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.
School of Biological Science and Medical Engineering, Southeast University, Nanjing 210096, China. ZYL22@cam.ac.uk
Zhi-Yong
ZY
Li
Umar
U
Sadat
Jean
J
U-King-Im
Tjun Y
TY
Tang
David J
DJ
Bowden
Paul D
PD
Hayes
Jonathan H
JH
Gillard
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