Etiology of Atrial Fibrillation The most common causes of atrial fibrillation are Hypertension Coronary artery disease Cardiomyopathy Valvular heart disorders: mitral stenosis, mitral regurgitation, tricuspid regurgitation Hyperthyroidism Binge alcohol drinking (holiday heart) Less common causes of atrial fibrillation include Pulmonary embolism Atrial septal defects and other congenital heart defects Chronic obstructive pulmonary disease (COPD) Myocarditis Pericarditis Lone atrial fibrillation is atrial fibrillation without an identifiable cause in patients < 60 years.