Staphylococcus aureus Myocarditis: Case Report and Literature Review

Abstract

Staphylococcus aureus is widely reported to be the most common bacterial cause of myocarditis, and usually occurs in the setting of bacteraemia and sepsis. Rarely, it occurs without associated infective endocarditis. Previous case reports of S. aureus myocarditis occur almost exclusively in immunocompromised patients. We report a case of S. aureus myocarditis with associated inflammatory thrombus in an immunocompromised patient. A 45-year-old man with a previous history of rheumatoid arthritis on long-term methotrexate presented with septic shock. He was found to have a methicillin-sensitive S. aureus bacteraemia. The patient subsequently developed olecranon bursitis requiring surgical wash out. Transthoracic echocardiogram revealed a very atypical echodense mass in the left ventricular apex, with normal systolic function and no associated valvular abnormalities. Cardiac magnetic resonance imaging showed oedema in the endomyocardium, consistent with acute myocarditis, associated with an apical mural thrombus. Repeat cardiac magnetic resonance 3 weeks following discharge from hospital showed marked improvement in endomyocardial oedema and complete resolution of the apical mural thrombus. He was treated with a 12-week course of antibiotics and anticoagulated with apixaban. Staphylococcal myocarditis without endocarditis is a rare disease entity, and significant disease manifestations can arise even without valvular involvement. Cardiac magnetic resonance is a useful diagnostic tool in bacterial myocarditis and characterisation of apical masses detected on transthoracic echocardiogram. The role of direct acting oral anticoagulants in this context remains unclear.