Flecainide Safety in Patients With Coronary Artery Disease and Atrial Fibrillation

The goal of this clinical trial is to learn whether the antiarrhythmic drug flecainide can be used as safely as standard rhythm-control drugs in people with atrial fibrillation (AF) and stable coronary artery disease (CAD). The study includes adults aged 18 years and older who have AF and known but stable coronary artery disease. The main questions this study aims to answer are: * Is treatment with flecainide as safe as standard rhythm-control drugs (sotalol or amiodarone) in this patient group? * Does flecainide lead to similar or fewer serious side effects, hospitalisations, or deaths compared with standard treatment? Researchers will compare patients treated with flecainide to patients treated with standard rhythm-control therapy (sotalol or amiodarone) to see whether flecainide is not worse in terms of safety outcomes. Participants will: * Be randomly assigned to receive either flecainide or standard rhythm-control medication * Take the assigned medication as part of routine clinical care * Attend regular follow-up visits at the hospital and have additional follow-up by telephone * Undergo routine heart tests such as electrocardiograms and echocardiography * Complete questionnaires about symptoms, quality of life, and daily functioning This study follows patients for at least one year and collects information on safety, heart rhythm outcomes, quality of life, and healthcare use.