Enhanced predictive power of quantitative TWA during routine exercise testing in the Finnish Cardiovascular Study

Introduction: We examined whether quantification of T-wave alternans (TWA) enhances this parameter's capacity to evaluate the risk for total and cardiovascular mortality and sudden cardiac death (SCD). Methods and Results: The Finnish Cardiovascular Study (FINCAVAS) enrolled consecutive patients (n = 2,119; 1,342 men and 777 women) with a clinically indicated exercise test with bicycle ergometer. TWA (time domain-modified moving average method) was analyzed from precordial leads, and the results were grouped in increments of 10 μV. Hazard ratios (HR) for total and cardiovascular mortality and SCD were estimated for preexercise, routine exercise, and postexercise stages. Cox regression analysis was performed. During follow-up of 47.1 ± 12.9 months (mean ± standard deviation [SD]), 126 patients died: 62 were cardiovascular deaths, and 33 of these deaths were sudden. During preexercise, TWA ≥ 20 μV predicted the risk for total and cardiovascular mortality (maximum HR >4.4 at 60 μV, P < 0.02 for both). During exercise, HRs of total and cardiovascular mortality were significant when TWA measured ≥50 μV, with 90 μV TWA yielding maximum HRs for total and cardiovascular death of 3.1 (P = 0.03) and 6.4 (P = 0.002), respectively. During postexercise, TWA ≥60 μV indicated risk for total and cardiovascular mortality, with maximum HR of 3.4 at 70 μV (P = 0.01) for cardiovascular mortality. SCD was strongly predicted by TWA levels ≥60 μV during exercise, with maximum HR of 4.6 at 60 μV (P = 0.002), but was not predicted during pre- or postexercise. Conclusion: Quantification of TWA enhances its capacity for determination of the risk for total and cardiovascular mortality and SCD in low-risk populations. Its prognostic power is superior during exercise compared to preexercise or postexercise.