Hashimoto K, et al. - In 47 subjects without significant structural heart disease, researchers investigated the impact of heart rate (HR) or cardiac autonomic nervous activity on T-wave alternans (TWA, which is a risk stratification predictor for sudden cardiac death) in daily life. They used 24-hour ambulatory electrocardiogram (AECG) to perform frequency domain (FD)-TWA analysis. They assessed the autonomic activity of the heart by measuring heart rate variability (HRV). Findings revealed a positive assocition of maximum FD-TWA with HR and LF/HF, while a negative association with HFnu was also observed. In the daily life of the participants, a noticeable diurnal variation of FD-TWA was evident. Compared to the HRV indices, HR could have a more robust influence on this variation.