Randomized trials have indicated that ICD therapy for primary prevention of sudden death is effective in many populations. The current indications for ICD insertion accepted by the Center for Medicare Services are shown in Table below. The most recent trials have used entry criteria based primarily on left ventricular ejection fraction (below 30% or 35%) and NYHA functional class. Most primary prevention trials have reported relative risk reductions in a range similar to those seen in the secondary prevention trials (20–30%). The CABG-Patch Trial and the Defibrillators in Acute Myocardial Infarction Trial (DINAMIT) failed to show benefit in patients who received their ICD either at the time of coronary revascularization or within 40 days of an acute myocardial infarction, respectively. These trials resulted in the specific exclusion of these conditions in the current guidelines.
Current Diagnosis & Treatment Cardiology 3rd Edition (McGraw-Hill) 2009