Evaluation of Abbreviated Versus Conventional Course of Dabigatran Etexilate Before Electric Cardioversion in Patients With Atrial Fibrillation (RE-SOUND Study)

Inclusion Criteria: * male and female subjects aged \>18 years old and \<75 years old * the diagnosis of non-valvular atrial fibrillation/atrial flutter duration of 48 hours or more (or unknown) documented by ECG. Duration of AF will be defined on the base of patient source documents * documented physician's decision to conduct electrical cardioversion * written informed consent form (ICF) signed by patient Exclusion Criteria: * effective treatment with oral anticoagulants within the last 30 days * need in anticoagulant treatment for disorder other than AF * rheumatic heart disease * mitral stenosis of unknown origin * mechanic heart valve * acute coronary syndrome within 12 months * percutaneous coronary intervention (PCI) or coronary artery bypass graft (CABG) surgery within the last 12 month or planned for the next 8 weeks * known hypersensitivity for dabigatran, dabigatran etexilate or to any of capsul's components * creatinine clearance \<30 ml/min * active bleeding, haemorrhagic diathesis, coagulopathy * major surgery within the previous month, surgery planned for the next 8 weeks, * clinically relevant bleeding within the last 30 days * symptomatic or endoscopically documented gastroduodenal ulcers within the last 30 days * intracranial haemorrhages in medical history * organ damages resulted from clinically relevant bleeding within 6 months before randomization. * major trauma or any craniocerebral trauma within 30 days before randomization. * any cancer within last 5 years * uncontrolled hypertension (systolic blood pressure \>180mm Hg and/or diastolic blood pressure \>100 mmHg). * chronic heart failure (CHF) III-IV functional classes (by NYHA) * severe ischemic stroke within the last 12 month before randomization * changes of liver functions with alanine aminotransferase (ALT)/aspartate aminotransferase (AST) \>3 upper limit of normal (ULN) * liver disease having impact on survival * pregnancy and breast feeding. Women of child bearing potential must agree to the requirements for pregnancy testing and contraceptive methods * any contraindications for electric cardioversion (see attachment # 1 for details). * any contraindications to cerebral MRI * any contraindications to TEE ( perforated viscus; esophageal pathology (stricture, trauma, tumor, scleroderma, Mallory-Weiss tear, diverticulum); tracheoesophageal fistula; active upper GI bleeding; recent upper GI surgery; esophagectomy, esophagogastrectomy.) * patients who on the discretion of physician will not benefit from 150 BID dose of dabigatran during study course * active hepatitis * anemia (hemoglobin level \<100g/L) or thrombocytopenia (platelet count \<100 × 109/L) * alcohol abuse * hyperthyroidism