Retrograde coronary sinus perfusion for myocardial protection during cardiopulmonary bypass

The pathophysiology of retrograde coronary sinus perfusion was studied in a vented, nonworking heart in vitro. The fraction of nutritional blood flow, estimated with the trapping index of radioactive microspheres (15 +/- 5 mu), is approximately one-fifth of total flow. The funoff is primarily through the thebesian system and venovenous channels, as is shown with Microfil injection studies. These results suggest that retrograde coronary sinus perfusion would be of marginal value in revascularizing a working heart but would be effective in protecting a hypothermic, nonworking myocardium. Canine experiments indicate that retrograde coronary sinus perfusion can provide efficient core cooling of the myocardium during cardiopulmonary bypass even in the presence of complete coronary artery occlusion. It is technically simple, delivers cardioplegic solutions to the myocardium without the risk of coronary ostial injury, and can be employed in the presence of severe aortic insufficiency and open aortic root. Retrograde coronary sinus perfusion therefore appears to be a valuable alternative mode of myocardial protection during cardiac operations.