The "LEONARDO" study is a non-randomized, multicenter, prospective study in which consecutive patients indicated for Atrial Flutter isthmus-dependent (AFL) ablation will be enrolled. Patients can be treated with any market released catheter for ablation. The decision to perform the ablation of AFL will be made based on clinical evaluation of the investigators according to their clinical practice. The study does not require specific surgical techniques. Patient time commitment for the study is approximately 12 months.The study has been designed to describe the italian clinical practice in relation to the approach of AFL ablation. In particular, the investigators will describe the methods for the validation of ablation success, the techniques adopted, and the patient management approaches in the participating centers.