Atrioventricular synchrony in the background of ventricular noise and undersensing.

The 24-hr electrocardiogram (ECG) interpretation in patients with double-chamber pacemakers may be challenging. The difficulty increases if not well-known pacemaker algorithm and device malfunction coexist. We show atrial synchronization pace (ASP) in a patient with ventricular lead damage. We provide detailed description of electrocardiogram and intracardiac electrogram. ASP may confuse 24-hr ECG monitoring interpretation, especially in patients with ventricular lead dysfunction.