The aim of this study is to evaluate whether performing complex fractionated atrial electrograms ablation improves outcomes in persistent or atrial fibrillation ablation.

Inclusion Criteria:

• Patients with persistent (more than 7 days, or less than 7 days needing pharmacologic or electric cardioversion)
• Presence of atrial fibrillation at the beginning of the procedure

Exclusion Criteria:

• Hypo or hyperthyroidism
• Persistent long-lasting or non-defined duration atrial fibrillation
• Hypertrophic myocardiopathy
• Implantable defibrillation or pacemaker implanted
• Moderate or severe mitral valve disease or mitral prosthetic valve
• Ejection fraction less than 30%
• Left atrial anteroposterior diameter more than 50 mm.
• Previous atrial fibrillation ablation
• Contraindication to anticoagulation
• Left atrium thrombus
• Current infective disease or sepsis
• Pregnant women
• Current unstable angor
• Acute myocardial infarction in last 3 months
• Atrial fibrillation secondary to ionic disturbance, thyroids disease or secondary to any other reversible or non cardiovascular disease
• Reduced expectancy of life (less than 12 months)
• Patient participating in another clinical study that investigates a drug or device
• Psychologically unstable patient or denies to give informed consent
• Any cause that contraindicate ablation procedure or antiarrhythmic drug