Eric K. Shang1, Chun Xu1, Derek P. Nathan1, Ronald M. Fairman1, Robert C. Gorman1, Joseph H. Gorman1, Sarah C. Vigmostad2, Benjamin M. Jackson1
1Surgery, University of Pennsylvania, Philadelphia, PA; 2University of Iowa, Iowa City, IA.
OBJECTIVES: Biomechanical analysis can predict mechanical stresses in cardiovascular structures. Prior models often assume uniform arterial wall thickness (WT). We hypothesize that including local WT in finite element analysis (FEA) of the carotid artery will effect wall stress (WS) distribution and maxima.
METHODS: CTAs in patients with carotid occlusive disease (n=5) were analyzed with custom algorithms to segment luminal and adventitial surfaces, providing local WT. A control model was defined with variable wall thickness (VWT) and hyperelastic material properties (MP). Experimental models tested the effects of: (1) uniform wall thickness (UWT), (2) soft and calcified plaque, and (3) linear MP. Commercial FEA software was used to load each model with 80 mmHg pulse pressure and compute Von Mises WS.
RESULTS: The mean (across n=5 patients) peak WS of the VWT model was 162±29 kPa. Peak WS decreased with the imposition of UWT (112±19 kPa, p=0.01) and with linear MP (105±24 kPa, p=0.01). UWT decreased both the average WS over the entire carotid bifurcation (31±4 kPa, p=0.04) compared to VWT control (42±9 kPa) and the mean normalized nodal variance (a measure of inhomogeneity) of the WS over the bifurcation (0.34±0.03 vs. 0.30±0.04, p=0.03).
CONCLUSIONS: Incorporation of local WT can significantly increase peak WS and cause less uniform WS distribution. Aortic wall thickness should be incorporated in FEA of aneurysms to accurately predict rupture risk and in other bioengineering analyses.
AUTHOR DISCLOSURES: R. M. Fairman, Nothing to disclose; J. H. Gorman, Nothing to disclose; R. C. Gorman, Nothing to disclose; B. M. Jackson, Nothing to disclose; D. P. Nathan, Nothing to disclose; E. K. Shang, Nothing to disclose; S. C. Vigmostad, Nothing to disclose; C. Xu, Nothing to disclose.
Changes in magnitude and distribution of wall stress in varying models as shown in a cross section of a single carotid artery.
Posted April 2012