Concomitant ablation is an effective treatment for patients with various types of atrial fibrillation undergoing heart surgery.

However, recurrences of tachycardias after concomitant ablation can happen and seem to be mostly related to reentry mechanism resulting in atrial tachycardias.

The aim of the study is to perform invasive re-mapping of ablated regions in the atria to assess durability of ablation lesions and prevalence of conduction gaps that can be targets for additional ablation to lower longterm arrhythmia recurrence.

Patients after concomitant ablation for treatment of atrial fibrillation will be enrolled. At ablation procedure pulmonary veins will be isolated and additional ablation lines will be performed in the left atrium (posterior wall box lesion, connecting lesion to the mitral annulus, connecting lesion to the left atrial appendage,...) and the right atrium (intercaval connecting lesion, cavotricuspid isthmus lesion,...) and left atrial appendage will be excluded (suture and excision, clipping device,...) at the discretion and expertise of the operator. Radiofrequency and/or cryoablation will be used at the discretion and expertise of the operator.

Invasive mapping with a high density mapping catheter connected to a three-dimensional electro-anatomical mapping system will be performed to assess pulmonary vein isolation and linear lesion durability 3 months after the initial concomitant ablation. Potential gaps will be identified and ablated with a radiofrequency ablation catheter.

Participants will be followed-up clinically and with holter ECG before and after the invasive re-mapping procedure up to the first year after the concomitant ablation procedure.

Inclusion Criteria:

• all patients scheduled for any kind of elective heart surgery having also indication (EHRA and/or HRS guidelines) to undergo concomitant ablation for any type of atrial fibrillation

Exclusion Criteria:

• life expectancy of less than one year,
• severe heart failure with left ventricular ejection fraction below 35%,
• emergency surgery due to a life threatening condition such as acute aortic dissection, papillary muscle rupture, acute endocarditis, major trauma,...

Patients undergoing elective surgery for treatment of heart valve disease, surgical coronary artery revascularization, benign cardiac tumors,... having also any type of atrial fibrillation with an indication to undergo concomitant ablation.