THE INFLUENCE OF VASODILATING BETA-BLOCKERS ON CARDIAC-FUNCTION AND VASCULAR-RESISTANCE IN ESSENTIAL-HYPERTENSION

In nearly all forms of established hypertension, the cardinal hemodynamic disturbance is an increased total peripheral resistance, while cardiac output is abnormally low, particularly during exercise. When left untreated, total peripheral resistance increases, cardiac output falls, and blood pressure increases over time. The coronary reserve is reduced, and renal as well as cerebral resistance increases and blood flow falls. Antihypertensive agents effect central hemodynamics differently. Ordinary beta-blockers do usually not reduce total peripheral resistance much below pretreatment level, and cardiac output is chronically depressed, particularly during exercise. However, the beta-blockers greatly reduce the workload on the heart by decreasing the heart rate-pressure product. Modern beta-blockers with vasodilating activity - like carvedilol - are based on a combination of beta-blockade and vasodilatation. Such beta-blockers also induce a marked decrease in the pressure-heart rate product, and some reduction in total peripheral resistance. They cause less depression of exercise cardiac output than ordinary beta-blockers. Blood flow to the kidneys and the brain is maintained. From a theoretical point of view, this type of antihypertensive treatment should maintain good blood pressure control, reduce cardiac workload and be associated with less side-effects than ordinary beta-blockers.