150 patients with common atrial flutter were randomized to 3 groups of 50 patients and each group underwent ablation catheter ablation with CelsiusTMDS® 8 mm, 3.5 mm irrigated tip Thermocool® or Thermocool® SF respectively. After the procedure, patients are being followed by clinical reviews, electrocardiograms at the 3rd, 6th and 12th months, 24h ECG-Holter examination at the first and 6th month and monthly phone consultation. Rate of recurrence and presence of other supraventricular arrhythmias are being recorded during follow-up.