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Elongation of the Thoracic Aorta and Stent-Graft Migration After TEVAR: Lessons Learned from the VALOR I Trial

Mark F. Fillinger¹, Ronald M. Fairman.^2
1Dartmouth-Hitchcock Medical Center, Lebanon, N.H.;²University of Pennsylvania, Philadelphia, Pa.

OBJECTIVES: Evaluation of stent-graft migration following thoracic endovascular aortic aneurysm repair (TEVAR) is challenging. The thoracic aorta can be tortuous, and previous studies suggest the thoracic aorta may be prone to elongation. This study evaluates thoracic aortic elongation and its association with stent-graft migration.

METHODS: In the VALOR I clinical trial, the Talent Thoracic Stent Graft (Medtronic, Santa Rosa, CA) was implanted in 195 patients at 38 clinical sites. CT scans were performed at discharge, 6 months, and 12 months post-procedure and sent to a Core lab (M2S, W Lebanon, NH) for evaluation. The stability of the thoracic aorta was evaluated by 3-D aortic centerline (CL) distance between the left common carotid artery (LCCA) and the celiac artery (CA). Stent-graft migration was evaluated using stent-graft CL distance to aortic branches to screen for migration, then stable fiducial landmarks immediately adjacent to the stent-graft (e.g. calcifications within the aortic wall or surgical clips) for more precise evaluation.

RESULTS: By the methods described, 171 CT scans were available for analysis (103 patients). The CL distance from LCCA to CA was 92±35 mm (mean±SD). On average, the stent-graft covered 60% (±19%) of the descending thoracic aorta, and 30% of patients had elongation of the thoracic aorta (LCCA-CA) >10 mm within 12 months of implantation. Based on fiducial landmarks, stent graft migration >10 mm was detected in 4 patients (3.9%), and all 4 had thoracic aortic elongation >10 mm. Three of these patients had no major adverse event related to stent graft migration; one required endovascular repair of a pseudoaneurym.

CONCLUSIONS: The length of a partially-stented thoracic aorta after TEVAR is not as stable as the fully-stented infrarenal aorta after EVAR, with nearly one-third elongating >1 cm within 1 year in this study. Due to this instability and the tortuosity of the thoracic aorta, centerline measurements to fiducial aortic landmarks (rather than branches) are required for appropriate evaluation of device migration. The rate of migration in the VALOR I trial was low, and in all cases migration occurred in patients with less stable thoracic aortic lengths. It is unclear whether stenting a larger portion of the thoracic aorta is merited in selected cases due to this phenomenon.

AUTHOR DISCLOSURES: M.F. Fillinger, Medtronic, WL Gore, M2S; Lombard, WL Gore, Cook; R.M. Fairman, Medtronic.