Comparative Analysis of Leaflet Materials, Stent Materials, and Stent Cell Density for Bileaflet Transcatheter Mitral...

The biomechanical performance of bileaflet transcatheter mitral valves (TMVs) depends on complex interactions between leaflet material behavior and stent design. However, the contributions of leaflet materials and constitutive models, stent materials, and stent geometry to valve function and durability remain poorly understood.

A parametric finite element study was conducted using a CAD model of a bileaflet TMV subjected to physiological pressure loading. Five leaflet material models were evaluated: 3 glutaraldehyde-fixed tissues-bovine pericardium (BP; FBP1, FBP2) and porcine pericardium (PP; FPP)-and 2 unfixed tissues-bovine (UBP) and porcine pericardium (UPP). BP was modeled as a linear elastic (FBP1) and Ogden (FBP2). Each was paired with 2 stent materials, cobalt chromium (CoCr) and nitinol, and 3 stent cell densities (low, medium, high), yielding 30 configurations. Von Mises stresses and relative leaflet opening were quantified.

UPP achieved the largest opening (30-32%) with the lowest leaflet 99th percentile stresses (0.048-0.050 MPa), while FBP1 produced the smallest opening (8-9%) and highest leaflet stresses (0.077-0.078 MPa). Leaflet 99th percentile stress was strongly inversely correlated with valve opening (Spearman r=-0.9, p<0.01). Stent material had a negligible effect on valve opening but affected stent stress notably, with nitinol exhibiting about 2-3 orders of magnitude lower stresses compared to CoCr. Increasing stent cell density improved stress distribution with only a modest reduction in opening.

Leaflet material model was the primary determinant of bileaflet TMV biomechanical performance, whereas stent material and cell density exerted secondary but meaningful effects. These findings offer insights that may guide the design of more optimized TMV replacement devices.