The Aortoiliac Artery Bifurcation Angle May Be a New Indicator for Predicting the Growth of Abdominal Aortic Aneurysm

Objectives: The aortoiliac artery bifurcation angle (AIABA) within abdominal aortic aneurysms (AAAs) may potentially influence subsequent aneurysm growth. The goal was to investigate the role of AIABA in AAA growth via contrast-enhanced CT. Methods: A total of 142 patients with AAAs who underwent contrast-enhanced CT at baseline and follow-up (minimum follow-up duration of 3 months) were included. The AIABA, proximal landing zone distance and maximal AAA diameter were measured via multiplanar reconstruction, and the growth rate of the aneurysms was calculated. Comprehensive statistical approaches were used to determine the relationships between AIABA and aneurysm growth. Results: Mean age of patients was 69.7 ± 8.3 years and 90.8% were men. AAAs with affected bifurcations had smaller bifurcation angles (53.3° ± 20.1° vs 61.1° ± 16.4°; p<0.05) and faster growth rates (3.28 ± 1.79 vs 2.14 ± 1.42 mm/year; p<0.05). Groups 1 to 6 of all AAAs were defined by the AIABA as follows: <30°, 31° to 45°, 46° to 60°, 61° to 75°, 76° to 90° and >90°. The growth rates of the AAAs in Groups 1, 2, 3, and 6 were 2.92-, 2.91-, 1.56-, and 3.48-fold greater than those in Group 5 (p<0.05) and were 2.62-, 2.60-, 1.39-, and 3.12-fold greater than those in Group 4 (p<0.05), respectively. According to both the univariate and multivariate analyses, the AIABA was independently negatively related to the aneurysm growth rate when the AIABA <90° (univariate analysis: r=−0.83, p<0.01; multivariate analysis: r=−0.89, p<0.01). Conclusion: AIABA is an independent predictor of AAA growth. Clinical Impact The aortoiliac artery bifurcation angle is an independent predictor of abdominal aortic aneurysm progression. Abdominal aortic aneurysm with an aortoiliac artery bifurcation angle < 45° or > 90° are likely to grow faster. Abdominal aortic aneurysms surveillance strategies based on diameter could be modified, a risky angle (< 45° or > 90°) of bifurcation should be considered even if the maximal diameter of the AAA is within the conventional safe range.