Unconventional Approach: Steroid Treatment for Eosinophilic Myocarditis Despite Negative Endomyocardial Biopsy

Eosinophilic myocarditis (EM) is a rare type of myocarditis that can present acutely with rapidly progressing symptoms leading to high rates of morbidity and mortality. EM is defined by eosinophilic infiltration of the myocardium and can be difficult to diagnose even with gold-standard techniques, such as endomyocardial biopsy (EMB), given the possibility of patchy myocardial infiltration. Here, we present a case of idiopathic EM complicated by a cardiac arrest that was empirically treated with high-dose intravenous steroids after negative EMB. The patient's symptoms and cardiac function significantly improved after treatment. This case highlights the ambiguity of certain presentations of EM, its complications, and the importance of empiric treatment to avoid poor outcomes.