Mechanical vs intrinsic components in the improvement of brachial arterial compliance. Comparison of the effects of atenolol versus ramipril in hypertensive patients.
The aim of this study was to compare the mechanical and intrinsic effects of an angiotensin converting enzyme inhibitor, vs a beta-blocker, on brachial arterial compliance. In a double blind study, 34 essential hypertensive patients were treated for 3 months with either ramipril 2.5-5.0 mg daily (n = 17, age 57 +/- 7 y, 11 males) or atenolol 50-100 mg daily (n = 17, age 53 +/- 8 y, 11 males). Blood pressure (BP), brachial artery diameter (D), brachial-radial pulse wave velocity (PWV) and effective compliance (Ceff), were measured before and at the end of the study. Isobaric evaluation (Ciso) was performed in the entire population studied at an average mean BP of 110 mmHg. Ramipril significantly reduced BP from 155 +/- 16/94 +/- 6 mmHg to 140 +/- 15/85 +/- 7 mmHg (p < 0.001) without affecting heart rate (HR; 74 +/- 10 vs. 75 +/- 12 bpm). In addition, it significantly improved both PWV (18%; p < 0.001) and arterial compliance (45%; p < 0.001), from which 35% was related to a pressure independent effect (p < 0.01). Atenolol also induced a reduction in both BP (159 +/- 17/96 +/- 10 to 133 +/- 13/81 +/- 8 mmHg; p < 0.001) and HR (76 +/- 10 to 57 +/- 7 bpm; p < 0.001). In a similar way, PWV (11%; p < 0.05) and Ceff (30%; p < 0.05) were significantly improved without significant change in Ciso. This suggests that blood pressure reduction was responsible for compliance improvement. In conclusion, it is suggested that atenolol induces only hemodynamic changes, mediated mainly by BP reduction. In contrast, the improved brachial buffering function observed after ramipril involves not only hemodynamic changes, but also changes mediated by other mechanisms, such as modification of wall structures.