Background The incidence of no reflow phenomenon limits the clinical outcomes of percutaneous coronary intervention (PCI). This randomized controlled study was designed to evaluate the immediate protective effects of intensive stalin pretreatment on myocardial perfusion and myocardial ischemic injury during PCI.Methods Altogether 228 patients with acute coronary syndrome (ACS) were randomly assigned to standard stalin group (SS group, n=115) and intensive statin group (IS group, n=113). Patients in the SS group received 20 mg simvastatin and patients in the IS group received 80 mg simvastatin for 7 days before PCI. Thrombolysis in myocardial infarction (TIMI) flow grade (TFG), corrected TIMI frame count (CTFC) and TIMI myocardial perfusion grade (TMPG) of the intervened vessel were recorded before and after stent deployment. Creatine kinase (CK) isoenzyme MB, troponin I and plasma level of high sensitive-C reactive protein (hs-CRP), P-selectin and intercellular adhesion molecule (ICAM) were measured before and 24 hours after the procedure.Results The TFG after stent deployment was significantly improved with less TIMI 0-1 and more TIMI 3 blood flow in the IS group than in the SS group (all P<0.05). Patients with no reflow phenomenon were less in the IS group (P<0.001). The CTFC was lower in the IS group than in the SS group (P<0.001). TMPG was also improved in the IS group than in the SS group (P=0.001). Although PCI caused a significant increase in CK-MB 24 hours after the procedure, the elevated CK-MB value was lower in the IS group than in the SS group (18.74±8.41 vs 21.78±10.64, P=0.018). Similar changes were also found in troponin I (0.99±1.07 in the IS group vs 1.47±1.54 in the SS group, P=0.006). CK-MB elevation occurred in 27.8% (32/115) of the patients in the SS group vs 15.9% (18/113) in the IS group (P=0.030). Myocardial necrosis was detected in 4.4% (5/115) of the patients in the SS group, whereas 0.9% (1/113) in the IS group (P=0.341). But no myocardial infarction was found. Similarly, the patients with increased level of troponin I were much more in the SS group (36.5%, 42/115) than in the IS group (19.5%, 22/113) (P=0.04). Among them, myocardial necrosis was detected in 13.0% (15/115) of the patients in the SS group, while 4.4% (5/113) in the IS group (P=0.021). Myocardial infarction was found in 4.4% (5/115) of the patients in the SS group and 0.9% (1/113) in the IS group (P=0.213).Conclusions Intensive statin pretreatment for 7 days before PCI can further improve myocardial blood perrusion, protect the myocardium from ischemic injury. These effects are associated with the lowered levels of hs-CRP, P-selectin and ICAM.