Safety and Efficacy Study of the Medtronic CoreValve® System in the Treatment of Symptomatic Severe Aortic Stenosis in High Risk and Very High Risk Subjects Who Need Aortic Valve Replacement

The purpose of the study is to evaluate the safety and efficacy of the Medtronic CoreValve® System in the treatment of symptomatic severe aortic stenosis in subjects who have a predicted high risk for aortic valve surgery and/or very high risk for aortic valve surgery.