Fatigue-induced changes in bioprosthetic heart valve three-dimensional geometry and the relation to tissue damage

Background and aim of the study:In a previous study, we used magnetic reson ance (MR) imaging to reconstruct, three-dimensionally, porcine bioprostheti c heart valve (PBHV) cusp geometry. Initial results using three valves indi cated that accelerated testing induced changes in cuspal shape, including f ocal regions of high curvature. Since for thin-walled shell structures, suc h as the PBHV cusp, curvature changes can affect the stress distribution in dependently from changes to mechanical properties, shape changes might have adverse effects on PBHV durability. Methods: The MR technique was applied to an expanded valve database to expl ore more fully shape change with fatigue. The spatial curvature distributio n was compared across valves subjected to a range of accelerated test times . Results: Results confirmed our initial findings that PBHV cusps undergo a c ontinuous, non-recoverable deformation with accelerated testing. This defor mation resulted in an increase in the portion of cuspal surface exhibiting high curvature values. In one cusp we mapped structural information obtaine d by small-angle light scattering back to the three-dimensional cuspal surf ace using an interpolation technique. Results from the mapped cusp demonstr ated a strong spatial correlation between elevated curvatures and structura l damage. Conclusions: The observed changes in cuspal shape accelerate PBI-IV damage due to an increase in flexural strains induced by an increase in curvature reversal during operation, rather than an increase in tension during closur e.