Purpose: To determine the relationship between asymmetrical intraluminal thrombus (ILT) deposition in abdominal aortic aneurysm (AAA) and growth rate and to explore its biomechanical perspective. Methods: Thirty-four patients with AAA underwent at least 2 computed tomography scans during surveillance. The volumes of the AAA (VAAA) and thrombus (VILT) and the maximum thrombus thickness (ILTthick) were computed. Thrombus distribution was evaluated by introducing the asymmetrical thrombus deposition index (ATDI), with positive and negative values (–1<ATDI<1) associated with anterior and posterior ILT deposition, respectively. Finite element analysis was applied to estimate wall stress. Aneurysms were divided into high and low growth rate groups based on the cohort’s median growth rate, and the abovementioned parameters were compared between groups. Results: Most AAAs had asymmetrical anterior thrombus deposition. The high and low growth rate groups did not present significant differences in maximum diameter, VAAA, VILT, or maximum ILTthick. However, the high growth rate group had significantly higher ATDI (p=0.02). The ATDI<0 group (posterior ILT distribution) presented a significantly lower median growth rate compared to that of ATDI≥0 group (anterior or symmetrical ILT deposition; p=0.029). The specificity of an ATDI<0 criterion for identifying AAAs with a growth rate below the cohort median was 89%. The ATDI<0 group had a significantly lower posterior maximum wall stress compared with that of the ATDI≥0 group (p=0.03). Overall peak wall stress did not differ between groups. Conclusion: Posterior thrombus deposition in AAAs is associated with significantly lower growth rate and lower posterior maximum wall stress compared with that of AAAs with anterior thrombus deposition and could potentially indicate a lower rupture risk.
WolfYGThomasWSBrennanFJ. Computed tomography scanning findings associated with rapid expansion of abdominal aortic aneurysms. J Vasc Surg. 1994;20:529–535.
4.
StenbaekJKalinBSwedenborgJ. Growth of thrombus may be a better predictor of rupture than diameter in patients with abdominal aortic aneurysms. Eur J Vasc Endovasc Surg. 2000;20:466–469.
5.
SattaJLääräEJuvonenT. Intraluminal thrombus predicts rupture of an abdominal aortic aneurysm. J Vasc Surg. 1996;23:737–739.
6.
HansSSJareunpoonOBalasubramaniamM. Size and location of thrombus in intact and ruptured abdominal aortic aneurysms. J Vasc Surg. 2005;41:584–588.
7.
GolledgeJIyerVJenkinsJ. Thrombus volume is similar in patients with ruptured and intact abdominal aortic aneurysms. J Vasc Surg. 2014;59:315–320.
8.
AilawadiGKnippBSLuG. A nonintrinsic regional basis for increased infrarenal aortic MMP-9 expression and activity. J Vasc Surg. 2003;37:1059–1066.
9.
SinhaIBethiSCroninP. A biologic basis for asymmetric growth in descending thoracic aortic aneurysms: a role for matrix metalloproteinase 9 and 2. J Vasc Surg. 2006;43:342–348.
10.
CroninPUpchurchGRJrPatelHJ. Asymmetric expansion of aortic aneurysms on computed tomography imaging. J Vasc Surg. 2013;57:390–398.e3.
11.
WangDHMakarounMSWebsterMW. Effect of intraluminal thrombus on wall stress in patient-specific models of abdominal aortic aneurysm. J Vasc Surg. 2002;36:598–604.
12.
DoyleBJCallananABurkePE. Vessel asymmetry as an additional diagnostic tool in the assessment of abdominal aortic aneurysms. J Vasc Surg. 2009;49:443–454.
13.
VorpDARaghavanMLWebsterMW. Mechanical wall stress in abdominal aortic aneurysm: influence of diameter and asymmetry. J Vasc Surg. 1998;27:632–639.
14.
YushkevichPAPivenJHazlettHC. User-guided 3D active contour segmentation of anatomical structures: significantly improved efficiency and reliability. Neuroimage. 2006;31:1116–1128.
15.
KontopodisNMetaxaEPagonidisK. Deformation and distensibility distribution along the abdominal aorta in the presence of aneurysmal dilatation [published online December10, 2013]. J Cardiovasc Surg (Torino).
16.
AntigaLSteinmanDA. Robust and objective decomposition and mapping of bifurcating vessels. IEEE Trans Med Imaging. 2004;23:704–713.
17.
SchneiderCARasbandWSEliceiriKW. NIH Image to ImageJ: 25 years of image analysis. Nat Methods. 2012;9:671–675.
18.
KontopodisNMetaxaEGionisM. Discrepancies in determination of abdominal aortic aneurysms maximum diameter and growth rate, using axial and orhtogonal computed tomography measurements. Eur J Radiol. 2013;82:1398–1403.
19.
KontopodisNMetaxaEPapaharilaouY. Changes in geometric configuration and biomechanical parameters of a rapidly growing abdominal aortic aneurysm may provide insight in aneurysms natural history and rupture risk. Theor Biol Med Model. 2013;10:67.
20.
RaghavanMLVorpDA. Toward a biomechanical tool to evaluate rupture potential of abdominal aortic aneurysm: identification of a finite strain constitutive model and evaluation of its applicability. J Biomech. 2000;33:475–482.
21.
Vande GeestJPSacksMSVorpDA. A planar biaxial constitutive relation for the luminal layer of intra-luminal thrombus in abdominal aortic aneurysms. J Biomech. 2006;39:2347–2354.
22.
LederleFAJohnsonGRWilsonSE. The aneurysm detection and management study screening program: validation cohort and final results. Aneurysm Detection and Management Veterans Affairs Cooperative Study Investigators. Arch Intern Med. 2000;160:1425–1430.
23.
FolkessonMSilveiraAErikssonP. Protease activity in the multi-layered intra-luminal thrombus of abdominal aortic aneurysms. Atherosclerosis. 2011;218:294–299.
24.
VorpDALeePCWangDH. Association of intraluminal thrombus in abdominal aortic aneurysm with local hypoxia and wall weakening. J Vasc Surg. 2001;34:291–299.
25.
ClarkeJA. An x-ray microscopic study of the postnatal development of the vasa vasorum in the human aorta. J Anat. 1965;99:877–889.
26.
HeistadDDMarcusML. Role of vasa vasorum in nourishment of the aorta. Blood Vessels. 1979;16:225–238.
27.
RaghavanMLKratzbergJCastrodeTolosaEM. Regional distribution of wall thickness and failure properties of human abdominal aortic aneurysm. J Biomech. 2006;39:3010–3016.
28.
SimãodaSilvaERodriguesAJMagalhães CastrodeTolosaE. Morphology and diameter of infrarenal aortic aneurysms: a prospective autopsy study. Cardiovasc Surg. 2000;8:526–532.
29.
SacksMSVorpDARaghavanML. In vivo three-dimensional surface geometry of abdominal aortic aneurysms. Ann Biomed Eng. 1999;27:469–479.
30.
RaghavanMLMaBHarbaughRE. Quantified aneurysm shape and rupture risk. J Neurosurg. 2005;102:355–362.
31.
LeeKZhuJShumJ. Surface curvature as a classifier of abdominal aortic aneurysms: a comparative analysis. Ann Biomed Eng. 2013;41:562–576.
ShumJDiMartinoESGoldhammeA. Semiautomatic vessel wall detection and quantification of wall thickness in computed tomography images of human abdominal aortic aneurysms. Med Phys. 2010;37:638–648.
