Power spectral analysis of the heart rate in hypertensive patients with and without left ventricular hypertrophy: the effect of a left ventricular mass reduction

Objective The aim of this study was to evaluate the spectral analysis of th e heart rate in normotensive subjects and in hypertensive patients with and without left ventricular hypertrophy (LVH), under basal conditions and aft er a reduction in left ventricular mass. Subjects and methods In 12 normotensive subjects and 22 hypertensive patien ts (14 with and eight without LVH), we performed 24 h electrocardiogram Hol ter monitoring, ambulatory blood pressure monitoring and an echocardiograph ic study. Sequences of 512 R-R intervals, during daytime, afternoon and nig ht-time periods, were taken for an evaluation of spectral analysis (Box-Jen kins method). We then calculated the absolute and percentage power spectral density of the peak centred at 0.10 Hz (low-frequency peak) and at 0.25 Hz (high-frequency peak). Results At baseline, a daytime to night-time decrease in the low-frequency peak was detected in normotensives (P < 0.01) and in hypertensives without LVH (P < 0.01), while no change was observed in hypertensives with LVH. The power spectral density low-frequency peak during the daytime and night-tim e was significantly greater in hypertensives with LVH than in those without LVH (P < 0.001) and in normotensive subjects (P < 0.001). Fourteen of thes e patients with LVH were given effective long-term antihypertensive treatme nt and were studied again 20 days after the treatment had been withdrawn, w hen blood pressure had increased to pretreatment values. in eight patients showing a reduction in LVH, we found a significant decrease in the power sp ectral density low-frequency peak and an increase in the high-frequency pea k during daytime and night-time in respect to basal conditions, and circadi an variations in the spectral indices of heart rate variability were restor ed. In contrast, in six patients without reversal of LVH, the power spectra l density low-frequency peak did not change in respect to basal conditions and remained significantly higher in comparison with the patients with LVH regression. Conclusion A reduction in LVH may be associated with restoration of daytime to night-time cardiac autonomic control, as evaluated by a power spectral analysis of the heart rate. J Hypertens 1998, 16:1641-1650 (C) Lippincott W illiams & Wilkins.