Clinical Evaluation of Percutaneous Implantation of the Medtronic CoreValve Aortic Valve Prosthesis (18Fr-Study)

Inclusion Criteria: * Native aortic valve disease, defined as valve stenosis with an aortic valve area \<1cm² (\<0.6cm2/m2) as determined by echocardiographic measure, * ≥ 75 years, or * Surgical risk calculated with logistic EuroSCORE ≥ 15 %, or * One or two (but not more than 2) of the following complicating factors: 1. Cirrhosis of the liver (Child class A or B), 2. Pulmonary insufficiency : Forced expiratory volume in one second (FEV1) \< 1 liter, 3. Previous cardiac surgery (Coronary artery bypass grafting (CABG), valvular surgery), 4. Pulmonary hypertension \> 60 mmHg and high risk of cardiac surgery other than valve replacement, 5. Porcelain aorta 6. Recurrent pulmonary embolus, 7. Right ventricular insufficiency, 8. Thoracic burning sequelae contraindicating open chest surgery, 9. History of mediastinum radiotherapy, 10. Severe connective tissue disease resulting in a contraindication to surgery, 11. Cachexia (BMI ≤ 18 kg/m²), * Aortic valve annulus diameter is ≥ 20 mm and ≤ 27 mm as determined by echocardiographic measure, * Ascending aorta diameter £ 45 mm at the sino-tubular junction, and * Signed Informed Consent. Exclusion Criteria: * Known hypersensitivity or contraindication to aspirin, heparin, ticlopidine, clopidogrel, Nitinol, or sensitivity to contrast media which cannot be adequately pre-medicated, * Any sepsis, including active endocarditis, * Recent myocardial infarction (\< 30 days), * Percutaneous coronary or vascular intervention within 15 days prior to the study procedure, or scheduled during or within 30 days after the study procedure, * Any left ventricular or atrial thrombus diagnosed by echocardiography, * Uncontrolled atrial fibrillation (heart rate greater than 100 bpm), * Mitral or tricuspid valvular insufficiency ( \> grade II), * Previous aortic valve replacement (mechanical valve OR stented bioprosthetic valve), * Any condition considered as contraindication for extracorporeal assistance, * Evolutive or recent CVA (cerebro vascular accident), * Poly arterial patients with either: 1. Femoral, iliac or aortic vascular condition (e.g. stenosis, tortuosity), that make insertion and endovascular access to the aortic valve impossible, or 2. Symptomatic carotid or vertebral arteries narrowing (\> 70%) disease, or 3. Abdominal or thoracic aortic aneurysm, * Bleeding diathesis or coagulopathy, or patient who will refuse blood transfusion, * Evolutive disease with life expectancy less than one year, * Creatinine clearance \< 20 ml/min, * Pregnancy, and * Enrolled in another investigational study.