Enhancement of canine coronary collateral flow by nafazatrom

The ability of oral nafazatrom treatment (10 mg/kg) 2 h preceding occlusion of the left anterior descending coronary artery for 6 h to limit expansion of myocardial injury was studied in anaesthetized canine hearts. Collateral blood flow was obtained with a load line analysis, employing aortic pressure, post-stenotic coronary pressure, and retrograde coronary flow from the occluded vessel. Contractile changes in the subendocardial ischemic perfused muscles were measured with ultrasonic techniques. Infarct size was determined post-mortem by a biochemical staining method and excision of necrosis. Post-stenotic coronary pressure was slightly below aortic pressure in both groups before coronary occlusion, and fell to 29 and 27% of aortic pressure in vehicle- and drug-treated hearts, respectively, after the insult. Retrograde flow was 2.4 +/- 0.6 vs. 4.1 +/- 0.7 ml/min in tylose- or nafazatrom-treated hearts. Collateral flow amounted to 1.5 +/- 0.06 vs. 2.5 +/- 0.04 ml/min in controls and drug-protected hearts. Contractility (dP/dtmax) and the %-segment shortening were greater in the ischaemic myocardium after nafazatrom treatment. Infarct size was 38 +/- 5.2 vs. 17 +/- 3.4 g/100 g left ventricle in the vehicle controls and nafazatrom group, respectively. Nafazatrom reduced infarct size by 46%. Besides other mechanisms, this was due to improved %-segment shortening and increased periinfarction collateral blood supply to jeopardized but viable myocardium. The drug may be of value in ischaemic heart disease as shown by the enhanced regional myocardial perfusion and improved contractility.