The spectrum of angiography‐derived IMR according to morphological and physiological coronary stenosis in patients with suspected myocardial ischemia

BACKGROUND: Coronary 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. METHODS: The 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. RESULTS: Of 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. CONCLUSION: In patients with suspected myocardial ischemia, coronary microcirculation is significantly associated with morphological and physiological coronary stenosis. (ClinicalTrials.gov: NCT05435898)