Effect of venous retroperfusion on experimental myocardial ischemia in the open-chest pig

Venous retroperfusion, by arterialization of the coronary sinus or the vein accompanying an ischemic artery, has been suggested as an alternative method of myocardial revascularization in patients with severe coronary disease in whom direct revascularization would be an unacceptable risk or technically impossible. This study was carried out to assess whether or not venous retroperfusion can increase myocardial blood flow in the area of ischemia after sudden occlusion of a normal coronary artery in an animal, the pig, with a coronary vasculature similar to that of humans. It was found that net flow measured with an electromagnetic flowmeter through either an aorta-to-coronary sinus shunt or an aorta-to-left anterior descending coronary vein shunt after occlusion of the left anterior descending artery was at first high but rapidly decreased toward zero flow within 1 hr. Blood flow in the ischemic region measured by the microsphere method 20 min after coronary occlusion did not increase. This disparity between electromagnetic flow and regional flow suggests that there are venous-to-thebesian or venous-to-venous shunts into the systemic and pulmonary circulation through vessels greater than 14 micron. It is unlikely that effective oxygen or metabolite exchange would occur in vessels this size.