Stent and leaflet stresses in 26-mm, third-generation, balloon-expandable transcatheter aortic valve

Transcatheter aortic valve replacement has proven successful in treating intermediate-risk, high-risk, and inoperable patients with severe aortic stenosis. Third-generation, balloon-expandable transcatheter aortic valves were developed with an outer sealing skirt to reduce paravalvular leakage. As transcatheter aortic valve replacement use expands, long-term durability questions remain. Valve design influences durability, where regions of increased leaflet stress are vulnerable to early degeneration. However, third-generation transcatheter aortic valve stresses are unknown. Our goals were to determine the stent and leaflet stresses of third-generation, balloon-expandable transcatheter aortic valves.

The commercial 26-mm Edwards SAPIEN 3 valve (Edwards Lifesciences, Inc, Irvine, Calif) underwent high-resolution micro-computed tomography scanning to develop a precise 3-dimensional geometric mesh of the stent and valve. Leaflet material properties were obtained from surgical bioprostheses, and stent material properties were based on cobalt-chromium. Simulations of systemic pressure loading were performed, and stress was calculated using finite element analyses.

At diastole, maximum and minimum principal stresses on transcatheter aortic valve leaflets were 2.7 MPa and -0.47 MPa, respectively. Peak leaflet stresses were observed at upper leaflet commissures, at their connection to the stent. Maximum and minimum principal stresses for the stent were 38.2 MPa and -44.4 MPa, respectively, at 80 mm Hg and were located just below the commissural stent.

Stress analysis of the 26-mm SAPIEN 3 valve using exact geometry from high-resolution scans demonstrated that peak stresses for both transcatheter aortic valve stent and leaflets were present at commissural tips where leaflets were attached. These regions would be most likely to initiate degeneration. The Dacron skirt had minimal effect on stresses on leaflets and stent.