Posterior Mitral Isthmus Line With Vein of Marshall Ethanolisation Compared With Anterior Mitral Lines in Patients With Persistent Atrial Fibrillation

The goal of this clinical study is to find out which treatment works best for people with persistent atrial fibrillation (a type of irregular heartbeat). Researchers are comparing two types of heart ablation procedures: * An anterior mitral line ablation (a treatment at the front part of the heart) * A posterior mitral line ablation (at the back of the heart), sometimes with an extra step using a small vein called the Vein of Marshall The main questions the study aims to answer are: * Which approach works better at fixing the heart rhythm? * Which approach is safer (less complications)? People who take part in this study will: * Undergo an ablation procedure as part of their standard care * Attend follow-up visits at 1, 3, and 6 months * Have tests like ECGs, heart ultrasound (echocardiogram), blood tests, heart rhythm monitors (Holter), and a heart CT scan

Inclusion Criteria: * Patients between the ages of 18 and 80 years, diagnosed with symptomatic persistent AF with clinical indication for left atrial ablation with a mitral isthmus line. Pulmonary vein will be isolated in all patients before starting the mitral isthmus line (during a previous or the same procedure) Exclusion Criteria: * Previous mitral line or any other left atrial ablation beyond pulmonary vein isolation * Left atrial (LA) thrombus. LA thrombus can be determined by preprocedural imaging: CT, transesophageal echocardiography or MRI. * LA diameter greater than 60 mm on long axis parasternal view, or left atrial volume more than 250 cc. * Left ventricular ejection fraction \