Tehran University of Medical Sciences The Research in Heart Yield and Translational Medicine (RHYTHM) 3115-7270 13 3 2018 07 15 108 114 EN Mohammad Alidoosti Tehran Heart Center, Tehran University of Medical Sciences, Tehran, Iran. Reza Lotfi Tehran Heart Center, Tehran University of Medical Sciences, Tehran, Iran. Masoumeh Lotfi-Tokaldany Tehran Heart Center, Tehran University of Medical Sciences, Tehran, Iran. Ebrahim Nematipour Tehran Heart Center, Tehran University of Medical Sciences, Tehran, Iran. Mojtaba Salarifar Tehran Heart Center, Tehran University of Medical Sciences, Tehran, Iran. Hamidreza Poorhosseini Tehran Heart Center, Tehran University of Medical Sciences, Tehran, Iran. Arash Jalali Tehran Heart Center, Tehran University of Medical Sciences, Tehran, Iran. 2017 06 21 2018 03 15 Background: Despite recent advances in interventional equipment and techniques, the angiographic no-reflow phenomenon occurs in a considerable number of patients undergoing primary percutaneous coronary intervention (PCI). We investigated the clinical, angiographic, preprocedural, and procedural characteristics associated with the no-reflow phenomenon among patients undergoing primary PCI. Methods: Between March 2008 and April 2013, 530 patients (78.5% male, mean age=58.11±12.39 y) with ST-segment-elevation myocardial-infarction who underwent primary PCI were categorized in 2 groups according to their postprocedural thrombolysis-in-myocardial infarction (TIMI) flow grades:  those with a maximum score of 2 (the no-reflow or slow-flow group) and the ones with a score of 3 (the reflow group). A multivariable logistic regression model was used to find the multiple correlates of the no-reflow phenomenon after PCI. Results: There were 166 (31.3%) patients in the no-reflow group and 364 (68.7%) in the reflow group. The no-reflow patients were older and had significantly longer target lesion lengths, higher SYNergy between percutaneous coronary intervention with TAXus and cardiac surgery (SYNTAX) scores, higher infarct-related artery SYNTAX scores, more thrombus burden, and a higher frequency of initial TIMI flow grades of 2 or lower. Our multivariable logistic regression analysis demonstrated that older age, higher numbers of Q waves, not using statin, longer target lesion lengths, higher thrombus grades, and higher infarct-related artery SYNTAX scores remained the independent correlates of increased no-reflow rates after primary PCI (area under the ROC curve=0.784,  95% CI: 0.742–0.826; P<0.001). Conclusion: Clinical, angiographic, and procedural features of patients undergoing primary PCI may be correlated with the occurrence of the no-reflow phenomenon. The thrombus grade and the infarct-related artery SYNTAX score could be among these factors. https://rhythm.tums.ac.ir/index.php/jthc/article/view/743 https://rhythm.tums.ac.ir/index.php/jthc/article/download/743/792