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

Objectives: We established an in vitro model to investigate the effects of valve sizing on the hemodynamic characteristics and leaflet motion of the T oronto SPV valve (St Jude Medical, inc, St Paul, Minn). Methods: Nine valve s were first implanted in fresh porcine aortic roots and then retested in g lutaraldehyde de-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 im plantations. The elasticities of the aortic roots and the composite roots w ere measured in the pressure range between 0 and 120 mm Hg, and the composi te 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 record ed 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 w ith 11% for the glutaraldehyde-treated root. Valve implantation in the fres h root reduced the distensibility to 22% but did not change distensibility in the glutaraldehyde-treated root. The effective orifice area was dependen t on the valve size, with the transvalvular gradient decreasing as the valv e size increased. For the same size of valve the hydrodynamic parameters we re slightly better if the valve was undersized by 1 mm, A significant diffe rence in favor of the undersized valves was found in open-leaflet bending d eformation. Conclusion: Leaflet motion of the stentless porcine aortic valv e in vitro is improved if the valve is slightly undersized, and this may be beneficial to the long-term durability of the prosthesis.