A previously healthy man in his 40s presented with a 3-month history of progressive dyspnea on exertion. Electrocardiography revealed inverted T waves in the inferior and anterior precordial leads. Echocardiography demonstrated marked hypertrophy of left ventricular (LV) apex. Apical-variant hypertrophic cardiomyopathy was diagnosed and a β-blocker was prescribed, but the patient’s symptoms did not improve.
Cardiac magnetic resonance (CMR) imaging, obtained for further investigation, revealed that the LV apical cavity was completely obliterated by a 5cm × 2.5–cm mass (Figure, A and Video). It was isointense on both precontrast T1-weighted and T2-weighted images. The mass signal did not change on application of a fat saturation sequence. The mass did not enhance on first-pass perfusion imaging or delayed hyperenhancement imaging. These tissue characteristics on the CMR sequences suggested that the apical mass was an apical LV thrombus, not apical hypertrophic cardiomyopathy. Moreover, CMR demonstrated extensive areas of LV endocardial fibrosis (Figure, B). Based on the CMR findings, the diagnosis was changed to endomyocardial fibrosis. β-Blocker therapy was discontinued and replaced with corticosteroids, and anticoagulation was started. Subsequently, the patient’s condition improved gradually.