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.

The primary objective of this study is to test the hypothesis that therapy directed primarily by a T wave alternans (TWA) test, measured non-invasively during exercise, is equivalent to therapy directed by an electrophysiological study (EPS) in predicting spontaneous ventricular tachyarrhythmic events (VTEs) in patients with ischemic heart disease, left ventricular dysfunction, and asymptomatic non-sustained ventricular tachycardia (NSVT). In the absence of any previous life-threatening ventricular arrhythmia (i.e., for primary prevention), ICD implantation is currently indicated in patients with ischemic heart disease, left ventricular dysfunction, asymptomatic non-sustained ventricular tachycardia, and a positive EPS. The objective of this study is to demonstrate that a TWA test directed therapy is equivalent to EPS directed therapy in guiding ICD implantation for the purpose of primary prevention of sudden cardiac death (SCD) in patients with ischemic heart disease, left ventricular dysfunction, and asymptomatic non-sustained ventricular tachycardia.

Inclusion Criteria:

Subjects previously enrolled in the ABCD trial sponsored by St. Jude Medical (ClinicalTrials.gov Identifier NCT00187291)

• patients with ischemic heart disease
• left ventricular ejection fraction (LVEF) < 40%
• non-sustained ventricular tachycardia

Exclusion Criteria:

Individuals who were not previously enrolled in the ABCD trial are not eligible for this genetic sub-study.

The target population for the ABCD genetic sub-study includes all living individuals currently enrolled in the ABCD trial (total study enrollment=629; 566 analyzed in the trial) Participants of the ABCD trial underwent TWA and EPS testing to determine their risk for ventricular arrhythmia and most have received an implantable cardioverter defibrillator (ICD). The ABCD trial collected extensive longitudinal clinical data including medical and medication histories, incidence of ventricular arrhythmias, defibrillator shocks, other cardiovascular events, and mortality.