Abstract: A dual chamber pacemaker is provided with a dynamic PVARP which tracks the occurrence of high rate atrial senses within the normal PVARP range. The dynamic PVARP is a short window of about 50 ms which is moved toward the time of occurrence of any sense signal within the window range of about 50-200 ms following the ventricular event. Senses which occur within the dynamic window are rejected, or blanked, while senses occurring within the window range but outside of the window are recognized and evaluated. The dynamic window technique accordingly enables the pacemaker to recognize tachycardia senses which would otherwise be blanked by a fixed length PVARP, while providing efficient suppression of FFRS events. The pacemaker also provides a technique for determining whether rejected senses are tachy atrial senses or FFRS, by modulating the AV interval and thus shifting the dynamic window which is coupled to the ventricular pulse.

Abstract: A rate adaptive pacemaker system, and method of operation, is provided which has a pacemaker which generates pacing pulses at a controlled pacing rate as a function of at least one monitored patient variable. The correlation of pacing rate with the patient variable is nonlinear, or dynamic, and is adapted to actual patient conditions. The value of the relationship between the pacing rate and the monitoring variable is determined at the lower rate limit and the upper rate limit, and the dynamic characteristic between these limits is automatically adjusted.