We examined 140 atrial fibrillation (AF) patients: mean age 58.67±0.85 years and mean term of last AF episode 8.07±1.86 months. Among them, 86.43 % patients had coronary artery disease; 8.57 % – myocardiofibrosis, 2.14 % – arterial hypertension, 2.14 % – metabolic cardiomyopathy, and 0.76 % – hypertrophic cardiomyopathy. 84.29 % of patients had concomitant arterial hypertension. In 43.5 % patients the current paroxysm was first. Transesophageal echocardiography was performed in all patients. We detected frequent findings of the thrombi formation markers in persistent AF patients group, i.e. dense spontaneous echo contrast, low average left atrial appendage velocity and thrombi. These markers have significant association with such changes in myocardium as signs of systolic and diastolic dysfunction, dilatation of left atrium and ventricle. Frequent detection of the thrombi formation markers make the method of transesophageal echocardiography a useful and indispensable tool in revealing high risk patients before cardioversion and for the detection those for long term anticoagulation therapy.