Emiliano Chisci1, Neri Alamanni2, Francesca Iacoponi3, Stefano Michelagnoli1, Setacci Carlo4
1Department of Surgery, "San Vascular and Endovascular Surgery Unit - Giovanni di Dio" Hospital, Florence, Italy; 2Configuratori.it, Florence, Italy; 3Department for innovation in biological, agro-food and forest systems (DIBAF) Università degli Studi della Tuscia, Viterbo, Italy; 4Vascular and Endovascular Surgery Unit, University of Siena,, Siena, Italy.
OBJECTIVES: To generate a scoring system to grade the risk of rupture of an abdominal aortic aneurysm (AAA) in individual patients.
METHODS: In a single hospital center, a sequence of vascular patients was enrolled between August 2011 and December 2011. Abdominal aorta was classified as non-aneurysmatic (<3 cm), aneurysmatic (>or= 3 cm), or ruptured AAA by angio-CT scan. Angio-CT scans were coupled with a computational fluid dynamics (CFD) evaluation performed using open source software (ElmerSolver, CSC Institute of Technology, Finland). CFD criteria studied were: the oscillatory shear index (OSI), the time averaged wall shear stress (TAWSS) and the residence relative time (RRT) on both 2-D and 3-D models. AAA rupture predictors (clinical, aortic diameter and CFD parameters) were analysed and a scoring system was generated using Arabic numerals for all significant variables in order to grade the individual patient risk of rupture.
RESULTS: There were 143 patients examined. Mean age of the patients was 74 years, and 111 of the patients were male. Seventy-three patients suffered from an AAA (of which 18; 25% were ruptured AAAs) and 52 had a non-aneurysmatic aorta. The mean diameter and its standard deviation (SD) in the normal aorta, AAA, and ruptured AAA groups were 2.06 (0.52) cm, 5.11 (1.67) cm, and 8.27 (2.13) cm respectively (p>0.001. The 2-D OSI index was the best CFD criterion following multivariate analysis and ROC curves evaluation. An AAA was deemed at low, moderate or high risk of rupture, respectively, according to whether the risk score was defined as AAA I (when the total score for all variables was <6), AAA II (6-14) or AAA III (> or = 15). The only protective factor was found in diabetes (OR=0.760; CI:0.643-0.897).
CONCLUSIONS: The risk score for AAA rupture herein reported seems to be a useful tool to help predict AAA rupture but needs to be validated in independent cohorts at a variety of centres before it can be recommended for application, preferably in a randomized comparison with other predictive models.
AUTHOR DISCLOSURES: N. Alamanni: Nothing to disclose; S. Carlo: Nothing to disclose; E. Chisci: Nothing to disclose; F. Iacoponi: Nothing to disclose; S. Michelagnoli: Nothing to disclose.
Posted April 2013