Löffler's endocarditis associated with unusual ECG change mimicking posterior myocardial infarction.

A73-year-old man with a history of bronchial asthma and atrial fibrillation was admitted to our hospital because of dyspnea and back pain. Blood analysis revealed a marked increase in total blood cell and eosinophil counts. The creatine kinase and creatine kinase-MB increased slightly. The ECG demonstrated significant ST-segment depression that mimicked acute posterior myocardial infarction. Emergent coronary angiography showed no stenotic lesions. The histological findings in endomyocardial biopsy showed thickened endocardium associated with significant eosinophilic infiltration, which was compatible with Löffler's endocarditis. After the administration of prednisolone, the patient's general condition, eosinophilia, ECG abnormalities, and histological findings were improved dramatically. The endomyocardial biopsy in the acute phase was helpful for diagnosis and therapeutic decision-making.