Idiopathic Ventricular Fibrillation in a 29-Year-Old Man.

A 29-year-old man with a recent history of cardiac arrest and placement of an implanted cardiac defibrillator (ICD) presented with palpitations and defibrillation shocks. Five months earlier, he had experienced ventricular fibrillation (VF) while seated at his desk job. After resuscitation, an extensive diagnostic evaluation for the etiology of his arrest was undertaken, including left heart catheterization with coronary angiography, a transthoracic echocardiogram, and cardiac magnetic resonance imaging. All of these studies were unremarkable, revealing no evidence of ischemic or structural cardiac disease. He was subsequently discharged after placement of a single-lead endocardial ICD.After discharge, the patient remained asymptomatic until this presentation, when he reported palpitations, light-headedness, and multiple device shocks while awake. These symptoms were coincident with the onset of a febrile, upper respiratory tract infection. Vital signs, physical examination, complete blood count, and electrolyte panel were normal. The patient’s 12-lead is shown in Figure 1. What is the most likely diagnosis for this patient, and what is the best course of treatment?Figure 1. ECG obtained on admission. Please turn the page to read the diagnosis.The patient’s telemetry tracing from an in-house syncopal episode demonstrates polymorphic ventricular tachycardia (PVT) triggered by premature ventricular depolarizations (PVCs) (Figure 2). The triggering PVCs …