Palpitations and a Left Ventricular Mass: An Odd Presentation of Left Dominant Arrhythmogenic Cardiomyopathy

A 20-year-old woman presented with palpitations. Echocardiography demonstrated a left ventricular mass involving the posterolateral apical wall and protruding into the ventricular cavity. Evaluation with magnetic resonance imaging (MRI) suggested fatty consistency with all edges well defined except the medial, which was ill defined, raising concern for an invasive liposarcoma. Open core needle biopsy demonstrated mature adipocytes infiltrating the myocardium with extensive interstitial fibrosis. The diagnosis was left-dominant arrhythmogenic cardiomyopathy. Two-year MRI follow-up demonstrates no change in size. This case illustrates the use and limits of cardiac MRI and the value of open cardiac biopsy in diagnosis.