Background and aim of the study: Stent mounting of a porcine aortic valve induces loss of mobility and reduces the effective orifice area. Any stentless design conserves the flexibility of the valvular apparatus, but unfortunately, these valves require a more elaborate implantation technique which is considered a major drawback by many surgeons. In an attempt to see if the insertion of the Toronto SPV stentless valve could be made easier, we altered the configuration by lowering the profile at the depth of both coronary sinuses. Theoretically, this could enable insertion of the valve by a single suture layer under the two coronary ostia, in addition to some fixation points at the commissures.
Methods: Two modified 20 mm Toronto SPV valves were tested in vitro for hydrodynamics in a computer-controlled pulse duplicator system and compared with two standard 20 mm valves. Animal implant studies using three standard versus three modified valves (21, 23 and 25 mm) were conducted in juvenile sheep for durability and biocompatibility over a period of three months.
Results: The standard Toronto SPV valve provided excellent hemodynamics. The altered configuration performed less optimally during hydrodynamic testing with increased transvalvular gradients. In animal implant studies, cusps adjacent to all reduced-height sinuses showed markedly accelerated fibrosis and substantial calcification, in contrast to only mild fibrosis on the inflow aspects of the standard leaflets.
Conclusions: The more pronounced the deformation of the stentless valve, the faster the calcification of the leaflets adjacent to the distorted sinuses. As both valves types were prepared using an identical preservation technique, the role of loss of mobility in leading to early failure is clearly demonstrated. These findings also underline the extreme importance of correct implantation technique for all stentless valves in order to prevent degeneration.