 The ABCD clinical study ClinicalTrials.gov Identifier NCT00187291 was designed to determine if a T-Wave Alternans TWA test is equivalent to an Electrophysiology Study EPS in predicting life-threatening heart rhythms in patients with ischemic heart disease, left ventricular dysfunction, and non-sustained tachycardia. The purpose of the ABCD Genetic sub-study is to identify genetic markers that predict TWA status and arrhythmia risk in this same population. 