Post-dissection thoraco-abdominal aortic aneurysms presenting with narrow true lumen: outcomes after fenestrated and branched endovascular repair from the international multicenter narrow true lumen dissection registry (NADIR) study group

Background Treatment for Chronic Post-Dissection Thoracoabdominal Aneurysms (CPD-TAAA) has evolved from high-risk open surgery to fenestrated and branched endovascular aneurysm repair (F/BEVAR). F/BEVAR is now a valid option for patients unfit for open repair or those with complex anatomy. A primary challenge in endovascular repair is false lumen exclusion and the presence of a thick, fixed lamella. When a narrow paravisceral true lumen (TL) < 25 mm is present, technical success may be compromised by difficult graft deployment and target vessel bridging, potentially leading to graft compression or vessel instability. Current literature lacks a defined assessment of how a narrow paravisceral TL specifically impacts outcomes. Furthermore, there is a research gap regarding direct comparisons between fenestrations, outer branches, and inner branches for custom-made devices, as well as the efficacy of off-the-shelf TAAA devices in this anatomical context. Evaluating these configurations is essential for optimizing graft design, refining patient selection, and guiding clinical decision-making for CPD-TAAA with restricted true lumen dimensions. Objectives The aim of the study is to evaluate the impact of a NTL on early and midterm outcomes of endovascular repair of CPD-TAAA with FB-EVAR using commercially available custom and OTS devices, endpoints include technical success, early and mid-term mortality or major adverse events (MAEs), as well as freedom from target artery instability and aortic adverse events. Results Among 544 patients (1705 target vessels), 438 (80%) had NTL. 52% of patients received a branched endograft, 30% a fenestrated, and 18% a fenestrated-branched, without differences between groups (P=.053). Patients with NTL more frequently received bridging stent reinforcement (P<.001), and renal inner branches (P=.038). Septotomy or false lumen occlusion were more often performed in NTL (27% vs 11%; P=.006). Patients with NTL had longer operating time (P=.031), fluoroscopy time (P=.007), and a higher dose area product (P=.046). Technical success was 95% in both groups (P=.750). Thirty-day mortality was 4%, and MAE occurred in 35%. NTL did not have a significant impact on MAE (Adjusted OR, 0.84, 95%CI 0.28-2.76; P=.766). Freedom from any aortic adverse event at 5 years was lower in NTL (73% vs 91%; P=.027) and was mostly related to secondary procedures of false lumen embolization (P=.027). Freedom from target vessel instability was 86±4% in the NTL and 92±4% in the No-NTL (P=.072). NTL patients had a similar primary patency (97±2% vs 98±2%; P=.380) but lower freedom from target vessel endoleak (89±4% vs 97±3%; P=.006). After adjustment, NTL diameter <10 mm (HR 2.45; 95%CI 1.37-4.36; P=.002) was significantly associated to target artery instability; use of inner branches (HR 0.11, 95%CI 0.02-0.87; P=.035) and bridging stent reinforcements (HR 0.54, 95%CI 0.31-0.96; P=.038) were protective. Conclusion NTL is the most common anatomical presentation in post-dissection TAAA, and its presence is ì associated with more complex procedures, but does not affect technical success, nor mortality, or MAE. Patients with a NTL experience a higher rate or reinterventions, consisting especially in false lumen embolization. NTL <10 mm is a risk factor for target vessel instability. Use of inner branches or reinforcement of bridging stents may be beneficial in these cases.