Background and Aim Of the Study: To investigate the effect of myocardial injury on the prognosis of patients with severe or critical coronavirus disease 2019 (COVID-19).Methods: Between February 10, 2020 and March 31, 2020, data of severe and critical COVID-19 patients were collected and retrospectively analyzed. Admission data included age, heart rates, mean arterial pressure, and myocardial injury markers including creatine kinase isoenzyme-MB (CK-MB), myoglobin, N-terminal pro-B-type natriuretic peptide (NT-proBNP), and interleukin-6. The endpoints included mortality, the incidence of malignant arrhythmia, and mechanical ventilation time. Univariate regression analysis, multivariate linear regression analysis, and binary logistic analysis were performed to develop the risk predictors in myocardial injury to the prognosis of severe and critical COVID-19 patients.Results: Seventy-four COVID-19 patients were included (mean age of 67.2 ± 14.6 years, male of 66.2%), including 42 severe and 32 critical cases. The mortality was 62.2% (n = 46). CK-MB (odds ratio = 5.895, p < .001, 95% confidence interval: 3.097-8.692) and interleukin-6 (odds ratio = 0.379; p = .005; 95% confidence interval: 1.051-1.769) were independent risk factors of increased mechanical ventilation time; myoglobin (odds ratio = 7.710; p = .045; 95% confidence interval: 1.051-56.571) were the independent predictor of incidence of malignant arrhythmia; age (odds ratio = 1.077; p = .009; 95% confidence interval: 1.019-1.139), myoglobin (odds ratio = 9.480; p = .032; 95% confidence interval: 1.211-78.188), and NT-proBNP (odds ratio = 4.852; p = .047; 95% confidence interval: 0.956-24.627) were the independent predictors of mortality.Conclusions: In severe and critical COVID-19 patients, the obvious myocardial injury was observed. Increases of CK-MB, myoglobin, NT-proBNP, interleukin-6, and age were independently associated with poor prognosis including increased ventilation duration, the incidence of malignant arrhythmia, and mortality. [ABSTRACT FROM AUTHOR]