Valiant Evo International Clinical Trial

Inclusion Criteria: 1. Subject is ≥18 years old 2. Subject understands and voluntarily has signed and dated the Patient Informed Consent approved by the Sponsor and by the Ethics Committee for this study 3. Subject presents a DTAA which is localized below the ostium of left subclavian artery (LSA) and above the ostium of celiac trunk 4. Subject has a DTAA that is one of the following: 1. A fusiform aneurysm with a maximum diameter that: * is ≥ 50 mm and/or: * is ≥ 2 times the diameter of the non-aneurysmal thoracic aorta and/or: * is \<50 mm and has grown ≥ 5 mm within previous 12 months 2. A saccular aneurysm or a penetrating atherosclerotic ulcer 5. Subject's anatomy must meet all of the following anatomical criteria as demonstrated on contrast-enhanced CT and/or on contrast-enhanced MRI obtained within four (4) months prior to implant procedure: 1. Proximal and distal non-aneurysmal aortic neck diameter measurements must be ≥ 16 mm and ≤ 42 mm 2. Proximal non-aneurysmal aortic neck length must be ≥ 20 mm (for FreeFlo configuration) and ≥ 25 mm (for Closed Web configuration) 3. Distal non-aneurysmal aortic neck length must be ≥ 20 mm 6. Subject has adequate arterial access site or can tolerate a conduit that allows endovascular access to the aneurysmal site with the delivery system of the appropriate sized device chosen for the treatment. Exclusion Criteria: 1. Subject has a life expectancy of less than 1 year 2. Subject is participating in another investigational drug or device study which would interfere with the endpoints and follow-ups of this study 3. Subject is pregnant 4. Subject requires planned placement of the covered proximal end of the stent graft to occur in zones 0 or 1 5. Subject has a thoracic aneurysm with a contained rupture or localized at the anastomosis of a previous graft (pseudo-/false aneurysm) 6. Subject has a mycotic aneurysm 7. Subject has a dissection (type A or B) or an intramural hematoma or an aortic rupture in addition to the thoracic aneurysm 8. Subject requires emergent aneurysm treatment, e.g., trauma or rupture 9. Subject has received a previous stent or stent graft or previous surgical repair in the ascending and/or descending thoracic aorta, and/or in the aortic arch 10. Subject requires surgical or endovascular treatment of an infra-renal aneurysm at the time of implant 11. Subject has had previous surgical or endovascular treatment of an infra-renal aortic aneurysm 12. Treatment with the Valiant Evo Thoracic Stent Graft would require intentional revascularization of the brachio-cephalic artery, the left common carotid artery or the celiac trunk 13. Subject has had or plans to have a major surgical or interventional procedure within 30 days before or 30 days after the planned implantation of the Valiant Evo Thoracic Stent Graft. This does not include planned procedures that are needed for the safe and effective placement of the stent graft (i.e., carotid/subclavian transposition, carotid/subclavian bypass procedure) 14. Subject has a significant and/or circumferential aortic mural thrombus at either the proximal or distal attachment sites that could compromise fixation and seal of the implanted stent graft 15. Subject has a connective tissue disease (e.g., Marfan's syndrome, aortic medial degeneration) 16. Subject has a bleeding diathesis or coagulopathy, or refuses blood transfusion. 17. Subject has had a myocardial infarction (MI) within 3 months of the procedure 18. Subject has had a Cerebrovascular Accident (CVA) within 3 months of the procedure 19. Subject has a known allergy or intolerance to the device materials 20. Subject has a known allergy to anesthetic drugs 21. Subject has a known hypersensitivity or contraindication to anticoagulants, or contrast media, which is not amenable to pretreatment 22. Subject has active or systemic infection at the time of the index procedure