Clinical applications of ambulatory blood pressure monitoring: the white coat syndrome.

The estimation of an individual's true blood pressure by conventional clinical measurement is subject to a number of errors, stemming partly from the inherent variability of blood pressure, and also from the white coat syndrome, which is an elevation of blood pressure limited to the clinic setting. This may occur in about 20% of patients with mild hypertension, and is hypothesized to be a learned or conditioned response. Ambulatory monitoring may help to identify such patients. Other potential clinical applications of the technique include evaluation of patients with resistant hypertension, with excessively labile blood pressure, or with autonomic insufficiency, which may be characterized not only by hypotensive episodes, but also by hypertensive episodes during the night. An unresolved question is the definition of the upper limit of normal ambulatory pressure, which is required before ambulatory monitoring finds wide clinical acceptance.