Abstract: Objective　To explore the relationship between smoking and the severity of coronary lesions in male patients ≤45 years old with premature myocardial infarction (PMI). Methods　Two hundred and eighty three male patients ≤45 years old with initial acute myocardial infarction (AMI) and underwent coronary angiography were included in the study. Patients were divided into two groups according to smoking status. The clinical baseline data were compared between the two groups, and binary Logistic regression model was used to analyze the correlation between smoking and SYNTAX score and the severity of coronary lesions. Results　A total of 283 cases were enrolled, and 232 patients (82.0%) were smokers. The leukocyte count, triglyceride (TG), very low density lipoprotein cholesterol (VLDL-C) and lipoprotein(a) were significantly higher in the smoking group than those in the non-smoking group (P＜0.05). SYNTAX score was significantly higher in the smoking group than that in the non-smoking group (P＜0.05). In patients with coronary single-vessel lesion and patients with multi-vessel lesions, the proportion of severe stenosis was significantly higher in smoking group than that in non-smoking group (P＜0.05). Logistic regression analysis showed that after adjusting confounding factors, patients in the smoking group faced a higher risk of a mid-high SYNTAX score (≥23, OR=3.000, 95%CI: 1.152-7.811) and coronary multi-vessel severe stenosis (OR=2.275, 95%CI: 1.098-4.713). Conclusion　Smoking is related with the severity of coronary lesions in male patients ≤45 years old with PMI, which significantly increases the risk of the mid-high SYNTAX score and coronary multi-vessel severe stenosis. 

Key words: smoking, male, coronary angiography, myocardial infarction, coronary stenosis, premature myocardial infarction, SYNTAX score