Change in coronary venous PO2 following myocardial infarction in unanesthetized dogs

Occlusion of either the anterior descending branch (LAD) or circumflex branch (CB) of the main left coronary artery was carried out in seven conscious dogs. Blood gases in the great cardiac vein and coronary sinus were determined before and after occlusion. The peripheral coronary pressure (PCP) in the occluded branch was also determined to provide an index of collateral blood flow. In dogs In which there occurred both an infarction and a delayed rise in PCP, venous PO2 from the occluded bed rose above the preocclusion value and also above the PO2 values of the nonoccluded bed. The rise in venous PO2 commenced about 18-24 hr after the coronary occlusion and paralleled the increase in PCP. In contrast, in dogs where following coronary occlusion there was either no infraction and a rapid rise in PCP, or infarction with a negligible rise in PCP, the venous PO2 did not change. The most plausible explanation for the rise in PO2 is that it represents the effect of collateral perfusion in an area of infarcted or ischemic myocardium in which oxygen consumption is depressed.