Aim To investigate the coronary artery lesion characteristics and its clinical implications in patients with acute non-ST-segment elevation myocardial infarction(NSTEMI).Methods 83 patients with acute NSTEMI and 109 patients with acute ST-segment elevation myocardial infarction(STEMI)were enrolled in the study with complete clinical and coronary angiographic data.Comparative analysis was done between the two groups,according to the following aspects such as the number of diseased coronary vessels,the coronary artery stenosis degree,the formation of collateral circulation and the part of clinical features.Results Patients of NSTEMI had less single branch lesions than patients of STEMI,there was a significant difference between them(p<0.05);Three branch lesions in NSTEMI group were more than that in STEMI group,significant difference was found(p<0.05);coronary artery lesions were more than that in patients of STEMI when stenosis degree was not less than 90%,but less in NSTEMI group when stenosis degree was less than 90%,they both have significant differences(p<0.05);cases of total coronary occlusion were similar between the two groups(p>0.05);collateral circulations above grade TIMIⅡ were more likely to see in the patients of NSTEMI,significant difference was also found(p<0.05).All the above coronary artery lesion characteristics decided the clinical features of patients with NSTEMI:the case history of previous angina pectoris and old myocardial infarction occurred more commonly(p<0.05);the peak value of CK-MB was obviously lower(p<0.01);serious acute complications such as acute pulmonary edema,cardiogenic shock and fatal arrhythmia were also remarkablely lower(p<0.05).LVEF,the mortality of patients with coronary heart disease being followed up for 3 years and patients among the hospitalization period showed no significant difference between the two groups(p>0.05);but the postinfarction angina pectoris increased obviously in NSTEMI group than that in STEMI group(p<0.05).Conclusions Complex coronary artery lesions,multiple-vessel lesions and severe stenosis,also the existed ischemic preconditioning before attack and collateral circulations were more evident in patients with acute NSTEMI,this is the main reason the non-ST-segment elevation myocardial infarction came into being and that decided the clinical features of patients with acute NSTEMI.