[The variability of the heart rate, arterial pressure and peripheral circulation as the indices of autonomic control in essential hypertension].

In recent years the influence of autonomic nervous system on cardiac rhythm and blood pressure has been increasingly studied by analysis of cardiovascular fluctuations, particularly in diabetic and normal persons under various physiologic conditions, while still few data exist on essential hypertension. To characterize the autonomic cardiovascular control in essential hypertension we studied 22 untreated hypertensives, diagnosed within 1 year (mean age 43 +/- 2 years, mean +/- SEM) and 16 age-matched normotensives. Recordings of RR interval, breathing activity, noninvasive blood pressure (Finapres) and skin arteriolar flow (infrared photoplethysmogram) were obtained while in supine position and after sympathetic activation induced by passive transition to upright posture (tilting table). Autoregressive power spectral analysis was then carried out, and low- (0.03-0.15 Hz, LF) and high-frequency fluctuations (0.15-0.35 Hz, HF) were measured. LF and HF have been considered as markers of sympathetic and parasympathetic activity on the heart, respectively, and as markers of sympathetic and mechanic chest activity on the circulation, respectively. In supine position both cardiac and vascular variability were similar in both hypertensive and normotensive groups. After tilting however the increase in the sympathetic component of cardiac variability was blunted in hypertensives with respect to normotensives (hypertensives LFnu from 43.6 +/- 4.7 nu to 59.4 +/- 5.1 nu, p less than 0.005; normotensives LFnu from 36.9 +/- 3.3 nu to 83.4 +/- 2.6 nu, p less than 0.001), the increase in LFnu being statistically (p less than 0.001) reduced in the hypertensive subjects.(ABSTRACT TRUNCATED AT 250 WORDS)