The purpose of this study is to determine the incidence of major vascular events (ischemic or haemorrhagics) at the third month after initiation of the antithrombotic treatment (oral anticoagulation or dual antiplatelet therapy) in both arms followed TAVI.

Transcatheter aortic valve implantation (TAVI) procedure using any of their vascular access is an option with proven benefit definitively for treatment of severe symptomatic aortic stenosis in patients considered unsuitable for conventional open heart surgery.

By avoiding the hemodynamic effects, cardiovascular and cerebral microembolic load of cardiopulmonary bypass circulation, it is assumed that the TAVI procedure is beneficial despite the risk of neurological complications. Currently antithrombotic therapy after the procedure is not standardized. International treatment guidelines recommends that post-operative patients with a conventional surgical aortic bioprosthesis maintain oral anticoagulation for 3 months after the procedure, unless otherwise noted for its continuation. Whereas some studies have postulated that in patients with aortic bioprostheses, dual antiplatelet therapy is as effective to prevent major cardiac and cerebrovascular events as oral anticoagulation, with a lower incidence of bleeding complications at 3 months of treatment, the investigators formulated the following hypothesis:

• There is a lower incidence of major cardiac and cerebrovascular events in patients with dual antiplatelet therapy compared to patients with oral anticoagulation for 3 months after implantation of an aortic bioprosthesis TAVI procedure.

Inclusion Criteria:

1. Adult patients (more than 18 years) with ability to understand and accept the participation in the clinical trial.
2. Patients with symptomatic degenerative severe aortic stenosis rejected for conventional surgical aortic valve replacement due to unacceptably high risk and accepted for TAVI procedure
3. Signed informed consent.
4. Patients who are not participating in any other clinical trial or research study.

Exclusion Criteria:

1. Patients under oral anticoagulation treatment
2. Patients who can not undergo MRI study
3. Recent stroke < 14 days prior, revascularized coronary artery disease or life expectancy < 12 months
4. Patients with proven allergy to aspirin, clopidogrel or acenocoumarol
5. Patients that after TAVI procedure can not undergo a regimen of dual antiplatelet therapy or oral anticoagulation for 3 months due to any new post-TAVI medical indication