Comparison of angiotensin-converting enzyme inhibitors and calcium antagonists in the treatment of mild to moderate systemic hypertension, according to baseline ambulatory blood pressure level

Abstract

This study was aimed at determining whether baseline ambulatory blood pressure (BP) levels influence the efficacy of angiotensin-converting enzyme inhibitors and calcium antagonists in the same manner. Accordingly, the ambulatory BP recordings of 236 mild to moderate hypertensive patients who had previously entered a clinical trial and had received either a calcium antagonist (n = 121) or an angiotensin-converting enzyme inhibitor (n = 115) were reviewed. The inclusion criterion was a clinic diastolic BP between 95 and 115 mm Hg at the end of the placebo period. Patients were classified according to the difference between their observed and predicted ambulatory BP (the latter assessed by regressing the observed ambulatory BP on the clinic BP). Reduction in ambulatory systolic and diastolic BP seemed to be greater (p < 0.0001, p = 0.01) in patients receiving an angiotensin-converting enzyme inhibitor than in those who were given a calcium antagonist. However, analysis of variance showed (1) there was a significant interaction (F = 6.37 p = 0.01) between the pharmacologic class and the baseline systolic ambulatory BP; and (2) the difference in diastolic ambulatory BP reduction between both classes was no longer significant when adjusted for baseline diastolic ambulatory BP. In patients with higher than predicted ambulatory BP levels, angiotensin-converting enzyme inhibitors and calcium antagonists had roughly a similar effect (reduction in systolic BP, 9 ± 8% vs 7 ± 6%, p = not significant; reduction in diastolic BP, 11 ± 8% vs 8 ± 6%, p = not significant). By contrast, in patients with lower than predicted ambulatory BP, angiotensin-converting enzyme inhibitors decreased ambulatory BP more than calcium antagonists did (systolic BP, 8 ± 7% vs 1 ± 7%, p < 0.0001; diastolic BP, 5 ± 8% vs 2 ± 7%, p = 0.04). Finally, further analysis found the threshold of efficacy to be 120/80 mm Hg in patients receiving an angiotensin-converting enzyme inhibitor and 135/85 mm Hg in those receiving a calcium antagonist.