Beta-blockade and brachial artery hemodynamics in hypertension

The effect of systemic adrenergic blockade on hypertensive brachial arteries was studied in humans with pulsed Doppler flowmetry. Blockade of beta-receptors by the nonselective beta-blocking agent propranolol did not modify the brachial artery diameter, whereas pindolol increased this parameter for the same degree of blood pressure reduction. The beta1-selective blocking agents atenolol and bisoprolol caused similar decreases in blood pressure and a reduction in the diameters of the brachial artery and abdominal aorta, respectively. The combination of alpha- and beta-blockade produced a rapid drop in blood pressure but did not change the brachial arterial diameter. Thus, following beta-blockade, the arterial diameter increased, did not change, or even decreased despite an adequate blood pressure reduction. It is suggested that beta-blockade in some instances resets the pressure-diameter curve and therefore has a direct action on the arterial wall independent of the mechanical effect of blood pressure reduction.