Surgical pathology of obstructed, right-sided, porcine-valved extracardiac conduits.

Thirty-seven specimens were available from 39 children and adolescents with congenital heart disease who have had operations at the Mayo Clinic (Rochester, Minn) to replace obstructed Hancock conduits that had been implanted 17 to 93 months (mean, 62 months). Stenosis affected the porcine valve alone in 17 (46%), the synthetic graft alone in 11 (30%), both the valve and the graft in six (16%), and other sites in three (8%). Valvular stenosis resulted from degenerative changes with secondary thrombosis and calcification, whereas insufficiency resulted from cuspid tears, thrombotic adhesions, and endocarditis. Nonvalvular obstruction resulted from progressive thickening of fenestrated neointimae, owing to organization of thrombotic debris lining the interface between the conduit and this tissue. Late postoperative conduit stenosis may develop asymptomatically and unpredictably by several different mechanisms.