POWER SPECTRAL-ANALYSIS OF HEART PERIOD VARIABILITY IN HYPERTENSIVE PATIENTS WITH LEFT-VENTRICULAR HYPERTROPHY

This study aimed to characterize sympathovagal balance by heart period power spectrum analysis in hypertensive patients with echocardiograph ic evidence of left ventricular hypertrophy. Twenty ambulatory patient s (11 men and 9 women), aged 50 +/- 10 years, with established essenti al hypertension and echocardiographic left ventricular hypertrophy, pe rformed 24-h blood pressure monitoring and electrocardiogram Holter re cording on 2 consecutive days. Twenty age- and sex-matched normal subj ects comprised the control group. Power spectrum analysis, performed u sing the fast Fourier transform algorithm, demonstrated lower values o f low acid high frequency power in hypertensives than in controls, whi le ultralow and very low frequency power were similar in the two group s. Very low frequency, low frequency, and high frequency power increas ed during the night in both groups, showing a similar circadian patter n. We found a direct correlation between daytime systolic (r = 0.51; ( P <.05) and diastolic (r = 0.52; P<.05) blood pressure and left ventri cular mass index. Moreover, negative correlations were found between l eft ventricular mass index and low frequency (r = -0.47; P <.05) and h igh frequency power (r = -0.47; P <.05). There was a direct correlatio n between nighttime decrease in systolic blood pressure and nighttime increase in high frequency power (r = 0.45; P <.05). As 24-h low frequ ency and high frequency power, obtained using the Fourier transform al gorithm, both reflect the parasympathetic modulation of heart rate, ou r results demonstrate that hypertensive patients with left ventricular hypertrophy are characterized by a sympathovagal imbalance with a red uction of vagal tone that is more evident with increasing severity of hypertension.