The role of ambulatory blood pressure monitoring in clinical practice.

The introduction of noninvasive techniques for the repetitive measurement of blood pressure in ambulant subjects has permitted improved precision in the assessment of hypertension during normal daily life. The traditional clinic (or "office") method of blood pressure measurement has the advantages of simplicity and low cost, and forms the basis of the current operational definitions of hypertension, but it is limited by the normal variability of blood pressure and the "white coat effect." By contrast, ambulatory blood pressure provides information on circadian variations in blood pressure and alterations due to changes in behavior, and may, therefore, be more appropriate for diagnosing hypertension. However, it is important to note that the values used to define normotension and hypertension for clinic blood pressure are not appropriate for ambulatory blood pressure. Recent population studies have proposed that the upper limit for 24-h ambulatory pressure should be 119 to 126/75 to 80 mm Hg, and failure to recognize this may account for at least some cases of "white-coat hypertension." There is increasing evidence that ambulatory blood pressure is more effective than clinic blood pressure in predicting the organ damage associated with hypertension, whereas data from intervention studies indicate that a reduction in ambulatory pressure is correlated with a reduction in left ventricular (LV) mass. Finally, ambulatory blood pressure measurements may provide a number of advantages in the development of antihypertensive therapies: by permitting better identification of trough and peak effects, by confirming that the efficacy of formulations for once-daily dosing is maintained throughout the 24-h period, and by minimizing the placebo effect.