Acute effects of smoking on QT dispersion in healthy males

BACKGROUND: Cigarette smoking increases the risk of ventricular fibrillation and sudden cardiac death (SCD). QT dispersion (QTD) is an important predictor of cardiac arrhythmia. The aim of this study was to assess the acute effect of smoking a single standard cigarette containing ۱.۷ mg nicotine on QT interval and QTD in healthy smokers and nonsmokers. METHODS: The study sample population consisted of ۴۰ healthy male hospital staff, including ۲۰ smokers and ۲۰ nonsmokers. They were asked to refrain from smoking at least ۶ h before attending the study. A ۱۲-lead surface electrocardiogram (ECG), recorded at paper speed of ۵۰ mm/s, was obtained from all participants before and ۱۰ min after smoking of a single complete cigarette. QT interval, corrected QT interval, QTD, and corrected QT dispersion (QTcD) were measured before and after smoking. RESULTS: Smokers and nonsmokers did not have any significant differences in heart rate (HR) (before smoking = ۶۷.۳۵ ± ۵.۱۴ vs. ۶۷.۷۰ ± ۵.۰۷, after smoking = ۷۶.۷۰ ± ۶.۵۰ vs. ۷۶.۸۵ ± ۶.۵۰, respectively), QTD (before smoking = ۳۷.۷۵ ± ۷.۱۶ vs. ۳۹.۱۵ ± ۶.۵۵, after smoking = ۴۴.۷۵ ± ۱۱.۹۷ vs. ۴۵.۵۰ ± ۹.۵۸, respectively), and QTcD (before smoking = ۳۹.۸۵ ± ۷.۴۰ vs. ۴۱.۵۵ ± ۶.۵۷, after smoking = ۵۰.۷۰ ± ۱۴.۳۱ vs. ۵۱.۵۰ ± ۱۱.۷۱, respectively). However, after smoking a single cigarette, HR, mean QTD, and QTcD significantly increased (all had P value <۰.۰۰۱) in comparison to the measures before smoking. CONCLUSION: Smoking of a single complete cigarette in both smokers and nonsmokers results in significant QTD increase, which can cause arrhythmia and SCD.   Keywords: Cardiac, Death, Electrocardiography, Smoking, Sudden