Early restoration of cardiac function in hearts with acute regional ischaemia. The importance of beta-adrenergic stimulation.

The effects of acute coronary artery occlusion in anaesthetized cats has been studied with regard to changes in cardiac function and regional myocardial blood flow. Occlusion of the left anterior decending coronary artery (LAD) is followed by a rapid reduction of peak systolic blood pressure (LVSP) and contractility (dP/dt) and increased left ventricular end-diastolic pressure (LVEDP). Five minutes after coronary occlusion heart rate, LVSP, and (dP/dt) was reduced and LVEDP increased. Global cardiac function measured by these variables was gradually restored to preocclusion values; LVSP after 10 min., heart rate and dP/dt after 20 min. After 40 and 60 min these variables were stable at preocclusion levels. LVEDP remained permanently elevated. In hearts with regional ischaemia and paced heart rate global cardiac function was mainly restored 20 min after coronary occlusion except for increased LVEDP, both in cats pretreated with non-selective beta-adrenergic blockade (propranolol) and in unblocked cats. In general, blood flow in non-ischaemic myocardium adjacent to the ischaemic region increased following coronary occlusion, although not significantly in the endocardium. The endocardial/epicardial blood flow ratio was stable in unblocked hearts and was reduced in beta-blocked hearts. In normally perfused myocardium remote from the ischaemic region, blood flow increased following occlusion both in beta-blocked and unblocked cats, most pronounced in the epicardium; the endo/epicardial blood flow ratio decreased.