We aimed to estimate the prevalence of resistant hypertension through both office and ambulatory blood pressure monitoring in a large cohort of treated hypertensive patients from the Spanish Ambulatory Blood Pressure Monitoring Registry. In addition, we also compared clinical features of patients with true or white-coat–resistant hypertension. In December 2009, we identified 68 045 treated patients with complete information for this analysis. Among them, 8295 (12.2% of the database) had resistant hypertension (office blood pressure ≥140 and/or 90 mm Hg while being treated with ≥3 antihypertensive drugs, 1 of them being a diuretic). After ambulatory blood pressure monitoring, 62.5% of patients were classified as true resistant hypertensives, the remaining 37.5% having white-coat resistance. The former group was younger, more frequently men, with a longer duration of hypertension and a worse cardiovascular risk profile. The group included larger proportions of smokers, diabetics, target organ damage (including left ventricular hypertrophy, impaired renal function, and microalbuminuria), and documented cardiovascular disease. Moreover, true resistant hypertensives exhibited in a greater proportion a riser pattern (22% versus 18%; P <0.001). In conclusion, this study first reports the prevalence of resistant hypertension in a large cohort of patients in usual daily practice. Resistant hypertension is present in 12% of the treated hypertensive population, but among them more than one third have normal ambulatory blood pressure. A worse risk profile is associated with true resistant hypertension, but this association is weak, thus making it necessary to assess ambulatory blood pressure monitoring for a correct diagnosis and management.

Background and aim: Clinical characteristics of resistant hypertensive patients in comparison to controlled patients have not been fully investigated in large cohorts. The aim of the study was to evaluate clinical differences, target organ damage and ambulatory blood pressure monitoring in resistant hypertensive patients and patients controlled on three or less drugs. Methods: In December 2010, from the Spanish Ambulatory Blood Pressure Monitoring Registry, we identified 14 461 patients fulfilling criteria of resistant hypertension and 13 436 hypertensive patients controlled on three or less drugs. Clinical characteristics were compared between these two groups. Results: Compared to controlled patients, those having resistant hypertension were older, more obese and had longer hypertension duration. They also had more frequently diabetes, dyslipidemia, reduced renal function, microalbuminuria, left-ventricular hypertrophy and previous history of cardiovascular events. In multivariate analyses, hypertension duration, obesity, abdominal obesity, left-ventricular hypertrophy, reduced estimated glomerular filtration rate, and microalbuminuria were independently associated with resistant hypertension. Resistant hypertensive patients had higher ambulatory blood pressures, but differences between office and ambulatory blood pressure (white-coat effect) were also more pronounced in this group, revealing a proportion of 40% of patients with normal 24-h blood pressure. On the contrary, values of 24-h blood pressure above 130 and/or 80 mmHg (masked hypertension) were present in 31% of apparently controlled patients. Conclusion: Resistant hypertension is associated with obesity, longer hypertension duration and kidney and cardiac damage. Ambulatory blood pressure monitoring reveals that white-coat hypertension is common among resistant hypertensive patients, as well as is masked hypertension among apparently controlled patients.