Abstract： Objective:To investigate the risk factors for combined coronary microvascular dysfunction (CMD) in patients with ischemia and non-obstructive coronary artery disease (INOCA).Methods:From October 2020 to May 2022, 100 INOCA patients with myocardial ischemic symptoms who underwent coronary angiography (CAG) suggestive of <50% stenosis in all three coronary arteries at the Tenth People′s Hospital of Tongji University were prospectively recruited. Myocardial perfusion imaging (MPI), transthoracic echocardiography and cadmium-zinc-telluride (CZT) SPECT coronary flow quantification were performed in the same month, and 93 INOCA patients (36 males and 57 females, age (63.0±10.9) years) were finally included. CMD was defined as coronary flow reserve (CFR)<2.5. Independent-sample t test, Mann-Whitney U test and χ2 test were used to compare MPI results and left ventricular volume parameters between CMD and non-CMD groups. ROC curve analysis was used to analyze the efficacy of each index in predicting CMD, and independent risk factors for CMD were screened by multivariate logistic regression analysis. Results:Among 93 INOCA patients, 29 were in the CMD group and 64 were in the non-CMD group. The age, proportion of hypertension, left ventricular mass index (LVMI), summed stress score (SSS), summed difference score (SDS), left ventricular internal diameter systolic (LVIDS), interventricular septum thickness (IVST), and left ventricular posterior wall thickness (LVPWT) in the CMD group were higher than those in the non-CMD group ( t values: 2.42-3.76, χ2=8.94, z values: -3.31, -3.41, all P<0.05). ROC curve analysis showed that LVMI, SSS, SDS, LVPWT, IVST and age were significant in predicting CMD (AUCs: 0.67-0.72). Multivariate logistic regression analysis showed that LVMI (odds ratio ( OR)=1.08, 95% CI: 1.01-1.17), SDS ( OR=5.37, 95% CI: 1.95-14.78), hypertension ( OR=5.68, 95% CI: 1.34-24.18) and age ( OR=1.10, 95% CI: 1.03-1.18) were risk factors for CMD. Conclusion:LVMI, SDS, hypertension and age are strongly associated with combined CMD in INOCA patients, which can be used for early risk stratification of INOCA patients.