Depressed low frequency power of heart rate variability as an independent predictor of sudden death in chronic heart failure

Aims Identification of patients with chronic heart failure at risk for sudd en death remains difficult. We sought to assess the prognostic value for al l-cause and sudden death of time and frequency domain measures of heart rat e variability in chronic heart failure. Methods and Results We prospectively enrolled 190 patients with chronic hea rt failure in sinus rhythm, mean age 61 +/- 12 years, 109 (57.4%) in NYHA c lass II and 81 (42.6%) in classes III or IV, mean cardiothoracic ratio 57.6 +/- 6.4% and mean left ventricular ejection fraction 28.2 +/- 8.8%, 85 (45 %) with ischaemic and 105 (55%) with idiopathic dilated cardiomyopathy. Tim e and frequency domain measures of heart rate variability were obtained fro m 24h Holter ECG recordings, spectral measures were averaged for calculatio n of daytime (1000h-1900h) and night-time (2300h-0600h) values. During foll ow-up (22 +/- 18 months), 55 patients died, 21 of them suddenly and two pre sented with a syncopal spontaneous sustained ventricular tachycardia. In mu ltivariate analysis, independent predictors for all-cause mortality were: i schaemic heart disease, cardiothoracic ratio greater than or equal to 60% a nd standard deviation of all normal RR intervals <67 ms (RR=2.5, 95% CI 1.5 -4.2). Independent predictors of sudden death were: ischaemic heart disease and daytime low frequency power <3.3 In (ms(2)) (RR=2.8, 95% CI 1.2-8.6). Conclusion Depressed heart rate variability has independent prognostic valu e in patients with chronic heart failure; spectral analysis identifies an i ncreased risk for sudden death in these patients. (C) 2000 The European Soc iety of Cardiology.