Randomized controlled trial of acute use of electronic cigarette or tobacco cigarette on parameters of ventricular repolarization.
Non-user or chronic electronic cigarette (EC) users will use an EC or control on three occasions:1) EC with nicotine, 2) EC without nicotine, 3) empty EC (control).
Chronic tobacco cigarette (TC) smokers will use a TC or control on three occasions: 1) TC with nicotine (subject's own brand), 2) research TC with very low nicotine, 3) straw (control). The electrocardiogram will be recorded before and after acute exposures and analyzed for parameters representative of ventricular repolarization.