Factors Associated With Lower Incidence of Rupture in Abdominal Aortic Aneurysms

Abstract

Introduction: The only current standard in international guidelines for estimating rupture risk of an abdominal aortic aneurysm (AAA) is the maximum diameter. The aim of this study was to evaluate anatomical factors in large (>80mm) AAA, in which the impact of diameter on rupture incidence is similar and profound, that may be associated with lower incidence of rupture. Methods: This was a retrospective study including patients with large (>80mm) aneurysms. Total of 62 patients were included in the study; matched 1:1 for age, and smoking (31 elective; 92±9.7mm vs. 31 ruptures; 95.7±12mm; p=0.5). Pre-operative computed tomography angiography was analyzed with a dedicated workstation and AAA anatomical characteristics were compared. The prognostic utility of several factors on rupture occurrence was also examined with receiver operating characteristic (ROC) curves. Results: Significantly different anatomical characteristics between elective vs ruptures were infra-renal aortic neck diameter at 5mm, 10mm and 15mm, neck length and calcification, common iliac length (CIA), pelvic artery index, left CIA and external iliac artery, total and true lumen volume. Intraluminal thrombus (ILT) volume did not differ (elective vs. ruptures; 233cc vs 245cc, p=0.76), although its form did (elective vs. ruptures; no thrombus 0% vs 20%, p=0.025; circular thrombus 63.3% vs 44%, p=0.03, respectively). After multivariate analysis, shorter left CIA (OR 1.07, CI. 1.01- 1.1, p=0.016) and smaller total aneurysm volume (OR 1.007, CI. 1.001-1.014, p=0.016) were associated with intact AAA. After a ROC curve analysis, left CIA < 50mm demonstrated lower incidence of rupture with sensitivity 60% and specificity 78%, while for total aneurysm volume of < 380cc the sensitivity and the specificity was 60% and 60%, retrospectively. Conclusion: Anatomical characteristics other than maximum diameter AAAs seem to be associated with incidence of rupture. Lower total aneurysm volume, but not ILT volume, and shorter left CIA may be associated with lower incidence of AAA rupture, even in large diameter AAA. Disclosure: Nothing to disclose