Evaluation of Two Different Regimens of the Antiarrhythmic Drug Amiodarone to Maintain Normal Sinus Rhythm After Electrical Cardioversion in Patients With Persistent Atrial Fibrillation

\--- The goal of this clinical trial is to learn if reduced doses of amiodarone can treat atrial fibrillation (AF) effectively while minimizing toxic side effects in patients with persistent AF after electrical cardioversion. The main questions it aims to answer are: * Can a reduced dose of amiodarone (100 mg/day) maintain sinus rhythm as effectively as the standard dose (200 mg/day) 12 months post electrical cardioversion? * What are the adverse effects of the standard and reduced doses of amiodarone during 12 months post electrical cardioversion? * How do genetic polymorphisms affect the efficacy and safety of amiodarone? * How do amiodarone plasma levels correlate with the maintenance of sinus rhythm and genetic polymorphisms? Researchers will compare the standard dose (200 mg/day) to the reduced dose (100 mg/day) to see if the reduced dose offers a better balance between efficacy and safety. Participants will: * Be treated with full dose amiodarone (200 mg/day) during the first month after electrical cardioversion. * Be randomized to either continue with the full dose (200 mg/day) or switch to the reduced dose (100 mg/day). The study is a multicenter, randomized clinical trial involving 312 patients with persistent AF after successful electrical cardioversion. Participants will be followed for 12-18 months to monitor the recurrence of AF and adverse effects.