Refractory Right Ventricular Myocarditis Induced by Immune Checkpoint Inhibitor despite Therapy Cessation and Immune Suppression

Background: Immune checkpoint inhibitors (ICIs) are currently widely used for treatment of various types of cancers. ICI-induced myocarditis, though uncommon, accounts for high risk of major adverse cardiac events and mortality, which makes appropriate diagnosis important. We here present a unique, challenging case of ICI-induced, refractory and isolated right ventricular myocarditis. Case Presentation A 32-year-old female with breast cancer presented with new onset chest pain and dyspnea shortly after initiation of Pembrolizumab. Coronary angiography showed normal coronary arteries and a cardiac magnetic resonance (CMR) revealed myocarditis primarily involving the right ventricle with chamber dilation and severe dysfunction. ICI therapy was stopped, and high dose steroid therapy was initiated and symptoms resolved. However, three months after initial presentation, the patient was hospitalized for DKA and decompensated right heart failure, and a repeat cardiac MRI at that time showed recurrent, isolated right ventricular ventricular (RV) myocardial inflammation/edema without LV involvement. High dose steroid therapy was started again and at 6-month follow up, surveillance CMR continued to show persistent right-sided myocarditis, patient was eventually treated with Abatacept with resolution of HF symptoms, RV dysfunction and dilation at 9-month follow up. Conclusions: We describe a unique case of isolated ICI-induced right ventricular myocarditis leading to right ventricular failure, that was refractory despite ICI therapy cessation and immune suppression by repeated high dose steroids. Co-stimulatory pathway modulation with Abatacept eventually lead to the normalization of RV function and dilation nine months after initial myocarditis onset.