 ST-elevation myocardial infarction STEMI is an urgent symptom associated with sudden myocardial ischemia and ST segment elevated in ECG. Primary percutaneous coronary intervention PCI re-open infarct artery efficiently for STEMI patients. However, patients are readmitted shortly after the primary PCI for several unfavorable clinical outcomes including thrombosis in stent, recurrence of myocardial infarction, stroke, and heart failure. This study is intended to test the predictive ability of a new biomarker soluble ST2 sST2 in peripheral blood. Previous studies have shown that elevated sST2 is highly associated with unfavorable clinical outcomes of patients with ischemia heart diseases and heart failure. This study will further investigate the ability of sST2 to predict unfavorable outcomes for STEMI patients after primary PCI. 