Long-term changes in canine vein graft after infusion of cardioplegic solution

We have studied the effects of cardioplegic solution (CS) on angiographic and histologic anatomy of bilateral vein grafts interposed into the carotid arteries of 10 dogs for up to 1 year. One vein (exp) was infused with cardioplegic solution (pH 7.7, K + 25 mEq/l, temperature 12 degrees C) every 15 min four times at pressures up to 80 mm and then interposed into the carotid system. The other vein (con) was kept in cold Ringer's lactate (12 degrees C) before interposition. Six weeks and up to 1 year after bypass, angiograms showed 80% graft patency of exp and con grafts. Immediate histologic examination showed no detectable differences among veins before and after perfusion and con veins. Histologic examination at 1 year showed enlargement of the grafts, smooth muscle hyperplasia, and increase in collagen, as well as disorientation of muscle fibers; cytoplasmic vacuolation occurred with equal frequency in both exp and con veins. Perfusion of the vein segment with cardioplegic solution did not appear to be detrimental to vein patency or histologic appearance so that this can be considered a safe method for delivery of cardioplegia in jeopardized ischemic myocardium at the time of bypass surgery.