Linear and non-linear 24 h heart rate variability in chronic heart failure

It has recently been demonstrated that SDNN of heart rate variability (HRV) is a useful independent prognostic tool in chronic heart failure (CHF). Th e purpose of the present study was to evaluate if spectral and non-linear a nalysis of 24-h HRV, considered markers of autonomic cardiac modulation, co ntain independent prognostic information in CHF patients. Twenty normal sub jects and thirty consecutive outpatients with clinically stable CHF were st udied for 2 years. Periods of 300 R-R intervals were analyzed from Holter r ecordings. The power spectral analysis, the slope of the linear relationshi p between log-power versus log-frequency (l/f), and the complexity content (using corrected conditional entropy; CCE) of the R-R series were calculate d. The normalized power of the low frequency spectral component (LF) and th e l/f slope were significantly lower in patients compared to controls (resp ectively 30.1+/-3.0 vs. 48.6+/-3.4 and -1.27+/-0.04 vs.-1.08+/-0.05: P<0.05 ). Moreover, the patients who died during the study presented a reduced LF (20.9+/--4.1 vs. 35.5+/-3.5 nu: P<0.05) and a steeper l/f slope (-1.40+/-0. 09 vs. - 1.21+/-0.04 nuts, P<0.05) compared to survivors. These results rem ained significant in a logistic model including heart rate and SDNN. The in formation content present in spectral and non-linear analysis of HRV in CHF patients has prognostic relevance independently from the time domain measu res of HRV. In particular, the reduction of LF power seems the best indicat or among those considered. (C) 2000 Elsevier Science B.V. All rights reserv ed.