Comparative response of the heart and coronary vasculature to catecholamines, aminophylline and papaverine.

The direct effects of norepinephrine, epinephrine, isoproterenol, aminophylline, dopamine and papaverine on coronary blood flow and oxygen consumption were examined in an isolated heart-lung preparation. Only papaverine and aminophylline significantly increased coronary blood flow, although microsphere studies indicated the increase in flow did not primarily involve the endocardial layer. Fractionation of flow into systolic and diastolic components also suggested that both drugs dilated large epicardial vessels. Correlation analysis indicated that alterations in heart rate and performance indices produced by these agents were not per se accompanied by changes in oxygen consumption and/or coronary flow as commonly supposed. Only cardiac work and ejection velocity were directly correlated with oxygen consumption, probably by direct action of the drug on coronary vascular resistance rather than on ventricular function.