| Research Abstract |
Blood pressure (BP) variation includes short-term and long-term variation. The former is regarded as being the BP variation over seconds, minutes or hours and the latter as being the dally BP variation (circadian BP variation). To determine the former, a direct intra-arterial method or indirect finger volume-oscillometric method is useful, while the ordinary arm-cuff method is used for determining the latter. Short-term BP variation is mediated by 1) the output of the central cardiovascular regulatory center in response to internal and external stimuli, 2) the responsiveness of the effector organ to the central output, and 3) the responsiveness of the buffering system. It is considered that the short-term BP variation per se as well as the BP level reflects hypertensive vascular damage. Circadian BP variation is mediated mainly by the circadian rhythm of sympathetic tone linked to the changes in physical and mental activities, e.g. the wake-sleep cycle. In several pathophysiological co
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nditions such as autonomic dysfunction, endocrine disorder, metabolic disease, and atherosclerotic disease, circadian BP variation is eliminated or reversed, indicating that it is mediated at least in part by an inherent rhythm, although it is uncertain whether this is primary or secondary. A circadian BP variation, i.e. nocturnal fall and diurnal rise in BP, is observed in the majority of essential-hypertensive patients as well as in normal subjects. The amplitude of the nocturnal fall in BP in elderly subjects is similar to that in young or adult subjects. Several types of antihypertensive drugs, like calcium-antagonist, converting-enzyme inhibitors, and -blockers without sympathomimetic action, induce a significant downward shift in the circadian BP pattern, indicating their hypotensive effect during the night when the BP is already decreased during sleep. It is possible that excessive nocturnal fall in BP by antihypertensive treatment in old patients induces cerebrovascular and cardiovascular ischemia. Considering the above, it is concluded that information on BP variation, both short-term and long-term (circadian), is indispensable for the diagnosis and treatment of hypertension. Less
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