Design of Korean Noninvasive Risk Evaluation Study for Sudden Cardiac Death from Infarction or Heart Failure – Myocardial infarction study of K-REDEFINE registry -

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.

Subclinical Atrial Fibrillation Burden and Adverse Clinical Outcomes in Patients With Permanent Pacemakers

BACKGROUND AND PURPOSE

Unlike clinical atrial fibrillation (AF), the significance of subclinical AF (SCAF) burden in patients with permanent pacemakers has not been fully evaluated.

METHODS

We investigated whether the SCAF burden was associated with increased risks of composite adverse outcomes, including progression to clinical AF, ischemic stroke, myocardial infarction, heart failure-related hospitalization, or cardiac death, in patients without previous AF. To quantify the 6-month SCAF burden, the total cumulative time spent in SCAF during every 6-month follow-up was summed.

RESULTS

During the median 5.2-year follow-up, 496 consecutive permanent pacemaker patients were classified into the no SCAF (no SCAF episode in any device analysis; n=152), low-burden SCAF (6-month SCAF <24 hours in at least one device analysis; n=287), or high-burden SCAF (6-month SCAF ≥24 hours in at least 1 device analysis; n=57) groups. The risk of composite adverse outcomes was greatest in the high-burden SCAF group (P<0.001) and was primarily driven by progression to clinical AF (P<0.001) and ischemic stroke (P<0.001). The presence of high-burden SCAF, which always preceded ischemic stroke events, was independently associated with composite adverse outcomes (odds ratio=20.1 [95% CI, 7.60-52.7], P<0.001) and progression to clinical AF (odds ratio, 36.2 [95% CI, 15.9-87.8], P<0.001).

CONCLUSIONS

In permanent pacemaker patients without preexisting AF, the presence of high-burden SCAF was closely associated with increased risks of composite adverse outcomes, particularly progression to clinical AF and ischemic stroke. Therefore, prospective studies deserve to be performed on the optimal anticoagulation therapy for permanent pacemaker patients with both high-burden SCAF and high stroke risk.