Pacing spikes without visible QRS complexes: Failure to capture?

A man in his 60s with advanced infra-Hisian conduction disease underwent dual-chamber pacemaker implantation with left bundle branch area pacing. Postimplant telemetry demonstrated intermittent pacing spikes apparently not followed by QRS complexes, raising concern for failure to capture or lead dislodgment. However, the patient remained asymptomatic and device interrogation showed preserved sensing, stable lead impedance, and normal capture thresholds. Careful inspection of the telemetry tracing revealed preserved T waves and subtle low-amplitude ventricular depolarizations despite the apparent absence of visible QRS complexes. The findings were attributed to telemetry processing artifact with preserved ventricular activation during unipolar left bundle branch area pacing.