Physician-Modified Grafts Show Higher Renal Stability Than TAMBE Devices

Durability of Renal Revascularization in Complex Aortic Repair

The management of pararenal and thoracoabdominal aortic aneurysms has shifted toward endovascular techniques, which offer high technical success rates and reduced perioperative morbidity compared to open surgery [1]. While custom-made or physician-modified endografts have long served as the standard for these complex repairs, the manufacturing lead time for custom devices can increase the risk of aneurysm-related mortality during the waiting period [2]. Off-the-shelf multibranched endografts were developed to address this limitation, providing immediate solutions for both elective and urgent cases [3]. However, the long-term durability of these standardized branch designs, particularly regarding renal artery patency and the need for reintervention, remains a subject of active clinical investigation [4]. A recent study provides a detailed comparison of five-year outcomes between these two distinct endovascular strategies, offering critical insights for device selection.

Vessel-Level Comparison of Endovascular Strategies

To evaluate the real-world performance of these devices, researchers conducted a retrospective review of patients treated for pararenal and thoracoabdominal aortic aneurysms at two specialized aortic centers between 2015 and 2025. The analysis compared renal artery outcomes between physician-modified endografts (PMEG, standard devices customized by the surgeon in the operating room to match patient-specific anatomy) and the Thoracoabdominal MultiBranch Endoprosthesis (TAMBE, a standardized, off-the-shelf multibranched device). The total study cohort included 716 patients with 1339 renal arteries. Within this population, the PMEG group comprised 633 patients and 1180 renal arteries, while the TAMBE group consisted of 83 patients and 159 renal arteries. To ensure a rigorous comparison, the researchers utilized a vessel-level analysis, evaluating each renal artery as an individual unit rather than focusing solely on patient-level outcomes. The study tracked several critical clinical variables, including the extent of the aneurysm, the size of the branch stents used, the specific antiplatelet regimen prescribed, the laterality (right versus left) of the renal artery, and the use of relining stents (additional stents placed within the initial branch to provide structural reinforcement). The primary outcome measured was freedom from target vessel instability (FTVI), a composite endpoint indicating the absence of complications such as stenosis, occlusion, or the need for reintervention in the treated vessel. Secondary outcomes included primary patency (PP), which measures continued unassisted blood flow; freedom from branch reintervention (FBR), indicating the absence of secondary salvage procedures; and freedom from branch endoleak (FBE), which tracks the absence of persistent blood flow outside the stent graft but within the aneurysm sac. For practicing vascular specialists, these metrics directly translate to the likelihood of a patient requiring a return to the operating room.

Five-Year Patency and Reintervention Rates

Longitudinal analysis revealed significant differences in the durability of the two endovascular approaches over a five-year follow-up period. The researchers found that renal arteries in the PMEG group had a higher freedom from target vessel instability compared to the TAMBE group (89.5% vs 82.7%, P=.005). This primary outcome suggests that the patient-specific modifications inherent to physician-modified grafts offer superior long-term stability for renal revascularization compared to the standardized off-the-shelf configuration. Secondary endpoints further delineated this performance gap, particularly regarding the need for secondary procedures. The PMEG group showed higher 5-year primary patency compared to TAMBE (93.7% vs 83.3%, P<.001), indicating a lower rate of vessel occlusion or significant narrowing. Furthermore, the PMEG group demonstrated higher 5-year freedom from branch reintervention compared to TAMBE (90.8% vs 82.5%, P=.002). For the clinician, these figures mean a patient treated with a physician-modified graft is statistically more likely to avoid the risks and costs associated with secondary endovascular procedures to salvage a failing renal branch. Despite these differences in patency and reintervention rates, both devices performed similarly in maintaining a secure seal at the branch interface. The freedom from branch endoleak was similar between PMEG and TAMBE (93.9% vs 98.2%, P=0.3), suggesting that the standardized design of the TAMBE device is highly effective at preventing persistent blood flow into the aneurysm sac from the renal branch site.

Anatomical Vulnerability in the Right Renal Artery

The disparity in overall outcomes between the two endovascular strategies appears largely driven by a significant performance gap in the right renal artery. When analyzing outcomes based on laterality, the researchers found that freedom from target vessel instability in the right renal artery was significantly higher in the physician-modified endograft group compared to the TAMBE group (91.3% vs 77.9%, P=.002). In contrast, the left renal artery demonstrated comparable durability across both device types, with freedom from target vessel instability reaching 87.6% in the physician-modified group and 87.9% in the TAMBE group (P=.375). This localized failure suggests that the standardized configuration of the TAMBE device may not adequately accommodate the specific anatomical take-off or steep angulation often encountered on the right side, whereas patient-specific modifications provide better anatomical alignment. To isolate the impact of the device type on vessel stability, the researchers utilized a Cox proportional hazard regression (a statistical model that determines the risk of a specific event occurring over time while controlling for multiple variables). This analysis adjusted for aneurysm extent, branch stent size, the use of relining stents, and dual antiplatelet therapy to ensure that observed differences were not due to baseline clinical variations. The regression model confirmed that the right renal arteries in the TAMBE group were 4.2 times more likely to develop target vessel instability than those in the physician-modified group (HR: 4.2, P<.001). These findings identify the right renal artery as the principal site of failure for the TAMBE device, signaling to clinicians that they must carefully evaluate right-sided renal anatomy when selecting an off-the-shelf multibranched endoprosthesis.

Impact of Aneurysm Extent on Device Performance

The anatomical context of the repair also significantly altered device performance. The researchers conducted a subgroup analysis categorizing patients into those with pararenal aortic aneurysms (PRA, which involve the segment of the aorta where the renal arteries originate) and those with thoracoabdominal aortic aneurysms (TAAA, which extend from the thoracic aorta into the abdominal segment). In patients with thoracoabdominal aortic aneurysms, freedom from target vessel instability was similar between groups (P=.691), demonstrating that the TAMBE device performs comparably to physician-modified grafts in more extensive aneurysmal disease. However, a distinct performance gap emerged in cases with more localized pathology. In patients with pararenal aortic aneurysms, TAMBE showed significantly lower freedom from target vessel instability compared to physician-modified endografts (P<.001). The analysis suggests that thoracoabdominal aortic aneurysm extent appears to confer protection against renal target vessel instability in TAMBE compared to pararenal extent. This protective effect in TAAA cases may be related to different hemodynamic forces or a more favorable angle of the renal artery take-off relative to the device manifold in extensive aneurysms. For practicing surgeons, these findings warrant a careful revisiting of anatomic selection criteria, suggesting that while off-the-shelf devices are highly valuable for extensive or urgent cases, further optimization of renal bridging stent design may be necessary to improve outcomes in localized pararenal repairs.

References

1. Hu Z, Zhang Z, Liu H, Chen Z. Fenestrated and Branched Stent-Grafts for the Treatment of Thoracoabdominal Aortic Aneurysms: A Systematic Review and Meta-Analysis. Frontiers in Cardiovascular Medicine. 2022. doi:10.3389/fcvm.2022.901193

2. Karaolanis G, Makaloski V, Jungi S, et al. Endovascular repair of pararenal and thoracoabdominal aortic aneurysms with inner and outer off-the shelf-multibranched endografts. A systematic review and meta-analysis.. Journal of Vascular Surgery. 2024. doi:10.1016/j.jvs.2024.08.013

3. Spath P, Campana F, Tsilimparis N, et al. SYSTEMATIC REVIEW AND META-ANALYSIS ON ENDOVASCULAR REPAIR OF NON-ELECTIVE THORACO-ABDOMINAL AORTIC ANEURYSMS AND ANEURYSMS INVOLVING VISCERAL ARTERIES.. Journal of Vascular Surgery. 2025. doi:10.1016/j.jvs.2025.08.030

4. Karelis A, Kölbel T, Mastracci TM, et al. Editor's Choice – Branched Endovascular Aneurysm Repair with Inner and Outer Branches: A Systematic Review and Meta-analysis. European Journal of Vascular and Endovascular Surgery. 2025. doi:10.1016/j.ejvs.2025.03.003