This is a prospective, observational, blinded study that will be conducted in two parts. The first study will assess the relationship between lipids/lipoproteins and fibrin clot properties among anticoagulated atrial fibrillation patients with and without renal dysfunction. The second study will assess the effects of statin therapy on lipids/lipoproteins and fibrin clot properties in anticoagulated atrial fibrillation patients with renal dysfunction. Renal dysfunction is defined as an estimated glomerular filtration rate below 50 ml/min/1.73m2 for the purposes for this trial.