Microvolt T-wave alternans during exercise and pacing are not comparable

Aims The absence of microvolt T-wave alternans (MTWA) identifies a group of patients who are at low risk for ventricular arrhythmia or sudden cardiac death. However, in exercised assessed MTWA, 20–40% of all test results are indeterminate. We hypothesised that MTWA during pacing would yield less indeterminate results. Methods and results Thirty patients with ischaemic cardiomyopathy and prior dual chamber implantable cardioverter defibrillator implantation were enrolled. All patients underwent sequential MTWA testing using an exercise (E), atrial-paced (A), and atrioventricular-paced (AV) protocol. The number of indeterminate tests was lower during pacing (A: 17%; AV: 3%) compared with exercise (37%) (E vs. A: P = 0.015, E vs. AV: P = <0.001). When positive and indeterminate test results were grouped as non-negative, the concordance rates between E and A, E and AV, and A and AV were 60% ( κ = 0.17), 57% ( κ = 0.058), and 70% ( κ = 0.348), respectively. If indeterminate results were excluded, agreements were 60% ( κ = 0.19), 50% ( κ = 0.129) and 67% ( κ = 0.33), respectively. Conclusion Indeterminate test results are less common during pacing. However, there is a low concordance rate between test results using different protocols. This necessitates further study to determine the predictive value of each method in high risk patients with ischaemic cardiomyopathy.