Abstract:A 64-year-old female patient received a 3-week treatment regimen of sintilimab (200 mg, d1), oxaliplatin (200 mg, d1) and tegafur gimercil and oteracil porassium capsule (60 mg, bid, d1~14) for gastric cardia adenocarcinoma. On the 7th day of the second cycle of treatment, the patient developed backache. Laboratory tests showed abnormal cardiac biomarkers. ECG presented abnormal Q waves in leads III and aVF, and flat T waves. After excluded from atherosclerosis-induced coronary artery disease via coronary CT scan, the patient was then diagnosed with immune-related myocarditis. The anti-cancer drugs were discontinued, and the patient was treated with methylprednisolone for 9 days, after which the symptoms relieved and the values of cardiac injury markers significantly decreased. Myocarditis is a rare and severe adverse effect of sintilimab, thus clinicians should closely monitor changes in cardiac injury markers and symptoms in patients receiving this drug.