The role of narrow aortic bifurcation in affecting EVAR treatment and outcomes

Objectives: The narrow aortic bifurcation is considered a risk factor for endograft thrombosis after aorto-biiliac endovascular aortic repair (EVAR) for aortic or iliac aneurysm. Nowadays, no consensus on the threshold diameter for the definition of narrow aortic bifurcation is reached and other aortic bifurcation features are rarely considered. The aim of the study is to assess the EVAR outcomes using bifurcated endograft according to anatomical characteristics of aortic bifurcation. Methods: The study included patients treated with primary EVAR from 2016 to 2022. A retrospective analysis of single-center prospectively collected database was performed. Patients were classified in standard aortic bifurcation (SAB; aortic bifurcation diameter >20mm), narrow aortic bifurcation (NAB; ≤20mm and >16mm) and extremely narrow aortic bifurcation (eNAB; ≤16mm). The three groups were compared in terms of patient demographics, risk factors, procedure setting (elective or urgent/emergent), type of deployed endograft. In NAB and eNAB groups, severe calcification (SC) and length of stenotic aortic bifurcation >10mm (long-NAB) were assessed from pre-operative imaging. In SAB, NAB and eNAB groups, following outcomes were evaluated: rate of intraoperative iliac endograft stenting (unilateral or kissing stenting), primary patency (PP), freedom from endograft-related reintervention (ffER) and overall survival during follow-up. Results: The total number of deployed aorto-biiliac endografts was 365 (mean age: 76.6 years ±7.4; male 89.3%): SAB 298 (81.6%), NAB 57 (15.6%) and eNAB 10 (2.7%) cases. Female gender, COPD and active smokers were more frequent in patients with smaller aortic bifurcation diameter (p=.002, .039 and .010, respectively). In NAB and eNAB groups, SC was reported in 18/67 cases (26.9%) and long-NAB in 15/67 cases (25.4%). Patients with eNAB have more frequent SC of aortic bifurcation (60% vs NAB 21.1%, p=.018) and long-NAB (50% vs NAB 17.5%, p=.023). In SAB, sNAB and eNAB, intraoperative iliac endograft stenting was performed in 34/298 (11.4%), 9/57 (15.8%) and 5/10 (50%), respectively (p=.001). Kissing stenting was performed more frequently in groups with smaller aortic bifurcation diameter (p=.010). Mean follow-up was 30.2 months ±21.5. At 1, 3 and 5 years, PP was 98.5%, 96.6% and 95.6%, respectively. eNAB had lower rate of PP compared to NAB group (p=.030). Long-NAB had lower rate of PP (p=.035). At 1, 3 and 5 years, ffER was 96.8%, 86.7% and 76.7%, respectively, with no differences between three groups (p=.423). At 1, 3 and 5 years, survival was 92.5%, 77.6% and 58.1%, respectively, with no difference between SAB, sNAB and eNAB (p=. 673). Conclusions: Female, COPD patients and active smokers have more frequently smaller aortic bifurcation diameter. eNAB patients have more challenging anatomical characteristics compared with NAB group, requiring higher rate of intraoperative stenting, especially kissing stenting. Mid-term PP seems to be negatively influenced by aortic bifurcation ≤16mm and long-NAB.