Study to Compare TWA Test and EPS Test for Predicting Patients at Risk for Life-threatening Heart Rhythms (ABCD Study)

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.

This is a prospective, multi-center study to demonstrate the following:

PRIMARY HYPOTHESIS: a TWA test directed therapy is equivalent to EPS directed therapy in predicting VTEs in patients with ischemic heart disease, LVEF less than 0.40, and asymptomatic non-sustained ventricular tachycardia. The study will determine whether the positive predictive value of TWA test directed therapy is equivalent to the positive predictive value of EPS directed therapy. The study will also determine whether the negative predictive value of TWA test directed therapy is equivalent to the negative predictive value of EPS directed therapy. The positive groups under TWA test directed therapy will be compared with the positive groups under EPS directed therapy, and the negative groups under TWA directed therapy will be compared with the negative groups under EPS directed therapy. SECONDARY HYPOTHESIS: The study will determine whether the positive predictive value of a TWA test (not including indeterminates) is equivalent to the positive predictive value of an EPS in predicting future VTEs. The study will also determine whether the negative predictive value of a TWA test (not including indeterminates) is equivalent to the negative predictive value of an EPS in predicting future VTEs. The TWA test positive groups will be compared with the EPS positive groups, and the TWA test negative groups will be compared with the EPS negative groups. The secondary hypothesis will also be tested against the primary endpoint defined above.