Abstract 16013: Non-Bacterial Thrombotic Endocarditis and Recurrent Cerebrovascular Accidents in Immune Checkpoint Inhibitor Myocarditis

Background: Nonbacterial thrombotic endocarditis (NBTE) is a rare condition associated with cancer, hypercoagulable state, and systemic emboli including stroke. This report presents a case of NBTE associated with metastatic lung adenocarcinoma and recurrent strokes despite anticoagulation for prior pulmonary embolism (PE) and highlights the challenges in management of NBTE. Case: 66-year-old man with stage IV non-small cell lung adenocarcinoma treated with pembrolizumab complicated by immune checkpoint inhibitor (ICI) myocarditis treated with high dose steroids and PE treated with rivaroxaban, presented with diplopia and gait instability. MRI brain revealed a left corona radiata infarct and rivaroxaban was switched to apixaban. Three weeks later, the patient developed left internal carotid artery (ICA) occlusion, and underwent emergent thrombectomy. A transesophageal echocardiogram revealed a new 1.8 cm mass on the mitral valve with negative blood cultures. Anticoagulation was switched to therapeutic enoxaparin. Cardiothoracic surgery was consulted, though patient opted for palliative care. Decision making: Patient presented with recurrent multifocal strokes despite treatment with multiple direct oral anticoagulants (DOACs), just weeks after ICI myocarditis. The challenges here were approach to anticoagulation in a patient with recurrent strokes despite anticoagulation, the risk of hemorrhagic conversion of stroke, and the mechanism of stroke. The mitral valve mass was presumed to be NBTE, due to his metastatic malignancy and negative blood cultures. However, a recent history of ICI-myocarditis raised the possibility of an immune mediated mechanism of NBTE, given the growing association of auto-immune diseases and NBTE. Conclusion: NBTE is a rare complication of metastatic disease that can commonly lead to stroke and is treated with optimal anticoagulation and addressing the underlying malignancy. However, this case highlights the failure of multiple oral anticoagulants to treat NBTE and raises the question of additional mechanisms of NBTE beyond malignancy and hypercoagulable state. Further studies are required to elucidate a common immune mediated mechanism of NBTE and ICI myocarditis.