Abstract: Objective  To determine the effects of heparin therapy before primary percutaneous coronary intervention (pPCI) on patients with acute STsegment elevation myocardial infarction (STEMI). Methods  A total of 117 STEMI patients were consecutively enrolled and randomly divided into observation group and control group. The STEMI patients of  observation group were immediately  given intravenous injection of 5 000 U unfractionated heparin, while those in  control group received the same dose of unfractionated  heparin during the surgery. The activation time of heparin,  activated coagulation time (ACT) before PCI,  peak value of myocardial injury markers,  index of  microcirculation resistance(IMR) of myocardia,  and other evaluation indexes of myocardial perfusion were observed. Major adverse events (MAES) after the operation were also recorded. Results  Compared with the control group,  observation group had significantly earlier administration of heparin (about 28 min),  longer ACT  (P=0.000),  and lower rate of high thrombus load (25.00% vs  43.90%, P=0.032); imagingready infarct related artery(IRA) TIMI flow rate 01 lower (45.00% vs  68.40%，P=0.011),  higher rate of  TIMI myocardial perfusion grading(TMPG) 3(75.30% vs 56.10%，P=0.032),  lower IMR (P=0.007) lower peak value of CKMB(P=0.007),  and smaller perfusion defect area(PDA) (P=0.031). Conclusion  Early heparin therapy before pPCI can improve IRA opening,  reduce total myocardial ischemia time,  and myocardial infarction area,  and ameliorate myocardial perfusion.  And it does not increase the risk of MAES.

Key words: coronary disease; , heparin;angioplasty, , transluminal, , percutaneous coronary, angina, unstable