Noninvasive risk assessment and prediction of cardiac outcomes in patients with congestive heart failure or myocardial infarction

Background: Heart rate turbulence (HRT) and T-wave alternans (TWA), recognized as promising noninvasive markers for ventricular tachyarrhythmias and cardiac death, have been studied predominantly in Western populations, specifically in patients with myocardial infarction (MI) or heart failure (HF) with reduced ejection fraction (EF).

Objective: The purpose of this study was to investigate the clinical implications of HRT and TWA in predicting adverse cardiac events, including cardiac death, ventricular tachyarrhythmia, and heart failure-related hospitalization (HFH).

Methods: The K-REDEFINE study, a prospective, observational, multicenter analysis of 26 tertiary hospitals in South Korea, investigated the prognostic implications of Holter-based variables including HRT and TWA in 1116 patients with acute MI or HF (age 60.8 ± 2.9 years; 76.3% male). All participants underwent 24-hour Holter recording within 6.8 ± 16.5 days after hospitalization. The primary composite outcome included cardiac death, ventricular tachyarrhythmias, and HFH.

Results: During 4.3 ± 1.2 years of follow-up, impaired HRT demonstrated the most powerful predictive value for the composite (adjusted hazard ratio [aHR] 3.41, 95% confidence interval [CI] 2.27-5.13) or individual events: cardiac death (aHR 4.08, 95% CI 2.17-7.70), ventricular tachyarrhythmia (aHR 3.72, 95% CI 1.29-10.77), and HFH (aHR 4.32, 95% CI 2.25-8.28). The predictive power of abnormal HRT remained consistently significant across subgroups of MI and HF, or across varying degrees of EF. When combined with reduced EF (<50%), the predictive power was further enhanced. However, abnormal TWA was significantly associated only with the composite outcome (aHR 1.51, 95% CI 1.06-2.16).

Conclusion: The K-REDEFINE study identified abnormal HRT, mostly assessed within 1 month after hospitalization, as a significant predictor not only for cardiac death and ventricular tachyarrhythmia but also for HFH.