Loss of ventricular capture

Patient

78-year-old man implanted with a dual-chamber pacemaker in the setting of a complete atrioventricular block with a right ventricular pacing lead positioned at the right ventricular outflow tract; recurrence of syncopes a few weeks after implantation;

Trace

This tracing shows correct sensing of sinus activity followed by ventricular pacing with capture; on one beat, ineffective ventricular pacing without capture;

Trace

Tracing recorded in continuity with the first tracing; increased number of ineffective ventricular pacings;

Trace

The EGM confirms the absence of ventricular capture with, on one beat, a junctional escape rhythm;

Trace

EGM interrogation confirms the elevation of the right ventricular threshold; this tracing is recorded after increasing the pacing amplitude and shows an effective permanent ventricular capture;

Exergue

In a patient implanted with a pacemaker, a ventricular pause may occur in 1) a specific algorithm to reduce the percentage of ventricular pacing able to tolerate the presence of ventricular pauses and blocked P waves; 2) ventricular oversensing (myopotentials, rupture potentials, interferences, etc.) inhibiting pacing (absence of pacing artifact); 3) inefficient pacing in relation to a threshold elevation (pacing artifact not followed by ventricular depolarization).