Abstract
A case of atrial fibrillation and premature ventricular complexes (PVC) in a patient with mitral valve prolapse and mitral annular disjunction is described. Rhythm disturbances occurred after a new coronavirus infection. Also, the patient has a history of combined treatment of left breast cancer, which contributed to the appearance of myocardial fibrosis as an arrhythmogenic substrate. Due to the ineffectiveness of conservative antiarrhythmic therapy, a radiofrequency catheter procedure was performed, which proved unsuccessful. The purpose of the article is to present the possible causes of cardiac arrhythmias and the role of magnetic resonance imaging in the diagnosis of arrhythmogenic myocardial fibrosis and mitral annular disjunction.