Objective: The purpose of this study was to determine the relationship between aneurysm sac size change at 1, 6, 12, and 24 months and a set of 10 independent "predictive" variables by using a general linear model analysis.
Methods: In a multicenter trial, 351 patients received the Zenith tri-modular bifurcated endograft. The predictive variables used for this analysis were endoleak by type, age, gender, smoking status, and the preprocedure variables of maximum aneurysm major diameter, minor neck diameter, proximal neck length, neck plaque/thrombus, and neck shape; and patent inferior mesenteric artery at predischarge. The aneurysm change was calculated as the difference from the predischarge (< or = 7 days of implant) maximum aneurysm major diameter measurement to the maximum aneurysm major diameter measurement at follow-up examination periods of 1, 6, 12, and 24 months. The same 10 predictive variables were used to assess the absolute change in maximum aneurysm minor diameter and aneurysm area. Additionally, the percent change from predischarge was also assessed for the major diameter, minor diameter, and aneurysm area.
Results: None of the independent variables were predictive of absolute sac size change or percent change at 1 month. At 6 months, the presence of an endoleak (P < .01) and preprocedure neck thrombus/plaque (P = .01) were significant predictors of absolute and relative aneurysm size change for all measurements (major diameter, minor diameter, and area) and were more likely to be associated with less sac shrinkage or to have sac growth. Additionally, preoperative maximum aneurysm major diameter was a significant predictor for absolute change in area (P < .01). Larger preprocedure aneurysm diameters were more likely to experience more shrinkage. The significant predictors of size change at 12 months included preprocedure maximum aneurysm major diameter, the presence of endoleak at 12 months, preoperative neck thrombus/plaque, and gender. At 24 months, significant predictors of aneurysm size change included preprocedure maximum aneurysm major diameter, endoleak at 24 months, and preprocedure neck thrombus/plaque. When the longitudinal model was used, the presence of an endoleak, thrombus/plaque within the proximal neck at preprocedure, and preprocedure maximum aneurysm major diameter were found to be significantly related to the size of the maximum aneurysm major diameter over time.
Conclusions: This study supports the concept that early and late sac size change following EVAR is influenced by identifiable independent predictive variables.