Prognosis after switching to electronic cigarettes following percutaneous coronary intervention: a Korean nationwide study

Background and Aims. Despite the increasing popularity of electronic cigarettes (E-cigarettes), the prognostic impact of switching to E-cigarettes in smokers with coronary artery disease who have undergone percutaneous coronary intervention (PCI) remains unclear. Methods. Using a nationwide cohort from the Korean National Health Insurance database, 17 973 adults (≥20 years) identified as smokers (based on a health screening examination within 3 years before PCI) who underwent health screening within 3 years after PCI were enrolled to determine changes in smoking habits. Patients were classified as continued combustible cigarette users, successful quitters, or switchers to E-cigarettes. The group switching to E-cigarettes was further divided into dual users (using both combustible and E-cigarettes) and those exclusively using E-cigarettes. Primary outcomes included major adverse cardiac events (MACEs), a composite of all-cause death, spontaneous myocardial infarction, and repeat revascularization. Results. Among the total population, 8951 patients (49.8%) continued using combustible cigarettes, 1694 (9.4%) were switched to E-cigarettes, and 7328 (40.7%) successfully quit smoking after PCI. During a median follow-up of 2.4 years, the cumulative incidence of MACE was lower among E-cigarette switchers (10%) or quitters (13.4%) than among continued combustible cigarette users (17%). When continued combustible cigarette users were used as the reference, the multivariable-adjusted hazard ratios with 95% confidence intervals for MACE were 0.82 (0.69–0.98) for switchers to E-cigarettes and 0.87 (0.79–0.96) for successful quitters. Compared with dual users, entirely switching to E-cigarettes was associated with a significantly lower MACE risk (hazard ratio 0.71; 95% confidence interval 0.51–0.99). Conclusions. Among smokers who underwent PCI for coronary artery disease, switching to E-cigarette use (particularly complete transition) or quitting smoking was associated with reduced MACE risk than with continued combustible cigarette use. Clinical Trial Registration. ClinicalTrials.gov