Abstract： AIM To investigate the risk factors for in-stent restenosis(ISR)in coronary heart disease patients who were admitted to hospital 5 years after coronary stent implantation.METHODS A total of 103 coronary heart disease patients who received drug-eluting stent implantation for the first time in our hospital from January 2016 to December 2017 and underwent coronary angiography again in our hospital 5 years after the procedure were selected as the study subjects.According to the coronary angiography results,they were divided into an in-stent restenosis(ISR)group(n=49)and a non-ISR group(n=54).Univariate analysis was used to compare the relevant clinical data between the two groups,and logistic regression analysis was performed on the relevant factors with statistically significant differences.RESULTS The low-density lipoprotein cholesterol(LDL-C),glycated hemoglobin(P<0.05),and D-dimer levels(P<0.01)in the ISR group were higher than those in the non ISR group.The family history of coronary heart disease and postoperative smoking rate in the ISR group were higher than those in the non ISR group(all P<0.05).The ROC curve was used to analyze the predictive value of various factors on the occurrence of ISR after PCI.The results showed that the area under the ROC curve of LDL-C in predicting the presence of ISR was 0.943(P<0.01),the optimal critical value was 2.34 mmol/L,the sensitivity was 85.7%,and the specificity was 94.4%;The area under the ROC curve of D-dimer is 0.778(P<0.01),and the optimal critical value is 0.49 μ G/L,sensitivity of 63.3%,specificity of 85.2%;The area under the ROC curve of glycated hemoglobin is 0.702(P<0.01),with an optimal critical value of 7.45%,sensitivity of 51.0%,and specificity of 98.1%.The area under the ROC curve of a family history of coronary heart disease was 0.599(P=0.082),and the area under the ROC curve of postoperative smoking was 0.716(P<0.01).CONCLUSION LDL-C,D-dimer,glycosylated hemoglobin level,family history of coronary heart disease,and smoking cessation after surgery are independent risk factors for ISR.