Abstract: Objective:To investigate the influence of lipoprotein(a) on the residual lesion stenosis of the infarction-related arteries in acute myocardial infarction(MI) patients in whom reperfusion therapy was not performed.To explore the function of Lp(a) in the natural course of MI.Methods:One hundred and twenty-four MI patients who not given reperfusion therapy were underwent coronary angiography in chronic stage.Morning fasting blood was collected and Lp(a),blood sugar,total cholesterol(TC) and triglycerides(TG) were measured.Residual stenosis and TIMI classification were compared between the low Lp(a) group(300 mg/L) and the high Lp(a) group(300 mg/L),non-DM and DM,low-TC(5.69 mmol/L) and high-TC(5.69 mmol/L),low-TG(1.69 mmol/L) and high-TG(1.69 mmol/L) groups.Results:Residual stenosis was more severe in high Lp(a) level group than in low Lp(a) level group(P0.01).TIMI classification in high Lp(a) level group is lower(P0.05).Conclusions:These findings suggest that elevated Lp(a) level aggravate residual lesion stenosis of the infarction-related arteries acute MI patients in whom reperfusion therapy is not performed.The measurement of serum Lp(a) level is propitious to observe the nature course of MI,it might be diagnosable and prognostic factor to evaluate the effect of thrombolytic therapy.