Background: Coronary slow flow (CSF) is an angiographic finding characterized by delayed distal vessel opacification despite normal epicardial coronary arteries. Its pathophysiology is multifactorial and involves microvascular dysfunction, endothelial impairment, and chronic inflammation. The uric acid-to-high-density lipoprotein (HDL) cholesterol ratio (UHR) has recently emerged as a novel composite biomarker reflecting both pro-oxidant and anti-inflammatory balance. This study aimed to evaluate the relationship between UHR and CSF.

Methods: In this retrospective cross-sectional study, 218 patients with normal or near-normal coronary arteries on angiography were analyzed. Patients were divided into 2 groups according to the presence of CSF based on thrombolysis in myocardial infarction (TIMI) frame count. Demographic, clinical, and laboratory parameters were compared between groups. Receiver operating characteristic (ROC) analysis was used to determine the discriminatory performance of UHR, and multiple logistic regression was performed to identify independent predictors of CSF.

Results: The mean UHR value was significantly higher in the CSF group compared with the control group (0.13 ± 0.04 vs. 0.09 ± 0.04, P < .001). Receiver operating characteristic analysis demonstrated that a UHR cut-off >0.107 predicted CSF with moderate discriminatory ability (area under the curve (AUC) = 0.733, 95% CI: 0.66-0.79, P < .001), with 73.5% sensitivity and 76.2% specificity. Multiple analyses suggested that UHR was independently associated with CSF (OR 1.20 per 0.01-unit increase, 95% CI 1.09-1.31, P < .001).

Conclusion: Elevated UHR was independently associated with CSF and may represent a readily available biomarker reflecting the metabolic-inflammatory balance contributing to coronary microvascular dysfunction. These findings should be interpreted as associative and hypothesis-generating.