Ablation procedure
Informed consent was obtained for all patients and the procedure was scheduled after 4 to 6 hours of fasting. Sedation with intravenous midazolam and buprenorphine was used as necessary during ablation. Bipolar electrograms were filtered through a bandpass of 30 to 500 Hz and recorded at high gains (0.1 mV/cm) at a paper speed of 100 mm/ sec. Femoral venous access was obtained to introduce three catheters into the RA. A steerable quadripolar catheter (Xtrem; Ela Medical, Le Plessis-Robinson, France deflectable quadripolar catheter; Bio) was positioned within the coronary sinus (CS). A Lifewire decapolar catheter 2-8-2 (St. Jude Medical, St. Paul, MN, USA) was positioned on the right atrium lateral wall. A 8mm tip ablation catheter EZ Street 8mm Biosense Webster, Diamond Bar (USA) or Therapy 8mm Abott-StJude medical, St Paul, Minn, (USA) were used to deliver a maximum power of 70 W and a maximum target temperature of 70 degrees. The ablation was performed under fluoroscopy or with 3 dimensional mapping system (Carto 3, Biosense Webster, Diamond Bar (USA) or Precision Abott-StJude medical, St Paul, Minn, (USA)) for patients undergoing concomitant pulmonary vein isolation (PVI) for atrial fibrillation ablation. The validation of the ablation efficacy was assessed after cessation of atrial flutter for patients in common flutter at baseline and after obtaining a stable bidirectional isthmus block at least 20 min after ablation.