Eosinophilic Myocarditis: A Challenging Diagnosis

Abstract

Eosinophilic myocarditis (EM) is a rare subtype of myocarditis that is characterized by eosinophilic infiltration of the myocardium and is associated with peripheral eosinophilia in most cases. The diagnosis is suspected in the presence of acute myocarditis and peripheral eosinophilia and is usually confirmed by endomyocardial biopsy (EMB) before starting steroid therapy. Here, we present a case of severe idiopathic eosinophilic myocarditis in a young man with a history of asthma and peripheral eosinophilia. He was treated with high-dose steroids despite negative EMB, and we noted a dramatic improvement in cardiac function. Our case highlights the importance of cardiac magnetic resonance (CMR) and clinical judgment in establishing the diagnosis of EM irrespective of the histopathologic result.

Keywords: cardiac magnetic resonance imaging; endomyocardial biopsy; eosinophilic myocarditis; hypereosinophilic syndromes; peripheral eosinophilia.

Figure 1. Electrocardiogram shows a right bundle branch block and a left anterior fascicular block

Figure 2. A. Transthoracic echocardiography (apical four-chamber view) shows severe LV dilation and dysfunction; B. Estimated EF using Simpson’s method

LV: left ventricle, EF: ejection fraction

Figure 3. CMR demonstrates diffuse subepicardial gadolinium enhancement (white arrows) in short axis (A) and apical four-chamber view (B) compatible with myocarditis

Note the presence of pericardial effusion (red arrow). CMR: cardiac magnetic resonance

Figure 4. A. Transthoracic echocardiography (apical four-chamber view) shows an improvement in LV function; B. Estimated EF using Simpson’s method

LV: left ventricle, EF: ejection fraction