Background: Aortocoronary vein grafts develop fibromuscular intimal hyperplasia within the first year of implantation. Tissue remodeling may promote development of graft atherosclerosis and thrombosis. Angiographic studies show that human aortocoronary vein grafts in situ for one or more years become stenosed, preferentially at the distal anastomosis versus the body or trunk of the graft or at the proximal anastomosis. Previous studies have not reported morphological data on the nature and distribution of intimal lesions around the distal graft/artery anastomoses.
Objective: To examine and quantify histological and morphometric changes within the intima of 27 aortocoronary vein grafts and their distal anastomoses.
Methods: Seventy-two hearts obtained at autopsy and one at heart transplantation were examined, photographed and fixed in 10% buffered formaldehyde solution. Three to seven 3 mm long segments of grafts and their distal anastomoses were sectioned, stained and examined by light microscopy.
Results: Eleven early grafts were implanted for six weeks or less, and they showed significant cellular hyperplasia mainly at the suture line. In 16 late grafts in situ 1.5 to 15 years, the degree of fibromuscular intimal thickening was greatest on the hood and at the suture line, whereas on the floor of the native artery and in the graft body the degree of thickening was approximately one-third and two-thirds, respectively, that seen on the hood.
Conclusions: Stenosis of aortocoronary vein grafts at their distal anastomosis is likely related to the preferential development of intimal thickening on the hood of the graft and at the suture line. Because fibromuscular intimal hyperplasia has been reported to play a role in the development of atherosclerosis and thrombosis in the body of vein grafts, this focal hyperplasia at the distal anastomosis may also play a role in vein graft failure.