AMBULATORY BLOOD-PRESSURE MONITORING - METHODOLOGIC ISSUES

Blood pressure, like heart rate, is a changing physiologic variable. L ike ambulatory electrocardiography, ambulatory blood pressure can be r ecorded intermittently throughout the day. Ambulatory blood pressure i s a dynamic variable influenced by multiple factors, and it correlates more strongly with target organ damage than do static office blood pr essure measurements. Office (but not ambulatory) measurements are subj ect to the placebo and physician presser effect. There is a greater pa tient variability of blood pressure measurements in the office compare d with ambulatory methods. Ambulatory blood pressure devices are porta ble rather than 'ambulatory', The auscultatory (listens for Korotkoff sounds) and oscillometric (detects maximal arterial vibrations and cal culates diastolic blood pressure) methods are used to detect blood pre ssure. Equipment is generally safe, although mild sleep derangements h ave been reported. The 24-h blood pressure and diurnal change are usua lly assessed. A 24-h ambulatory blood pressure mean of 140/90 mm Hg or above is clearly abnormal, though recent data suggest that the 95th c entile is 134/84 mm Hg. Correlation of individual blood pressure readi ngs with diary entries may be instructive. New American and British va lidation criteria have been published to assess the performance of eac h new device that becomes available. It should not be assumed that new er ambulatory devices have been tested (particularly by a third party) or are better. Test/retest 24-h ambulatory blood pressure shows less variability than office measurements; however, the percentage of patie nts with a mean difference greater than +/- 5 mm Hg on repeat 24-h blo od pressure measurement after 1 week is still surprisingly high (49.3% , systolic; 52.1%, diastolic). European trials are in progress to asse ss the prognosis of hypertension assessed by ambulatory compared with office blood pressure. Ambulatory blood pressure monitoring has been r estricted for use in several clinical situations and is not used for t he routine evaluation and managment of hypertension.