Beneficial effects of coronary venous retroinfusion but not left atrial administration of superoxide dismutase on myocardial necrosis in pigs

The efficacy of coronary venous versus left atrial administration of superoxide dismutase was studied in 24 open chest pigs which had 60 min of left anterior descending coronary artery occlusion followed by 3 h reperfusion. The pigs were randomly assigned to three treatment protocols: group A (n = 8) superoxide dismutase (5 mg kg-1) was infused into the great cardiac vein for 30 min beginning 15 min before reperfusion; group B (n = 8) superoxide dismutase (5 mg kg-1) was infused into the left atrium in a similar manner to group A; group C (n = 8) bovine serum albumin (5 mg kg-1) was infused into the great cardiac vein in the same manner as group A. Infarct size, expressed as percent of area at risk, was significantly smaller in group A (28.2 +/- 13.0%) than groups B (58.7 +/- 8.3%) and C (61.6 +/- 7.2%) (P less than 0.05). The results indicate that retroinfusion of superoxide dismutase into the great cardiac vein before reperfusion may be an effective treatment for the prevention of reperfusion injury, even in the absence of a well developed coronary collateral circulation. Antegrade (left atrial) administration of the same amount of superoxide dismutase did not decrease infarct size in pigs. The most likely explanation for this difference in efficacy is that drug delivery with left atrial administration is dependent on antegrade flow with reperfusion which is less reliable and less efficient than coronary venous retroinfusion. The latter provides a predictably high concentration of superoxide dismutase to the jeopardized myocardium during the period of ischaemia before reperfusion.