Clinical Strategy for the Diagnosis and Treatment of Immune Checkpoint Inhibitor–Associated Myocarditis

Importance: In the last decade, immune checkpoint inhibitors (ICIs) have been approved for the treatment of many cancer types. Immune checkpoint inhibitor-associated myocarditis has emerged as a significant and potentially fatal adverse effect. Recognizing, diagnosing, and treating ICI-associated myocarditis poses new challenges for the practicing clinician. Here, the current literature on ICI-associated myocarditis is reviewed. Observations: Clinical presentation and cardiac pathological findings are highly variable in patients with ICI-associated myocarditis. Although endomyocardial biopsy is the criterion standard diagnostic test, a combination of clinical suspicion, cardiac biomarkers (specifically troponin), and cardiac imaging, in addition to biopsy, is often needed to support the diagnosis. Importantly, the combination of a cytotoxic T-lymphocyte-associated protein 4 inhibitor with a programmed cell death protein 1 or programmed death-ligand 1 inhibitor increases the risk of developing ICI-associated myocarditis. Conclusion and Relevance: This review aims to provide a standardized diagnostic and therapeutic approach for patients with suspected ICI-associated myocarditis. A complete history of recent cancer treatments and physical examination in combination with cardiac biomarkers, cardiac imaging, and endomyocardial biopsy represent a pragmatic diagnostic approach for most cases of ICI-associated myocarditis. The addition of novel biomarkers or imaging modalities is an area of active research and should be evaluated in larger cohorts.