Microscopic and immunohistological studies on intimal hyperplasia of the arterially implanted autovein graft and its anastomosis in dogs.

The fate of intimal hyperplasia of arterially implanted autovein bypass grafts and their distal end-to-side anastomoses in dogs was studied microscopically and immunohistologically. The bypass grafting was done under conditions of abnormal blood flow and high peripheral resistance. Intimal hyperplasia of the graft first became evident 7 days after implantation and the thickness increased to about 500 microns 3 months or more after the implantation. The intimal hyperplasia was related to an active proliferation of smooth muscle cells which proved positive for alpha-smooth muscle actin staining. Moreover, it was more dominant at the toe and heel of the anastomosis and moderately apparent on the floor of the host artery. The constituent elements of the hyperplastic intima at the anastomosis were fibroblast-like cells and extracellular collagen fibers which were negative for alpha smooth muscle actin staining. This study revealed that the features of intimal hyperplasia at the distal anastomosis in autovein bypass grafting differed from those of the implanted autovein graft itself; the former being related to excessive proliferation of fibroblasts and collagen fibers while the latter displayed an active proliferation of smooth muscle cells.