Background
The ASSIST trial compared clinical outcomes and the evolution of both the true and false lumen (e.g., remodeling) over ≥1 year in patients with complicated type B aortic dissection subjected to thoracic endovascular aortic repair (TEVAR) in combination with distal true lumen scaffolding using a self-expanding Nitinol open stent (E-XL; JOTEC, Hechingen, Germany) versus TEVAR alone.

Methods
ASSIST was a multicenter, prospective, single-arm study (recruiting from 2012 to 2014) comparing clinical and imaging data from 39 consecutive patients (mean age 59.4 ± 13) who underwent TEVAR and the JOTEC E-XL open stent with data from matched control subjects treated with TEVAR alone and selected on the basis of 1:1 propensity score matching. Clinical data were collected by an independent clinical research organization, and serial computed tomographic images were subjected to blinded core laboratory analysis.

Results
There were no differences in baseline demographics, clinical profiles, morphological data, procedural details, and early outcomes between the 2 groups. Differences emerged with regard to the evolution of both true lumen distal to the stent graft, false lumen over the entire length of dissection, and remodeling (p < 0.001). At 1 year, TEVAR with E-XL had false lumen thrombosis at the level of the celiac trunk in 53.8% versus 17.9% with TEVAR alone (p = 0.004). Kaplan-Meier survival analysis indicated favorable clinical outcomes with additional E-XL.

Conclusion
TEVAR for acute complicated type B aortic dissection proved safe and efficacious and promotes remodeling of the stent-grafted thoracic aorta. Additional scaffolding of true lumen distal to TEVAR with a self-expanding bare-metal stent supports significant distal true lumen expansion, false lumen regression, and thrombosis with evidence of improved remodeling at 1 year.