Impact of smoking on outcomes in patients with ST-segment elevation myocardial infarction treated with primary percutaneous coronary intervention.

INTRODUCTION: Smoking is a well­established risk factor for cardiovascular diseases. However, in patients with ST­segment elevation myocardial infarction (STEMI), smoking has been associated with better clinical outcomes; this phenomenon became known as the "smoker's paradox." OBJECTIVES: The aim of this study was to evaluate the association between smoking and clinical outcomes in STEMI patients treated with primary percutaneous coronary intervention (PCI), using 3 large national registries. PATIENTS AND METHODS: We retrospectively analyzed the data of 82 235 hospitalized STEMI patients treated with primary PCI. Among the analyzed population, 30 966 patients (37.96%) were smokers, and 51 269 (62.36%) were nonsmokers. We evaluated the baseline characteristics, pharmacotherapy, clinical outcomes, and readmission causes in a 36­month follow­up. RESULTS: The smokers were significantly younger (median [interquartile range] age, 58 [52-64] vs 68 [59-77] years; P <0.001) than the nonsmokers, and there were more men in this group. The patients who smoked were less likely to have traditional risk factors, as compared with the nonsmokers. In the unadjusted analysis, in­hospital and 36­month mortality and rehospitalization rates were lower in the smokers group. However, after adjustment for baseline characteristics that differed between the 2 groups, the multivariable analysis showed that tobacco use was one of the independent risk factors for 36­month mortality (hazard ratio, 1.11; 95% CI, 1.06-1.18; P <0.001). CONCLUSIONS: In the present large­scale, registry­based analysis, the observed lower 36­month crude rates of adverse events among the smokers, as compared with the nonsmokers, might be partially explained by a significantly lower burden of traditional risk factors and younger age of the smokers. After accounting for age and other baseline differences, smoking was found to be one of the independent risk factors for 36­month mortality.