Comparison of porcine pulmonary and aortic root material properties

Background: The pulmonary autograft remodels when subjected to systemic pressure and subsequent dilation can lead to reoperation. Inherent material property differences between pulmonary and aortic roots may influence remodeling but are currently unknown. The objective of this study was to determine stiffness across a wide range of strain and compare nonlinear material properties of corresponding regions of native aortic and pulmonary roots.

Methods: Tissue samples from porcine aortic and pulmonary roots-sinuses and supravalvular artery distal to the sinotubular junction-were subjected to displacement-controlled equibiaxial stretch testing. Stress-strain data recorded were used to derive strain energy functions for each region. Stiffness from low to high strains at 0.15, 0.3, and 0.5 strain were determined for comparisons.

Results: Aortic and pulmonary roots exhibited qualitatively similar material properties; both had greater nonlinearity in the sinus than supravalvular artery. The pulmonary artery was significantly more compliant than the ascending aorta both circumferentially and longitudinally throughout the strain range (p < 0.03), except at high strain circumferentially (p = 0.06). However, no differences in stiffness were seen circumferentially or longitudinally between pulmonary and aortic sinuses (p > or = 0.3) until high strain, when the pulmonary sinuses were significantly stiffer (p < 0.05) in both directions.

Conclusions: Differences in stiffness between porcine aortic and pulmonary roots are regionally specific, supravalvular artery versus sinus. These regional differences may impact the mode of remodeling to influence late autograft dilation.