Clinical trial outcomes and thoracic aortic morphometry after one year with the Valiant Navion stent graft system

On February 17, 2021, Medtronic Incorporated issued a global voluntary recall of the Valiant Navion Thoracic Stent Graft System (the device under study in the Valiant Evo Global Clinical Program that is the subject of this publication), and instructed physicians to immediately cease use of the Valiant Navion system and return any unused product. Medtronic initiated the recall in response to three clinical trial subjects recently observed with stent fractures, two of whom have confirmed type IIIb endoleaks. The data collection, analysis, and manuscript submission occurred before the notice of this recall, and, specifically, the 100 procedures reviewed for this series were free of events at 1 year related to the reason for this device recall. The authors of this article and the manufacturer were unaware of the recently detected adverse events at the time of the preparation of the manuscript, and the 1-year trial results, and imaging-based analyses described are unchanged. Management of thoracic aortic aneurysms continues to be a challenging problem and outcomes are dependent on patient anatomy. The present publication focuses on the importance of achieving proximal and distal seals and the consideration of the temporal changes of the aortic morphology as a part of the TEVAR planning process. The authors believe there is still scientific merit in disclosing this information, despite the current nonavailability of the Valiant Navion system.

The Valiant Navion stent graft system (Medtronic Inc, Santa Rosa, Calif) is a third-generation device with improved conformability. We have reported the 1-year clinical trial outcomes, with a focus on an imaging-based analysis of the aortic morphology. We assessed the effects of graft implantation on the native anatomy and the effects of the 1-year changes in thoracic aorta morphology on the original seal zones of the stent graft.

A total of 100 subjects were enrolled in a prospective single-arm clinical trial investigating the Valiant Navion stent graft system. An independent core laboratory (Syntactx, New York, NY) assessed the anatomic characteristics and performance outcomes.

Through 1 year of follow-up, the freedom from all-cause mortality, aneurysm-related mortality, and secondary procedures was 89.8%, 97.0%, and 94.8% respectively. Of the 100 patients, 5 had undergone a total of six secondary procedures, and 9 patients had developed an endoleak (type Ia and Ib in 1, type Ia in 1, type Ib in 3, and type II in 4 patients) within the first year. After 1 year, 2 of 76 patients (2.6%) had had an increase in their maximum aneurysm diameter of ≥5 mm, 62 (81.6%) had had stable sacs, and 12 (15.8%) had experienced sac shrinkage. Although no deployment failures had occurred, 36 of the 100 proximal (36%) and 31 of the 100 distal (31%) attachment zones were considered short according to our definitions. The stent graft had conformed to the native anatomy at implantation, because the preprocedural thoracic aorta tortuosity (1.45 ± 0.02) had not significantly changed at 1 month after implantation (1.46 ± 0.02). Despite a natural increase in thoracic tortuosity after 1 year (1.49 ± 0.02), wall apposition had been maintained over time, as evidenced by the low endoleak rates. Aortic elongation and dilation had occurred at the proximal end of the graft by an average of 1.2 mm and 1.6 mm, respectively. Aortic remodeling was more pronounced at the distal end, with an average increase of 4.2 mm in length and 2.8 mm in diameter.

The included patients had had positive 1-year outcomes with high freedom from mortality, endoleak development, and secondary procedures. Aortic elongation and dilation were more prevalent at the distal end, emphasizing the importance of distal attachment zone consideration as part of preoperative planning. Because aortic remodeling can be expected to continue over time, additional follow-up and imaging analysis in the trial will be necessary to assess the aortic morphology and its effects on stent graft performance.