Action of glucagon on canine left ventricular performance and coronary hemodynamics

The effects of glucagon on coronary resistance and myocardial performance were evaluated in a canine heart-lung preparation in which changes in left ventricular compression of the coronary vessels, due to inotropic effects, could be largely prevented. Glucagon (0.2 mg) caused an increase in left ventricular performance as evaluated by maximal dp/dt, time to peak ventricular pressure, and end diastolic pressure. Although coronary flow increased slightly, the increase was significant only when heart rate was allowed to increase and followed the same time course as the change in heart rate. It therefore appeared to be the result of an indirect metabolic effect. The increase in flow involved only the systolic component. This effect was not blocked by propranolol. No redistribution of coronary flow was demonstrated using microspheres. Myocardial efficiency, as evaluated by cardiac work versus oxygen consumption, increased slightly after glucagon injection.