Gap Steering (GPS) Technique: An Adjunct for Challenging Renovisceral Branch Cannulation in Total Transfemoral Fenestrated Endovascular Aortic Repair

Objective: Fenestrated Endovascular Aortic Repair (F-EVAR) using Physician-Modified Endografts (PMEGs) has become an important option in the treatment of complex aortic aneurysms, particularly when custom-made devices are not available. However, difficult target vessel (TV) cannulations, notably with misalignment, often limit total transfemoral repair. To address this condition, we developed the Gap Steering (GPS) technique, which is a transfemoral-only adjunctive method using a steerable sheath to create a controlled gap between the stent graft and the aortic wall, enabling on-demand cannulation. In this study, we aimed to evaluate the technical feasibility and procedural features, outcomes, and risks associated with the GPS technique in difficult target vessel cannulation owing to fenestration misalignment. Methods: We retrospectively reviewed 42 patients (14 thoracoabdominal, 28 complex abdominal aortic aneurysms) undergoing F-EVAR using PMEGs with bridging stent placement between October 2020 and January 2025. Although not designed as a comparative study, patients were stratified by treatment period: Pre-GPS technique group (n = 10, TV = 30) and Post-GPS technique group (n = 32, TV = 114). The GPS technique was used as the primary bailout for difficult cannulations in the Post-GPS technique group. Among the 114 TVs, the GPS technique was selectively applied to 18 challenging vessels (15.8%). Results: Among 18 target vessels treated with the GPS technique, successful cannulation was achieved in 14 (77.8%), with no GPS technique–related complications. At the per patient level, the Post-GPS technique group showed significantly higher technical success (96.8% vs 60.0%, p=0.008) and a higher target vessel success rate (100% vs 80.0%, p=0.052). TV instability was significantly lower (3.1% vs 30.0%, p=0.03). At the per-vessel level, TV technical success was higher (100% vs 93.3%, p=0.042), with lower rates of TV occlusion (0.0% vs 6.7%, p=0.042) and TV instability (0.9% vs 13.3%, p=0.007). All GPS technique-treated vessels remained patent at the 14 month median follow-up. Conclusion: The GPS technique is a feasible adjunct for difficult cannulations in F-EVAR using PMEGs. It avoids additional devices and is particularly suited for total transfemoral repair using currently available steerable sheaths. Clinical Impact Difficult renovisceral target vessel cannulation remains a major limitation to achieving total transfemoral F-EVAR using physician-modified endografts (PMEGs). This challenge often necessitates upper-extremity access or complex adjunctive maneuvers, increasing procedural invasiveness and access-related risks. The Gap Steering (GPS) technique offers a practical adjunctive strategy using a commercially available steerable sheath to achieve controlled directional guidewire manipulation at the fenestration–aortic wall interface. It enables selective cannulation without additional access routes, larger delivery systems, or device modification. This reproducible and fully transfemoral approach has the potential to improve procedural efficiency and expand the applicability of PMEG-based F-EVAR in complex aortic repair.