Implantable Cardioverter Defibrillator Versus Optimal Medical Therapy In Patients With Variant Angina Manifesting as Aborted Sudden Cardiac Death

Inclusion Criteria: * Age 18 years or older * Patients experienced successfully resuscitated cardiac arrest due to documented ventricular fibrillation or sustained rapid ventricular tachycardia * Diagnosed as variant angina, defined by spontaneous coronary spasm with ST elevation (≥0.1mV) in the coronary angiogram and/or documented coronary spasm on ergonovine provocation coronary angiography Exclusion Criteria: * Significant (\>50%) coronary artery stenosis on coronary angiography * Organic heart disease known to be associated with sudden cardiac arrest. * Heart failure with reduced ejection fraction (Left Ventricular Ejection Fraction \< 35%) * Presence of LV akinesia or aneurysm * Hypertrophic cardiomyopathy * Arrhythmogenic right ventricular dysplasia * Chronic Heart Failure New York Heart Association functional class III or IV * prior history of atrial or ventricular arrhythmia requiring class I or III antiarrhythmic drugs (flecainide, propafenone, amiodarone, sotalol and dronedarone) * Prior catheter ablation for ventricular arrhythmia * Primary cardiac electrical diseases (long QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia) * Prior pacemaker or Implantable Cardioverter Defibrillator * 2nd or 3rd degree AV block not related to coronary ischemia, requiring permanent pacemaker * Patients with poor neurologic outcome (defined as cerebral performance category scale ≥3) * Life expectancy \<2 years * Psychiatric illnesses that may be aggravated by device implantation or that may preclude systematic follow-up