Objective To explore the correlation between serum thymosin α1 level and left ventricular ejection fraction(LVEF)in patients with acute anterior wall ST-segment elevation myocardial infarction(STEMI)after receiving percutaneous coronary intervention(PCI).Methods A total of 74 patients with acute anterior wall STEMI(acute anterior wall STEMI group)and 38 patients having no myocardial infarction(control group),who were admitted to the Shanghai Sixth People's Hospital of China from December 2019 to February 2022,were enrolled in this study.According to the LVEF value after the recanalization of anterior descending coronary artery with PCI during hospitalization period,the patients of acute anterior wall STEMI group were divided into LVEF＜50％subgroup(n=33)and LVEF≥50％subgroup(n=41).Serum thymosin α1 level was determined by enzyme linked immunosorbent assay(ELISA),the results were compared between the groups.Logistic regression analysis was used to analyze the correlation between thymosin α1 level and LVEF.The receiver operating characteristic(ROC)curve of serum thymosin α1 level for predicting cardiac function in patients with acute anterior wall STEMI after receiving PCI was drawn.Results The serum thymosin α1 level in LVEF≥50％subgroup was significantly higher than that in the LVEF＜50％subgroup(P=0.032).During the post-PCI hospitalization period,the serum thymosin α1 level was positively correlated with LVEF.Logistic regression analysis revealed that serum thymosin α1 level was an independent predictor for LVEF＜50％in patients with acute anterior wall STEMI after receiving PCI.The area under ROC of serum thymosin α1 level for predicting LVEF≥50％in patients with acute anterior wall STEMI during hospitalization was 0.644(P=0.034).The area under ROC of serum thymosin α1 level combined with peak troponin I level and with peak NT-proBNP level for predicting LVEF＜50％in patients with acute anterior wall STEMI during hospitalization was 0.780(P＜0.01)and 0.702(P=0.003)respectively.When taking the median serum thymosin α1 level as the cut-off value,the proportion of LVEF≥50％patients was higher among the patients having the post-PCI serum thymosin α1 level＞2,890 ng/L.Conclusion In patients with acute anterior wall STEMI,the serum thymosin α1 level is closely related to the LVEF value during the post-PCI hospitalization period,it is an independent predictor for cardiac function improvement after PCI.It is expected that the serum thymosin α1 level may become a new indicator for predicting the improvement of cardiac function in patients with STEMI after recanalization of anterior descending coronary artery with PCI.