Discordant effects of beta-blockade on central aortic systolic and brachial systolic blood pressure: considerations beyond the cuff.

ABSTRACT

The role of beta-blockers in uncomplicated hypertension has been challenged recently. Compared with other antihypertensives, beta-blockers are less effective for preventing cardiovascular events in patients with uncomplicated hypertension. Moreover, a recent meta-analysis of placebo-controlled clinical trials concluded that atenolol is not more efficacious than placebo for preventing cardiovascular events in patients with hypertension. Although these agents lower blood pressure measured conventionally over the brachial artery with a blood pressure cuff, they do not exert a commensurate effect on blood pressure in the central aorta. Central aortic blood pressure and aortic augmentation index are strong predictors of left ventricular hypertrophy, an independent risk factor for cardiovascular events. Emerging data are illuminating the antihypertensive paradox whereby antihypertensive agents may elicit discordant effects on central and peripheral blood pressure and hemodynamics. Vasodilatory antihypertensives, such as renin-angiotensin-aldosterone system inhibitors and calcium channel blockers, elicit reductions in central aortic blood pressure equal to or greater than that in the brachial artery. Conversely, beta-blockers lower central aortic blood pressure to a lesser degree even when blood pressure measured by sphygmomanometry is reduced substantially. Given the strong relationship between central aortic blood pressure and target organ damage, the effectiveness of beta-blockers may be overestimated in practice on the basis of conventional blood pressure measurements alone. Differences in central and peripheral blood pressure may account for the lack of cardiovascular protection afforded by beta-blockers in clinical trials and could account for a portion of the apparent "benefit beyond blood pressure" reduction with other classes of antihypertensive agents. Future studies should aim to better clarify the role of central aortic blood pressure in the treatment of hypertension. In the meantime, the effects of antihypertensive drugs on blood pressure "beyond the brachial blood pressure cuff" should be considered when prescribing antihypertensive agents for a patient.