The daily variation in blood pressure (circadian blood pressure rhythm) is characterized by a nocturnal fall and a diurnal rise. The circadian blood pressure rhythm seems to be mediated mainly by the circadian rhythm of sympathetic tone, linked to changes in physical and mental activities, e.g. the waking-sleeping cycle. Statistically significant circadian blood pressure rhythms have been confirmed in approximately 80% of mild to moderate essential hypertensive patients as well as in normal subjects. However, the normal pattern of circadian blood pressure rhythm is reversed in elderly people and in those with Cushing's syndrome, those undergoing glucocorticoid treatment, and those with hyperthyroidism, central and/or peripheral autonomic dysfunction (Shy-Drager syndrome, tetraplegia, diabetic or uremic neuropathy, etc), chronic renal failure, renal or cardiac transplantation, congestive heart failure, eclampsia, sleep apnea syndrome, malignant hypertension, systemic atherosclerosis and accelerated hypertensive organ damage. However, in those with primary aldosteronism, renovascular hypertension, pheochromocytoma without paroxysmal hypertension, or those with cardiac pacing, a nocturnal blood pressure fall is ordinarily observed. It may be that a fall in cardiac output rather than in peripheral resistance may be mainly responsible for the nocturnal fall in blood pressure. It also seems that a nocturnal heart rate fall is not responsible for it, since the nocturnal blood pressure fall remained unchanged in patients undergoing cardiac pacing and was disturbed in patients with Cushing's syndrome or hyperthyroidism in whom the circadian heart rate rhythm remained unchanged. An alteration in the circadian blood pressure rhythm is non-specifically observed for different pathophysiological conditions, and a disturbance in any part of the hierarchy of factors that regulate the circadian rhythm of sympathetic neural tone seems to disturb the circadian blood pressure rhythm. We conclude that alterations in the circadian blood pressure rhythm can be attributed to (1) a disturbance in the mechanism mediating the circadian blood pressure rhythm, e.g. a disturbance in hypothalamo-pituitary-adrenal periodicity or in the sympathetic nervous system; or (2) a compensatory mechanism that maintains organ blood flow in response to organ ischemia. We postulate that though the circadian blood pressure rhythm is mainly mediated by a change in physical and mental activity, it is also mediated at least in part by an inherent rhythm.
|Journal||Journal of hypertension|
|Issue number||SUPPL. 7|
|Publication status||Published - 1990|
ASJC Scopus subject areas
- Internal Medicine
- Cardiology and Cardiovascular Medicine