Objective To investigate the expression of serum human cartilage glycoprotein 39(YKL-40)and soluble growth stimulating gene 2 protein(sST2)in elderly patients with acute myocardial infarction(AMI)and their relationship with myocardial fibrosis and myocardial injury.Methods From January 2020 to April 2023,a cohort of 212 AMI patients admitted in Department of Cardiovascular Diseases of Dongguan Hospital of Traditional Chinese Medicine were enrolled and assigned into the patient group,and another 80 ostensibly healthy volunteers taking physical examinations during the same period were subjected and served as control group.Serum levels of YKL-40 and sST2 and the indicators related myocardial fibrosis and injury[including hyaluronic acid(HA),type Ⅲ procollagen(PCⅢ),type Ⅲ procollagen amino terminal peptide(PⅢNP),cardiac troponin Ⅰ(cTnⅠ),creatine kinase isoenzyme(CK-MB),and N-terminal B-type natriuretic peptide precursor(NT-proBNP)]at admission were detected,and the correlation of serum YKL-40 and sST2 levels with myocardial fibrosis and injury was analyzed.According the occurrence of ma-jor adverse cardiovascular events(MACE)during 28-day follow-up,the patients were stratified in-to MACE(68 cases)and non-MACE(144 cases)subgroups.Multivariate logistic regression analysis was employed to analyze the determinants of serum YKL-40,sST2,myocardial fibrosis,and myocardial injury to the occurrence of MACE.Results The patients had significantly higher serum levels of YKL-40,sST2,PCⅢ,HA,PⅢ NP,cTnⅠ,CK-MB and NT-proBNP than the con-trol group(P＜0.01).Both serum YKL-40 and sST2 levels were positively correlated with the levels of PC Ⅲ,HA,PⅢ NP,cTnⅠ,CK-MB and NT-proBNP.The serum levels of YKL-40,sST2,PCⅢ,HA,PⅢNP,cTnⅠ,CK-MB and NT-proBNP were obviously higher in the MACE sub group than the non-MACE sub group(P＜0.01).Multivariate logistic regression analysis indicated that YKL-40(OR=1.964,95％CI:1.643-2.348,P=0.000),sST2(OR=2.457,95％CI:2.020-2.989,P=0.000),PC Ⅲ(OR=1.654,95％CI:1.312-2.084,P=0.000),HA(OR=1.505,95％CI:1.185-1.912,P=0.001),PⅢ NP(OR=1.483,95％CI:1.120-1.963,P=0.006),cTnⅠ(OR=1.365,95％CI:1.102-1.690,P=0.004),CK-MB(OR=1.514,95％CI:1.009-2.272,P=0.045)and NT-proBNP(OR=1.824,95％CI:1.011-3.290,P=0.046)were influencing factors for MACE in elderly AMI patients.Conclusion Serum YKL-40 and sST2 levels are abnormally higher in elderly AMI patients,and are closely associated with myocardial fibrosis and injury.