Microvolt T-wave alternans and electrophysiologic testing predict distinct arrhythmia substrates: implications for...

Better risk stratification of patients receiving an implantable cardioverter-defibrillator (ICD) for primary prevention of sudden cardiac death (SCD) is needed. Although microvolt T-wave alternans (MTWA) and electrophysiologic study (EPS) are independent markers for SCD, the Alternans Before Cardioverter Defibrillator (ABCD) trial found the combination to be more predictive than either test alone.

The purpose of this study was to test the hypothesis that EPS and MTWA measure different elements of the arrhythmogenic substrate and, therefore, predict distinct arrhythmia outcomes.

The ABCD trial enrolled 566 patients with ischemic cardiomyopathy, left ventricular ejection fraction (LVEF)

MTWA and EPS were abnormal in 71% and 39% of patients, respectively. There were 28 S-VTEs and 10 U-VTEs. MTWA was predictive of U-VTEs (event rate 2.7% in abnormals vs 0% in normals, P = .04), whereas EPS was not (1.5% vs 3.2%, P = .55). In contrast, EPS predicted S-VTEs (9.7% vs 2.2%, P <.01), but MTWA did not (5.5% vs 4.4%, P = .57). Whereas the extent of left ventricular contractile dysfunction alone (LVEF 0.30.

The study data suggest that EPS and MTWA identify distinct arrhythmogenic substrates and, when used in combination, may better predict the complex electroanatomic substrates that underlie the risk for SCD.