Experimental right ventricle to pulmonary artery discontinuity: outcome of polyurethane valved conduits

The ideal substitute for the treatment of ventricle-pulmonary artery discontinuity remains a topic of controversy, because of calcifications and degeneration of biologic substitutes leading to subsequent reoperations. Because polyurethane valves used in ventricular assist devices show a satisfactory biocompatibility, the aim of this study was to evaluate a valved conduit composed of a Dacron graft incorporating a trileaflet 25 mm polyurethane valve.

The conduit was implanted between the right ventricle and the main pulmonary artery in adult sheep, with ligation of the proximal pulmonary artery. The animals received no medications. Serial hemodynamic data were collected at the time of implantation and at postoperative intervals of 6 and 12 months.

The peak pressure gradient across the valve increased significantly between implantation (0.17 +/- 5.6 mm Hg) and 6 months after operation (7.3 +/- 3 mm Hg, p = 0.0007) and remained stable thereafter (6.7 +/- 3 mm Hg at 12 months), whereas the cardiac output remained unchanged (4.6 +/- 0.6 L/min at implantation, 4 +/- 0.6 L/min at 6 months, and 3.9 +/- 1.1 L/min at 12 months). At the completion of the study, valve samples were processed and vapor coated with carbon for microscopic examination. There was one instance of nonadherent thrombus formation inside a cusp but no structural failures. The other valves were free of calcium deposits and no significant amounts of phosphorus could be detected by scanning electron microscopy and energy dispersive spectrometry.

These data demonstrate the good hemodynamic performance, low thrombogenicity, and acceptable durability of the polyurethane valves implanted in the right side of the heart in a chronic sheep model.