Percutaneous Aortic Valve 18F System for the Treatment of Patients With Severe Aortic Stenosis

Inclusion Criteria All candidates for the study must meet the following inclusion criteria: 1. Severe aortic valve stenosis determined by echocardiogram and Doppler, defined as: mean gradient \>40 mmHg or peak jet velocity \>4.0 m/s and an aortic valve area ≤0.8 cm2 or aortic valve area index ≤0.5 cm2/m2 2. Symptomatic aortic valve stenosis demonstrated by angina, congestive heart failure, NYHA Functional Class ≥ II, or syncope 3. Patient is an extreme risk candidate for open surgical aortic valve repair such that the site Investigators (interventional cardiologist and cardiothoracic surgeon) agree that medical factors preclude operation, based on the conclusion that the probability of death or serious morbidity exceeds the probability of meaningful improvement due to the patient's co-morbidities (such as, but not limited to, severe COPD, porcelain aorta, previous thorax irradiation) or logistic EuroSCORE ≥ 20 4. ≥ 70 years old 5. Patient has been informed of the nature of the study and has provided written informed consent 6. Patient and treating physician agree that the patient will return for all required post-procedure follow-up visits Exclusion Criteria Candidates will be excluded from the study if any of the following criteria are present: 1. Patient is a surgical candidate for aortic valve replacement 2. Congenital bicuspid or unicuspid valve determined by echocardiography 3. Native valve annulus diameter is \<17mm or \>22mm determined by the screening CT scan 4. Extreme asymmetrical calcification of the native aortic valve determined by the screening CT scan 5. Native valvular or peripheral vascular anatomy is not appropriate for the DFM bioprosthesis and 18F delivery system 6. Left ventricular ejection fraction (LVEF) \<30% determined by resting echocardiogram 7. Evidence of an acute myocardial infarction (Refer to Definitions in Section 8) within 30 days prior to the study procedure 8. Any percutaneous coronary or peripheral interventional procedure performed within 30 days prior to the study procedure 9. Any planned surgical or percutaneous coronary or peripheral procedure to be performed during the study procedure or prior to 30 day follow-up visit 10. Need for emergency surgery for any reason 11. Untreated clinically significant ( \> 70% obstruction) coronary artery disease requiring revascularization 12. Prior aortic or mitral valve surgery 13. Pre-existing prosthetic heart valve in any position 14. Mitral insufficiency greater than moderate determined by resting echocardiography 15. Echocardiographic evidence of intra-cardiac mass, thrombus or vegetation 16. Thoracic aortic aneurysm (TAA) 17. Abdominal aortic aneurysm (AAA) \>4.5 cm 18. Presence of an endovascular stent graft for treatment of AAA or TAA 19. Hypertrophic cardiomyopathy 20. Hemodynamic instability (e.g. requiring inotropic support) 21. Trans-esophageal echocardiography (TEE) is contraindicated 22. Renal insufficiency (creatinine \> 3.0 mg/dL) and/or end-stage renal disease requiring dialysis at the time of screening 23. Active endocarditis or sepsis within 6 months prior to the study procedure 24. Stroke or transient ischemic attack (TIA) within 6 months prior to the study procedure 25. Cardiogenic shock within 30 days prior to the study procedure 26. Active peptic ulcer or upper GI bleeding within 3 months prior to the study procedure 27. Leukopenia (WBC \<3000/mm³), acute anemia (Hb \<9 g/dL), or thrombocytopenia (platelet count \<100,000 cells/mm3) 28. History of bleeding diathesis or coagulopathy or refusal of blood transfusions 29. A known hypersensitivity or contraindication to aspirin, heparin, ticlopidine or clopidogrel, or sensitivity to contrast media, which cannot be adequately pre-medicated 30. Currently participating in an investigational drug or another device trial 31. Previously enrolled in this study 32. Patient refusal of surgery 33. Life expectancy thought to be \<12 months 34. 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)