AbstractBackgroundCoronary microvascular dysfunction is crucial in determining myocardial ischemia; however, the relationship between epicardial coronary diameter stenosis (DS) and the index of microcirculatory resistance (IMR) remains unclear. We sought to explore the distribution of coronary angiography‐derived IMR (angio‐IMR) in patients with suspected myocardial ischemia.MethodsThe study included 480 patients with suspected myocardial ischemia, all of whom underwent coronary angiography. According to the severity of coronary DS, patients were divided into three groups: mild (DS < 50%), intermediate (DS 50%–70%), and severe (DS > 70%). Angio‐IMR and fractional flow reserve (FFR) were calculated based on coronary angiography images through the principle of computational flow and pressure simulation.ResultsOf the 480 patients, the mean age was 67.23 ± 9.44 years, with 55.4% male. There were 193 (40.2%) patients in the mild group, 189 (39.4%) patients in the intermediate group, and 98 (20.4%) patients in the severe group. The average angio‐IMR of the mild group was 30.8 ± 14.9, which was significantly higher than those of the intermediate group (26.7 ± 13.0) and the severe group (17.9 ± 8.4) (p< .001). In the correlation analysis, angio‐IMR was negatively correlated with DS (rho = −0.331,p= .001) and positively correlated with angio‐FFR (rho = 0.483,p< .001). By multivariate logistic regression analysis, angio‐FFR ≤ 0.8 (odds ratio, 0.184; 95% confidence interval, 0.106–0.321) was the only independent predictor of coronary microvascular dysfunction.ConclusionIn patients with suspected myocardial ischemia, coronary microcirculation is significantly associated with morphological and physiological coronary stenosis. (ClinicalTrials.gov: NCT05435898)