Diastolic Properties of the Sorin Solo, ATS 3F, Edwards Prima Plus and Medtronic Freestyle Stentless Valves: An Independent In-Vitro Comparison

Background and aim of the study: Currently, little is known of the diastolic properties of stentless valves that affect stress and strain on leaflets and, hence, their durability. In a pressurized aortic root model, a series of in-vitro tests was conducted to determine how stentless valves behave in diastole, and how they adapt to different annulus-to-sinotubular junction (STJ) ratios. Methods: Sixteen 25 mm stentless aortic valves (four each of the Sorin Solo, ATS 3F, Edwards Prima Plus and Medtronic Free Style) were sutured into a 32 mm Valsalva graft, suspending the commissures into the expandable region (42 mm). The neoaortic root was pressurized and the size of the STJ progressively reduced by wrapping the neocommissural ridge with Dacron rings. Endoscopic views and ultrasound imaging were used to observe the geometry of the leaflets, regurgitation, and the height and level of leaflet coaptation at different annulus-to-STJ ratios. Results: Pericardial prostheses built to mimic a cylinder (ATS 3F and Sorin Solo) showed the greatest tolerance to STJ dilatation and a larger coaptation surface, but also a tendency to roll in on themselves in an italic S-shape if oversized. Valves built to mimic native aortic leaflets (porcine Prima Plus and Medtronic Freestyle) showed a reduced tolerance to STJ dilatation, resulting in regurgitation and a smaller coaptation surface, but also a reduced tendency to roll if oversized. Conclusion: Despite similar systolic performances, stentless prostheses behave differently during diastole. The 3F and Solo valves benefit from a better tolerance to STJ dilatation, while the Prima Plus and Freestyle benefit from a more stable shape of closure under conditions of oversizing.