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High Structural Stress and Presence of Intraluminal Thrombus Predict Abdominal Aortic Aneurysm 18F-FDG Uptake: Insights From Biomechanics

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  • Yuan Huang
  • Zhongzhao Teng
  • Maysoon Elkhawad
  • Jason M Tarkin
  • Nikhil Joshi
  • Jonathan R Boyle
  • John R Buscombe
  • Timothy D Fryer
  • Yongxue Zhang
  • Ah Yeon Park
  • Ian B Wilkinson
  • David E Newby
  • Jonathan H Gillard
  • James H F Rudd

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    Rights statement: Circulation: Cardiovascular Imaging is published on behalf of the American Heart Association, Inc., by Wolters Kluwer Health, Inc. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution, and reproduction in any medium, provided that the original work is properly cited.

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    Licence: Creative Commons: Attribution (CC-BY)

Original languageEnglish
JournalCirculation: Cardiovascular Imaging
Volume9
Issue number11
DOIs
Publication statusPublished - 10 Nov 2016

Abstract

BACKGROUND: Abdominal aortic aneurysm (AAA) wall inflammation and mechanical structural stress may influence AAA expansion and lead to rupture. We hypothesized a positive correlation between structural stress and fluorine-18-labeled 2-deoxy-2-fluoro-d-glucose ((18)F-FDG) positron emission tomography-defined inflammation. We also explored the influence of computed tomography-derived aneurysm morphology and composition, including intraluminal thrombus, on both variables.

METHODS AND RESULTS: Twenty-one patients (19 males) with AAAs below surgical threshold (AAA size was 4.10±0.54 cm) underwent (18)F-FDG positron emission tomography and contrast-enhanced computed tomography imaging. Structural stresses were calculated using finite element analysis. The relationship between maximum aneurysm (18)F-FDG standardized uptake value within aortic wall and wall structural stress, patient clinical characteristics, aneurysm morphology, and compositions was explored using a hierarchical linear mixed-effects model. On univariate analysis, local aneurysm diameter, thrombus burden, extent of calcification, and structural stress were all associated with (18)F-FDG uptake (P<0.05). AAA structural stress correlated with (18)F-FDG maximum standardized uptake value (slope estimate, 0.552; P<0.0001). Multivariate linear mixed-effects analysis revealed an important interaction between structural stress and intraluminal thrombus in relation to maximum standardized uptake value (fixed effect coefficient, 1.68 [SE, 0.10]; P<0.0001). Compared with other factors, structural stress was the best predictor of inflammation (receiver-operating characteristic curve area under the curve =0.59), with higher accuracy seen in regions with high thrombus burden (area under the curve =0.80). Regions with both high thrombus burden and high structural stress had higher (18)F-FDG maximum standardized uptake value compared with regions with high thrombus burdens but low stress (median [interquartile range], 1.93 [1.60-2.14] versus 1.14 [0.90-1.53]; P<0.0001).

CONCLUSIONS: Increased aortic wall inflammation, demonstrated by (18)F-FDG positron emission tomography, was observed in AAA regions with thick intraluminal thrombus subjected to high mechanical stress, suggesting a potential mechanistic link underlying aneurysm inflammation.

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