nfluence of leaflet calcification patterns on the biomechanics of bioprosthetic mitral valves

Objective: to identify characteristic patterns of calcium distribution in explanted bioprosthetic heart valves and evaluate their influence on the biomechanics of the device. Materials and methods. Thirty-three bioprosthetic mitral valve leaflets explanted due to structural valve degeneration were analyzed. Multislice computed tomography (MSCT) images were used to identify pathological calcification within each leaflet. Calcified regions were segmented from top-view projections using a radiographic density threshold of 130 HU. The resulting dataset was clustered according to the number of pixels representing calcified areas, yielding three distinct classes: no calcification, mild calcification, and severe calcification. For each class, a three-dimensional computational model of the bioprosthesis was constructed. Biomechanical behavior was evaluated numerically in a series of computer simulation experiments using the finite element method. Each model included the supporting frame and three valve leaflets, with physiologically relevant boundary conditions simulating pressures in the left atrium and left ventricle. The analysis assessed maximum principal stress, strain, and their spatial distribution across the prosthesis. Results . Calcification of one or two valve leaflets resulted in a slight reduction in the average stress and strain values of the intact leaflet – from 0.319 to 0.303 MPa and from 0.134 to 0.130 mm/mm, respectively. Increased calcium content also lowered the peak stress and strain values, from 2.884 to 2.117 MPa and from 0.384 to 0.333 mm/mm. A clear relationship was observed between calcification pattern and local stress concentrations, which exceeded the leaflet’s mean stress values by 40–50%. Co-localization of mild or severe calcification clusters on one or two leaflets produced qualitative alterations in the closure mechanism, including «overlap» of mineralized leaflets over adjacent intact ones. Conclusion. The findings demonstrate a relationship between the stress–strain behavior of bioprosthetic valve leaflets and the spatial pattern of calcification. While an increase in calcium volume up to 28% does not substantially affect mean stress or strain values, it significantly reduces their peak values.