Immune checkpoint inhibitor–associated myocarditis with ST-segment elevation-like electrocardiogram: a case report

Immune checkpoint inhibitor (ICI)–associated myocarditis (ICIAM) is a rare yet potentially life-threatening complication. Its clinical and ECG manifestations are nonspecific, posing challenges for early diagnosis and increasing the risk of misdiagnosis. A 61-year-old male with lung adenocarcinoma and a history of tuberculosis developed chest tightness, palpitations, elevated cardiac troponin I (cTnI), and ST-segment elevation in leads V1–V4 after three cycles of chemotherapy combined with ICI. Initially diagnosed as an acute ST-elevation myocardial infarction (STEMI), coronary angiography ruled out obstructive coronary disease. Despite standard STEMI treatment, symptoms persisted, accompanied by frequent ventricular premature beats, ventricular tachycardia, and persistently high cTnI levels, which were inconsistent with typical STEMI progression. Suspecting ICIAM, the patient was treated with low-dose methylprednisolone (40 mg/day) instead of high-dose pulse therapy (500–1000 mg/day) to reduce the risks of infection and tuberculosis reactivation. Symptoms improved, arrhythmias subsided, and cTnI levels declined rapidly. ICIAM may mimic STEMI on ECG, necessitating careful differentiation. For high-risk patients unsuitable for high-dose glucocorticoids, low-dose regimens may serve as an effective individualized treatment.