[Study on patency of small caliber synthetic vascular prosthesis--with special reference to antithrombogenesity of fibrin layer].

The influence of antithrombogenesity of stable and thin fibrin layer on patency of small diameter graft was studied. Newly developed segmented polyurethane grafts (SPG), 4 cm in length and 3 mm in internal diameter, were interposed between divided carotid arteries in 20 mongrel dogs. The change of antithrombogenesity was evaluated by 111In-oxine labeled platelet scintigraphy. Autologous radiolabeled platelets were injected immediately or 1 week after implantation. Grafts and native arteries were explanted 48 hours after injection, and submitted for gamma well counting. Platelet accumulation was quantitated by a Graft/Blood Ratio (GBR) that compared radio-activity in the graft or native artery (luminal surface area 1 cm2) to simultaneously collected blood (1 ml). In SPG, GBR was significantly declined during 1 week (2.65 +/- 0.65 in immediate group, 0.72 +/- 0.18 in early group, p less than 0.05). Also each GBR in immediate or early group was by far greater than GBR in native arteries. Histologically the luminal surface in patent grafts was thinly covered with the fibrin layer, which was anchored firmly to the porous structure. On the other hand thrombus was formed at the anastmotic site in obstructive grafts. In conclusion, the stale and thin fibrin layer formed on the luminal surface has a reduced thromboactivity and maintains early graft patency. However its antithrombogenesity is far beyond that of native arteries and limits patency.