Immune Checkpoint Inhibitor Myocarditis With Normal Cardiac Magnetic Resonance Imaging: Importance of Cardiac Biopsy and Early Diagnosis

Immune checkpoint inhibitors (ICIs) have improved the management and the prognosis of patients with cancer but are associated with an increased risk of toxicities that can affect every organ. ICI-associated myocarditis has a low incidence (< 1%) but a high fatality rate (30%-50%). Herein we report a patient treated with ICI admitted for suspicion of myocarditis. Cardiac magnetic resonance imaging (cMRI) was normal. An endomyocardial biopsy (EMB) was in favour of ICI-related myocarditis with cardiac lymphohistiocytic infiltrate. This case highlights the role of a systematic evaluation with electrocardiography and troponin and the potential value of EMB in patients without a suggestive cMRI.