Pacemaker Overdrive Causing Recurrence of Rate-Dependent Ventricular Tachycardia

Pacemaker overdrive is an accepted method for treating drag resistant ventricular tachyarrhythmia. We report a paradoxic response to this mode of therapy in a 47-year-old man without demonstrable organic heart disease and His bundle documented ventricular tachycardia. Normally functioning ventricular demand pacemaker at a pacing rate of 107 per minute caused recurrent episodes of ventricular tachycardia. The latter also occurred with spontaneous acceleration of patient's heart rate, treadmill exercise, emotional stress and atrial pacing. The mechanisms involved are unknown. Propranolol therapy was effective.