Spectral characteristics of heart rate and blood pressure variability in primary aldosteronism.

A disturbance of the autonomic cardiovascular function has been postulated in primary aldosteronism as a possible mechanism for hypertension. Using the method of spectral analysis of heart rate and blood pressure variability, the aim of this study was to assess sympathovagal interactions modulating cardiovascular function and baroreflex control in patients with primary aldosteronism. Seventeen patients (7 with adenomas and 10 with idiopathic hyperaldosteronism) and a control group of 11 essential hypertensives (EH) and 10 normotensive subjects were studied. Continuous finger blood pressure was measured using a Finapres device and heart rate was measured using an electrocardiographic monitor. The studies were conducted in each patient for 20 min in the supine position and 10 min during a passive head-up tilt to 60 degrees. The low frequency and the low frequency-to-high frequency ratio of systolic and diastolic blood pressures were significantly higher both in primary aldosteronism and in EH patients compared with normotensives (P < .01). Impaired response to tilt was found in the heart rate and blood pressure variability in primary aldosteronism and EH patients; the increase in low frequency was smaller than in normotensives. Baroreflex gain (assessed by alpha index) was less in primary aldosteronism and EH patients as compared with normotensives. These findings may suggest that volume expansion or sympathetically mediated central translocation of the blood volume, or both, could stimulate the cardiopulmonary receptors and impair the baroreflex gain. Our findings suggest that an enhanced peripheral vascular responsiveness to a normal sympathetic outflow may be involved in the pathogenesis of hypertension in primary aldosteronism.