Functional and histologic changes in vein grafts exposed to crystalloid potassium cardioplegic solution

Abstract

A canine external jugular vein to iliac artery interposition model was devised to evaluate the potential deleterious effects of cold potassium cardioplegic solution exposure to saphenous vein grafts during aortocoronary bypass procedures. The right jugular vein was harvested from 11 animals and halved, one segment being perfused with 1 liter of normal saline solution (NS) at 4°C over a period of 31.7 ± 2.5 min at a perfusion pressure of 50.5 ± 2.6 mm Hg, and the other segment perfused with 1 liter of crystalloid potassium cardioplegic solution (CP) at 4°C over a period of 24.8 ± 3.2 min at a perfusion pressure of 53.0 ± 1.5 mm Hg. The measured differences in the perfusion times and pressures were not significant at P < 0.05. The grafts were then interposed into the iliac artery systems of their respective animals, and transgraft pressure gradients were measured by direct needle puncture technique and found to be 12.6 ± 5.9 mm Hg for the CP-treated grafts and 19.9 ± 9.6 mm Hg for the NS-treated grafts. At the time of graft harvest 7.4 ± 0.23 months later transgraft pressure gradients were again measured and found to be 2.5 ± 1.8 mm Hg for the CP-treated and 2.9 ± 1.7 mm Hg for the NS-treated grafts. Statistical comparison of the early and late transgraft pressure gradients within each group of grafts that were patent at the time of harvest (CP- and NS-treated) revealed no significant difference, and there was no significant difference in harvest gradients between the CP- and NS-treated grafts ( P > 0.05). Gross and histologic study of the grafts revealed no apparent differences between the two groups, and micrometric study of the thickness of the various vein wall layers at three different sites along each graft revealed no significant difference at any site except the media and the total wall thickness in the mid-portion of the grafts, where the CP-treated grafts were thicker ( P < 0.05). It is concluded that, in this canine model, exposure of vein grafts to cold potassium cardioplegic solution causes no more deleterious changes than exposure to normal saline solution.