Ventricular Safety Pacing Triggered by Right Ventricular Lead Dislodgement

Pacing on the tail of paced QRS: What is the mechanism?

An electrocardiogram on the day after implantation of a dual-chamber pacemaker revealed 2 closely coupled pacing spikes at 100-ms intervals, with the latter being on the trailing edge of the paced QRS complex. Differential diagnoses of such closely coupled pacing pulses include atrial lead displacement, lead reversal on the pulse generator, ventricular premature complex in the post-atrial ventricular blanking period, and backup pacing pulse following a loss of capture. Critical analysis of the pacemaker timing intervals led to the mechanism and cause of the problem.