The study aims to assess the right and left atrial electrophysiological substrate in atrial fibrillation patients using the invasive electroanatomic map (basal and with extraestimulus) as well as its correlation with cardiac magnetic resonance and electrocardiographic imaging. The results will also be compared when the patient is in sinus rhythm and atrial fibrillation.

Inclusion Criteria:

• Atrial fibrillation paroxysmal or persistent with criteria for percutaneous ablation

Exclusion Criteria:

• Cardiomiopathy (FEVI<40%) or significant valvulopathy.
• MRI not possible or contraindicated.
• Previous atrial fibrillation ablation.

Patients with persistent or paroxysmal atrial fibrillation, without cardiomyopathy (LVEF> 40%) or significant valvulopathy who will undergo first AF ablation.