['To determine whether tirofiban can prevent microcirculation dysfunction during delayed percutaneous coronary intervention (PCI) of spontaneously recanalized and severe narrowing coronary artery in patients with acute myocardial infarction.', '62 patients who have a single angiographically confirmed narrowing culprit coronary artery for more than 75% between 7 and 14 days after the onset of acute myocardial infarction were randomly divided into the tirofiban group (32 cases) and the placebo group (30 cases). All the patients received measurement of the index of microcirculatory resistance (IMR) before tirofiban/placebo administration and PCI. After PCI, IMR value was measured again.', 'There was no significant variation between the two groups before PCI (11.67 ± 6.45 of placebo group vs. 14.65 ± 12.45 of tirofiban group, P=0.158). After PCI, the IMR value of the tirofiban group is significantly lower than that of the placebo group (23.63 ± 9.91 of placebo group vs. 16.75 ± 9.98 of tirofiban group, P=0.008).'] Does intracoronary injection of tirofiban prevent microcirculation dysfunction during delayed percutaneous coronary intervention in patients with acute myocardial infarction?