Vessel asymmetry as an additional diagnostic tool in the assessment of abdominal aortic aneurysms.
OBJECTIVE
Abdominal aortic aneurysm (AAA) rupture is believed to occur when the local mechanical stress exceeds the local mechanical strength of the wall tissue. On the basis of this hypothesis, the knowledge of the stress acting on the wall of an unruptured aneurysm could be useful in determining the risk of rupture. The role of asymmetry has previously been identified in idealized AAA models and is now studied using realistic AAAs in the current work.


METHODS
Fifteen patient-specific AAAs were studied to estimate the relationship between wall stress and geometrical parameters. Three-dimensional AAA models were reconstructed from computed tomography scan data. The stress distribution on the AAA wall was evaluated by the finite element method, and peak wall stress was compared with both diameter and centerline asymmetry. A simple method of determining asymmetry was adapted and developed. Statistical analyses were performed to determine potential significance of results.


RESULTS
Mean von Mises peak wall stress +/- standard deviation was 0.4505 +/- 0.14 MPa (range, 0.3157-0.9048 MPa). Posterior wall stress increases with anterior centerline asymmetry. Peak stress increased by 48% and posterior wall stress by 38% when asymmetry was introduced into a realistic AAA model.


CONCLUSIONS
The relationship between posterior wall stress and AAA asymmetry showed that excessive bulging of one surface results in elevated wall stress on the opposite surface. Assessing the degree of bulging and asymmetry that is experienced in an individual AAA may be of benefit to surgeons in the decision-making process and may provide a useful adjunct to diameter as a surgical intervention guide.
Doyle
Barry J
BJ
Department of Mechanical and Aeronautical Engineering, Centre for Applied Biomedical Engineering Research, Materials and Surface Science Institute, University of Limerick, Limerick, Ireland.
Callanan
Anthony
A
Burke
Paul E
PE
Grace
Pierce A
PA
Walsh
Michael T
MT
Vorp
David A
DA
McGloughlin
Timothy M
TM
D000368:Aged; D017544:Aortic Aneurysm, Abdominal / Q000150:complications / Q000000981:diagnostic imaging* / Q000601:surgery; D001019:Aortic Rupture / Q000000981:diagnostic imaging / Q000209:etiology* / Q000601:surgery; D001027:Aortography / Q000379:methods*; D005260:Female; D020342:Finite Element Analysis; D006801:Humans; D021621:Imaging, Three-Dimensional; D007494:Ireland; D008297:Male; D008953:Models, Anatomic; D008955:Models, Cardiovascular; D010414:Pennsylvania; D011237:Predictive Value of Tests; D011857:Radiographic Image Interpretation, Computer-Assisted; D018570:Risk Assessment; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed