Structural features of saphenous vein and internal thoracic artery endothelium: correlates with susceptibility and resistance to graft atherosclerosis.

Examination of saphenous vein (SV) and internal thoracic artery (ITA) endothelium at the time of coronary bypass surgery has confirmed the known susceptibility of SV to endothelial cell loss during preparation for grafting. In contrast the ITA showed only minimal cell loss. An ultrastructural morphometric analysis of the abluminal surface of the endothelium of both vessels showed significant differences in the numbers and depth of penetration of cytoplasmic processes or folds. Whereas the SV, perfusion-fixed at 110 mmHg, possessed relatively few (15/100 micron) and shallow (less than 1 micron deep) processes the ITA had significantly more (27/100 micron) and deeper (18% greater than 1 micron) processes. The ITA endothelial cells were also smaller and thicker. We suggest that the differences in the numbers and depth of the processes, which are believed to play a role in endothelial attachment, may account for the differing susceptibility of the two vessels to endothelial damage during grafting. This in turn correlates with the known susceptibility of SV grafts and resistance of ITA grafts to atherosclerotic changes.