Fulminant Myocarditis With Prolonged Active Lymphocytic Infiltration After Hemodynamic Recovery

Fulminant myocarditis is a highly mortal syndrome. Meanwhile, the clinical course in surviving patients is generally self-limiting. This is a rare case of fulminant myocarditis with prolonged lymphocytic infiltration after hemodynamic recovery. A 64-year-old man was diagnosed with fulminant myocarditis and required intensive care with veno-arterial extracorporeal membrane oxygenation. Left ventricular function gradually improved but complete atrioventricular block (CAVB) persisted. Follow-up endomyocardial biopsies (EMBs) showed prolonged active infiltration of lymphocytes along with ¹⁸F-FDG uptake in ¹⁸F-FDG PET/CT until about 70 days after the onset. Therefore, he underwent immunosuppressive therapy for 3 months. Follow-up EMB revealed no evidence of infiltration of lymphocytes and no abnormal ¹⁸F-FDG uptake despite irreversible CAVB. Although repeated EMB and ¹⁸F-FDG PET/CT was not a standard strategy, it played an important role in the treatment decision in the present case.