Association of lymphocyte-to-monocyte ratio with the no-reflow phenomenon in patients who underwent a primary percutaneous coronary intervention for ST-elevation myocardial infarction Alparslan Kurtul, Mikail Yarlioglues, Ibrahim Etem Celik, Mustafa Duran, Deniz Elcik, Alparslan Kilic, Fatih Oksuz and Sani Namik Murat Background Recently, it has been shown that the lymphocyte-to-monocyte ratio (LMR) is a novel inflammatory marker. A decreased LMR is associated significantly with a high risk for vascular endpoints in patients with peripheral arterial disease. We aimed to investigate whether LMR on admission is associated with no-reflow after a primary percutaneous coronary intervention (PCI) in patients with ST-elevation myocardial infarction (STEMI). Patients and methods A total of 857 patients (mean age 58.9 ± 13.1 years, 75.6% men), who were admitted to our hospital for STEMI and undergoing primary PCI within 12 h of onset of symptoms, were recruited. LMR was calculated by dividing the lymphocyte count by the monocyte count. The patients were divided into two groups according to the postprocedural thrombolysis in myocardial infarction (TIMI) flows: no-reflow and normal-reflow. No-reflow was defined as a final TIMI flow of 2 or less or final TIMI flow of 3 with a myocardial blush grade of less than 2. Results Admission LMR levels were significantly lower in patients with no-reflow than in patients with normal-reflow (1.85 ± 1.01 vs. 3.64 ± 1.74, P < 0.001). A receiver-operating characteristic analysis indicated that an LMR value of less than 2.292 and had a 76.3% sensitivity and a 72.5% specificity in predicting no-reflow. Multivariate analysis showed that LMR less than 2.292 [odds ratio (OR) 2.657, P = 0.030], Killip class at least 2 at admission (OR 3.442, P = 0.039), baseline infarct artery patency (OR 0.260, P = 0.004), neutrophil count (OR 1.213, P = 0.002), and total stent length (OR 1.059, P = 0.001) were independent factors for predicting no-reflow. Conclusion Our results suggested that LMR could be a simple and useful marker to predict high risk of patients for no-reflow in patients with STEMI who underwent primary PCI. Coron Artery Dis 26:706–712 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. Coronary Artery Disease 2015, 26:706–712 Keywords: lymphocyte-to-monocyte ratio, no-reflow phenomenon, primary percutaneous coronary intervention, ST-elevation myocardial infarction Department of Cardiology, Ankara Education and Research Hospital, Ankara, Turkey Correspondence to Alparslan Kurtul, MD, Department of Cardiology, Ankara Education and Research Hospital, Ankara, Turkey Tel: + 90 506 235 8669; fax: + 90 312 3633396; e-mail: alpkurtul@yahoo.com Received 29 May 2015 Revised 29 July 2015 Accepted 7 August 2015 Introduction Primary percutaneous coronary intervention (PCI) improves prognosis and is the current standard of care for acute ST-segment elevation myocardial infarction (STEMI) patients [1]. Despite successful recanalization of the infarct-related artery, perfusion of the ischemic myocardium is not or is incompletely restored in up to 30% of patients; this is referred to as the no-reflow phe- nomenon [2,3]. The no-reflow phenomenon is associated with short-term and long-term adverse clinical outcomes, including mortality in patients with STEMI [4,5]. The mechanisms of the no-reflow phenomenon are complex and multifactorial. The pathophysiology of no-reflow involves microvascular obstruction secondary to distal embolization of clot, microvascular spasm, inflammation, and thrombosis [6,7]. Noninvasive markers of the no- reflow phenomenon may provide important prognostic information. The systemic inflammatory response, which is usually measured by peripheral blood-based parameters, such as C-reactive protein, neutrophil, or platelet count, has been shown to be a predictive factor in various cardiovascular diseases, including STEMI [8–10]. Lymphocytes and monocytes are also key immune cells in the inflammatory response and a lower lymphocyte count and a high monocyte count have been associated independently with the prognosis of various cardiovascular diseases [11 –17]. The lymphocyte-to-monocyte ratio (LMR) is another inflammatory marker [18]. Recently, studies have shown that LMR is associated with prognosis in various cancers [18–20]. However, to the best of our knowledge, the clinical availability of LMR in cardiovascular diseases has not been known. Therefore, the aim of the present study was to investigate the predictive value of admission LMR for postinterventional no-reflow phenomenon in patients with STEMI treated with primary PCI. 706 Original research 0954-6928 Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/MCA.0000000000000301 Copyright r 2015 Wolters Kluwer Health, Inc. All rights reserved.