Very low frequency power of heart rate variability is a powerful predictor of clinical prognosis in patients with congestive heart failure

Background The present study examined whether the very low frequency (VLF) power of heart rate variability (HRV) is predictive of clinical prognosis in patients with congestive heart failure (CHF). Method and Results The study recruited 54 consecutive CHF patients with emergency admission because of exacerbation of pulmonary congestion. Holter monitoring was performed after improvement of pulmonary congestion. The frequency components of HRV were calculated in the frequency domain (VLF, low frequency (LF), high frequency (HF), total power (TP) and the ratio of LF to HF power). The left ventricular ejection fraction was calculated, and plasma brain natriuretic peptide (BNP) and norepinephrine were also measured at discharge. Within a mean follow-up period of 19.8+/-11.7 months, 18 patients experienced cardiovascular events; 7 patients died and 11 patients required rehospitalization because of worsening of CHF. In univariate analysis, diabetes mellitus (DM), BNP and New York Heart Association (NYHA) functional class were significant as risk factors for cardiac events. VLF power, LF power and TP were the strong predictors for cardiac events in HRV. In multivariate analysis, VLF power predicted cardiac events independently of LF power, TP, DM, BNP and NYHA functional class (chi-square= 6.24, p=0.01). Conclusions VLF power is an independent risk predictor in patients with CHF.