Ambulatory electrocardiogram (ECG)-based T-wave alternans (TWA) quantified by the modified moving average method (MMA) can be used to identify patients at risk for sudden cardiac death. However, there is no information available on ambulatory ECG-based TWA as quantified by the frequency domain (FD) method to identify patients with an implantable cardioverter defibrillator (ICD) who are at high risk for ventricular tachyarrhythmias. Further, there are few data regarding the comparison of clinical utility of FD-TWA with MMA-TWA, heart rate variability (HRV), and heart rate turbulence (HRT).Methods and Results:
In 41 patients with ICD, of whom 14 patients had a past history of at least one appropriate ICD discharge, FD-TWA, MMA-TWA, HRV, and HRT were analyzed from 24-hour Holter ECG monitoring recordings. Only positive results of FD-TWA and abnormal HRV (standard deviation of all normal-to-normal intervals ≤111 ms) were significantly more frequently observed in patients with than without appropriate ICD discharge. Patients with FD-TWA positive had a significantly higher risk of appropriate ICD discharge than those with FD-TWA negative (50% vs 16%; odds ratio, 5.3 [95% confidence interval, 1.2–23.7], P = 0.02). When FD-TWA and HRV were combined, the specificity (93% vs 59%, P = 0.003) and predictive accuracy (83% vs 66%, P = 0.07) for the identification of patients with appropriate ICD discharge were greater than those for FD-TWA only.Conclusion:
The ambulatory ECG-based FD-TWA might be useful to detect patients with ICD who are at high risk for ventricular tachyarrhythmias, and the combination of FD-TWA and HRV might improve the ability to detect such high-risk patients.