The Influence of One‐Year Treatment by Angiotensin Converting Enzyme Inhibitor on Baroreflex Sensitivity and Flow‐Mediated Vasodilation of the Brachial Artery in Essential Hypertension—Comparison with Calcium Channel Blockers

Abstract

Background. Both baroreflex sensitivity and flow‐mediated vasodilator function have been recognized to have prognostic significance in cardiovascular diseases. Long‐term antihypertensive treatment effects on these parameters, however, remain unclear. Subjects and Methods. We examined the effects of long‐term treatment by angiotensin converting enzyme inhibitors (ACEI) or calcium channel blockers (CCB) on baroreflex and flow‐mediated vasodilator function in patients with essential hypertension (EH). We recruited 36 patients aged 56 ± 11 years, with systolic blood pressure ≧160 mmHg and/or diastolic blood pressure ≧95 mmHg. Patients were assigned either to treatment by long‐acting ACEI (n = 12) or CCB (n = 24). All patients were followed for 12 months. Optimal BP was achieved by two optional increases in treatment: dose‐doubling of the primary drug during the first three months and the addition of diuretics or β‐blockers thereafter. Target blood pressure was 140/90 mmHg or a fall ≧20/10 mmHg. Baroreflex sensitivity was examined by spectral analysis of blood pressure and RR interval variabilities before treatment and after 3 and 12 months of treatment. The flow‐mediated vasodilator function was determined before and 12 months after treatment by measuring the change in brachial artery diameter during increases in flow induced by reactive hyperemia. Results. Baseline blood pressures were similar between the ACEI and CCB groups (172 ± 5/103 ± 2 vs. 172 ± 4/101 ± 3 mmHg). Blood pressures after 3 and 12 months of treatment also did not differ between the ACEI and CCB groups (149 ± 4/91 ± 2 vs. 145 ± 2/ 85 ± 2 mmHg, and 133 ± 5/84 ± 2 vs. 133 ± 2/81 ± 2 mmHg, respectively). Baseline baroreflex sensitivity was similar between the groups (6.7 ± 0.8 vs. 5.9 ± 0.6 msec/mmHg). This parameter remained unchanged at three months but increased after 12 months of treatment in both the ACEI (9.5 ± 1.6 msec/mmHg, p = 0.05) and CCB (9.1 ± 1.2 msec/mmHg, p = 0.006) groups. Percent increases in brachial arterial diameter and flow during reactive hyperemia increased in the group treated with ACEI (12.4 ± 3.5 vs. 25.8 ± 6.3% and 618 ± 72 vs. 953 ± 166, p < 0.05 for both) but both parameters remained unchanged in the group treated with CCB. Conclusion. These data suggest that long‐term blood pressure control with modern antihypertensive drugs improves baroreflex function. Treatment with ACEI may be more favorable for flow‐mediated vasodilator function than treatment with CCB.