[Effect of beta blockade on hemodynamics in physical exertion]

Abstract

Beta-receptor blocking agents are known for more than 20 years. They are of definite use in the therapy of arterial hypertension and coronary heart disease. Beta-blockers lower the sympathoadrenergic discharge to the heart and circulation, particularly if the former is increased. Beta-blockers induce a negative chronotropic and inotropic effect and inhibit beta 2-mediated vasodilation. Thus beta-sympathicolysis during physical activity results in damping of heart rate increase and of elevation of cardiac contractility. Systolic blood pressure does not increase much, and usually there is no decline in diastolic blood pressure, due to elevated peripheral resistance. With adequate dosage, there may even be a slight increase in diastolic pressure, an effect eventually vaning in chronic therapy. Pulmonary capillary wedge pressure is elevated to above normal via inhibition of contractility and relaxation of the heart. Stroke volume, cardiac output and the double-product decrease, the arteriovenous oxygen difference under exercise increases clearly and the maximum aerobic performance capacity decrease in healthy individuals. In coronary patients, this may protect against cardiac overload and increase symptom-free physical work capacity, due to a relative decrease in the myocardial O2 requirement and improved coronary perfusion resulting from prolonged diastole. With verified indication (hypertensive-hyperkinetic impairments of cardiovascular function, coronary heart disease), the goal is an overlapping, endurance-oriented training to reduce the overall sympathetic activation, in order to minimize medication in the long run.