Objective Uniaxial Identification of Transition Points in Non-Linear Materials: Sample Application to Porcine Coronary Arteries and the Dependency of Their Pre- and Post-Transitional Moduli with Position

Purpose This study aimed to develop an objective method for the elastic characterisation of pre- and post-transitional moduli of left anterior descending (LAD) porcine coronary arteries. Methods Eight coronary arteries were divided into proximal, middle and distal test specimens. Specimens underwent uniaxial extension up to 3 mm. Force–displacement measurements were used to determine the induced true stress and stretch for each specimen. A local maximum of the stretch-true stress data was used to identify a transition point. Pre- and post-transitional moduli were calculated up to and from this point, respectively. Results The mean pre-transitional moduli for all specimens was 0.76 MPa, as compared to 4.86 MPa for the post-transitional moduli. However, proximal post-transitional moduli were significantly greater than that of middle and distal test specimens (p < 0.05). Conclusion Post-transitional uniaxial properties of the LAD are dependent on location along the artery. Further, it is feasible to objectively identify a transition point between pre- and post-transitional moduli.