Fig. 2.

Implantable cardioverter-defibrillator electrogram showing polymorphic ventricular tachycardia initiated by a short-coupled premature ventricular contraction degenerating into ventricular fibrillation before a successful shock was applied in a 47-year old man treated with bisoprolol 2.5 mg daily who initially presented with out-of-hospital cardiac arrest one year earlier. Following this recurrence, bisoprolol was replaced with quinidine 600 mg daily, and he remained asymptomatic until last follow-up (3.5 years).