Empirical Study Of Handmade Expanded Polytetrafluoroethylene Valved Conduit In Right Ventricular Outflow Tract Reconstruction

Objective:Reconstruction of right ventricular outflow tract had been needed in many complex congenital heart diseases with pulmonary stenosis or atresia or in the ROSS operation. Non-valved conduit between right ventricle and pulmonary artery usually produced severe pulmonary regurgitation, and leaded to right ventricular volume overload, increasing right ventricular end-diastolic pressure, tricuspid regurgitation and then dysfunction of ventricles, increase of arrhythmia and even sudden death at last. Rebuilding the function of pulmonary valve can prevent these complications effectively. Homograft conduit is thought to be the best material for right ventricular outflow tract reconstruction. However, homograft is expensive; its availability in small size appropriate for neonates and infants is severely limited; and results of its long-term function in clinical studies have been disappointing. Other materials used in right ventricular outflow tract reconstruction all performed worse then homograft. Long-time observation is still required for some new materials. ePTFE is a non-toxic material with smooth surface, stable physical and chemical properties, high fatigue resistance, long-term durability and excellent histocompatibility. It will not deform, deteriorate, degrade or calcify for long-term implantation and never irritate tissues, cause inflammatory reaction or denaturation of protein. The inner face of ePTFE artificial vessels keeps smooth for long-term use without obstruction. The elasticity and flexibility of the ePTFE patch (0.1mm) and its structure which keeps cells from adhesion and fiber from deposition make it a good substitute for heart valves. Valved conduits made of ePTFE artificial vessel and patch may overcome the shortcomings of the homograft.Methods:A kind of valved conduit was design and made by hand using ePTFE artificial vessel and patch. This valved conduit was applied to reconstruct the right ventricular outflow tract of pigs in an animal experiment. During the operation and 6 months later, the pressure in the cardiac chambers and vessels was measured directly. The early and midterm performance of the conduit and valve were evaluated by echocardiography before and after operation. At 6 months all animals were sacrificed. The hearts were removed and the implanted valved conduits were excised. A histological and structural evaluation was performed by means of light microscopy and scanning electron microscopy after a macroscopic inspection.Results:All of the five valved conduits performed well, without stenosis or severe incompetence after operation. Only one animal showed mild regurgitation. However it had changed to trace regurgitation a month later. The reason might be that the stentless and faxable ePTFE vessel had been twisted, buckled or extruded and sequently led to distortion and regurgitation of the valve. So it is important to cut the conduit appropriately and put it to a proper location. The anastomotic pressure grade, cross conduit and valve pressure gradient, right ventricular diastolic pressure and pulmonary artery pressure immediately after reconstruction and 6 months after operation were not significant change compared with preoperative results. Only postoperative right ventricular systolic pressure was significant higher (P=0.037). However the aortic systolic pressure increased at the same time(P=0.007). This suggested that it's not due to the conduit problem but the blood pressure contributed to the increased right ventricular systolic pressure. The diameter of both proximal and distal anastomotic orifice showed a tendency of decreasing but not significant(P>0.05). Pathological examination did not observe stenosis and thrombus in any part of the conduits. The valves were pliable without stenosis or insufficient. The inner faces of the conduit and the surfaces of the valves were smooth without any cell infiltration, fibber deposition or calcification under optical microscope. However a layer of structureless matter and scattered highlighting substances were observed on the leaves under scanning electron microscope. This may affect long-term use of the valved conduit.Conclusions:This handmade ePTFE valved conduit show excellent early and middle term hemodynamic behaves and required a long-term observation.