Aneurysm Sac Shrinkage after Endovascular Repair: Predictive Factors and Long-Term Follow-Up

Background: The aim of this study was to determine the predictive factors of reduction in diameter >= 10 mm of the aneurysm sac after endovascular treatment and analyze evolution in these patients. Methods: Between December 1997 and December 2008, all patients electively treated at our center for an infrarenal abdominal aortic aneurysm (AAA) were included in a prospective registry. We did a retrospective study between patients whose aneurysm was reduced by at least 10 mm in diameter on computed tomography scan during follow-up (Group 1) and the other patients who did not (Group 2). A univariate and multivariate statistical analysis was performed. Results: The files of 197 patients (mean age 74.8 years) with a mean follow-up of 54.8 months were reviewed. One hundred two patients (51.8%) had a reduction of >= 10 mm of AAA diameter (Group 1); this reduction was achieved after an average follow-up of 23.6 months. The delay to obtain at least a 10-mm diameter reduction was not influenced by any preoperative characteristics of patients or characteristics of the AAA. Patients in Group 1 were younger (74 vs. 76 years, P = 0.039), with a longer (31 vs. 27.7 mm, P = 0.038) and narrower upper neck (23.1 vs. 24.0 mm, P = 0.02) compared with Group 2. After multivariate analysis, these 3 variables were independently predictive of reduction in AAA diameter. In Group 1, secondary procedures were performed in 13 patients after a diameter reduction of >= 10 mm, including 3 type 1 endoleaks treated after 36 months (1 case) and after 123 months (2 cases) and 1 type 3 endoleak treated after 78 months. In Group 2, secondary procedures were performed in 28 patients, including 9 type 1 endoleaks treated after a median time of 26 months and no type 3 endoleak. Secondary procedures were significantly more frequent in Group 2 than in Group 1 (29.4% vs. 12.7%, respectively; P = 0.005). Freedom from secondary procedure at 5 years was 87.9% in Group 1 and 65.4% in Group 2 (P = 0.003). Freedom from AAA rupture at 8 years was significantly superior in Group 1 than in Group 2 (100% vs. 83.5%, P = 0.008). Conclusions: Sac shrinkage after endovascular aortic aneurysm repair is more likely observed in younger patients with long and small proximal neck anatomy and is associated with better long-term outcomes. However, late failures do occur even in those with significant sac shrinkage; therefore, follow-up should continue lifelong.