Fulminant necrotizing eosinophilic myocarditis after COVID‐19 vaccination survived with mechanical circulatory support

Abstract A 69‐year‐old man was hospitalized for heart failure 7 days after coronavirus disease 2019 (COVID‐19) mRNA vaccination. Electrocardiography showed ST‐segment elevation and echocardiography demonstrated severe left ventricular dysfunction. Venoarterial extracorporeal membrane oxygenation and Impella 5.0 were instituted because of cardiogenic shock and ventricular fibrillation. Endomyocardial biopsy demonstrated necrotizing eosinophilic myocarditis (NEM). Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV2) PCR test was negative. He had no infection or history of new drug exposure. NEM was likely related to COVID‐19 vaccination. He was administered 10 mg/kg of prednisolone following methylprednisolone pulse treatment (1000 mg/day for 3 days). Left ventricular function recovered and he was weaned from mechanical circulatory support (MCS). Follow‐up endomyocardial biopsy showed no inflammatory cell infiltration. This is the first report of biopsy‐proven NEM after COVID‐19 vaccination survived with MCS and immunosuppression therapy. It is a rare condition but early, accurate diagnosis and early aggressive intervention can rescue patients