Interpreting treatment-induced blood pressure reductions measured by ambulatory blood pressure monitoring.

It is well known that 24-h ambulatory blood pressure monitoring (ABPM) provides a more accurate picture of a patient's blood pressure (BP) compared with clinic BP measurement. Twenty-four-hour ABPM better predicts hypertension-related risks such as end-organ damage including left ventricular hypertrophy, cardiovascular (CV) events and mortality. Threshold BP values for hypertension based on 24-h ABPM results have been established, including daytime and night-time averages. Nevertheless, the relationship between 24-h ABPM and clinic BP measurement in patients on antihypertensive therapy, and in particular how each may change in response to antihypertensive therapy, is less clear. This review will provide an overview of current knowledge on the relation between clinic BP and ambulatory BP reductions in clinical trials on antihypertensive therapies. Reduction in CV risk and its correlation with the magnitude of reduction in both clinic and ambulatory BP are explored. The most striking result is that reduction in clinic BP and ambulatory BP do not correspond in a 1:1 fashion, that is, smaller changes in 24-h ABPM correspond to significantly larger changes in clinic BP.