Degenerative changes of vein grafts in preparation media: preliminary studies by electron microscopy and fibrinolytic autography

Vein harvesting by long blunt and blind dissection. A standardized technique in the dog

A standardized method for harvesting veins from dogs is described. It involves skeletization of the vein and its collaterals by longitudinal blind and blunt dissection, thus separating the vein from its surroundings. This is followed by elevation and cutting of the subdermal tissue with an electrosurgical pencil. The method was found to be faster and less traumatic than the prevailing method which involves cutting the skin with a longitudinal incision and dissection of the vein in small increments.

Experimental vein grafts in the rat: re-endothelialization and permeability to albumin

Intimal thickening in vein grafts is one of the major factors leading to graft failure. Studies have suggested that delayed re-endothelialization and an enhanced permeability to proliferative factors (macromolecules) in the blood are associated with the development of intimal thickening in these vessels. The aim of this study was to determine the pattern of re-endothelialization of vein grafts and the permeability of the new endothelium to a large molecule. Iliolumbar vein to iliac artery grafts 5 mm long were inserted microsurgically into 32 male albino Wistar rats. Graft re-endothelialization and permeability, at times ranging from 2 to 140 days after grafting, were studied by scanning electron microscopy and vital staining with Evans Blue dye, which binds to plasma albumin and was used as a model of a large molecule. Re-endothelialization of the graft had commenced by 2 days after grafting and in most animals was completed by 15 days. Some grafts exhibited local areas devoid of endothelium up to 4 weeks after grafting. The mechanism of re-endothelialization involved the migration of a sheet of endothelium across the anastomosis from the adjacent artery. This sheet subsequently linked up with islands of cells which developed in the centre of the graft by 5 days. Evans Blue dye was detected in all areas where endothelium had been removed by the grafting operation. Permeability of the graft to the dye was seen during the 2–4 week period after grafting, a time at which previous studies have shown that intimal thickening develops in this vein grafting model. Thus, delayed re-endothelialization and prolonged permeability to a large molecule (albumin) does occur in some experimental vein grafts. This may be the basis for intimal thickening which is known to occur in vein grafts.