A study published today in Circulation: Arrhythmia and Electrophysiology, a peer-reviewed journal of the American Heart Association, found that synthetic cooling ingredients added to e-cigarettes caused irregular heartbeats and increased cardiovascular risk in mice and lab-grown human heart cells. The research is the first to show that these cooling agents, commonly used in flavored vapes, may negatively affect heart health.
The study tested the effects of synthetic coolants WS-3 and WS-23, which are widely used in e-cigarettes to create a chilling sensation without a distinct flavor. These coolants fall outside restrictions that target characterizing flavors, allowing their continued use in many products. According to the study, adding these coolants to e-cigarettes containing nicotine and solvents increased premature heartbeats in mice, with WS-23 tripling the number compared to nicotine-only aerosols. The coolants also affected heart rate variability, indicating stress responses that raise the risk of high blood pressure and other cardiovascular issues.
In lab-grown human heart cells, coolants did not alter normal resting rhythm but slowed the rhythm and sped up electrical recharge when the cells were hormonally stressed, mimicking the impact of nicotine on stress hormones. The study suggests that coolants could cause arrhythmias by disrupting the heart's electrical timing. Lead researcher Alex Carll, Ph.D., M.S.P.H., noted that tobacco-flavored vapes do not disrupt cardiac conduction as much as those with menthol or synthetic coolants, and that coolant levels in vapes should be considered for regulation.
Sales of e-cigarettes with synthetic cooling ingredients increased 872.1% between 2020 and 2023 in the U.S., according to a 2024 report from the CDC Foundation and Truth Initiative. Menthol-flavored e-cigarette sales also rose by 175.8% during a similar period. These trends underscore the timeliness of the research, as cooling flavors become more popular.
Jason J. Rose, M.D., M.B.A., who was not involved in the study, emphasized that while the FDA authorizes some flavored e-cigarettes for adults, that does not mean they are safe. He urged parents to talk with children about the risks of vaping. The study leaves open questions about long-term effects and impacts on vulnerable populations, such as pregnant women and those with heart disease. More research is needed to confirm these findings in humans.
