Early rhBNP on Myocardial Work in Patients With STEMI

Inclusion Criteria: * 1\. Anterior myocardial infarct (anterior myocardial infarct is defined as persistent chest pain for 30 mins at least, with ST-segment elevation of at least 0.2 mV in two or more contiguous precordial leads) within 12 hours after onsets of symptom; 2\. No contraindication for rhBNP; 3\. Left anterior descending (LAD) as culprit vessel, with TIMI 0-1 grade. Exclusion Criteria: * 1.Cardiogenic shock (systolic BP \<90mmHg after fluid infusion or systolic BP\<100mmHg after vasoactive drugs); 2\. History of myocardial infarct; 3.Severe arrhythmia: with III degree A-V block ,atrial fibrillation,ventricular fibrillation,ventricular tachycardia; 4\. Any history of severe renal or hepatic dysfunction (hepatic failure, cirrhosis, portal hypertension or active hepatitis); neutropenia or thrombocytopenia; known acute pancreatitis; 5\. Pregnant or lactating; 6\. life expectancy≤12 months; 7\. Inability to follow the protocol and comply with follow-up requirements or any other reason the investigator feels would place the patient at increased risk;