CONGRESS ABSTRACT

Immune checkpoint inhibitors (ICIs) are increasingly used in oncology but may cause severe immune-related adverse events, including myocarditis, a rare condition associated with high mortality. Predominant right ventricular (RV) involvement and overlap with neuromuscular toxicity represent an exceptionally uncommon and aggressive presentation. We report the case of a 68-year-old overweight male smoker with bladder cancer treated with pembrolizumab, admitted for acute dyspnea and neck pain, preceded by several days of diplopia. He had no prior cardiovascular history, and baseline echocardiography before ICI therapy showed normal biventricular size and systolic function. On admission, the patient was tachycardic and normotensive, with metabolic acidosis and hyperlactatemia. Electrocardiography revealed an idioventricular rhythm with ST-segment elevation in leads V1–V3. Transthoracic echocardiography demonstrated preserved left ventricular systolic function but severe RV dilation and systolic dysfunction with moderate tricuspid regurgitation. Pulmonary embolism was excluded, while laboratory tests showed markedly elevated high-sensitivity troponin levels. Urgent coronary angiography revealed normal coronary arteries. The patient was admitted to the coronary intensive care unit and treated with inotropic support and intravenous diuretics. Given the severe isolated RV dysfunction and ventricular arrhythmias, ICI-related myocarditis was strongly suspected and high-dose intravenous corticosteroids were promptly initiated. Despite immunosuppressive therapy, the clinical course rapidly deteriorated with progressive biventricular failure and systemic hypoperfusion. Neurological evaluation confirmed myasthenia gravis. Plasma exchange was initiated, followed by escalation to veno-arterial extracorporeal membrane oxygenation and additional immunosuppression with abatacept and ruxolitinib. The disease remained refractory, complicated by multiorgan failure, leading to death 10 days after hospital admission. This case highlights the fulminant nature of ICI-related myocarditis with predominant RV involvement, particularly when associated with neuromuscular immune toxicity. Early recognition of disproportionate RV dysfunction in the presence of elevated cardiac biomarkers and normal coronary arteries is crucial, although prognosis remains poor despite aggressive multidisciplinary management.