Portico TAVI Implant With Transfemoral Delivery System

Inclusion Criteria: 1. Subject has given written study Informed Consent for participation prior to procedure. 2. Subject is ≥ 18 years of age or legal age in host country. 3. Subject's aortic annulus diameter meets the range indicated in the Instructions for use as measured by echocardiogram (echo) or CT conducted within the past 90 days. 4. Subject has senile degenerative aortic stenosis with echocardiography (echo) derived mean gradient \>40mmHg or jet velocity greater than 4.0 m/s or an initial valve area of \<1.0 cm2 (or aortic valve area index ≤ 0.6 cm2/m2). (Baseline measurement taken by echo within 30 days of procedure). 5. Subject has symptomatic aortic stenosis as demonstrated by NYHA Functional Classification of II or greater. 6. Subject is deemed high operable risk and suitable for TAVI per the medical opinion of the Subject Selection Committee (See Section 3.1 for the definition of the Subject Selection Committee) 7. Subject's predicted operative mortality or serious, irreversible morbidity risk is \<50% at 30 days. 8. In the opinion of the Subject Selection Committee and based upon angiographic measurements, the subject has suitable peripheral vessels and aorta to allow for access of the 18 French delivery system. 9. Subject has structurally normal cardiac anatomy. 10. Subject is willing and able to comply with all required follow-up evaluations. Exclusion Criteria: 1. Subject has a history of a cerebral vascular accident (CVA) or transient ischemic attack (TIA) within the past 6 months (≤180 days) of the index procedure. 2. Subject has carotid artery disease requiring intervention. 3. Subject has evidence of a myocardial infarction (MI) within the past 6 months (≤180 days) of the index procedure. 4. Subject has hypertrophic cardiomyopathy. 5. Subject has a native aortic valve that is congenitally unicuspid, bicuspid, quadricuspid or non-calcified as seen by echocardiography. 6. Subject has mitral or tricuspid valvular regurgitation (\>grade III) or moderate to severe mitral stenosis. 7. Subject has aortic root angulation \>70 degrees (horizontal aorta). 8. Subject has a pre-existing prosthetic valve or prosthetic ring in any position. 9. Subject refuses blood transfusion or surgical valve replacement. 10. Subject has left ventricular ejection fraction (LVEF) \< 20%. 11. The subject has documented, untreated coronary artery disease (CAD) requiring revascularization. 12. Subject has severe basal septal hypertrophy. 13. Subject has had a percutaneous interventional or other invasive cardiac or peripheral procedure ≤ 14 days of the index procedure. 14. Subject has a history of or has active endocarditis. 15. Subject has echocardiographic evidence of intracardiac mass, thrombus, or vegetation. 16. Subject has hemodynamic instability (requiring inotropic support or mechanical heart assistance). 17. Subject is in acute pulmonary edema or requiring intravenous diuretic therapy to stabilize heart failure. 18. Subject with significant pulmonary disease. 19. Subject has significant chronic steroid use. 20. Subject has a known hypersensitivity or contraindication to anticoagulant or antiplatelet medication. 21. Subject has renal insufficiency as evidenced by a serum creatinine \> 3.0 mg/dL (265µmol/L) or end-stage renal disease requiring chronic dialysis. 22. Subject has morbid obesity defined as BMI ≥ 40. 23. Subject's iliac arteries have severe calcification, tortuosity (\>two 90 degree bends), diameter \<6mm, or subject has had an aorto-femoral bypass. 24. Subject has ongoing infection or sepsis. 25. Subject has blood dyscrasias (leukopenia, acute anemia, thrombocytopenia, history of bleeding diathesis, or coagulopathy). 26. Subject has a current autoimmune disease that, in the opinion of the Principal Investigator precludes the subject from study participation. 27. Subject has significant aortic disease, including: * aortic abdominal aneurysm (AAA) ≥ 4cm * thoracic aneurysm (defined as a maximal luminal diameter of 5 cm or greater) * marked tortuosity * significant aortic arch atheroma or narrowing of the abdominal or thoracic aorta * severe tortuosity of the thoracic aorta. 28. Subject has a pre-existing endovascular stent graft in the supra- or infrarenal aorta or pre-existing stent grafts in the ileo-femoral arteries. 29. Subject has an active peptic ulcer or has had gastrointestinal (GI) bleeding within the past 90 days prior to the index procedure. 30. Subject is currently participating in another investigational drug or device study. 31. Subject requires emergency surgery for any reason. 32. Subject has a life expectancy \< 12 months. 33. Subject has other medical, social or psychological conditions that, in the opinion of the Subject Selection Committee, preclude the subject from study participation. 34. Subject is suffering from dementia or admitted to a chronic care facility which would fundamentally complicate rehabilitation from the procedure or compliance with follow-up visits. 35. Subject has a known allergy to contrast media, nitinol alloys, porcine tissue, or bovine tissue.