Implantation of<unk>  is meant to prevent sudden cardiac death and is indicated under various conditions. Two broad but distinct categories are primary and secondary prevention. Primary prevention refers to patients who have not suffered a life-threatening arrhythmia episode. Secondary prevention has the strongest evidence for benefit and it refers to survivors of cardiac arrest secondary to ventricular fibrillation or hemodynamically unstable sustained ventricular tachycardia after reversible causes are excluded. Similarly,<unk>  use in primary prevention is to prevent cardiac death in patients who are at risk for sustained ventricular tachycardia or ventricular fibrillation. This population accounts for the bulk of all<unk>  implants. There are a multitude of guideline indications for<unk>  use in primary preventions with varying degree of supporting evidence. Periodically, both the American College of Cardiology (ACC)/American Heart Association (AHA) and European Society of Cardiology provide an update to this guideline. Some of the Class I indications are as follows: * With LVEF ≤ 35% due to prior Myocardial Infarction (MI) who are at least 40 days post-MI and are in NYHA Functional Class II or III * With LV dysfunction due to prior MI who are at least 40 days post-MI, have an LVEF ≤ 30%, and are in NYHA Functional Class I * With nonischemic DCM who have an LVEF ≤ 35% and who are in NYHA Functional Class II or III * With nonsustained VT due to prior MI, LVEF < 40%, and inducible VF or sustained VT at electrophysiological study * With structural heart disease and spontaneous sustained VT, whether hemodynamically stable or unstable * With syncope of undetermined origin with clinically relevant, hemodynamically significant sustained VT or VF induced at electrophysiological study
Implantable cardioverter-defibrillator
Transvenous pacing
Transcutaneous pacing
Pericardial window
Cardioversion
Cardiac pacemaker
Defibrillation
Automated external defibrillator