Longitudinal Stent Malapposition After Microcatheter Removal Is Associated With Incomplete Occlusion After Pipeline Flow Diversion

BACKGROUND AND OBJECTIVES: Flow diversion is an established treatment strategy for intracranial aneurysms; however, incomplete aneurysm occlusion remains a clinically relevant challenge. Adequate stent-vessel wall apposition is considered critical for aneurysm healing, yet the impact of longitudinal malapposition on long-term outcomes has not been well defined. We aimed to evaluate whether longitudinal stent malapposition detected on cone-beam computed tomography (CBCT) after microcatheter removal is associated with incomplete aneurysm occlusion after Pipeline flow diversion. METHODS: We retrospectively analyzed 54 intracranial aneurysms treated exclusively with the Pipeline embolization device between 2019 and 2024. In coil-assisted cases, coils were delivered through a jailed 0.0165-inch microcatheter (SL-10). CBCT was routinely obtained immediately after microcatheter removal and before angioplasty to assess intrinsic stent configuration. Longitudinal malapposition was defined as incomplete stent-vessel wall apposition measuring ≥5 mm. The primary end point was aneurysm occlusion at 12 months graded by the O'Kelly-Marotta (OKM) scale. Incomplete occlusion was defined as OKM grades A-C. RESULTS: At 12 months, complete occlusion (OKM D) was achieved in 36 aneurysms (67%), whereas 18 (33%) demonstrated incomplete occlusion. Longitudinal malapposition ≥5 mm was identified in 7 aneurysms (13%). Incomplete occlusion occurred in 71% of aneurysms with malapposition compared with 28% without malapposition (odds ratio 6.5, 95% CI 1.1-37.8; P = .03). In coil-assisted cases, malapposition was observed in 4 of 31 aneurysms (13%), all of which resulted in incomplete occlusion. CONCLUSION: Longitudinal malapposition ≥5 mm detected on CBCT after microcatheter removal was significantly associated with incomplete aneurysm occlusion at 12 months after Pipeline flow diversion. This association was particularly evident in coil-assisted procedures. These findings suggest that longitudinal malapposition may represent a clinically relevant and potentially modifiable procedural factor, and that CBCT assessment after catheter removal may help guide procedural optimization and risk stratification.