Study objectives: To determine the correlation between ambulatory and clinic blood pressure in assessing antihypertensive response to beta-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 beta-blocker treatment decisions may yield less than optimal assessment of the antihypertensive response or degree of beta-blockade.