Association between aneurysm shoulder stress and abdominal aortic aneurysm expansion: a longitudinal follow-up study.
BACKGROUND
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.


RESULTS
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).


CONCLUSIONS
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.
Li
Zhi-Yong
ZY
School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China. ZYL22@cam.ac.uk
Sadat
Umar
U
U-King-Im
Jean
J
Tang
Tjun Y
TY
Bowden
David J
DJ
Hayes
Paul D
PD
Gillard
Jonathan H
JH
D000368:Aged; D000369:Aged, 80 and over; D001012:Aorta, Abdominal / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D001019:Aortic Rupture / Q000453:epidemiology / Q000503:physiopathology; D001696:Biomechanical Phenomena; D001794:Blood Pressure / Q000502:physiology; D005260:Female; D020342:Finite Element Analysis; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012782:Shoulder / Q000503:physiopathology*; D014057:Tomography, X-Ray Computed; D014664:Vasodilation / Q000502:physiology