Abstract
Eosinophilic myocarditis (EM) is a rare but potentially fatal complication of sustained eosinophilia that is characterized by eosinophilic infiltration into myocardial tissue. There are various etiologies of EM that can be classified into general categories: reactive, clonal, and idiopathic. We present a case of EM caused by chronic eosinophilic leukemia, a rare myeloproliferative neoplasm that frequently presents with sustained peripheral eosinophilia. This case displays several serious complications of EM, including recurrent ventricular tachycardia storm, cardiogenic shock, and mural thrombus formation despite anticoagulation. Diagnosis of EM can be difficult as formal diagnosis requires an endomyocardial biopsy. Once EM is suspected, identifying the underlying etiology of eosinophilia is critical for timely implementation of disease-specific therapy.