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We thank Dr Georgakarakos et al for the interest they have shown in our study.1Li Z.Y. U-King-Im J. Tang T.Y. Soh E. See T.C. Gillard J.H. Impact of calcification and intraluminal thrombus on the computed wall stresses of abdominal aortic aneurysm.J Vasc Surg. 2008; 47: 928-935Abstract Full Text Full Text PDF PubMed Scopus (150) Google Scholar They confirmed our finding in their study that a good correlation existed between maximum wall stress and the relative amount of thrombus. However, by employing partial correlation analysis and controlling the geometric variations, they reported that the difference between the above was not statistically significant. This might imply that peak wall stress was affected by the geometric variations rather than the amount of thrombus alone. We would like to impress on the point that although this may be the case, the geometric variation is itself dependent on the volume and location of the thrombus. The concentricity or eccentricity of thrombus by changing the centerline curvature can alter the peak wall stress. The location and volume of thrombus may also affect the pattern of aneurysm expansion.2Shin I.S. Kim J.M. Kim K.L. Jang S.Y. Jeon E.S. Choi S.H. Kim D.K. et al.Early growth response factor-1 is associated with intraluminal thrombus formation in human abdominal aortic aneurysm.J Am Coll Cardiol. 2009; 53: 792-799Abstract Full Text Full Text PDF PubMed Scopus (33) Google Scholar, 3Kazi M. Thyberg J. Religa P. Roy J. Eriksson P. Hedin U. Swedenborg J. Influence of intraluminal thrombus on structural and cellular composition of abdominal aortic aneurysm wall.J Vasc Surg. 2003; 38: 1283-1292Abstract Full Text Full Text PDF PubMed Scopus (289) Google Scholar There is an analogy between the role of thrombus in altering the aneurysm wall stress and the role of calcification in atheromatous plaques. Conventionally, the amount of calcification was used as an indicator of plaque vulnerability but our group has shown that location is another key determinant of plaque vulnerability.4Li Z.Y. Howarth S. Tang T. Graves M. J U.K.-I. Gillard J.H. Does calcium deposition play a role in the stability of atheroma? Location may be the key.Cerebrovasc Dis. 2007; 24: 452-459Crossref PubMed Scopus (64) Google Scholar Similarly, we hypothesize that in addition to the volume of intraluminal thrombus, its location and impact on the geometry of the arterial lumen can affect the wall stress and ultimately result in variable pattern of aneurysm growth. A prospective longitudinal is therefore required to assess the changes in thrombus volume, resultant change in lumen curvature, and pattern of aneurysm growth/expansion, before we can say that tortuosity of lumen centerline is the key determinant of increasing the aneurysm wall stress. Another important area worth exploring is the material behavior of intraluminal thrombus. It is most likely a non-homogeneous material with a complex property. A large ex vivo experiment is needed for future study in this area to improve our understanding of aneurysm material properties and failure strength. This can help in creating more realistic computational models, which could be used as a clinical adjunct in the future for effective decision making in aneurysm repair. Regarding “Impact of calcification and intraluminal thrombus on the computed wall stresses of abdominal aortic aneurysm”Journal of Vascular SurgeryVol. 50Issue 2PreviewWe read with great interest the article by Li et al, concerning the effect of intraluminal thrombus on the values of peak wall stress, in 3D reconstructed individualized abdominal aortic aneurysm (AAA) models.1 After having used the method of Finite Element Analysis, the authors concluded that the relative amount on thrombus reduces the maximum stress in AAA in a rather linear way (r = 0.863, P < .001). This is one of the largest series (20 patients) with a rather interesting finding, adding to the existing information about the biomechanical influence of thrombus on maximum stress and consequently on the risk of rupture. Full-Text PDF Open Archive