Increased gain in baroreceptor-heart rate reflex in patients with primary aldosteronism

Reduced baroreflex sensitivity has been reported in several kinds of human hypertension. However, the nature of the baroreceptor-heart rate reflex in hypertension due to excess mineralocorticoid has never been fully explored.

Thirty patients with primary aldosteronism, 60 patients with essential hypertension (World Health organization stages I or II) and 45 normotensive subjects were enrolled. The groups did not differ in mean age. Blood pressure was similar between patients with primary aldosteronism and those with essential hypertension. Blood pressure (Finapres) and the RR interval (ECG) were monitored continuously at rest. The closed loop gain between systolic blood pressure and RR interval variabilities was used to measure the sensitivity of the baroreceptor-heart rate reflex.

Baroreflex sensitivity in the group with primary aldosteronism was significantly greater than in the essential hypertensive group, but did not differ significantly between the group with aldosteronism and the normotensive group. Three to four weeks after removal of an adrenal adenoma (n = 25), both systolic and diastolic blood pressure were decreased significantly in the aldosteronism group but were still higher than in the normotensive group. The baroreflex sensitivity was reduced by about 40% after adrenalectomy compared to pre-operative values. The decrease in the baroreflex gain following adrenalectomy was correlated negatively with the decrease in systolic blood pressure (r = -4.00, P=0.05).

These results demonstrate that hypertension due to excess mineralocorticoids is characterized by an increase in the gain of the baroreceptor-heart rate reflex. The reduction in baroreflex gain following adrenalectomy may delay the normalization of blood pressure.