Chemicals in vapes trigger potentially deadly heart issue: study

By Stephen Beech

Chemicals in vapes may trigger potentially deadly cardiac arrest, suggests a new study.

Menthol flavors and synthetic ingredients with an "icy" taste can lead to abnormal heart rhythms, say American scientists.

They found that man-made cooling ingredients added to e-cigarettes caused abnormal heartbeats, known as arrhythmias, and increased cardiovascular risk measures in mice and lab-grown human heart cells.

The study is the first to show that synthetic cooling agents in e-cigarettes may negatively affect heart health.

The findings raise concern that people who use vapes may have an increased risk of irregular heart rhythm and possibly sudden cardiac arrest.

Principal investigator Alex Carll said: "Because synthetic coolants create a chilling sensation without flavor, they fall outside of e-cigarette restrictions that focus on 'characterizing flavors.'

"Synthetic coolants WS-3 and WS-23 have become really popular in vapes, partly because they reduce harshness and make inhalation feel smoother."

In previous research, Carll and colleagues found that exposure to e-cigarette aerosols rapidly disrupted heart rhythm in mice, causing abnormal heartbeats that happened either too early or were completely skipped.

For the new study, published in the journal Circulation: Arrhythmia and Electrophysiology, the research team conducted two types of lab tests.

In the first, mice inhaled aerosols from e-cigarettes containing nicotine with or without cooling agents.

Their heart's rhythm and conduction patterns were monitored during exposure.

In the second test, lab-grown human heart cells were exposed to cooling agents and to norepinephrine to simultaneously mimic the impact of nicotine on stress hormones.

All of the cooling ingredients in e-cigarettes affected heart rate variability, which indicate stress responses that increase the risk for mistimed heartbeats, high blood pressure and other cardiovascular issues.

Adding the synthetic coolants to e-cigarettes already containing nicotine and solvents increased irregular heartbeats in the mice, especially for WS-23, which tripled the number of premature heartbeats when compared to e-cigarettes containing just nicotine and solvents.

With coolant exposures, the mistimed heartbeats corresponded with increased heart rate and a slower electrical recharge between beats.

In human heart cells, the coolants didn't change normal resting heart rhythm or recharge rate.

But when the cells were hormonally stressed, coolants slowed their rhythm and also sped up their recharge between heartbeats.

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In the mice, coolants did not significantly increase the amount of nicotine absorbed into the bloodstream after inhalation.

Carll, from the University of Louisville School of Medicine, Kentucky, said: "Together, these findings suggest coolants could cause arrhythmias by making the heart electrically ready too soon or too late for the next beat.

"In general, we've seen tobacco-flavored vapes do not disrupt cardiac conduction in mice as much as vapes with either menthol or synthetic coolants.

"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."

Carll suggests that, based on the latest findings, policymakers review the current rules regarding coolants used in vapes.

He said: "Coolants are added to e-cigarettes at very high levels, often more than nicotine or any other flavoring.

"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.

"It is still unclear how coolants in vapes affect people with higher risk for heart rhythm conditions.

"This includes pregnant women and those with hypertension, heart disease, obesity or Type 2 diabetes.

"We also don't know if the short-term effects of coolants lead to long-term harm."

Carll added: "Importantly, lab-grown human heart cells often overlook the complicated interactions between the respiratory and cardiovascular systems in humans, therefore, more research is needed."

A 2023 scientific statement from the American Heart Association called for more long-term research on e-cigarette use by people with pre-existing heart and lung disease.

Menthol-flavored e-cigarette sales increased by 175.8% from 2019 and 2023.

Sales of e-cigarettes with synthetic cooling ingredients, such as WS-3 or WS-23, increased 872.1% between 2020 to 2023, in the U.S., according to a report.

WS-3 and WS-23 are also legal in the UK.

Jason Rose, who was the volunteer chair of the 2023 scientific statement writing group, said: "This research is timely since menthol and cooling flavors are becoming more popular.

"The study results are not surprising because ingredients in e-cigarettes, particularly synthetic flavoring agents, independently carry health risks.

"We just don't know the long-term impact of vaping."

Rose, from the University of Maryland School of Medicine, added: "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."