Averaged stress-strain curves, E-modulus at high strains, and extensibility obtained from biaxial tensile tests.

Averaged stress-strain curves (A, B), E-modulus at high strains (C), and extensibility (D) obtained from biaxial tensile tests. The E-moduli (E) in both circumferential and radial direction increase with age in the aortic valve (p<0.05). In the pulmonary valve the E-modulus does not change with age. The leaflets of the 11 and 20-year-old donors are more extensible than the adult leaflets (F). In addition, in these young donors, the pulmonary leaflets were slightly more extensible than the aortic leaflets. As the data of the 8-month old donor could be considered as an outlier, we also performed linear regression analysis of the data set excluding the 8-month data and added the corresponding linear regression lines to Figs E and F. This reveals that after the age of 11, leaflet extensibility significantly decreases with age in circumferential (AV: p<0.01, PV: p<0.05) and radial direction (PV: p<0.01). AV: aortic valve, PV: pulmonary valve.