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).