Endomyocardial Fibrosis Associated With Hypereosinophilic Syndrome: Diagnostic and Management Insights From a Case Report.

Endomyocardial fibrosis (EMF) is a rare form of restrictive cardiomyopathy associated with eosinophilic disorders, characterized by apical subendocardial fibrosis and thrombus formation. Cardiac magnetic resonance (CMR) provides a comprehensive, noninvasive evaluation, enabling diagnosis, assessment of disease activity, and guidance of therapy. A 73-year-old man with a history of chronic eosinophilia was referred following detection of left ventricular hypertrophy and T-wave inversion on electrocardiogram. Transthoracic echocardiography was inconclusive. CMR revealed a nondilated left ventricle with mildly impaired systolic function, severe left atrial enlargement, and no inducible ischemia. Late gadolinium enhancement demonstrated apical subendocardial fibrosis extending into the right ventricular apex, with an overlying left ventricular thrombus. These findings were diagnostic of EMF. The patient was treated with a direct oral anticoagulant. At 8-month follow-up, repeat CMR showed resolution of the thrombus and persistent fibrotic scarring. Quantitative T2 mapping demonstrated normal values, excluding ongoing myocardial inflammation. Immunosuppression was therefore not initiated, and anticoagulation was continued. The patient remained clinically stable without thromboembolic events. This case highlights the pivotal role of CMR in diagnosing and managing EMF. LGE imaging provided the characteristic pattern of apical fibrosis with thrombus, while T2 mapping enabled discrimination between chronic fibrosis and active inflammation, guiding therapy away from unnecessary immunosuppression. CMR thus represents the gold-standard imaging modality in EMF, offering both diagnostic confirmation and longitudinal monitoring of treatment response.