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.

Catheter ablation of Atrial Flutter has become an accepted alternative to pharmacologic therapy.The current guidelines recommend the catheter ablation at the first episode of AFL (Class IIa) or in any case of recurrent episodes of AFL (Class I). Recent studies have already demonstrated a high degree of procedural efficacy (higher than 90%). However, there are still two main areas of investigation. First, what is the best method to obtain an effective lesion. Second, what is the most reliable method to validate the procedure success.The present study is aimed at investigating these aspects in the current Italian clinical practice.

Inclusion Criteria:

• Patient undergoing ablation of atrial flutter isthmus-dependent
• Patient able to sign an authorization to use and disclose health information or an Informed Consent.
• Patient available to attend scheduled follow-up visits at the center for at least 12 months

Exclusion Criteria:

• Patient is participating in another clinical study that may have an impact on the study endpoints

All consecutive patients, clinically indicated for an atrial flutter ablation, will be enrolled after signing of an informed consent form and an authorization to use and disclose health information.