Abstract: AIM:To explore circulating markers predictive of angiographic morphologic features indicating burden of thrombus formation in infarct-related arteries (IRA) in the acute phase of ST-segment elevation myocardial infarction (STEMI). METHODS: One hundred and ninety-five consecutive acute myocardial infarction (AMI) patients treated with primary percutaneous coronary intervention (PCI) within 12 h of symptom onset were divided into two groups by cineangiography results obtained during PCI: high-burden thrombus formation (HBTF) group (n=84) and low-burden thrombus formation (LBTF) group (n=111). Blood samples were collected before PCI for measurement of circulating levels of high-sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), soluble intercellular cell adhesion molecule-1 (sICAM-1), p selectin (PS) and white blood cell (WBC) count. RESULTS: The circulating levels of PS and WBC were substantially higher in HBTF patients than those in LBTF patients (13.62±8.13 vs. 7.80±4.17; 11.24±3.62 vs. 10.00±3.35, each P<0.05). Using logistic regression analysis, PS (OR 1.259, 95% CI 1.125-1.408, P=0.000) was an independent predictor of thrombus formation. CONCLUSION: PS level is an independent predictor of angiographic morphological features that indicate high-burden thrombus formation in AMI.