pacing mode. The pacemaker senses atrial heartbeats and determines whether the rate of sensed atrial heartbeats is pathological or physiological. For physiological atrial heartbeat rates, the pacemaker functions in an AV synchronous pacing mode. For pathological atrial rates, atrial heartbeats occur too frequently for safe AV synchronous pacing so the heart is paced in the forced synchrony mode. In the forced synchrony mode, the pacemaker, upon sensing a natural atrial heartbeat, waits a predetermined atrial protection interval, paces the atria with an atrial stimulation pulse, waits a physiologically appropriate AV delay interval, and then delivers a ventricular pacing pulse at a time which maintains a stable ventricular rate.