Hemodynamic Effects of β-Blocking Compounds Possessing Vasodilating Activity

Abstract

The cardinal hemodynamic disturbance in established essential hypertension is an increased total peripheral resistance. Monotherapy with conventional beta-blockers lowers blood pressure usually without any significant fall in total peripheral resistance. Generally, cardiac output is reduced at rest as well as during exercise. In recent years, beta-blockers with vasodilating activity have been developed. Labetalol induces nonselective beta-blockade and in addition reduction in vascular resistance mainly through alpha-blockade. Long-term hemodynamic data indicate gradual normalization of cardiac output, stroke volume, and total peripheral resistance--possibly due to regression of structural changes in the left ventricle and in the arterioles. Prizidilol is a nonselective beta-blocker with a direct vasodilator effect. One year results showed a very marked fall in blood pressure and total peripheral resistance and dramatic increase in posttreatment exercise stroke volume. Cardiac output was unchanged in spite of a reduction in heart rate. Due to side effects, the drug has been withdrawn. Dilevalol, which is the R-R' isomer of labetalol, is also a nonselective beta-blocker, but its vasodilating activity seems to be mainly due to partial beta 2-agonist activity. Preliminary data indicate a reduction in blood pressure--mainly due to a fall in total peripheral resistance. Studies in elderly patients or in patients with reduced left ventricular function seem to indicate that the drug might be used without deterioration of the heart pump function. Although antihypertensive properties of dilevalol have been extensively studied and are defined, the exact position of dilevalol among antihypertensive drugs will be more precisely determined in future studies.