AIM  To investigate the effect of advanced heparinization on infarct-related vessel (IRA) bl-ood flow before emergency percutaneous coronary intervention (PCI) in patients with ST-segment elevation myocardial infarction (STEMI) and its time dependence.

  METHODS  A total of 376 STEMI patients who received emergency PCI within 12 hours after onset were randomly divided into experimental group (n=181) and control group (n=195).The experimental group received intravenous injection of unfractionated heparin (UFH) 60 U/kg immediately after diagnosis, with a maximum dose of 5000 U. In the control group, UFH2000 U was used in the artery after successful puncture. Both groups were supplemented to 80～100 U/kg before PCI. The blood flow of IRA before PCI, the proportion of slow blood flow, hospital death, heart failure, bleeding and hospital stay after PCI were compared between the two groups. The effect-s of symptom onset to UFH administration time and UFH administration to coronary angiography time on IRA recanalization were analyzed.

  RESULT  The recanalization rate of IRA before PCI in the experiment-al group was higher than that in the control group, while the thrombus aspiration and hospital stay in t-he experimental group were significantly lower than those in the control group (P<0.05).The proportion of visible intracoronary thrombus before PCI, slow flow after PCI, in-hospital heart failure, bleeding and death was lower in the experimental group than in the control group, and the difference was not statistically significant. Advanced heparinization was positively correlated with IRA recanalization before PCI (OR=1.819, 95%CI: 1.166～2.837, P<0.05). In the experimental group and the control group, there was a time dependence between symptoms onset to UFH administration time and IRA recanalization (<3 hours: 50.0% vs. 29.2%, P<0.05), symptoms onset to UFH administration time negatively correlated with IRA recanalization before PCI (OR=0.945, 95%CI: 0.816～0.986, P<0.05). In the experimental group, the proportion of IRA recanalization before PCI was higher in t-he patients whose time from UFH administration to coronary angiography was more than 30 minutes, and the difference was statistically significant (P<0.05), the time from UFH administration to coronary angiography more than 30 minutes was positively correlated with IRA recanalization before PCI (OR=2.610, 95%CI: 1.153～5.911, P<0.05).

  CONCLUSION  Advanced heparinization increases the recanalization rate of IRA before emergency PCI in STEMI patients, improves the prognosis, and do not increases the risk of bleeding. The earlier UFH is given after the onset of symptoms, the stronger the effect of improving IRA recanalization is. The use of UFH immediately after diagnosis can be used as an auxiliary anticoagulant regimen for PCI in STEMI patients without UFH contraindications.