2.1. Planar biaxial testing

FPAs from 472 subjects (age range 12 – 82 years, mean age 53 ± 16 years, 78% male) were obtained from Live On Nebraska within 24 hours of subject’s death. Prior to excision from the body, the in situ length of the FPA segment was measured using an umbilical tape. The tape was placed alongside the surgically exposed artery between the locations at which the artery was transected representing the true in situ length of the arterial segment. The artery and the tape were then cut together, and while the umbilical tape maintained its length, the artery typically shortened due to in situ pre-stretch. Pre-stretch was then defined as the ratio of the in situ arterial length (umbilical tape length) to the excised artery length(Kamenskiy et al. 2016). Geometric data including arterial wall thickness (H), outer radius of the load-free ring (ρ_o), inner and outer radii of the stress-free circumferential strip (R_i, R_o), inner radius of the longitudinal strip (R_zo), and circumferential (α) and longitudinal (β) opening angles were measured optically.

Planar biaxial tests were performed on 13 × 13 mm arterial segments (when permitted by vessel size) submerged into 0.9% phosphate-buffered saline at 37°C. A total of 19 different protocols were used to obtain sufficient data density for constitutive modeling. For additional details of these tests, please refer to Kamenskiy et al(Kamenskiy et al. 2017) or Desyatova et al(Desyatova et al. 2017a).