The aim of the study was to determine clinical and echocardiographic predictors of effective cardioversion in patients with typical atrial flutter (AFl). We evaluated 430 patients with typical AFl: 377 (87.7 %) males and 53 (12.3 %) females with mean age 57.0±0.5 years, hospitalized for cardioversion. Among those patients 315 (73.3 %) had coronary artery disease and 115 (26.7 %) – myocardiofibrosis. Concomitant arterial hypertension was diagnosed in 282 (65.6 %) patients. Heart failure NYHA I class was diagnosed in 53 (12.3 %), NYHA II class – in 265 (61.6 %), NYHA III class – in 112 (26 %) patients. The mean duration of arrhythmia episode was 80.8±6.4 days. All subjects underwent echocardiography. Pharmacological cardioversion was ineffective in all of them. According to effectiveness of the cardioversion (transesophageal stimulation or electrical) patients were divided into two groups: 1st (n=391) – with conversion into sinus rhythm and 2nd (n=39) – with ineffective cardioversion. 2nd group patients frequently had concomitant atrial fibrillation (53.8 % vs. 19.9 %, Р<0.0001), thyroid abnormalities (25.6 % vs. 12.8 %, Р=0.03), chronic obstructive pulmonary diseases (30.8 % vs 13 %, Р=0.003), and had significantly longer AFl episode (143.8±4.9 vs 74.5±5.0 days, Р=0.002). Amplitude of F wave on ECG was significantly reduced (2.6±0.1 vs 2.9±0.05 mm, Р=0.01) as well as A wave amplitude on the transesophageal ECG (8.3±0.6 vs 13.4±0.3 mm, Р<0.0001). Left ventricular dilatation was detected as well. In conclusion, patients with typical AFl and ineffective cardioversion significantly more frequently had concomitant pathology, i.e. atrial fibrillation, thyroid abnormalities, chronic obstructive pulmonary diseases and left ventricular dilatation. Electrophysiological remodeling of the atria led to the significantly reduced F wave on ECG and A wave on the transesophageal ECG.