Influence of e-cigarettes and their constituents on cardiac rhythm and arrhythmias

Electronic cigarettes (e-cigs) have rapidly gained popularity in the past 20 years. However, the health impacts of their use remain unclear. E-cigs generate aerosols by heating e-liquids containing solvent vehicles, nicotine, additives, and flavorant chemicals. This process not only aerosolizes the liquid ingredients but also generates a complex mixture of by-products, many of which are harmful. Recent studies have demonstrated that inhaling e-cig aerosols can disrupt cardiac electrophysiology and rhythm as well as autonomic regulation of the heart. Furthermore, recent and historical observations indicate that many individual e-cig constituents, such as nicotine, aldehydes, flavorants, polycyclic aromatic hydrocarbons, metals, and carbon monoxide, can impair cardiac electrophysiology and rhythmicity. Although it remains largely unclear which constituents pose the greatest harm, a growing body of in vivo animal experiments, in vitro studies, and clinical studies collectively indicate that e-cigs adversely alter electrophysiology and thus may increase risk for severe and fatal arrhythmias. Nonetheless, more studies are needed to determine how these effects translate to e-cig users and relate to specific constituent compounds. Here, we summarize the existing science detailing how e-cig aerosols and their individual constituents disturb cardiac electrophysiology and promote arrhythmia. Although direct evidence that e-cigs cause arrhythmias in humans remains elusive, research continues to advance the biological plausibility of a causal relationship between e-cig use and life-threatening disruptions in cardiac electrophysiology.