The effect of sizing on the in vitro hydrodynamic characteristics and leaflet motion of the toronto SPV* stentless valve

Abstract

Objectives:We established an in vitro model to investigate the effects of valve sizing on the hemodynamic characteristics and leaflet motion of the Toronto SPV valve (St Jude Medical, Inc, St Paul, Minn). Methods: Nine valves were first implanted in fresh porcine aortic roots and then retested in glutaraldehyde-treated porcine aortic roots. Three valves were 1- to 2-mm oversized, 3 were 1- to 2-mm undersized, and there were 3 size-for-size implantations. The elasticities of the aortic roots and the composite roots were measured in the pressure range between 0 and 120 mm Hg, and the composite roots were then tested in a pulsatile flow simulator. The transvalvular gradient and regurgitation were measured and the effective orifice area and performance index were calculated for each root. Leaflet motion was recorded on videotape. Results: The external diameter of the fresh root increased by 35% as the hydrostatic pressure rose from 0 to 120 mm Hg, as compared with 11% for the glutaraldehyde-treated root. Valve implantation in the fresh root reduced the distensibility to 22% but did not change distensibility in the glutaraldehyde-treated root. The effective orifice area was dependent on the valve size, with the transvalvular gradient decreasing as the valve size increased. For the same size of valve the hydrodynamic parameters were slightly better if the valve was undersized by 1 mm. A significant difference in favor of the undersized valves was found in open-leaflet bending deformation. Conclusion: Leaflet motion of the stentless porcine aortic valve in vitro is improved if the valve is slightly undersized, and this may be beneficial to the long-term durability of the prosthesis. (J Thorac Cardiovasc Surg 1999;117:92-8)