Is Ambulatory Blood Pressure Monitoring Finally Catching On?

Abstract

Evaluation of blood pressure (BP) using ambulatory BP monitoring (ABPM) may play an important role in predicting cardiovascular (CV) prognosis and is increasingly being used in clinical practice. ABPM may be particularly useful in assessing BP in patients with discrepancies between office and home BP readings in both patients with white coat hypertension and masked hypertension, in patients with labile hypertension to establish nondipper status, in patients with resistant hypertension and episodic hypotension, and to determine BP control in patients taking multiple medications with early morning surges in BP. ABPM is considered the gold standard in BP measurement and is also increasingly being used to verify BP in large clinical trials. ABPM provides information about BP during daily activities and during sleep. Nighttime BP measured by ABPM is superior to office BP measurement in predicting CV events. BP has a reproducible circadian profile with higher values while awake and active and lower values during rest and sleep and an early morning increase for 3 hours during a transition of sleep to wakefulness. In most people, BP drops by 10% to 20% during the night (nighttime dipping). Those without nighttime dipping appear to be at higher risk of CV disease. Recent studies have drawn attention to the potential importance of controlling not only daytime but also nighttime BP. In this regard, control of the early morning surge may prove to be particularly important in preventing stroke. ABPM is performed by using a device that is easily worn by the patient for 24 to 48 hours, and BP is usually measured every 15 to 20 minutes during the day and every 30 to 60 minutes at night. Patients also record an activity log, which can be correlated with BP changes. These BPs are recorded on the device and the average daytime (awake) or nighttime (sleep) BPs are determined from the data by a computer program. The percentage of BP readings exceeding the upper limit of normal reflects vascular ‘‘load’’ and is considered to provide a more quantifiable measure of systolic and diastolic BP effect than an individual BP measurement. Dipping status is determined by a 10% fall in systolic and diastolic BP comparing daytime with nighttime (and nap time) readings. The diagnosis of hypertension using ABPM depends on the time span over which it is interpreted. The following readings are defined as hypertension on ABPM: a 24-hour average BP >135 ⁄85 mm Hg, a daytime (awake) average BP >140 ⁄90 mm Hg, and a nighttime (asleep) average BP >125 ⁄ 75 mm Hg. ABPM continues to sharpen the relationship between BP profile and CV risk, and this is demonstrated in a report from the International Database of Ambulatory Blood Pressure Monitoring in Relation to Cardiovascular Outcomes (IDACO). This report provides some useful ‘‘side by side’’ comparisons of ambulatory BP measurements and office BP From the Department of Medicine, Hypertension Program, University of Pennsylvania School of Medicine, Philadelphia, PA Address for correspondence: Debbie L. Cohen, MD, Renal Division, University of Pennsylvania School of Medicine, 210 White Building, Philadelphia, PA 19104 E-mail: cohendl@mail.med.upenn.edu