Objective: To determine the relative importance of factors known to cause therapy-resistant hypertension, and to derive an efficient approach to the evaluation of this problem in clinical practice.
Design: Consecutive sample.
Setting: University hospital hypertension clinic and clinical research center.
Patients: Fifteen patients referred for management of refractory hypertension and found to have a seated diastolic blood pressure greater than 95 mm Hg while taking a standard dose of hydrochlorothiazide, propranolol, and hydralazine or its equivalent for at least 4 weeks.
Measurements and Main Results: Seven patients (group 1) had normal, resting mean intra-arterial blood pressure (mean pressure < 107 mm Hg) and eight had elevated pressure (group 2). Patients in group 1 had minimal or no target organ involvement whereas those in group 2 had higher minimum vascular resistance by forearm plethysmography and greater interventricular septal wall thickness. Factors contributing to resistant hypertension, particularly in group 1, were "office hypertension" (clinic systolic blood pressure at least 20 mm Hg higher than home systolic blood pressure), pseudohypertension (cuff diastolic blood pressure at least 15 mm Hg higher than simultaneously determined intra-arterial pressure), and "cuff-inflation hypertension" (intra-arterial diastolic blood pressure rise of at least 15 mm Hg during cuff inflation).
Conclusion: Home blood pressure monitoring and echocardiography are recommended as initial steps in the evaluation of patients with resistant hypertension. Intra-arterial blood pressure measurement is particularly helpful in patients with resistant hypertension who do not have office hypertension yet have normal septal thickness on echocardiography.