Long-term behaviour of cryopreserved arterial grafts versus prosthetic micrografts

Introduction. When a patient has no suitable vessels for use as grafts ill bypass or reconstruction procedures, two of the options available are the use of a cryoprescrved vessel or ail expanded polytetrafluoroethylene (ePTFE) prosthesis. This study was designed to compare the long-term behaviour of these vascular substitutes. Material and methods. We established three study groups by grafting the following vessel substitutes to the iliac artery in Sprague-Dawley rats: arterial autografts (GI, n = 12), cryopreserved syngenic arterial grafts (cryoisografts) (GII, n = 12), and ePTFE micrografts (GIII, n = 12). The animals were sacrificed 180 days after surgery, at which time the graft specimens were morphologically evaluated by light and electron microscopy, immunolabelling (ED1/alpha-actin) and morphometric analysis of the neointima. Results. At the time of sacrifice, graft patency was 100% for the autografts and cryoisografts, while 10% of the ePTFE micrografts showed fully-occlusive thrombosis. Intimal hyperplasia was observed in grafts ill GI and GII; the neointima being thinner ill the cryoisografts (54.36 +/- 2.26 mum) than the autografts (161.30 +/- 3.91 mum). The endothelium formed over the prosthetic micrografts was unstable, with areas of subendothelial thickening (9.37 +/- 3.18 mum). Cell loss and medial layer degeneration were observed in both GI and GII specimens, while the GIII grafts were colonised by cells on their luminal surface. Conclusions. All three grafts show good long-term tolerance when used in ail arterial setting. Following long-term implant, autografts and cryoisografts show similar alterations that give rise to the complete loss of the muscle component of the tunica media along with the formation of a stable neointima. This new layer takes oil the role of the tunica media.