Morphological studies of cellular responses to experimental arterial grafts

Although previous experimental studies' indicate that 100% patency can be expected after microsurgical implant of 3-5 mm diameter carotid artery interposition autografts in dogs, less than 50% patency can be expected following implant of 2-5 mm diameter microvascular prosthetic or xenograft material in the same animal model. 233 Clinical studies of the outcome after graft implants in patients describe similar results with small vessel replacement using materials other than autologous vessels. Acceptable patency rates with larger diameter prosthesic grafts are routinely obtained4; however, the cause of failure of such microvascular grafts remains unknown. Harashina et al.5 suggested that failure of reconstitution of the endothelial layer may preclude patency; Nelson et al. ,6 indicated that graft failure may be related to occlusion (by clot) of the adventitial and transmural microcirculation. To obtain information regarding the cellular response to microvascular arterial grafting procedures and to determine if our methods of analyses in the test animals are consistent with other studies and might yield some possible causes of graft failure, morphological studies comparing patent and occluded grafts were accomplished. Grafts and host vessels were examined histologically and by transmission electron microscopy (TEM) at 1 and 5 weeks after implant of canine arterial autograft and antigenically denatured human umbilical artery xenograft material (HUAG) in a trial group of four dogs.