Ambulatory blood pressure monitoring: research and clinical applications.

Intra-arterial ambulatory blood pressure monitoring has shown that blood pressure undergoes a marked fall during sleep and marked repeated rises during emotional stimuli, including those elicited when blood pressure is assessed by the physician. This leads to an overestimate of blood pressure levels, which is so variable between patients, and so persistent and unpredictable that it seriously interferes with the diagnosis of hypertension. The ambulatory measurement technique has shown that, to a substantial degree, 24-h blood pressure variations can be attributed to neural influences triggered by environmental stimuli. However, blood pressure oscillates at different frequencies throughout the day and night and thus the overall blood pressure variability can be divided into a non-rhythmic and a rhythmic component, its size in each individual being buffered by the arterial baroreflex. In the light of these findings, ambulatory blood pressure monitoring is not only an important tool in cardiovascular research but also has potential for improving the diagnosis of hypertension and the evaluation of antihypertensive treatment. Ambulatory blood pressure data can be correlated, to a greater degree than clinic blood pressure, with the target-organ damage sustained by both treated and untreated hypertensive patients. However, widespread use of this approach in clinical practice must await the establishment of ambulatory blood pressure norms and demonstration of its prognostic superiority over traditional blood pressure assessments. Further, non-invasive ambulatory blood pressure monitoring (the only approach feasible on a routine basis) has limited accuracy and markedly increases the cost of dealing with hypertension.