A new study published today in Circulation: Arrhythmia and Electrophysiology, a peer-reviewed journal of the American Heart Association, reveals that synthetic cooling agents added to e-cigarettes can cause abnormal heartbeats (arrhythmias) and increase cardiovascular risk measures in mice and lab-grown human heart cells. This is the first study to demonstrate that synthetic cooling ingredients, such as WS-3 and WS-23, may negatively affect heart health.
The U.S. restricts the sale of many flavored e-cigarettes, like cotton candy flavors, to reduce youth appeal. However, most states exempt menthol and other cooling ingredients that create a chilling sensation. These cooling agents, including WS-3 and WS-23, are increasingly popular because they reduce harshness and make inhalation feel smoother. According to a 2024 report from the CDC Foundation and Truth Initiative, sales of e-cigarettes with synthetic cooling ingredients increased 872.1% between 2020 and 2023 in the U.S., while menthol-flavored e-cigarette sales rose 175.8% from 2019 to 2023.
In the study, researchers exposed mice to aerosols from e-cigarettes containing nicotine with or without cooling agents and monitored their heart rhythm and conduction patterns. They also exposed lab-grown human heart cells to cooling agents and noradrenaline to mimic the impact of nicotine on stress hormones. Key findings include: all cooling ingredients affected heart rate variability, indicating stress responses that increase risk for high blood pressure and other cardiovascular issues; adding synthetic coolants to e-cigarettes with nicotine increased irregular heartbeats, especially WS-23, which tripled premature heartbeats compared to e-cigarettes with nicotine alone; and in hormonally stressed human heart cells, coolants slowed rhythm and sped up electrical recharge between beats.
“Coolants, especially WS-23, intensified the cardiovascular effects of e-cigarette exposures in the mice, causing more mistimed heartbeats and greater signs in heart rhythm of fight-or-flight stress responses, which in turn increase the risk of dangerous mis-timed heartbeats and sudden cardiac arrest,” said Alex Carll, Ph.D., M.S.P.H., principal investigator and an associate professor at the University of Louisville School of Medicine. “Coolant levels in vapes should be considered for regulation, especially if further studies confirm that they increase the harmful effects of vaping on the heart.”
The study has limitations, including that mice may respond differently than humans, and only male mice were used. Additionally, lab-grown heart cells may not fully capture complex interactions between respiratory and cardiovascular systems. Future research is needed to confirm these findings in people and assess long-term effects. The American Heart Association’s 2023 scientific statement, Cardiopulmonary Impact of Electronic Cigarettes and Vaping Products, called for more long-term research on e-cigarette use by people with pre-existing heart and lung disease.
“It is important for parents to talk with their children to make sure they understand that no vaping or tobacco product is safe or risk-free, even if it has been authorized by the FDA,” said Jason J. Rose, M.D., M.B.A., an associate professor at the University of Maryland School of Medicine and volunteer chair of the 2023 statement. The full study is available online at Circulation: Arrhythmia and Electrophysiology.
