DEVELOPMENT OF A POLYURETHANE-VALVED CONDUIT WITH VALSALVA SINUSES FOR THE RECONSTRUCTION OF THE RIGHT VENTRICULAR OUTFLOW TRACT (RVOT)

Objectives: Around 20% of congenital heart defects require a surgical reconstruction of the right ventricular outflow tract (RVOT), often performed using valved conduits. Several studies have already proven the importance of Valsalva sinuses in such prostheses. Currently existing prostheses require permanent coagulation (mechanical prosthesis), have limited durability (xeno/hornografts) and availability in small diameters. Thus, the aim of this work is to design and manufacture a complete prosthetic polymeric valved conduit with Valsalva sinuses. Methods: A two-part core which ensures sinus formation and valve integration into the conduit was manufactured. The conduit was then produced by polyurethane atomization (spraying), allowing the production of a fine-fibrous structure with a special micro-porous surface, which can favour a neo-intimal layer formation. The micro-porous structure was observed and studied under microscopy. The prostheses mechanical and structural properties - tensile strength, compliance, burst strength, permeability and suture retention - as well as the valve functionality were subsequently tested in vitro. Results: Laboratory samples with a 22mm internal diameter were produced for in vivo experiments in calves. Structure variations were applied through process parameters changes. Valve opening and closing was investigated with high-speed video and functionality was assessed for pressure differences of 20, 40 and 80mmHg. The conduits showed sufficient compliance to propagate the pressure pulse and to withstand pressure peaks. The prostheses were impermeable up to 100mmHg pressure. The tensile, suture retention and burst strength were satisfactory. Conclusions: The production of valved conduits is possible using polymer atornization. In vitro tests showed satisfactory results for mechanical properties and functionality. These results encourage the optimization and conduction of further research in this field. A chronic implantation of the conduits in calves is planned and results are expected August 2011. Further in vivo experiments and in vitro fatigue testing will be carried out to assess the conduits durability.