Endomyocardial Biopsies in the Diagnostic Workup of Immune Checkpoint Inhibitor Associated Myocarditis.

PURPOSE OF REVIEW: To identify the role of endomyocardial biopsy in the diagnosis, prognostication, and future understanding of mechanisms for immune checkpoint inhibitor myocarditis. RECENT FINDINGS: The use of endomyocardial biopsy in immune checkpoint inhibitor myocarditis has led to recognizing a spectrum of disease that correlates with mild symptoms to more fulminant presentations. The primary infiltrate observed is CD8+ T cells but more studies are suggesting that the presence of CD68+ macrophages may portend worse prognosis. Currently, endomyocardial biopsy still has a role in diagnosing immune checkpoint inhibitor myocarditis especially when there is uncertainty from non-invasive diagnostic tools. Emerging evidence suggests endomyocardial biopsy can help with prognosis determination and potentially even guide future cancer therapy. Future research into understanding mechanisms of immune checkpoint inhibitor myocarditis will require endomyocardial biopsy for tissue acquisition.