Full title: Factors portending endoleak formation after thoracic aortic stent-graft repair of complicated aortic dissection Short title: Sze; Endoleaks after repair of aortic dissection

Background: Endoleaks after stent-graft repair of aortic dissections are poorly understood but appear substantially different from those seen after aneurysm repair. We studied anatomical and clinical factors associated with endoleaks in patients who underwent stent-graft repair of complicated type B aortic dissections. Methods and Results: From 2000 to 2007, 37 patients underwent stent-graft repair of acute ( 14 days; n=23), subacute (15-90 days; n=10) or chronic (>90 days; n=4) complicated type B aortic dissections using Gore Thoracic Excluder (n=17) or TAG stent-grafts (n=20) under an investigator-sponsored protocol. Endoleaks were classified as imperfect proximal seal, flow through fenestrations and/or branches, or Complex (both). Variables studied included coverage of the left subclavian artery (LSCA), aortic curvature, completeness of proximal apposition, dissection chronicity, and device used. Endoleaks were found during follow-up (mean 22 months) in 59% of patients, and were associated with coverage of the LSCA (Complex, p<.001), small radius of curvature (Type 1 and Complex, p=.05), and greatest length of unapposed proximal stent-graft (Complex, p<.0001). During follow-up, 10 endoleaks resolved spontaneously, 6 required reintervention for false lumen dilatation, and 2 were stable without clinical consequences. Conclusions: Endoleaks are common after stent-graft repair of aortic dissection, and may lead to false lumen enlargement necessitating re-intervention. Anatomic complexities such as acute aortic curvature and covered side branches were associated with endoleaks, illustrating the need for dissection-specific device development.