The Ambulatory BP Monitoring Effect

Abstract & Commentary

Synopsis: The presser effect of ABPM for the first time could influence the diagnosis of hypertension.

Source: Hermida RC, et al. J Am Coll Cardiol. 2002; 40:710-707.

Ambulatory blood pressure monitoring (ABPM) is a useful adjunct for evaluating white coat hypertension, but little is known about its effect on BP. Thus, Hermida and associates from Spain studied 538 patients with mild-to-moderate office hypertension using ABPM for 48 hours. Approximately one third were on no therapy and one third had more than 1 study. In both treated and untreated patients, significant reductions in BP were noted on the second day (P < .001), but not in heart rate. This presser effect was statistically significant for the first 6-9 hours of monitoring. Mean nocturnal BP was the same on both days. In those with repeated tests 3 months apart, this presser effect was absent. Hermida et al concluded that this presser effect of ABPM for the first time could influence the diagnosis of hypertension.

Comment by Michael H. Crawford, MD

This study makes a strong case for extending initial ABPM beyond 24 hours in order to accurately diagnose white coat hypertension. Apparently the novelty of the first several hours of experience with the device elevates BP significantly compared to the second day whether it is contiguous (48 hours of monitoring) or 3 months later. The magnitude of the pressure drop on day 2 averaged 6-7 mm Hg systolic and 4-5 mm Hg diastolic. Also, about three quarters of the subjects experienced a significant decline in BP. Interestingly, the results were not related to heart rate or levels of physical activity. In addition, the findings were independent of sex and BP treatment. This study is robust because of a large number of subjects with a range of blood pressure and other characteristics. The application of a 2-day monitoring rule will help more accurately define hypertensive subjects and lead to better clinical and research outcomes, albeit at a higher cost. 

Dr. Crawford is Professor of Medicine, Mayo Medical School; Consultant in Cardiovascular Diseases, and Director of Research, Mayo Clinic, Scottsdale, AZ.