A retrospective study of immune checkpoint inhibitor-associated myocarditis in a single center in China

Background: Immune checkpoint inhibitor ( ICI)-associated myocarditis is a rare and potentially fatal immune-related adverse event (irAE). The study aimed to observe the occurrence of myocarditis caused by ICIs. Methods: The clinical manifestations, diagnosis, and treatment of immune myocarditis were explored through retrospective analysis of the detailed data of typical ICI-associated myocarditis from our center and a literature review. Results: From January 1, 2018, to December 31, 2019, a total of 283 patients were treated with PD-1 or PD-L1 monoclonal antibodies (McAbs) alone or combination therapy at our center. There were 3 cases of ICI-associated myocarditis, of which the incidence rate was 1.06% (3/283); among these cases, 2 were treated with nivolumab alone, and 1 was treated with camrelizumab combined with gemcitabine. One case died on day 56 because of heart and respiratory failure, and the other died on day 34 because of tumor progression. The third case recovered after treatment. The typical clinical manifestations are palpitations, dyspnea, and fatigue. One patient had no clear symptoms. Electrocardiograms (ECG) showed grade 3 of atrioventricular block and frequent ventricular premature contraction in one case, and frequent ventricular and atrial premature contraction in the other case. Most of the cardiac biomarkers decreased or returned to normal after glucocorticoid treatment. Conclusions: ICI-associated myocarditis is a rare adverse event but has a high mortality rate. Early diagnosis of myocarditis and prompt glucocorticoid therapy may be helpful to improve the prognosis.