Neutrophil-to-lymphocyte ratio as an independent risk factor for slow flow/no-reflow after percutaneous coronary intervention in patients with acute myocardial infarction: a single-center retrospective cohort study

Abstract Background Slow flow/no-reflow after percutaneous coronary intervention (PCI) is a common complication of acute myocardial infarction (AMI) and is associated with larger infarct size and worse outcomes, yet simple tools for pre-procedural risk estimation remain limited. We investigated whether the neutrophil-to-lymphocyte ratio (NLR) independently predicts slow flow/no-reflow after PCI in patients with AMI, and whether adding high-sensitivity cardiac troponin I (hs-cTnI) and culprit-vessel location improves prediction. Methods This single-center retrospective study included consecutive patients with AMI who underwent PCI between January 2023 and December 2025. Slow flow/no-reflow was defined as a post-procedural Thrombolysis in Myocardial Infarction (TIMI) flow grade of 2 or less in the culprit vessel. Multivariable logistic regression identified independent risk factors. Discrimination was assessed with the area under the receiver operating characteristic curve (AUC); the combined model was compared with NLR alone using paired bootstrap testing of the AUC difference and a nested likelihood-ratio test. Internal validation used bootstrap optimism correction and 10-fold cross-validation. Results Of 305 patients, 53 (17.4%) developed slow flow/no-reflow. Log-transformed NLR (odds ratio [OR] 1.88, 95% confidence interval [CI] 1.22–2.88, P = 0.004) and log-transformed hs-cTnI (OR 1.24, 95% CI 1.01–1.53, P = 0.043) were independent risk factors, whereas a left anterior descending culprit vessel, including the left main, was inversely associated with slow flow/no-reflow (OR 0.44, 95% CI 0.22–0.86, P = 0.016). The combined model achieved an AUC of 0.735 (95% CI 0.659–0.805) versus 0.674 for NLR alone (ΔAUC 0.061, 95% CI 0.003–0.123, P = 0.039); the optimism-corrected AUC was 0.719 and the 10-fold cross-validated AUC 0.722, and calibration was good (Hosmer–Lemeshow P = 0.101). Adding thrombus burden, left ventricular ejection fraction, AMI type, age, or sex did not improve discrimination (ΔAUC ≤ 0.002). Conclusions NLR is an independent risk factor for slow flow/no-reflow after PCI in patients with AMI. Combining NLR with hs-cTnI and culprit-vessel location adds discriminative value that is retained after internal validation. NLR is easy to obtain at admission and may support pre-procedural risk stratification, but external validation is needed before clinical use.