Questionable dysfunction of a dual-Chamber pacemaker in a 17-year-old female: differential diagnoses of missing ventricular beats.

The case of a 17-year-old female who had been implanted a dual-chamber DDD pacemaker because of third-degree atrioventricular block is reported. There is a history of continued dizziness and even occasional syncopes. At heart rates of 111/min to 124/min, 24-h Holter electrocardiography revealed isolated missing ventricular beats in an otherwise continuous atrially sensed and triggered, ventricularly paced rhythm. Differential diagnoses of a putative pacemaker dysfunction are presented, comprising 2:1-block at maximum programmed heart rate, intermittent lead fracture, anti-pacemaker-mediated tachycardia algorithm, ventricular oversensing, P wave signal undersensing, and atrial oversensing.