Determination of hyperelastic properties for umbilical artery in preeclampsia from uniaxial extension tests.

OBJECTIVE

Preeclampsia often results in altered hemodynamics and structurally remodeled umbilical arteries in the fetus--alterations that may be associated with arterial stiffening. We therefore hypothesized that the mechanical function of preeclamptic (PE) umbilical arteries had increased stiffness compared to control.

STUDY DESIGN

Umbilical arteries were collected from control (n=9) and PE (n=6) pregnancies without any other complications. Samples were tested uniaxially in axial and circumferential directions for the passive mechanics. The umbilical artery was modeled as a fiber reinforced hyperelastic material in both control and PE conditions.

RESULTS

The PE arteries were stiffer than control arteries at stresses of 20-160 mmHg in the axial direction and 65-200 mmHg in the circumferential direction (P<0.05). The PE umbilical arteries exhibited a 58% and 48% increase in circumferential moduli at the systolic and diastolic blood pressure respectively compared to the controls (P<0.05). A hyperelastic model showed a substantial increase in both isotropic and anisotropic contribution in the mechanical behavior. Collectively, the changes observed correlated to a higher collagen fiber density in the PE group with increased hyperelastic material parameters (P<0.05).

CONCLUSION

PE umbilical arteries demonstrated stiffer biomechanics compared to the controls due to the change in collagen fiber content. These altered biomechanical and structural changes provide a potential snapshot into systemic vasculature remodeling occurring in the newborn.