This is a pilot prospective, comparative, monocentric, randomized study with 2 groups. People with a severe aortic stenosis and a high risk of surgery are referred to a Trans catheter aortic valve implantation (TAVI).

The proposed study is to show the interest of a cardiac computed tomography (CT) to improve the TAVI procedure. The Cardiac computed tomography (CT) shows the exact geometry of the aortic annulus and help the physician to find the right position of the prosthesis during the procedure. The hypothesis is that performing a cardiac CT before the TAVI could reduce the number of vascular peripheral complication, the number of stroke and can minimize the aortic regurgitation during the follow up.

Inclusion Criteria:

• Patient with a symptomatic severe aortic stenosis with a too high risk of surgical valvular replacement. This patient will be selected for a TAVI. In this study, we only randomized patient for a TAVI with an Edwards prosthesis
• male or female patient, older than eighteen years old
• who have given their written consent
• who are affiliated to the French social security system
• which has a too high risk of surgical valvular replacement (EuroSCORE logistic > 20% or Society of Thoracic Surgeons Score > 10, or contre indicated to a cardiac surgery by a heart team
• Severe Aortic stenosis with symptoms like dyspnea, heartache, syncope, heart failure

Exclusion Criteria:

• Patient who can't give his written consent because of his physical or mental status
• Adult patient protect by law (article L1121-8),
• Person deprived of liberty (article L1121-8),
• Pregnant women
• Patient in terminal phase of illness,
• Terminal kidney failure
• Allergy to iodine
• bicuspids ou unicuspid aortic,
• Diameter of the left ventricular outflow tract < 18mm or > 25mm,
• Diameter of the femoral artery < 7mm, tortuosity or calcifications
• Septal hypertrophy
• Apical thrombosis.