MMP9 and myocardial infarction: Therefore, BNP has a close bearing on myocardial infarction.17 As shown in the results of this study, compared with patients with intravenous bolus of tirofiban, those who received intracoronary bolus of tirofiban have significantly reduced levels of CK-MB, MMP-9 and BNP, indicating that intracoronary bolus of tirofiban may play a role in alleviating myocardial injury of patients with STEMI complicated with diabetes who underwent PCI and found to have high thrombus burden in coronary artery.