Ventricular tachycardia induced by pacing algorithm designed to avoid atrial fibrillation.

A patient with a dual chamber pacemaker was admitted to the emergency room after out-of-hospital cardioversion for syncopal sustained monomorphic ventricular tachycardia. Device interrogation revealed an abnormally timed ventricular spike after a ventricular premature beat at the beginning of the event, caused by a pacemaker algorithm designed to avoid atrial fibrillation, non-competitive atrial pacing. Despite the absence of significant coronary lesions, in the setting of a vulnerable substrate - a hypokinetic and hyperechogenic region of ventricular myocardium - an upgrade to a dual-chamber implantable cardioverter-defibrillator was performed, and substrate ablation was planned.