Frederick syndrome in a patient with a history of myopericarditis

Abstract

Background. Frederick’s syndrome is a rare cardiac conduction disorder, characterized by the simultaneous presence of atrial fibrillation and complete atrioventricular block, with extremely low incidence in young patients, especially as a complication following myopericarditis, reported in less than 1% of cases. Objective(s). Presentation of a rare case of Frederick’s syndrome following mixed myopericarditis in a 46-year-old patient, treated with pacemaker implantation and symptom improvement. Materials and methods. A detailed evaluation was performed including patient history, thorough clinical examination, routine laboratory tests and paraclinical investigations, electrocardiogram (ECG), and transthoracic echocardiography to establish an accurate diagnosis and monitor the progression of Frederick’s syndrome in mixed postmyopericarditis. Results. A 46-year-old man with no cardiovascular history developed influenza A pneumonia in February 2024, complicated by viral and bacterial myopericarditis. Four months later, he developed atrial fibrillation resistant to cardioversion, treated with betablockers and anticoagulants. He later reported vertigo, frequent presyncope, weakness, and dyspnea. ECG showed atrial fibrillation and third-degree AV block with a ventricular rate of 30–50 bpm. Echocardiography revealed moderate cardiac dilation and pulmonary hypertension (PASP 48 mmHg). A single-chamber Vitatron Medtronic pacemaker was implanted, improving symptoms with continued medical therapy. Conclusion(s). Frederick’s syndrome following myopericarditis is a rare cardiac complication resulting from impaired cardiac electrical conduction, requiring careful monitoring, an individualized therapeutic approach, and strict adherence to guidelines for managing third-degree AV block.