Pacemaker inhibition due to anodal ring electrode contact.

A 79-year-old patient with a permanent DDD pacemaker due to a complete AV block and severe bradycardia was seen with complaints of syncope. A surface ECG rhythm strip verified the loss of ventricular output with 6-second periods of asystole. Subsequent investigation using the pacemaker's annotated event markers and multiple polarity intracardiac electrograms indicated spurious signals arising from the anodal ring. On fluoroscopic examination intermittent contact was observed between the anodal ring of the pacing lead and the ring electrode of an abandoned lead. Reprogramming of the pulse generator's ventricular channel to the unipolar sensing configuration corrected the problem.