Estimation of sleep quality from ultradian dynamics of heart rate variability in patients with heart failure

Abstract

Background: To date, assessment of sleep quality has been performed using all-night polysomnography with no other options. The purpose of this study is to try to evaluate sleep quality with a new method accessible to outpatients with heart failure. Methods: All-night polysomnogaraphy (EEG) and electrocardiaography (ECG) were performed in 7 patients with heart failure and 8 patients with normal cardiac function. Five-minute data of all-night EEG and RR intervals were serially obtained by shifting the data range every 50 sec and subjected to spectral analysis to detect slow wave activity (SWA) and high-frequency components (RR-HF) of heart rate variability. The ultradian rhythms were extracted by applying wavelet analysis to the sequential changes of SWA and RR-HF. Results: In patients with normal cardiac function, the ultradian rhythms of SWA and RR-HF had a large amplitude (SWA: 51 ± 8 %, RR-HF: 49 ± 13 %) of oscillations during early sleeping periods. These ultradian rhythms were synchronized with a high squared coherence of 0.80 ± 0.08. In patients with heart failure, however, the ultradian rhythms of SWA and RR-HF were significantly attenuated in amplitude ( SWA, 39 ± 21 %,p < 0.05, RR-HF, 32 ± 15 %, p < 0.05 ) with squared coherence of 0.63 ± 0.25. Conclusions: The present findings suggest that the ultradian dynamics of RR-HF derived from all-night ECG might serve as a new potential, quantitative measure for evaluating sleep quality in outpatient clinic.