Association between hemoglobin A1c levels and coronary flow reserve in angina with nonobstructive coronary arteries: a retrospective observational study

Background Hemoglobin A1c (HbA1c) measures chronic glycemic levels, and its elevation is associated with vascular endothelial dysfunction and microcirculatory impairment, contributing to increased cardiovascular risk. In the assessment of angina with nonobstructive coronary arteries (ANOCA), coronary flow reserve (CFR) reflects vasodilatory capacity of the coronary microvasculature and is associated with adverse cardiovascular events, whereas IMR quantifies microvascular resistance during hyperemia. However, the association between HbA1c levels and invasive microvascular indices in ANOCA remains unclear. Methods This study included 104 patients with ANOCA who underwent invasive coronary physiological assessment. CFR and IMR were measured using the thermodilution method. Associations between admission clinical parameters, including demographic characteristics and laboratory variables (particularly HbA1c), and CFR or IMR were examined using univariate and multivariate analyses. Results The study population had a mean age of 65.8 ± 13.0 years, 50.0% were male, mean HbA1c was 6.0 ± 0.7%, mean CFR was 4.3 ± 2.4, and mean IMR was 14.2 ± 8.8. Multivariate analysis demonstrated a significant negative association between HbA1c and CFR (β = −0.250, 95% CI: −1.619 to − 0.155, P = 0.018). In contrast, no significant association was observed between HbA1c and IMR. Conclusions In patients with ANOCA, higher HbA1c levels were independently associated with reduced CFR but not with IMR. These findings suggest a potential association between chronic glycemic status and coronary vasodilatory function in ANOCA.