Effect of practolol on blood flow distribution in the myocardium during acute regional ischaemia in cats

The β-adrenergic blocking agent practolol was given to 11 cats with acute coronary artery ligation, and regional myocardial tissue blood flow was measured by the distribution of 15 μm labelled microspheres. Practolol reduced heart rate and cardiac contractility, but left ventricular end-diastolic pressure rose in eight animals. In three animals, however, the haemodynamics were essentially unchanged and these are referred to as non-responders. No changes in regional myocardial blood flow were observed after practolol administration, either in ischaemic, border or normal areas of the left ventricle. This indicates less serious imbalance between oxygen demand and delivery in ischaemic tissue. There was no endocardial/epicardial redistribution of tissue flow. Practolol did not appear to improve coronary perfusion, and beneficial clinical effects of practolol are therefore probably related to reduction of myocardial oxygen demands.