Metabolic effects of high doses of insulin during acute left ventricular failure in dogs

Metabolic effects of pharmacological doses of insulin were studied during acute ischaemic heart failure in 7 dogs. Severe depression of left ventricular performance was induced by embolization of the left main coronary artery with 50 micron plastic microspheres. This was followed by a significant reduction in myocardial blood flow and oxygen consumption. After a period of stabilization of the haemodynamic and metabolic variables, 300 IU of insulin free of glucagon and calcium was injected as a bolus dose. Glucose and potassium were given to maintain their plasma concentrations. Insulin significantly improved performance of the failing left ventricle. Myocardial blood flow was significantly increased, whereas myocardial oxygen consumption was unchanged. Insulin significantly reduced arterial concentrations and myocardial uptake of free fatty acids, while myocardial uptake of glucose and lactate showed a non-significant increase. In conclusion, pharmacological doses of insulin significantly improve cardiac pump function without increasing myocardial oxygen consumption during acute ischaemic left ventricular failure in dogs. This may be partly related to reduced myocardial uptake of free fatty acids relative to that of glucose.