Multi-site cardiac pacing system having conditional refractory period

Abstract

Multi-site cardiac pacing systems for providing pacing to multiple sites in a patient's heart, e.g., in a single heart chamber or in right and left heart chambers, while avoiding inappropriate responses to double sensing of an evoked depolarization conducted between the sites. A conditional refractory period and further post-event time periods, e.g. a conventional refractory period, are started upon a sense event or pacing pulse sensed at or delivered to a first pace/sense site. A sense event detected at another sense site that occurs during the conditional refractory period is characterized as a conditional refractory event, and it restarts shortened post-event time periods and terminates the conditional refractory period. The restarted post-event time periods are reduced in length by the elapsed time between the starting and termination of the conditional refractory period. The undue prolongation of the post-event period due to a sense event resulting from sensing of delayed propagation of a depolarization between the spaced apart pace/sense sites is avoided. However, the full length post-event time periods are restarted if a sense event is then detected during the previously restarted post-event time periods. Multi-site single heart chamber pacemaker and right and left heart chamber pacemaker embodiments of the invention are disclosed. In an atrial synchronous, bi-ventricular pacemaker embodiment, the undue prolongation of the post-event period due to a ventricular event sense event resulting from sensing of delayed propagation of a single ventricular depolarization between the left and right ventricles is avoided, and legitimate atrial sense event signals occurring thereafter are not characterized as refractory and are able to restart the AV delay.