Association between red cell distribution width coefficient of variation and coronary slow flow

Aims: Coronary slow flow (CSF) is an angiographic phenomenon characterized by delayed distal coronary opacification in the absence of significant epicardial stenosis. Red cell distribution width (RDW), a routinely measured hematologic parameter, has been proposed as a potential marker of inflammation and microvascular dysfunction. However, although several studies have demonstrated an association, its role as an independent predictor of CSF remains to be fully established. This study aimed to evaluate the association between RDW coefficient of variation (RDW-CV) and CSF using multivariate logistic regression and receiver operating characteristic (ROC) analyses. Methods: We retrospectively analyzed 153 patients with normal or near-normal coronary arteries on angiography, classified into CSF (n = 73, 47.7%) and non-CSF (n = 80, 52.3%) groups based on corrected TIMI frame counts. Clinical, demographic, and laboratory data were compared between groups. Variables with p < 0.10 in univariate analysis were included in multivariate logistic regression. Diagnostic performance was assessed using ROC curve analysis. Results: RDW-CV values were slightly higher in the CSF group (13.83 ± 1.24%) compared with the non-CSF group (13.69 ± 1.41%, p = 0.419). In multivariate analysis, RDW-CV showed a non-significant trend toward predicting CSF (OR = 1.338, 95% CI: 0.967–1.852, p = 0.079). Hyperlipidemia (n = 31, 40.4% vs. n = 16, 21.7%), CRP, HDL, and LDL were independent predictors of CSF. RDW-CV alone demonstrated poor discriminative ability (AUC = 0.571), whereas the multivariate model achieved good performance (AUC = 0.833). Conclusion: RDW-CV is not a strong stand alone predictor of CSF but may contribute to diagnostic accuracy when integrated with other clinical and laboratory variables. Further prospective studies with larger populations are warranted to clarify its prognostic role.