Abnormalities in blood pressure circadian rythm. Physiopathological mechanisms and clinical implications.

A wide range of definitions is used to distinguish the hypertensives with a blunted circadian pattern of blood pressure, labeled as " non dippers ", f rom those presenting with a normal night blood pressure fall, designated as " dippers ". Consequently the prevalence of non dipping phenomenon is quit e uncertain : from 6 to 40% of the hypertensive subjects. The mechanisms of night blood pressure fall remain unclear, but the involve ment of autonomic nervous system turns out to be partly demonstrated. From a clinical point of view, non dippers and dippers characteristics are not o bviously different, but the prognosis of non dipper patients appears to be rather poor, with a more frequent target organ damage and a higher rate of cardiovascular events, as compared to dippers, even in a general population . In order to improve the identification of non dippers, an ambulatory blood pressure monitoring should be performed in patients with autonomic nervous system impairment and in subjects with target organ damage more severe than expected from office or home blood pressure measurements.