Ambulatory blood pressure measurement

Ambulatory blood pressure measurement (ABPM) consists of wearing a portable device connected to an armband that automatically measures blood pressure at regular intervals. What advantages does ambulatory blood pressure monitoring provide over measurement in the doctor's office, and what are the risks? To answer these questions, we reviewed the literature using the standard Prescrire methodology. Mean blood pressure recorded over 24 hours is generally lower than office blood pressure measurement: a value of 140/90 mmHg obtained during an office visit usually corresponds to a 24-hour average of 125/80 to 130/80 mmHg. Several cohort studies have examined the possible added prognostic value of ambulatory blood pressure measurement, but only one study included an appropriate comparator. There is no evidence that ambulatory blood pressure measurement is more reliable than repeated measurement during several office visits for predicting cardiovascular events. Only one trial has compared antihypertensive treatment adjustment based on ambulatory recording versus office measurements in terms of cardiovascular prevention. The results, which favoured ambulatory recording, are undermined by methodological flaws. White coat hypertension refers to elevated blood pressure only in the presence of a healthcare professional. A white coat effect suggested by a first ambulatory blood pressure measurement is not confirmed by a second ambulatory blood pressure measurement in over 50% of patients, who in fact have permanent hypertension. Ambulatory blood pressure measurement is inconvenient for the patient and sometimes painful. Between 2% and 7% of patients report local adverse effects such as skin reactions and oedema. In practice, ambulatory recording can be a useful second-line method for measuring blood pressure, especially when a white coat effect is suspected, or when considering treatment modification for a patient with what appears to be refractory hypertension. When office measurements and ambulatory recording yield conflicting results, it should not be assumed that ambulatory blood pressure measurement is more reliable.