Can We Improve the Predictive Value of an Electrophysiological Test? Lessons From a Multicenter Prospective Trial
Author Block:	Guy Amit, MD, Avraham Wagshal, M.D., David S.. Rosenbaum, MD and Ottorino Costantini, MD. Metrohealth Medical Center, Case Western Reserve University, Cleveland, OH, Soroka Medical Center, Beer Sheva, Israel, Metrohealth Campus, Case Western Reserve University, Cleveland, OH
Introduction: Current guidelines for defibrillator (ICD) therapy include most patients with an ejection fraction (EF) ≤ 0.35. Although a positive electrophysiological study (EPS) predicts a higher risk of sudden cardiac death (SCD) some patients with a negative EPS are still at risk. However, the definition of a “negative” EPS includes patients with inducible polymorphic ventricular tachycardia and ventricular flutter by 3 extrastimuli. This study tested the hypothesis that by defining such EPS as positive the negative predictive value of an EPS would be improved. Methods: The Alternans Before Cardioverter Defibrillator (ABCD) Trial enrolled 566 patients with ischemic cardiomyopathy and EF ≤ 0.40. All patients underwent both a microvolt T Wave Alternans test (MTWA) and EPS. The Kaplan-Meier analyses for the primary end-point of appropriate ICD therapy or SCD after 1 year of follow -up, were compared for the standard definition of a negative EPS (if ventricular fibrillation, polymorphic ventricular tachycardia or ventricular flutter were induced by 3 extra-stimuli) vs. a "new", more restrictive negative EPS definition (where such tests were grouped with the positive ones). The EPS results were then stratified by the MTWA test result. Results: The EPS was negative in 344 (61%) patients by the standard definition, and in 261 (46%) patients by the more restrictive definition. The 1-year primary end point event rate was 7% for the whole cohort. The 1 year event rates were 4.3% and 4.5% for the two definitions, respectively. However, in patients with normal MTWA test, the event rates were 2.2% (n= 2/98) and 1.3% (n= 1/78) for the “standard” and “new” definitions of a negative EPS, respectively. Conclusions: A more restrictive definition of EPS negativity doesn't improve the predictive value of a stand-alone EPS. However, the combination of a negative EPS result and a normal MTWA test identified patients who are at an extremely low risk of an event, especially when using the “new”, more restrictive definition of a negative EPS. These data may help in identifying a very low risk group, who may not benefit from a prophylactic ICD.