CONGRESS ABSTRACT

Over the past decade, immune checkpoint inhibitors (ICIs) have dramatically transformed the treatment of several solid and hematologic malignancies. Despite their proven clinical benefit, ICIs are associated with immune-related adverse events (irAEs), among which cardiovascular toxicities are increasingly recognized as rare but potentially life-threatening complications. In particular, ICI-associated myocarditis is characterized by high mortality, a frequently fulminant course, and a markedly arrhythmogenic phenotype, often involving conduction disturbances and heart failure with reduced ejection fraction. Concomitant peripheral myositis, occasionally leading to respiratory failure, may further worsen prognosis. We report three cases of ICI-associated myocarditis observed at our hospital, highlighting the heterogeneity of clinical presentation, management and outcomes. All patients were male and had advanced-stage malignancies, including non–small cell lung cancer, clear cell renal carcinoma, and urothelial carcinoma. Cardiovascular symptoms developed shortly after the first or second cycle of immunotherapy. Clinical manifestations ranged from cardiogenic shock and sustained ventricular tachyarrhythmias to high-grade atrioventricular block (file 3) , accompanied by marked elevation of cardiac and muscle injury biomarkers. In all cases, coronary angiography excluded obstructive coronary artery disease. Two patients, who were not candidates for advanced therapies due to significant comorbidities, experienced rapid clinical deterioration with fatal outcomes; the diagnosis of ICI-associated myocarditis was confirmed at autopsy (file 1) . The third patient, presenting with overlapping myocarditis and myositis with extraocular muscle involvement, showed clinical and functional improvement following early initiation of high-dose corticosteroids and additional immunosuppressive therapy with tocilizumab (file 2) . These cases emphasize the critical importance of early recognition, prompt diagnostic evaluation, and timely initiation of immunosuppressive treatment in patients with suspected ICI-related myocarditis. Further research is needed to better define the underlying pathogenic mechanisms, identify high-risk patients, and develop effective preventive and therapeutic strategies to reduce cardiovascular complications associated with immune checkpoint inhibition.