Inhibition of Aldosterone to Reduce Myocardial Diffuse Fibrosis in Patients With Paroxysmal and Persistent Atrial Fibrillation in Preventing Recurrent Episodes of Atrial Fibrillation

Inclusion Criteria: * Patients ≥ 18 years of age, male or female. * Paroxysmal or persistent atrial fibrillation on one occasion, detected on 12-lead ECG or Holter monitoring with atrial fibrillation episode lasting ≥ 30 seconds within last 12 months prior to the screening visit. * Women with childbearing potency must use effective contraception (e.g. implants, hormonal depot injections, combined oral contraceptives, intra-uterine devices or vasectomized partner). Men enrolled in this study must agree to use adequate barrier birth control measures during the treatment period of the study. Reliable contraception should be maintained throughout the study and for 30 days after study drug discontinuation. * Written informed consent signed before any study-specific procedure. Exclusion Criteria: * Permanent AF. * Previous radiofrequency ablation and / or previous surgical therapy of AF. * Heart failure (New York Heart Association \[NYHA\] ≥ II or/and left ventricular ejection fraction \[LVEF\] less than 40%). * Severe coronary artery disease (acute coronary syndrome (ACS) within 6 months prior to the screening visit, previous coronary artery bypass graft \[CABG\] or stabile angina pectoris classified with Canadian Cardiovascular Society \[CCS\] ≥II). The definition of ACS is from the current European Society of Cardiology (ESC) and American College of Cardiology (ACC) / American Heart Association (AHA) guidelines. * Stroke or transient ischemic cerebral attack within 6 months p…