Abstract 15674: Can Heart Rate Turbulence and T-Wave Alternans on Holter Electrocardiograms Predict Serious Cardiac Events in Patients After Myocardial Infarction?

Abstract

Backgrounds: Patients who survive a myocardial infarction (MI) are at risk of serious events such as sudden cardiac death (SCD). Although the implantable cardioverter-defibrillator (ICD) reduces mortality after MI, there is no reliable method to predict SCD. Because of the relatively low accuracy of Left ventricular ejection fraction (LVEF), noninvasive measures of autonomic tone and cardiac electrical substrate have been developed to identify patients at risk of SCD. Recent studies have reported that heart rate turbulence (HRT) and T-wave alternans (TWA), which can be assessed simply using 24-hr Holter electrocardiogram is a significant index for cardiac events. Material and Methods: A total of 464 patients who was first diagnosed with myocardial infarction and treated with percutaneous coronary intervention (age 63 ± 12, 70.9% male) were analyzed. All patients performed 24-h Holter ECG monitoring during hospitalization (mean duration after MI 2.7 ± 1.8 days) to measure HRT, modified moving average method (MMA)-TWA and other conventional parameters. HRT was determined positive when both turbulence onset and turbulence slope were abnormal and MMA-TWA was determined positive when the maximal voltage was > 64 μV. The cardiac mortality and sudden cardiac death were analyzed for 2 years. Results: HRT was positive in 48 patients (10.3%) and MMA-TWA was positive in 250 patients (53.9%). During 2 years follow-up, 23 patients (4.9%) were died from cardiac disease, including 19 patients (4.1%) with SCD. On univariative analysis, HRT was a significant predictor for cardiac death (Hazard ratio, 4.29; 95% C.I. 1.66-10.98; P = 0.003) and SCD (Hazard ratio, 5.75; 95% C.I. 2.14-15.41; P = 0.001). On multivariative analysis, HRT had the significant value, with a hazard ratio of 3.25 (95% C.I. 1.09-9.74, P = 0.035) for SCD. Older age, lower LVEF, non-use of beta-blocker, presence of non-sustained ventricular tachycardia were another predictor of cardiac events. However, MMA-TWA can not predict cardiac events in this study. Conclusion: The present study revealed that HRT was a significant predictor of SCD. However, MMA-TWA can not predict cardiac events in acute phase of myocardial infarction.