OBJECTIVE:

Ambulatory blood pressure monitoring (ABPM) is a tool to diagnose resistant hypertension (RH). The objective of this study is to describe the pattern of 24-h ABPM in patients using at least three anti hypertensive drugs without blood pressure (BP) control, classifying them as true RH or white-coat RH.

METHODS:

A cross-sectional study involving resistant hypertensives that were submitted to clinical, laboratory and 2D-echocardiographic evaluation. Ambulatory blood pressure monitoring was used to diagnose true or white-coat RH. The chi-squared test was used for comparisons among categorical variables and Kruskall-Wallis test for continuous ones.

RESULTS:

Of the 286 patients, 161 (56.3%) were classified as true RH and 125 (43.7%) as white-coat RH. Sex, age, office BP and the cardiovascular risk factors for both groups were similar. True resistant hypertensives had more target organ damage then white-coat resistant hypertensives; nephropathy (40.1 versus 23.9%, P=0.007) and left ventricular hypertrophy (83.3 versus 76.3%, P=0.05). In ABPM, the true RH group had a smaller nocturnal systolic and diastolic BP reduction (6.4+/-8.8 versus 9.8+/-7.5 mmHg, P=0.0004; 10.4+/-9.6 versus 13.6+/-9.2 mmHg, P=0.001) and 68.7% of them were non-dippers versus 49.6% in the white-coat RH group (P=0.001). True RH also had a larger 24 h pulse pressure (65.8+/-13.7 versus 51.5+/-10.0 mmHg, P < 0.0001).

CONCLUSIONS:

Ambulatory blood pressure monitoring is a fundamental tool to diagnose RH, and to check treatment efficacy. The presence of a greater pulse pressure and a lower nocturnal blood pressure reduction in true RH patients may be responsible for this increased cardiovascular risk profile.