Composite and plain tubular synthetic graft conduits in right ventricle-pulmonary artery position: fate in growing lambs.

Our goal was to identify the most appropriate material for right ventricle-pulmonary artery conduits in growing animals. We used 100 lambs that were 3 to 4 weeks old (mean weight 11.7 kg). Follow-up was up to 24 months. Group I received plain tubular conduits: (1) Dacron knitted fabric, (2) collagen-coated knitted fabric, (3) Milliknit and Microknit material, (4) woven Dacron fabric, (5) three-dimensional Dacron fabric (crossweave 500 and 800), or (6) polytetrafluoroethylene. Group II received either a (1) woven Dacron fabric conduit with a built-in tissue valve or (2) polytetrafluoroethylene graft with a built-in St. Jude Medical valve. We did angiograms and catheterizations every 3 to 6 months and killed the lambs at 6, 12, 18, or 24 months. Tubular Dacron fabric woven or knitted grafts, regardless of matrix, pore size, thickness, or coating, caused formation of a thick acellular pseudointima buildup, which led to progressive obstruction starting as early as 3 months. Polytetrafluoroethylene grafts in groups I and II showed the formation of thin inner and outer capsules (0.5 mm) and none developed obstruction despite wall calcification. Conduits of woven Dacron fabric with a built-in tissue valve degenerated rapidly, leading to calcification thrombosis and obstruction within 3 months; no lamb survived 12 months. Polytetrafluoroethylene conduits with a St. Jude Medical valve in lambs receiving anticoagulants remained free of obstruction and continued to function well. It appears that synthetic conduits of polytetrafluoroethylene perform well in either of the situations here tested and may be the best choice at present.