Feasibility Study for GORE® TAG® Thoracic Branch Endoprosthesis to Treat Proximal Descending Thoracic Aortic Aneurysms

Inclusion Criteria: 1. Presence of DTA aneurysm deemed to warrant surgical repair which requires proximal graft placement in Zone 2: 1. Fusiform (≥ 55 mm), or 2. Fusiform (\>2 times native aortic diameter), or 3. Saccular (no diameter criteria) 2. Age ≥18 years at time of informed consent signature 3. Subject is capable of complying with protocol requirements, including follow-up 4. Informed Consent Form (ICF) is signed by Subject or legal representative 5. Must have appropriate proximal aortic landing zone, defined as: 1. Must require coverage of the left subclavian artery (LSA) origin for exclusion of the lesion 2. Aortic inner diameters between 16-48 mm 3. Landing zone, which must include the LSA ostium, cannot be aneurysmal, heavily calcified, or heavily thrombosed, 4. Acceptable proximal landing zone outer curvature length for the required device 5. Landing zone must be native aorta 6. Must have appropriate distal aortic landing zone, defined as: 1. Outer curvature length must be ≥2cm proximal to the celiac artery 2. Aortic inner diameters between 16-48mm (diameter should be between 16-42mm if using distal TAG® Device extension) 3. Landing zone cannot be aneurysmal, heavily calcified, or heavily thrombosed 4. Native aorta or previously implanted GORE® TAG® Device 7. Must have appropriate LSA landing zone, defined as: 1. LSA length of ≥3 cm proximal to first major branch vessel if using Aortic Component with 8 mm portal diameter, or LSA length of ≥2.5 cm proximal to first major branch vessel if using Aortic Component with 12 mm portal diameter 2. LSA inner diameters of 6-15 mm if using Aortic Component with 8 mm portal diameter, or inner diameters of 11-18 mm if using Aortic Component with 12 mm portal diameter 3. Target branch vessel landing zone cannot be aneurysmal, heavily calcified, or heavily thrombosed Exclusion Criteria: 1. Concomitant aneurysm/disease of the ascending aorta, aortic arch, or abdominal aorta requiring repair 2. Previous endovascular repair of the ascending aorta 3. Previous endovascular repair of the DTA with a non-Gore device 4. Surgery within 30 days of treatment 5. Infected aorta 6. Dissection of the DTA 7. Intramural hematoma of the DTA without DTA aneurysm 8. Life expectancy \<2 years 9. Myocardial infarction or stroke within 6 weeks prior to treatment 10. Patient has a systemic infection and may be at increased risk of endovascular graft infection 11. Pregnant female at time of informed consent signature 12. Degenerative connective tissue disease, e.g. Marfan's or Ehler-Danlos Syndrome 13. Participation in another drug or medical device study within one year of study enrollment 14. Known history of drug abuse within one year of treatment 15. Significant thrombus or atheroma in the aortic arch 16. Tortuous or stenotic iliac and/or femoral arteries preventing introducer sheath insertion and the inability to use a conduit for vascular access 17. Planned coverage of left carotid or celiac arteries 18. Patient has known sensitivities or allergies to the device materials 19. Patient has known hypersensitivity or contraindication to anticoagulants or contrast media, which is not amenable to pre-treatment 20. Previous instance of Heparin Induced Thrombocytopenia type 2 (HIT-2) or known hypersensitivity to heparin 21. Diameter taper outside of the device sizing range between proximal and distal landing zones of aorta and the inability to use additional devices of different diameters to compensate for the taper 22. Mycotic aneurysm 23. Persistent refractory shock (systolic blood pressure \<90 mm Hg) 24. Patient has body habitus or other medical condition which prevents adequate visualization of the aorta Additionally, the following exclusion criteria apply for Subjects enrolled in Stage 1: 25. Aberrant right subclavian or left vertebral arteries 26. Occluded/stenosed/hypoplastic right vertebral artery 27. Presence of a patent left internal mammary artery (LIMA) graft 28. Bilateral carotid artery disease 29. Known incomplete Circle of Willis 30. Known left vertebral artery ending in posterior inferior cerebellar artery (PICA)