RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM, RR INTERVAL, AND BLOOD-PRESSUREVARIABILITY DURING POSTURAL CHANGES IN BORDERLINE ARTERIAL-HYPERTENSION

This study aimed to examine the changes in RR interval and blood press ure (BP) variability and humoral factors during postural changes in bo rderline arterial hypertension. Twenty-nine patients (44 +/- 3 year; B P, 145 +/- 3/84 +/- 3 mm Hg) with borderline hypertension and a contro l group of 38 subjects (35 +/- 2 year; BP, 123 +/- 3/70 +/- 2 mm Hg) u nderwent power spectrum analysis of RR interval and BP (low frequency (LF), 0.05 to 0.15 Hz; high frequency (HF), 0.15 to 0.40 Hz) in the su pine and standing positions. Concentrations of plasma renin activity, angiotensin II, and aldosterone in supine and standing positions had b een determined in the hypertensive group. Borderline hypertensives are characterized by higher oscillations of systolic and diastolic BP, bu t not of RR interval in the supine position versus the control group. Low frequency and HF components of systolic and diastolic BP expressed as absolute data are also significantly higher in borderline hyperten sives. Moreover, standing tended to increase the LF/HF ratio of both R R interval and BP variability compared to controls. The standing posit ion was able to further activate the LF but not the HF component of BP variability. In borderline hypertension renin release during postural changes correlated well with the decrease in the power of the HF vaga l component of RR interval variability (r = -0.70, P <.001) and with t he increase of the LF component of diastolic blood pressure variabilit y (r = 0.43, P =.03). In conclusion, our results indicate that in bord erline arterial hypertension, LF and HF oscillations of BP are already significantly increased at rest. Standing was capable of significantl y activating the LF component, but not the HF component, of BP variabi lity.