Pathological study of implanted dacron grafts in surgery of thoracic aortic aneurysms.

We studied woven dacron grafts that had been implanted in 5 patients of thoracic aortic aneurysms. In addition to usual stains, immunocytochemical analysis was performed using monoclonal antibodies to the muscle actin (HHF35) and to the macrophage (HAM56). In the graft of 5 and 24 days implantation, thin thrombi containing red cells and fibrin covered the luminal surface in some places, and macrophages came into the thrombi. In the grafts of 12 and 38 months implantation, intimal hyperplasia of 0.2-1.0 mm thickness was seen at the anastomotic segments with the accumulation of smooth muscle cells. Except for the anastomotic segments, connective tissue matrix with collagen fibers covered the luminal surface, and in some hollows of the graft crimps, old and fresh thombi were seen in layers. Organizing thrombi of 1.0 mm thickness attached where the branched graft was anastomosed to the main graft. Anastomotic intimal hyperplasia in the graft of 148 month implantation was 0.4-1.0 mm in thickness and 5-10 mm in length, and aside from the intimal hyperplasia, an endothelial lining did not cover the luminal surface of the graft. In the thoracic aorta, woven dacron graft implantation did not cause a critical stenosis with the intimal hyperplasia. The mural thrombi formed at the branched graft, however, threatened to result in graft occlusion or embolization.