Risk Factor and Outcome Analysis of Bird-Beak Configuration After Thoracic Aortic Endovascular Repair for Stanford Type B Aortic Dissection

Abstract Objective: To explore the risk factors for bird-beak configuration occurrence and its outcomes after thoracic endovascular aortic repair (TEVAR) for Stanford type B aortic dissection (TBAD). Methods: A total of 701 patients with TBAD diagnosed by thoracic aortic computed tomography angiography and treated using TEVAR from January 2010 to December 2022 were retrospectively enrolled. According to the occurrence of a bird-beak configuration in the proximal end of the stent-graft, the patients were divided into a bird-beak group ( n = 291) and a non-bird-beak group ( n = 410). The baseline and perioperative data, the incidence of clinical adverse events during follow-up were compared between the 2 groups. Multivariate logistic regression was performed to analyze the risk factors and prognosis associated with the formation of the bird-beak configuration. A sub-analysis was further undertaken within the bird-beak group based on the presence ( n = 84) or absence ( n = 207) of an immediate intraoperative endoleak. The Kaplan-Meier method was used to analyze the incidence of events in the bird-beak subgroup. Results: Baseline analysis showed that compared with the non-bird-beak group, the bird-beak group comprised significantly more men, and was associated with a higher frequency of calcium channel blocker use, but a lower proportion of stroke history (all P < 0.05). The perioperative data demonstrated that the bird-beak group received longer stents, had a higher percentage of proximal landings in aortic Zone 2, and exhibited a greater proportion of immediate intraoperative endoleaks (all P < 0.05). The distal stent diameter and the proportion of proximal bare stents were both significantly smaller in the bird-beak group than in the non-bird-beak group ( P < 0.05). Multivariate logistic regression suggested that proximal landing in aortic Zone 2 (odds ratio (OR) = 1.839, 95% confidence interval (CI): 1.133–2.985; P = 0.014) and stent length (OR = 1.013, 95% CI: 1.002–1.025; P = 0.021) were independent risk factors for the formation of the bird-beak configuration, whereas the use of proximal bare stents (OR = 0.019, 95% CI: 0.010–0.039; P < 0.001) was an independent protective factor. Short- and long-term follow-up revealed no significant differences in the incidence of aortic-related or overall clinical adverse events between the 2 groups (all P > 0.05). In the subgroup analysis, the incidence of distal stent-graft-induced new entry, new endoleak, aortic-related adverse events, and overall clinical adverse events was higher in the immediate intraoperative endoleak group than in the non-immediate intraoperative endoleak group (all P < 0.05). Kaplan-Meier analysis further demonstrated that the immediate intraoperative endoleak group displayed a significantly higher incidence ( P log-rank = 0.005) of aorta-related adverse events and a greater overall incidence of clinical adverse events than the non-immediate intraoperative endoleak group ( P log-rank = 0.031). Conclusion: During TEVAR for TBAD, proximal landing in aortic Zone 2 and stent length are independent risk factors for bird-beak configuration formation, whereas proximal bare stent use serves as a protective factor. While the bird-beak configuration is associated with the occurrence of immediate intraoperative endoleak during TEVAR, it does not exert a significant adverse effect on the prognosis of patients with TBAD. However, the bird-beak configuration combined with an immediate intraoperative endoleak is associated with worse outcomes.