Perioperative infarction: effects of cardiopulmonary bypass on collateral circulation in an acute canine model.

Significant intracoronary collateralization [circumflex (Cx) to anterior descending (AD)] can be established acutely by selective hypertensive perfusion of the circumflex (through left main) after acute occlusion of the AD in working canine hearts. Intracoronary collateral flow can be estimated by a collateral circulation index (CCI) = distal coronary diastolic pressure x 100/aortic diastolic pressure. The effects of 60 to 90 min of normothermic, total cardiopulmonary bypass (TCPBP) on such collaterals were evaluated in four dogs with CCI > 80%, and compared to six control dogs with CCI < 80% and without TCPBP. Three hours after AD ligation, control dogs had minimal myocardial injury despite significantly lower CCI. In contrast, the four study dogs placed on TCPBP experienced an abrupt fall of the CCI to 30% (P < 0.03), severe ischemia, and infarction in each; two became pump dependent. Thus, ventricular pressure work seems to be an important determinant of flow through collateral channels. These results suggest that preservation techniques for myocardium supplied by collaterals during coronary surgery may require considerations other than intermittent perfusion via existing coronary inflow.