Subjects are eligible for entry in this study if ALL the following conditions are met: 1. Age ≥ 18 years 2. Symptomatic, severe native calcific aortic stenosis in subjects at low, intermediate or high surgical risk AVA ≤ 1.0 cm2 or AVA index ≤ 0.6 cm2/m2 or Jet velocity ≥ 4.0 m/s or mean gradient ≥ 40 mmHg or dimensionless Index <0.25 3. New York Heart Association Functional Class ≥ 2 4. Requires aortic valve replacement and is indicated for TAVR as determined by the Heart Team (composed of an experienced interventional cardiologist and an experienced cardiac surgeon) 5. Eligible for transfemoral delivery of a TAVR 6. Native aortic annulus suitable for safe placement of Siegel 23mm, 26mm or 29 mm transcatheter heart valve. Preprocedural measurements by TTE and CT of aortic annulus area (23mm: 330- 440 mm2 , 26mm: 430-550 mm2, 29mm: 540-690 mm2) 7. Understands the study requirements and the treatment procedures and provides written informed consent 8. Subject agrees to complete all required scheduled follow-up visits.

Subjects will be excluded for entry in this study if ANY of the following conditions are met: Anatomical 1. Cardiac anatomy precluding safe placement of a transcatheter aortic valve. 2. Iliofemoral vessel characteristics (vessel diameter <5.5mm for smaller THV systems [20-26mm valve sizes] or <6.0mm for larger THV systems [29mm or larger valve sizes]) that would preclude safe placement of commercially available transcatheter aortic valves (SAPIEN 3 or Evolut) 3. Pre-existing prosthetic heart valve or ring except in the mitral position. 4. Unicuspid aortic valve 5. Severe aortic regurgitation (>3+) 6. Severe mitral or severe tricuspid regurgitation(>3+) requiring intervention. 7. Moderate to severe mitral stenosis. 8. Hypertrophic obstructive cardiomyopathy (HOCM) 9. Echocardiographic evidence of intracardiac mass, thrombus or vegetation requiring treatment. 10. Significant aortic disease including abdominal aortic or thoracic aneurysm defined as maximal luminal diameter 5.5 cm or greater or ascending aortic aneurysm defined as maximal luminal diameter 5 cm or greater. Clinical 11. Evidence of an acute myocardial infarction ≤ 30 days before enrollment. 12. Any percutaneous coronary or peripheral interventional procedure performed within 30 days prior to the index procedure 13. Blood dyscrasias as defined: leukopenia (WBC < 3000 cell/mL, anemia (Hgb < 9 g/dL), thrombocytopenia (platelet count < 50,000 cells/mL), history of bleeding diathesis or coagulopathy. 14. Untreated clinically significant Coronary Artery Disease (CAD) requiring revascularization 15. Cardiogenic shock manifested by low cardiac output, vasopressor dependence, or mechanical hemodynamic support within the past 30 days. 16. Hemodynamic or respiratory instability requiring inotropic support, mechanical ventilation or mechanical heart assistance within 30 days of enrollment 17. Need for emergency surgery for any reason 18. Ventricular dysfunction with left ventricular ejection fraction (LVEF) < 25% as measured by resting echocardiogram 19. Recent (within 6 months) cerebrovascular accident (CVA) or transient ischemic attack (TIA). 20. Symptomatic carotid or vertebral artery disease or successful treatment of carotid stenosis within 30 days of enrollment 21. Renal insufficiency (eGFR < 30 ml/min per the Cockcroft-Gault formula) and/or renal replacement therapy, or end stage renal disease requiring chronic dialysis 22. GI bleeding within the past 3 months 23. Severe lung disease (FEV1 < 50% predicted) or currently on home oxygen 24. History of cirrhosis or any active liver disease 25. Significant abdominal or thoracic aortic disease (such as porcelain aorta, abdominal aortic aneurysm > 5.0 cm, severe calcification, aortic coarctation, etc.) that would preclude safe passage of the delivery system 26. Severe pulmonary hypertension (e.g., PA systolic pressure ≥ 2/3 systemic pressure) 27. A known hypersensitivity or contraindication to any of the following which cannot be adequately pre-medicated: aspirin, heparin, ticlopidine and clopidogrel, contrast media, nickel, cobalt ,chromium, titanium, molybdenum, rhenium, polyethylene materials. 28. Ongoing sepsis, including active endocarditis 29. BMI > 50 kg/m2 30. Subject refuses a blood transfusion 31. Life expectancy < 12 months due to associated non-cardiac co-morbid conditions 32. Other medical, social, or psychological conditions that in the opinion of an Investigator precludes the subject from appropriate consent 33. Severe dementia (resulting in either inability to provide informed consent for the trial/procedure, prevents independent lifestyle outside of a chronic care facility, or will fundamentally complicate rehabilitation from the procedure or compliance with follow-up visits) 34. Currently participating in an investigational drug or another investigational device trial 35. Subject is contraindicated for cardiac CT 36. Subject belongs to a vulnerable population (Vulnerable subject populations are defined as individuals with mental disability, persons in nursing homes, children, impoverished persons, homeless persons, nomads, refugees, and those permanently incapable of giving informed consent. Vulnerable populations also may include members of a group with a hierarchical structure such as university students, subordinate hospital and laboratory personnel, employees of the Sponsor, members of the armed forces, and persons kept in detention).