Postdissection thoracoabdominal aortic aneurysm 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 The impact of a narrow true lumen (NTL) on the outcomes of fenestrated-branched endovascular repair in patients with postdissection thoracoabdominal aortic aneurysms (PD-TAAAs) is underreported. Methods Data from an international, multicenter registry were analyzed, to identify patients treated for PD-TAAAs (2015-2025) at 23 centers. All patients underwent fenestrated-branched endovascular repair using custom or off-the-shelf endografts. NTL was defined by a true lumen diameter <25 mm identified at any aortic level on preoperative computed tomography angiogram. Short-term endpoints compared between NTL and no-NTL patients included technical success, procedural metrics, 30-day mortality, and major adverse events (MAEs). Midterm endpoints included 5-year freedom from aortic adverse events (related mortality, rupture, reintervention, endograft instability) and freedom from target artery instability. Results Among 544 patients (1705 target vessels), 438 (80%) had an NTL. Device design did not differ between groups (52% branches, 30% fenestrated, and 18% fenestrated-branched combination; P = .053). Patients with an 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 NTLs (27% vs 11%; P = .006). Patients with NTLs 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). Overall 30-day mortality was 4%, and MAEs occurred in 35%. NTLs did not have a significant impact on MAEs (adjusted odds ratio, 0.84; 95% confidence interval [CI], 0.28-2.76; P = .766). Freedom from any aortic adverse event at 5 years was lower in patents with NTL (73% vs 91%; P = .027), driven primarily by secondary procedures of false lumen embolization (P = .027). Freedom from target vessel instability was 86% +/- 4% in the NTL group and 92% +/- 4% in the no-NTL group (P = .072). Patients with NTLs 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 (hazard ratio [HR], 2.45; 95% CI, 1.37-4.36; P = .002) was significantly associated with target artery instability. Use of inner branches (HR, 0.11; 95% CI, 0.02-0.87; P = .035) and bridging stent reinforcement (HR, 0.54; 95% CI, 0.31-0.96; P = .038) were protective. Conclusions NTL is the most common anatomic presentation in PD-TAAAs and is associated with more complex procedures, but does not affect technical success, mortality, or MAEs. Patients with an NTL experience a higher rate or reinterventions, primarily false lumen embolization. NTL <10 mm is a risk factor for target vessel instability, and reinforcement of bridging stents may be beneficial in these cases.