Impact of calcification and intraluminal thrombus on the computed wall stresses of abdominal aortic aneurysm
Received 9 July 2007; accepted 6 January 2008. published online 28 March 2008.
Background
Increased biomechanical stresses within the abdominal aortic aneurysm (AAA) wall contribute to its rupture. Calcification and intraluminal thrombus can be commonly found in AAAs, but the relationship between calcification/intraluminal thrombus and AAA wall stress is not completely described.
Methods
Patient-specific three-dimensional AAA geometries were reconstructed from computed tomographic images of 20 patients. Structural analysis was performed to calculate the wall stresses of the 20 AAA models and their altered models when calcification or intraluminal thrombus was not considered. A nonlinear large-strain finite element method was used to compute the wall stress distribution. The relationships between wall stresses and volumes of calcification and intraluminal thrombus were sought.
Results
Maximum stress was not correlated with the percentage of calcification, and was negatively correlated with the percentage of intraluminal thrombus (r = −0.56; P = .011). Exclusion of calcification from analysis led to a significant decrease in maximum stress by a median of 14% (range, 2%-27%; P < .01). When intraluminal thrombus was eliminated, maximum stress increased significantly by a median of 24% (range, 5%-43%; P < .01).
Conclusion
The presence of calcification increases AAA peak wall stress, suggesting that calcification decrease the biomechanical stability of AAA. In contrast, intraluminal thrombus reduces the maximum stress in AAA. Calcification and intraluminal thrombus should both be considered in the evaluation of wall stress for risk assessment of AAA rupture.
aUniversity Department of Radiology, Cambridge University Hospitals Foundation Trust, Cambridge, United Kingdom
cCambridge Vascular Unit, Cambridge University Hospitals Foundation Trust, Cambridge, United Kingdom
bDepartment of Engineering, University of Cambridge, Cambridge, United Kingdom.
Reprint requests: Zhi-Yong Li, PhD, Box 219; Level 5, University Department of Radiology, Cambridge University Hospitals Foundation Trust, Hills Rd, Cambridge CB2 2QQ, UK.
ABSTRACT