Preferential vascular effects of amlodipine in reducing stiffness in muscular not elastic arteries in essential hypertension & the metabolic syndrome

Abstract

Introduction: Arterial stiffness and wave reflection are independent prognosticators of cardiovascular morbidity and mortality. There are two types off arteries in the body; elastic and muscular. The elastic arteries receive the blood directly from the heart while the muscular arteries distribute the blood to various organs of the body. The elasticity of the major arteries decreases with age and therefore may play a key role in the development and control of hypertension and subsequently the choice of drug therapy. The aim of the study is to evaluate the effects of the amlodipine, on arterial stiffness in essential hypertension, compared to hydrochlorothiazide. Methodology: We randomised 24 hypertensive patients hypertension (clinic blood pressure (BP) > 140/90 mmHg and ambulatory >135/85 mmHg) to amlodipine 5 mg or hydrochlorothiazide 12.5 mgs in a single blind parallel group study for one month and measured aortic pulse wave velocity (PWV) and augmentation index (AIx) at baseline and one month after treatment. The patients were studied fasting, having abstained from smoking, caffeinated beverages and alcohol 12 h prior to the measurements. Brachial BP and heart rate (Omron), pulse wave velocity (PWV, Complior) and augmentation index (AIx, SphymoCor), a measure of wave reflection, were measured in the supine position after a rest of 15 min. Results were analysed with JMP (SAS for Windows) using Wilcoxon-Rank Sums test and ANOVA. Results are expressed as mean ± SEM, p < 0.05 considered significant. Results: Both drugs produced a similar reduction in brachial BP but there was a greater reduction in the aortic systolic BP (20 ± 3 vs 7 ± 2 mmHg, p < 0.01) and AIx (5 ± 2 vs 1 ± 1%, p < 0.05) with amlodipine. There was no change in PWV with either drug. Conclusion: This short-term study suggests that the effects of amlodipine on arterial stiffness are primarily on muscular rather than elastic arteries. This should be kept in mind when choosing the HTN treatment in elderly and those with diseases affecting the aorta.