Association Between Aneurysm Shoulder Stress and Abdominal Aortic Aneurysm Expansion A Longitudinal Follow-Up Study

School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China.
Circulation (Impact Factor: 14.43). 10/2010; 122(18):1815-22. DOI: 10.1161/CIRCULATIONAHA.110.939819
Source: PubMed


Aneurysm expansion rate is an important indicator of the potential risk of abdominal aortic aneurysm (AAA) rupture. Stress within the AAA wall is also thought to be a trigger for its rupture. However, the association between aneurysm wall stresses and expansion of AAA is unclear.
Forty-four patients with AAAs were included in this longitudinal follow-up study. They were assessed by serial abdominal ultrasonography and computed tomography scans if a critical size was reached or a rapid expansion occurred. Patient-specific 3-dimensional AAA geometries were reconstructed from the follow-up computed tomography images. Structural analysis was performed to calculate the wall stresses of the AAA models at both baseline and final visit. A nonlinear large-strain finite element method was used to compute the wall-stress distribution. The relationship between wall stresses and expansion rate was investigated. Slowly and rapidly expanding aneurysms had comparable baseline maximum diameters (median, 4.35 cm [interquartile range, 4.12 to 5.0 cm] versus 4.6 cm [interquartile range, 4.2 to 5.0 cm]; P=0.32). Rapidly expanding AAAs had significantly higher shoulder stresses than slowly expanding AAAs (median, 300 kPa [interquartile range, 280 to 320 kPa] versus 225 kPa [interquartile range, 211 to 249 kPa]; P=0.0001). A good correlation between shoulder stress at baseline and expansion rate was found (r=0.71; P=0.0001).
A higher shoulder stress was found to have an association with a rapidly expanding AAA. Therefore, it may be useful for estimating the expansion of AAAs and improve risk stratification of patients with AAAs.

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    • "More interestingly, the authors demonstrated that PWS (hazard ratio:25), outweighed gender (hazard ratio:3) as a rupture predictive tool and that after accounting for wall stress and gender, diameter would not predict rupture [18]. Furthermore, low stress values have been associated with slow growth rate in small AAAs [19], whereas rapid growth rate of small AAAs can be strongly related with high values of wall stress at the inflection site between the neck and the sac [20]. "
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