Association between preoperative neutrophil-to-lymphocyte ratio and left internal mammary artery end-diastolic velocity in patients undergoing CABG

Background: Systemic inflammation has been implicated in endothelial dysfunction and adverse cardiovascular outcomes. The neutrophil-to-lymphocyte ratio (NLR) is a readily available marker of systemic inflammation; however, its relationship with preoperative left internal mammary artery (LIMA) end-diastolic velocity (EDV) remains poorly understood. We evaluated the association between preoperative NLR and native LIMA EDV in patients undergoing coronary artery bypass grafting (CABG). Methods: This prospective observational study included 150 consecutive patients undergoing isolated CABG. Patients were categorized by preoperative NLR as low (<2), intermediate (2-4), or high (>4). Preoperative LIMA Doppler ultrasonography assessed vessel diameter, flow volume, peak systolic velocity (PSV), and EDV. Associations were evaluated using Spearman correlation and univariable and multivariable linear regression analyses. Results: Of 150 patients, 40 (26.7%), 104 (69.3%), and 6 (4.0%) were classified into the low, intermediate, and high NLR groups, respectively. C-reactive protein (CRP) differed significantly across all three groups (all adjusted p≤0.029), while fibrinogen and erythrocyte sedimentation rate (ESR) were higher in the intermediate and high groups than in the low group. Among LIMA Doppler parameters, only EDV showed a graded decrease across NLR categories (median 35, 27, and 20 cm/s, respectively; all pairwise adjusted p≤0.014); diameter, flow volume, and PSV did not differ significantly. NLR was strongly inversely correlated with LIMA EDV (Spearman's rho=-0.885, p<0.001), while CRP, fibrinogen, and ESR also showed significant inverse correlations. In multivariable analysis, higher NLR remained independently associated with lower LIMA EDV after adjustment for demographic characteristics, cardiovascular risk factors, and left ventricular ejection fraction (B=-6.298, 95% confidence inter val: -7.071 to -5.524; p<0.001). Conclusion: Higher preoperative NLR was independently associated with lower native LIMA EDV, while other inflammatory markers were also inversely associated with EDV. These findings indicate an association between systemic inflammatory status and native LIMA diastolic hemodynamics but do not establish causality or clinical prognostic significance. Prospective studies incorporating postoperative graft assessment and clinical follow-up are warranted.