Ventricular asystole due to inhibition of ventricular backup pacing by a dual chamber pacemaker: possible pitfalls of default settings.

A 62-year-old patient presented with dizzy spells after her dual chamber pacemaker (Medtronic Enrhythm P1501DR), implanted for complete AV block, had been reprogrammed to deliver antitachycardia therapy (ATP) for paroxysmal atrial tachycardia. Her symptoms were caused by inhibition of ventricular backup pacing during ATP, leading to ventricular asystoles. Inhibition was the result of premature ventricular beats occurring prior to ATP: when ventricular backup pacing is left in the default setting, this pacemaker withholds backup pacing if any of the four preceding events is a sensed event. This case illustrates the possibly hazardous effects of default pacemaker settings, especially in pacemaker-dependent patients. (Neth Heart J 2010;18:323-6.).