Considerations for Migration Assessment for the Nellix Endovascular Aortic Sealing System with Centerline Measurements
Paul D. Bishop, MSEE RVT, Anthony Rizzo, MD, Brittani L. Covella, BS, Sean P. Lyden, MD.
Cleveland Clinic, Cleveland, OH, USA.
OBJECTIVES: As with Endovascular Aortic Repair (EVAR) devices, the Endologix Nellix Endovascular Aortic Sealing (EVAS) system should be evaluated for device migration. Assessment of migration requires characterizing each Nellix device location relative to a reference branch vessel and comparing changes over time. The goal of the study is to describe methods for characterizing Nellix graft location for migration analysis. METHODS: Follow-up contrast enhanced DICOM computed tomography (CT) from subjects treated with the Nellix investigational device were assessed with TeraRecon Aquarius Intuition software. Two centerlines were automatically generated for each Nellix graft lumen and extending proximally into the native aorta. A third centerline was manually created in the center of the native aorta. Distances between a reference artery and proximal most circumferential appearance of the bilateral Nellix stents were captured for each centerline. Paired t-tests were used to evaluate for differences in length measurements between centerlines. Statistical significance was assumed at p<0.05.
RESULTS: A total of 117 consecutive CT scans assessed as part of a Core Laboratory analysis were used for this study. All CT scans had a slice thickness ≤3mm. The SMA (n=57) and lowest Renal Artery (n=60) were used as a reference landmark. Length measurements derived from automated centerlines were statistically longer for automated vs. native aortic centerlines for both right (11.9 vs. 10.1mm, p<.001) and left (10.9 vs. 10.0mm, p<.001) Nellix stents. Mean difference between centerline methods was 2.5mm with a maximum difference of 11.3mm
CONCLUSIONS: The Nellix EVAS system should be assessed as two independent grafts when evaluating for device movement. With migration thresholds as little as 5mm, it is critical to use consistent methods to evaluate Nellix graft location for each graft. Differences alone between centerline methods alone could lead to incorrect findings when evaluating migration.
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