Objective:To explore the prognostic evaluating value of serum tenascin-X in patients with acute ST-segment elevation myocardial infarction (STEMI).Methods:The clinical data of 121 patients with STEMI in the Affiliated Sinopharm Dongfeng General Hospital, Hubei University of Medicine from August 2017 to August 2018 were retrospectively analyzed. The clinical data were collected, the serum tenascin-X level was measured by enzyme-linked immunosorbent assay. The patients were followed up for 3 years, the major adverse cardiovascular events (MACE) were identified as endpoint events. The receiver operating characteristic (ROC) curve was used to evaluate the predictive value of serum tenascin-X for MACE in patients with STEMI. The Kaplan-Meier survival curve was drawn, the rates of non-MACE survival in patients with different serum tenascin-X levels were analyzed by log-rank method. Multivariate Cox regression was used to analyze the independent risk factors of MACE in patients with STEMI.Results:Until the end of follow-up, among 121 patients with STEMI, 42 cases (34.7%) developed MACE (MACE group), and 79 cases had not MACE (non-MACE group). The left ventricular ejection fraction (LVEF) in the MACE group was significantly lower than that in the non-MACE group: (47.14 ± 6.70)% vs. (52.67 ± 4.41)%, the C-reactive protein (CRP), B-type natriuretic peptide (BNP), cardiac troponin I (cTnI) and tenascin-X were significantly higher than those in non-MACE group: (27.92 ± 8.06) mg/L vs. (8.77 ± 3.49) mg/L, (918.31 ± 315.47) μg/L vs. (220.47 ± 108.37) μg/L, (214.73 ± 80.46) μg/L vs. (81.35 ± 28.96) μg/L and (110.67 ± 42.55) μg/L vs. (65.21 ± 28.06) μg/L, and there were statistical differences ( P<0.01). ROC curve analysis result showed that the area under the curve of serum tenascin-X to predict the MACE in patients with STEMI was 0.806 (95% CI 0.724 to 0.872), and the optimal cut-off was 93.25 μg/L, the sensitivity was 69.0%, the specificity was 86.1%. Kaplan-Meier survival curve analysis result showed that the rate of non-MACE in 80 patients with low serum tenascin-X level (<93.25 μg/L) was significantly higher than that in 41 patients with high serum tenascin-X level (≥93.25 μg/L): 83.8% vs. 29.3%, and there was statistical difference ( χ2 = 42.47, P<0.01). Multivariate Cox regression analysis result showed that the CRP, BNP and tenascin-X were the independent risk factors of MACE in patients with STEMI ( HR = 1.092, 1.001 and 1.018; 95% CI 1.051 to 1.135, 1.000 to 1.002 and 1.008 to 1.027; P<0.01 or <0.05). Conclusions:The significant increase in serum tendon protein X levels in patients with STEMI has predictive value for the MACE, and it is an independent predictor of MACE within 3 years.