1/f spectrum slope of 24 hour heart rate variability signal in normal and hypertensive subjects

The power spectrum density of the heart rate beat to beat variability signal shows, in a frequency range of less than 0.01 Hz, a behaviour inversely proportional to frequency. This finding has been related to the chaotical component of the signal and the expression of the complexity of the heart rate control mechanisms. The authors tested the 1/f mathematical model on the 24 hour heart rate in 40 subjects, half normal and half young essential hypertensive. The authors found that 1/f slope is 1.12/spl plusmn/0.14 in the normal subjects and 1.24/spl plusmn/0.15 in the hypertensive ones (p<0.02). The data suggest a loss of complexity in cardiovascular control in essential hypertension.<
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