Abstract
Publisher Summary This chapter discusses the effect of loss of beta-adrenergic activity upon myocardial blood flow and upon the oxygen balance of the heart during exercise in conscious dogs. In an experiment described in the chapter, a control exercise run elicited an increase in heart rate, peak left ventricular, and mean aortic blood pressure. Propranolol has a depressant effect on myocardial function and coronary blood flow during exercise in conscious dogs. The lower myocardial oxygen consumption may be caused by the reduction in heart rate and in myocardial contractile force, two important determinants of myocardial oxygen consumption. During exercise after propranolol, the oxygen delivery to oxygen consumption ratio and the coronary sinus oxygen content was significantly lower than during the control run. These results indicate that propranolol alters the balance between myocardial oxygen supply and demand during exercise so that a given level of myocardial oxygen consumption is achieved with a proportionally lower myocardial blood flow and a higher oxygen extraction.
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