Objectives There are two kind of atrial flutter during circumferential ablation for atrial fibrillation (AF): new onset left atrial flutter (LAFL), with a history of atrial flutter (AFL). What is the relationship of AFL and AF? Whether there are some differences in clinical course and mechanism between the new onset LAFL and the with a history of AFL remained unclear. The aim of this study was to assess the impacts of circumferential ablation on the occurrence of arrhythmias in follow-up in 2 groups: (1) patients with a history of AFL and AF, and (2) patients with new onset LAFL. Methods Data from 465 patients who had circumferential pulmonary vein ablation (CPVA) or segmental pulmonary vein ablation (SPVA) were analyzed. Patients with a history of AFL ablation and patients who had concomitant AFL ablation were included from analysis. Forty-one patients constituted the history of AFL group (group 1, aged 57±13 years, 7 females) and twenty-eight patients constituted the new onset LAFL group (group 2, aged 55±12 years, 6 females). bipolar recordings were obtained from the tricuspid annulus, coronary sinus, interatrial septum and left atrium. Target sites were identified by early, fragmented or double potentials and by concealed entrainment. Linear lesions were created between target sites and nearby anatomical barriers (1) typical atrial flutter (cycle length, 242±39 ms). cavotricuspid isthmus ablation was performed. (2) new onset LAFL (cycle length, 282±153 ms). 20 episodes of AAFs were documented in 20/28 (71.4%) patients. Target sites were identified around pulmonary veins (n=10), gap in linear lesion (n=7), left atrial roof lines (1 case). For those cases the ablation line between PV and mitral annulus was performed. Patients in Group 2 had larger left atria, higher incidence of AFL pre-CPVA, and lower ejection fraction. Results There was no significant difference in post-CPVA AF recurrence between Groups 1 and 2, but AFL incidence after CPVA was higher in Group 2 (33% vs 4%, P < 0.0001). Ablation of AFL in group 1 patients resulted in an 88% acute success rate (group 2, 86%) and 12% (group 2,17%) recurrence over a mean follow-up of 287±101 days.Conclusions In patients with a history of atrial flutter, post-CPVA AF recurrence is similar to patients with new onset LAFL. However, LAFL is associated with a higher recurrence of AFL after PVAI. In a significant number of patients with LAFL, mitral Isthmus ablation is needed and can be performed effectively. Its electrophysiological conse-quences could be considered analogus to the results achieved by cavotricuspid isthmus ablation. Objectives There are two kind of atrial flutter for circumferential ablation for atrial fibrillation (AF): new onset left atrial flutter (LAFL), with a history of atrial flutter (AFL). What is the relationship of AFL and AF? differences in clinical course and mechanism between the new onset LAFL and the with history with AFL yet unclear. The aim of this study was to assess the impacts of impact of circumferential ablation on the occurrence of arrhythmias in follow-up in 2 groups: (1) patients with a history of AFL and AF, and (2) patients with new onset LAFL. Methods Data from 465 patients who had circumferential pulmonary vein ablation (CPVA) or segmental pulmonary vein ablation (SPVA) were patients. ablation and patients who had concomitant AFL ablation were included from analysis. Forty-one patients constituted the history of AFL group (group 1, aged 57 ± 13 years, 7 females) and twenty-eight patients constituted the new onset LAFL group (group 2, aged 55 ± 12 years, 6 females). bipolar recordings were obtained from the tricuspid annulus, coronary sinus, interatrial septum and left atrium. Target sites were identified by early, fragmented or double potentials and by concealed entrainment. Linear lesions were created between target sites and nearby anatomical barriers (1) typical atrial flutter (cycle length, 242 ± 39 ms). (2) new onset LAFL (cycle length, 282 ± 153 ms). 20 episodes of AAFs were documented in 20/28 (71.4%) patients. Target sites were identified around pulmonary veins (n ​​= 10), gap in linear lesion (n = 7), left atrial roof lines Patients in Group 2 had larger left atria, higher incidence of AFL pre-CPVA, and lower ejection fraction. Results There was no significant difference in post-CPVA AF recurrence between Groups 1 and 2, but AFL incidence after CPVA was higher in Gro up 2(33% vs 4%, P <0.0001). Ablation of AFL in group 1 patients resulted in an 88% acute success rate (group 2,86%) and 12% (group 2,17%) recurrence over a mean follow- up of 287 ± 101 days. Conclusions In patients with a history of atrial flutter, post-CPVA AF recurrence is similar to patients with new onset LAFL. However, LAFL is associated with a higher recurrence of AFL after PVAI. In a significant number of patients with LAFL, mitral Isthmus ablation is needed and can be performed effectively. Its electrophysiological conse-quences could be considered analogus to the results achieved by cavotricuspid isthmus ablation.