and ventricular electrograms in sinus rhythm (left) and intermittent atrial-sensed ventricular paced rhythm at right. Insert shows identical ventricular electrogram morphology in two panels ...

Resetting of a cardiac rhythm can be easily understood ... In contrast, in the VVI mode, the ventricular premature contraction is sensed by the pacemaker so the next pacing stimulus is advanced.

Following out-of-hospital cardiac arrest, every minute of delay until first shock decreases the odds of successful defibrillation.