Engager Direct Aortic Clinical Study

Inclusion Criteria: * Severe aortic stenosis as defined by Doppler echocardiography: aortic valve area ≤ 0.8 cm2 (or AVA index ≤ 0.5 cm2/m2), or mean gradient ≥ 40 mmHg, or max velocity ≥ 4m/s * NYHA Functional Class II or greater; * Logistic EuroSCORE I ≥ 20%, or comorbidity judged by the heart team to pose an absolute or relative contraindication for conventional aortic valve replacement; * Non-calcified ascending aortic site ≥ 50 mm from the aortic valve basal plane; * Age ≥ 18 years; * The patient has been informed of the nature of the study and has consented to participate, authorizing the collection and release of his/her medical information by signing a consent form ("Patient Informed Consent Form"). Patient should understand the implications of participating in the study and should be legally competent to provide informed consent. Exclusion Criteria: * Unicuspid or bicuspid aortic valve; * Echocardiographic evidence of intracardiac mass, thrombus, or vegetation; * Left ventricular ejection fraction \< 25%; * Left ventricular outflow obstruction, such as Hypertrophic Obstructive Cardiomyopathy and severe septal hypertrophy; * Mitral or tricuspid regurgitation greater than 2+ by angiography or moderate by echocardiography; * Patients with life expectancy less than 12 months due to an underlying non-cardiac co-morbid disease; * Known hypersensitivity or contraindication to aspirin, heparin, ticlopidine, clopidogrel, Nitinol or contrast medium that cannot be adequately controlled with pre-medication; * Sepsis or acute endocarditis; * Blood dyscrasia such as acute anemia, leucopenia, or thrombocytopenia; bleeding diathesis, or coagulopathy; * Renal insufficiency assessed by creatinine clearance \< 20 ml/min and/or end-stage renal disease requiring chronic dialysis; * Active peptic ulcer or GI bleeding within 3 months from the planned index procedure; * Untreated clinically significant coronary artery disease requiring revascularization; * Cardiogenic shock, suspected cardiogenic shock, or hemodynamic instability requiring inotropic support or mechanical heart assistance; * Significant aortic disease, including abdominal and thoracic aortic aneurysm, defined as maximal luminal diameter of 5 cm or greater; * Need for emergency surgery, cardiac or non-cardiac; * History of myocardial infarction in the last 6 weeks; * History of TIA or CVA in the last 6 months; * Therapeutic invasive cardiac procedure, with the exception of BAV, performed within 30 days of the planned date of valve implantation, or 6 months in the case of drug-eluting stents; * Pre-existing prosthetic heart valve or prosthetic ring in any position; * Patent RIMA or pre-existing patent RIMA graft at direct aortic access site and/or trajectory; * Patient refuses a blood transfusion; * Pregnant or breastfeeding women; * Patient is currently enrolled in another investigational device or drug trial that may influence the outcome of this trial.