White-coat resistant hypertension.

The aim of this study was to evaluate whether sustained hypertensives with high clinic blood pressure, despite multiple drug treatment, show a true resistant hypertension or a "white-coat effect," and whether the pretreatment white-coat effect is maintained despite pharmacological therapy. The occurrence of resistant hypertension was determined in 250 consecutive essential hypertensives who had had an ambulatory blood pressure monitoring before treatment assignment. Twenty-seven of 250 hypertensives with persistently high clinic blood pressure despite 3 months of adequate pharmacological therapy underwent further ambulatory blood pressure monitoring. Using our internal standards, seven patients had a true resistant hypertension whereas 20 subjects showed a large white-coat effect (white-coat resistant hypertension), ie, high clinic blood pressure (> 140/90) but "normal" ambulatory daytime (< 139/90 mm Hg) and 24 h (135/85 mm Hg) blood pressure. Using other cutoff points for ambulatory blood pressure, 134/90 and 135/85 mm Hg for daytime blood pressure, 10 and 13 patients, respectively, were reclassified as true resistant hypertensives and 17 and 14, respectively, were white-coat resistant hypertensives. Interestingly, in white-coat resistant hypertensives the large differences between clinic and ambulatory daytime blood pressure (white-coat effect), recorded before treatment assignment, were not affected by drugs and remained constant over time. Left ventricular mass index in white-coat resistant hypertensives was significantly lower than in truly resistant hypertensives, suggesting that prognosis could differ between these groups. In this study, using either our internal standards or some other cutoffs reported in the literature, the white-coat phenomenon was an important cause of resistant hypertension. The use of ambulatory blood pressure monitoring in these patients may avoid misdiagnosis of resistant hypertension, unnecessary overtreatment, and expensive procedures to look for possible secondary hypertension.