This study will examine the use of a TAVR (Transcatheter Aortic Valve Replacement), which is a minimally invasive procedure designed to replace the aortic valve inside the heart. The TAVR procedure is performed by a heart surgeon and/or an interventional cardiologist. This less invasive surgical approach called TAVR is offered to those patients who are high risk for undergoing open heart surgery to replace the aortic valve. In this study, TAVR will be performed using the JenaValve Pericardial TAVR System, which is intended to help treat severe aortic stenosis. The JenaValve replacement valve is placed inside the aortic valve by using the JenaValve delivery system. The JenaValve replacement valve may be implanted in one of two ways: (1) transapical - where the valve is implanted through the chest wall, and (2) transfemoral - where the valve is implanted through an artery in the groin. The choice of which implant method will be used is decided by the doctor. The choice of which approach is used is at the clinical discretion of the study physicians. The TAVR procedure typically takes 1-2 hours to complete. The JenaValve TAVR device, once implanted, is designed to remain permanently in place.