Circadian variation of blood pressure and the assessment of antihypertensive therapy
White, W.B.
Blood Pressure Monitoring 4 Suppl. 1: S3-S6
1999
ISSN/ISBN: 1359-5237 PMID: 10822410 Document Number: 508558
The inherent variability of activity and the awake-sleep cycle creates changes in hemodynamics that may influence the outcome of a variety of cardiovascular disorders. Recently, data suggest that increased variability of blood pressure may promote excessive hypertensive target organ disease. Several epidemiologic studies have demonstrated that myocardial ischemia, myocardial infarction and sudden cardiac death have an excess incidence in the first several hours post-awakening. Additionally, surveys of the incidence of stroke (both ischemic and hemorrhagic) have shown an excess for the hours between 8 a.m. and noon. The pathophysiologic bases for the increased number of cardiac and cerebrovascular events in the early morning hours may be both due to hemodynamic and hematorrheologic factors. During the past several years, therapeutic studies have evaluated the effects of antihypertensive therapies on blood pressure and heart rate during the circadian or 24 h period. There are a few studies that have evaluated nighttime dosing of conventional antihypertensive therapies but these have generally been statistically underpowered to demonstrate differences of morning versus evening dosing on circadian blood pressure. Since the timing of dosing (and hence the delivery of antihypertensive therapy) may be clinically relevant, prospective and well-performed clinical trials of chronotherapy are necessary. In this review, we evaluate new data on the clinical impact of cardiovascular chronotherapy and the importance of timing of dosing on pharmacodynamics.