Daniela Valdez-Jasso, North Carolina State University


Modeling the Mechanical Properties of Large Ovine Arterial Walls using both in-vivo and in-vitro data.


Abstract: In this study the differences among viscoelastic properties were analyzed across 7 locations along the large arteries in 11 sheep in-vitro and in one location among 7 sheep in-vivo. For the in-vitro study, experimental data were comprised of blood pressure and area recorded at one frequency mimicking the resting heart rate. For the in-vivo data, a pace-maker was implanted in the sheep allowing data collection at frequencies ranging from 50-160 BPM. A 4-parameter Kelvin viscoelastic model and a 7-parameter generalized viscoelastic model were employed to assess material properties of the arterial wall. This analysis was carried out via solution of the associated inverse problem (least squares problem). Sensitivity analysis was used to rank the model parameters from the most to the least sensitive, as well as to compute the standard errors and confidence intervals. Results reveal that both the vessel elastic properties (e.g. Young's modulus) and the inclusion of viscoelastic behavior in the model are important for capturing the observed pressure-area dynamics. In addition, results show that data fitting using the same models vary in accuracy between in-vivo and in-vitro, which may be due to the auto-regulation of the vessels. In general, the Kelvin viscoelastic model has shown to be an efficient simple model for a fixed frequency sampling. In the case of the aleatory frequency sampling of in-vivo data, the generalized model is more appropriate.

Advisors: M.S. Olufsen and M.A. Haider (NCSU)

Collaborators: H.T. Banks and S.L. Campbell (NCSU), D. Bia, R. Armentano and Y. Zocalo (Universidad de la Republica, Uruguay)