ObjectiveTo explore the independent risk factors for early failure of internal mammary artery grafts after coronary artery bypass grafting (CABG), to construct and preliminarily evaluate a risk prediction model for the decline of internal mammary artery bridges, and to optimize postoperative risk stratification and management strategies for patients. MethodsA retrospective analysis was conducted on patients who underwent CABG at the Fuwai Hospital of the Chinese Academy of Medical Sciences from January 2016 to January 2020. The primary endpoint was the failure of the internal mammary artery bridge one year after surgery, and the secondary endpoint was major adverse cardiac and cerebrovascular events (MACCE) within five years after surgery, including all-cause death, myocardial infarction, stroke, or revascularization. Patients were divided into a failure group and a non-failure group based on whether there was early failure of the internal mammary artery bridge after surgery. Independent risk factors for the failure of the internal mammary artery bridge were explored through the least absolute shrinkage and selection operator regression and multivariate logistic regression, and a failure risk prediction model was constructed and cross-validated. Patients were stratified for MACCE risk according to the total score of independent risk factors, and the 5-year cumulative MACCE-free rate was drawn using the Kaplan-Meier method. ResultsA total of 657 patients were included, among whom there were 54 patients in the failure group, including 38 males and 16 females, with an average age of (61.85±8.03) years; there were 603 patients in the non-failure group, including 467 males and 136 females, with an average age of (60.45±8.23) years. Multivariate logistic regression analysis showed that non-left main lesion [OR=3.28, 95%CI (1.41, 7.62), P=0.006], pulsatility index (PI)>3.0 [OR=2.63, 95%CI (1.20, 5.75), P=0.016], quantitative flow ratio (QFR)>0.80 [OR=5.57, 95%CI (2.98, 10.41), P<0.001] and in-hospital complications [OR=4.02, 95%CI (1.59, 10.19), P=0.003] were independent risk factors for the failure of internal mammary artery grafts after CABG. Compared with the prediction model in previous literature [area under receiver operating characteristic curve was 0.632, 95%CI (0.561, 0.694)], the risk prediction model constructed with QFR>0.80, PI>3.0, non-left main lesion and in-hospital complications had a higher predictive ability for early failure of internal mammary artery grafts [area under curve: 0.758, 95%CI (0.694, 0.820); net reclassification index: 0.272, 95%CI (0.18, 0.37); comprehensive discriminative improvement index: 0.109, 95%CI (0.059, 0.158); P<0.05]; the risk score of independent risk factors for internal mammary artery graft failure demonstrated significant MACCE risk stratification efficiency in the 5-year patient follow-up, with the high-risk group showing a significantly higher incidence of MACCE compared to the medium and low-risk groups (P=0.001). ConclusionQFR>0.80, PI>3.0, non-left main lesions, and in-hospital complications are independent risk factors for early failure of internal mammary artery grafts after CABG. The constructed risk prediction model based on this has preliminary capabilities in predicting the risk of internal mammary artery graft failure and MACCE risk stratification, which is beneficial for the postoperative management of CABG patients and improving their mid-long term prognosis.