Smoker's Paradox in Patients With ST-Segment Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention.

BACKGROUND Prior studies have found that smokers undergoing thrombolytic therapy for ST-segment elevation myocardial infarction have lower in-hospital mortality than nonsmokers, a phenomenon called the "smoker's paradox." Evidence, however, has been conflicting regarding whether this paradoxical association persists in the era of primary percutaneous coronary intervention. METHODS AND RESULTS We used the 2003-2012 National Inpatient Sample databases to identify all patients aged ≥18 years who underwent primary percutaneous coronary intervention for ST-segment elevation myocardial infarction. Multivariable logistic regression was used to compare in-hospital mortality between smokers (current and former) and nonsmokers. Of the 985 174 patients with ST-segment elevation myocardial infarction undergoing primary percutaneous coronary intervention, 438 954 (44.6%) were smokers. Smokers were younger, were more often men, and were less likely to have traditional vascular risk factors than nonsmokers. Smokers had lower observed in-hospital mortality compared with nonsmokers (2.0% versus 5.9%; unadjusted odds ratio 0.32, 95% CI 0.31-0.33, P<0.001). Although the association between smoking and lower in-hospital mortality was partly attenuated after baseline risk adjustment, a significant residual association remained (adjusted odds ratio 0.60, 95% CI 0.58-0.62, P<0.001). This association largely persisted in age-stratified analyses. Smoking status was also associated with shorter average length of stay (3.5 versus 4.5 days, P<0.001) and lower incidence of postprocedure hemorrhage (4.2% versus 6.1%; adjusted odds ratio 0.81, 95% CI 0.80-0.83, P<0.001) and in-hospital cardiac arrest (1.3% versus 2.1%; adjusted OR 0.78, 95% CI 0.76-0.81, P<0.001). CONCLUSIONS In this nationwide cohort of patients undergoing primary percutaneous coronary intervention for ST-segment elevation myocardial infarction, we observed significantly lower risk-adjusted in-hospital mortality in smokers, suggesting that the smoker's paradox also applies to ST-segment elevation myocardial infarction patients undergoing primary percutaneous coronary intervention.