The preDIlatation in tRanscathEter aortiC Valve implanTation Trial

Inclusion Criteria: 1. Diameter of \>5mm for Evolut R and \>6mm for CoreValve of the vessel. 2. Aortic valve diameter of ≥20mm and ≤29mm as measured by echo. 3. Ascending aorta diameter ≤ 43mm at the sinotubular junction. 4. Severe aortic stenosis, defined as aortic valve area of \< 1.0 cm2 (or aortic valve area index of \< 0.6 cm2/m2) by the continuity equation, AND mean gradient \> 40 mmHg or maximal aortic valve velocity \> 4.0 m/sec by resting echocardiogram. 5. STS score of ≥ 8 OR LogEuroSCORE\> 20%, OR * 80 years old OR * 65 years old with 1 or 2 (but not more than two) from the following criteria: * Liver cirrhosis (Class A or B). * Pulmonary insufficiency: VMS\<1 liter. * Previous heart surgery (CABG, vascular surgery). * Porcelain aorta. * Pulmonary artery systolic pressure \>60 mmHg and high risk for heart surgery. * Relapsing pulmonary embolism. * Right ventricular insufficiency. * Thoracic wall injuries that contraindicate an open heart surgery. * History of radiation therapy of the mediastinum. * Connective tissue disease that contraindicates an open heart surgery. * Frailty/cachexia. 6. Patients will be informed on the nature of the study and provide written consent. Exclusion Criteria: 1. A known hypersensitivity or contraindication to any of the following which cannot be adequately pre-medicated: aspirin or heparin and bivalirudin, ticlopidine and clopidogrel, nitinol (titanium or nickel), contrast media 2. Ongoing sepsis, including active endocarditis. 3. Any percutaneous coronary or peripheral interventional procedure with a bare metal or drug eluting stent performed within 30 days prior to Heart Team assessment. 4. Echocardiographic evidence of LV or LA thrombus. 5. Mitral or tricuspid valve insufficiency (\> grade II). 6. Previous aortic valve replacement (mechanical or bioprosthetic). 7. Recent (within 6 months of Heart Team assessment) cerebrovascular accident (CVA) or transient ischemic attack (TIA). 8. Patients with: Femoral, iliac or aortic vascular disease (stenosis etc) that precludes the insertion of a transcatheter sheath. OR Symptomatic carotid or vertebral artery disease (\> 70% stenosis). 9. The patient has a bleeding diathesis, coagulopathy or denies blood transfusion. 10. Estimated life expectancy of less than 12 months due to associated non-cardiac co-morbid conditions. 11. Creatinine clearance \< 20 ml/min. 12. Active gastritis or ulcer. 13. Pregnancy. 14. Severe left ventricular dysfunction with left ventricular ejection fraction (LVEF) \< 20%. 15. Unicuspid or bicuspid aortic valve. 16. Mixed aortic valve disease (aortic stenosis and aortic regurgitation\> 2+). 17. Liver failure (Child-Pugh class C). 18. Severe dementia (resulting in either inability to provide informed consent for the study/procedure, prevents independent lifestyle outside of a chronic care facility, or will fundamentally complicate rehabilitation from the procedure or compliance with follow-up visits). 19. Extreme aortic valve calcification and calcific asymmetry (if semiquantitively measured: grade 4, Agatston score: grade 4 AgS\>5000 AU). 20. Aortic valve area of \< 0.4 cm2.