Objective:To explore the influencing factors of postoperative graft stenosis in patients undergoing left internal mammary artery-left anterior descending branch (LIMA-LAD) coronary artery bypass graft (CABG) surgery.Methods:A retrospective analysis of the clinical data of 86 patients who were admitted to the Second Affiliated Hospital of Hainan Medical College and received coronary angiography after CABG surgery from July 2019 to December 2020 due to recurrent chest tightness, chest pain and other symptoms. According to the degree of stenosis of the LIMA-LAD graft, the patients were divided into stenosis group ( n=25) and non-stenosis group ( n=61). The graft stenosis of patients in the stenosis group was ≥50%, and the graft stenosis of patients in the non-stenotic group was less than 50%. The general information, past medical history, CABG intraoperative data, current visit data and biochemical indicators of the two groups were compared. Measurement data were expressed as mean±standard deviation ( Mean± SD), comparison between groups was by t-test; count data comparison between groups was by Chi-square test. Logistic regression analysis was used to screen out the influencing factors of graft stenosis after CABG. Use the rms package in the R 4.0.2 software to build a nomogram prediction model. Using receiver operating characteristic (ROC) curve to evaluate the discriminative degree of the model. Use the calibration curve and deviation correction C-index to evaluate the nomogram prediction model. Use X-tile software to obtain the cutoff value of the nomogram model integral, use Kaplan-Meier method to draw the survival curve, and use Log-rank to test. Results:Logistic regression analysis showed that smoking, hypertension, pre-CABG left anterior descending branch (LAD) stenosis <75%, pre-CABG left internal mammary artery (LIMA) blood flow, and coronary angiography diffuse lesions are independent risk factors that affect LIMA-LAD graft stenosis after CABG ( P<0.05). The C-index value predicted by the nomogram model was 0.879 (95% CI: 0.818-0.955, P<0.001). The area under the ROC curve was 0.712 (95% CI: 0.594-0.801, P<0.001), with good discrimination. The calibration curve shows that the accuracy of the model prediction was good. Through the X-tile software screening to obtain the model score cutoff value, the patients were divided into low-risk group (≤54 points), medium-risk group (>54 points and ≤112 points), and high-risk group (>112 points). The results of survival analysis showed that the incidence of postoperative graft stenosis in the three groups was 20.9%, 50.0% and 80.0%, respectively. Conclusions:Smoking, hypertension, LAD stenosis before CABG <75%, LIMA blood flow before CABG, and coronary angiography diffuse lessions are independent risk factors that affect LIMA-LAD graft stenosis after CABG. The construction of a nomogram prediction model can provide a reference for evaluating the patency of the LIMA-LAD graft vessel before CABG operation, and reduce the probability of LIMA-LAD graft vessel stenosis after CABG operation.