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Transcatheter aortic valve replacement (TAVR) has recently been shown to be equivalent to surgical aortic valve replacement (SAVR) in intermediate-risk patients. As TAVR expands to SAVR population, TAVR vs. SAVR durability becomes increasingly important. While TAVR durability is unknown, valve design, particularly leaflet stress, impacts durability. While leaflet stress cannot be measured directly, stress can be determined by finite element modeling. Such models require leaflet mechanical properties. Balloon-expandable TAVR is comprised of bovine pericardial leaflets treated in the same fashion as surgical bioprosthetic leaflets. Our aim was to determine leaflet mechanical properties of Carpentier-Edwards bioprostheses for future TAVR and SAVR computational models.
Leaflets (n=35) from twelve Carpentier-Edwards Model 3000TFX Perimount Magna aortic bioprostheses (21mm, 23mm, and 25mm) were excised and subjected to displacement-controlled equibiaxial stretch testing. Stress-strain data were fit to Fung constitutive model to describe material properties in circumferential and radial directions. Leaflet stiffness was calculated at specified physiological stress, corresponding to zero pressure, systemic pressure, and between zero and systemic pressure.
Bioprostheses 21mm had significantly thinner leaflets than larger bioprostheses. Non-linear stress-strain relationship was observed in all leaflets along circumferential and radial directions. No significant difference in leaflet stiffness at systemic pressure or between zero and systemic pressure was found among the three bioprosthetic sizes. However, 23mm bioprosthetic leaflets were significantly more compliant than 21mm and 25mm leaflets at zero pressure in circumferential direction. No differences in leaflet stiffness in circumferential vs. radial directions were observed.
Bovine pericardial leaflets in Carpentier-Edwards Perimount Magna bioprostheses showed no differences in material properties among different sizes at systemic pressure. The thinner 21mm leaflets did not lead to any corresponding differences in leaflet stiffness, suggesting that the thinner TAVR leaflets may have similar stiffness as their thicker SAVR counterparts.
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