Objective Transcatheter aortic valve replacement is established therapy for high-risk and inoperable patients with severe aortic stenosis, but questions remain regarding long-term durability. Valve design impacts durability. Increased leaflet stresses in surgical bioprostheses have been correlated with degeneration; however, transcatheter valve leaflet stresses are unknown. From 2007–2014, a majority of US patients received first-generation balloon-expandable transcatheter valves. Our goal was to determine stent and leaflet stresses in this valve design using finite element analyses. Methods 26mm Edwards Sapien (Edwards Lifesciences, Inc, Irvine, CA) underwent high-resolution micro-computed tomography scanning to develop precise 3D geometry of leaflets, stent, and dacron. Stent was modeled using 3D elements and leaflets using shell elements. Stent material properties were based on stainless steel, while those for leaflets were obtained from surgical bioprostheses. Non-cylindrical Sapien geometry was also simulated. Pressure loading to 80 and 120mmHg was performed using ABAQUS, finite element software (Dassault Systemes, Waltham, MA). Results At 80mmHg, maximum principal stresses on Sapien leaflets were 1.31MPa. Peak leaflet stress was observed at commissural tips where leaflets connected to the stent. Maximum principal stresses for stent was 188.91MPa, and located at stent tips where leaflet commissures were attached. Non-cylindrical geometry increased peak principal leaflet stresses by 16%. Conclusions Using exact geometry from high-resolution scans, 26mm Sapien showed that peak stresses for both stent and leaflets were present at commissural tips where leaflets were attached. These regions would be prone to initiate leaflet degeneration. Understanding stresses in first-generation transcatheter valves allow comparison to future designs for relative durability.

Failed pulmonary autografts retained nonlinear response to mechanical loading typical of healthy human arterial tissue. Remodeling increased wall thickness but decreased wall stiffness in failed autografts. Increased compliance may explain progressive autograft root dilatation in autograft failures.

Failed pulmonary autografts retained a nonlinear response to mechanical loading typical of healthy arterial tissue. Despite similar wall thickness between autografts and aorta, autograft stiffness in this patient population was significantly reduced compared with native aortic roots. We demonstrated that biomechanical remodeling was inadequate in these specimens to achieve native aortic mechanical properties, which may have resulted in progressive autograft root dilatation.