AV SYNCHRONOUS CARDIAC PACING SYSTEM DELIVERING MULTI-SITE VENTRICULAR PACING TRIGGERED BY A VENTRICULAR SENSE EVENT DURING THE AV DELAY

A pacing system for selectively sensing spontaneous ventricular cardiac depolarizations at first and second spaced apart ventricular sites during the time-out of an AV delay and delivering pace pulses to the spaced apart ventricular sites in a triggered pacing mode. The first and second ventricular sites are preferably right ventricular (RV) and left ventricular (LV) pace/sense electrode sites, and RV event and LV event signals are sensed at the RV and LV pace/sense electrodes. A V-A pacing escape interval and a ventricular refractory period, a trigger pace window, an upper rate interval and further post-event time periods are started upon a RV or LV sense event or a first ventricular pace pulse delivered upon time-out of the AV delay. A triggered ventricular pace pulse or pulses is delivered to one or both of the RV and LV pace/sense electrode sites upon detecting an RV sense event or LV sense event during the AV delay. In one triggered pacing mode, a RV or LV pace pulse is delivered upon a RV or LV sense event during the AV delay to one of the RV or LV pace/sense electrode sites. In another triggered pacing mode, a triggered pace pulse is delivered to the other one of the RV or LV pace/sense electrode sites after a triggered pacing delay timed from a non-refractory RV or LV sense event occurring during the AV delay. In still another triggered pacing mode, a first pace pulse is delivered upon a RV or LV sense event, the triggered pacing delay is timed out, and a second pace pulse is delivered to the other one of the RV or LV pace/sense electrode sites after time-out of the triggered pacing delay. Triggered ventricular pacing is disabled during the V-A escape interval. Such a system could be employed in pacemakers that are part of a cardio defibrillator system if desired.