Discordant β-blocker effects on clinic, ambulatory, resting, and exercise hemodynamics in patients with hypertension

Study Objectives. To determine the correlation between ambulatory and clinic blood pressure in assessing antihypertensive response to P-blockade, to test whether blood pressure response to metoprolol is associated with the heart rate response, and to determine whether exercise and resting heart rate responses to metoprolol are correlated. Design. Post hoc analysis of a prospective cohort study Setting. University-affiliated general clinical research center. Patients. Fifty-one patients aged 35-65 years with uncomplicated hypertension. Intervention. All patients received metoprolol at a dosage titrated to achieve a diastolic blood pressure below 90 mm Hg. Measurements and Main Results. Clinic and 24-hour ambulatory blood pressure measurements were obtained and exercise treadmill testing was performed before and after metoprolol treatment. Based on ambulatory blood pressure data, 24 patients (47%) responded (defined as at least a 10% reduction in diastolic blood pressure) to metoprolol compared with 36 patients (71%) based on clinic blood pressure data (p=0.027). Clinic blood pressure was associated with a 67% false-positive rate (responsive blood pressure by clinic data that was actually nonresponsive by ambulatory data). Blood pressure responders and nonresponders exhibited similar reductions in exercise heart rate (24% and 23%, p=0.74). However, responses to metoprolol measured by exercise heart rate versus resting heart rate were not significantly correlated (r=0.24, p=0.105). Conclusion. Reliance on clinic blood pressure or resting heart rate for making P-blocker treatment decisions may yield less than optimal assessment of the antihypertensive response or degree of beta-blockade.