Non-invasive Quantification of Atrial Fibrosis by MRI in Atrial Fibrillation

Inclusion Criteria: All persons \> 18 years, which have: gp paroxysmal or persistant FA 1. paroxysmal or persistent FA (under one year), 2. refractory to at least one antiarrhythmic drug therapy 3. eligible for an ablation procedure with cryotherapy 4. the patient may benefit from surveillance. gp permanent FA permanent AF ( defined as chronic arrhythmia after 2 failed attempts to electrical cardioversion and / or more than one year old) , and hospitalized for cardiac reasons or not in different cardiology Timone . Exclusion Criteria: * age \< 18 years, * cons -indications to MRI ( claustrophobia, pacemakers and implantable cardiac defibrillators , metal chips intra ocular , valvular mechanical prosthesis ) , allergy to gadolinium , * renal impairment ( creatinine clearance \<60 mL / min) * pregnant or nursing ( a pregnancy test must be performed for women of childbearing age at the time of inclusion , the result of this test will be communicated to them . * the MRI examination takes place three months after the inclusion women of childbearing potential should be placed under effective contraception)