Circadian rhythm of blood pressure in primary aldosteronism and renovascular hypertension--analysis by the cosinor method.

The circadian rhythm of blood pressure in 11 patients with primary aldosteronism (ALD) and 15 patients with unilateral renovascular hypertension (RVH) was analyzed using the cosinor method which fits a cosine function to a series of data. In ALD, both systolic (SP) and diastolic blood pressures (DP) increased in the late evening; the amplitude and acrophase of the circadian rhythm for SP were 7.3 (5.3 to 9.3, mean and 95% confidence limits) mmHg and 20:47 (19:42 to 21:52) hours, respectively, and for DP 2.6 (1.3 to 3.9) mmHg and 21:34 (19:40 to 23:28) hours, respectively. After excision of an adrenal adenoma in 6 patients, the circadian rhythm of SP and DP was abolished. In RVH, the acrophase of the circadian rhythm of SP and DP differed by about 12 hours; the amplitude and acrophase for SP were 5.7 (3.9 to 7.5) mmHg and 17:49 (16:35 to 19:02) hours, respectively, and for DP 1.5 (0.2 to 2.7) mmHg and 6:08 (2:44 to 9:31) hours, respectively. After various surgical interventions in 8 patients, the circadian rhythm of SP persisted with little change in acrophase, while that of DP disappeared. The difference in circadian rhythm suggests a difference in mechanisms of blood pressure control in ALD and RVH.