Heart Risks of E-Cigarette Cooling Agents: New AHA Study Links WS-3 and WS-23 to Arrhythmias
A study published today in the American Heart Association journal Circulation: Arrhythmia and Electrophysiology has found that synthetic cooling ingredients commonly added to e-cigarettes can cause abnormal heartbeats, raising concerns about potential cardiovascular risks for people who use these products.
Core Facts: What the Study Found
Researchers at the University of Louisville tested two widely used synthetic cooling agents — WS-3 and WS-23 — by exposing mice and lab-grown human heart cells to e-cigarette aerosols containing these compounds alongside nicotine. The key findings:
- WS-23 tripled the number of premature heartbeats in mice compared to e-cigarettes containing only nicotine and solvents.
- All cooling agents tested affected heart rate variability, a marker of cardiac stress linked to higher risk of high blood pressure and cardiovascular problems.
- In mice, coolants caused the heart’s electrical system to recharge either too quickly or too slowly between beats, creating conditions for arrhythmias.
- In human heart cells under hormonal stress (simulating nicotine’s effect on stress hormones), coolants slowed rhythm and disrupted electrical recovery patterns.
The study is the first peer-reviewed research to link synthetic e-cigarette cooling agents to cardiac arrhythmias. Lead researcher Alex Carll, Ph.D., noted that “synthetic coolants create a chilling sensation without flavor, so they fall outside of e-cigarette restrictions that focus on ‘characterizing flavors.’”
Key Details: Why This Matters Now
WS-3 and WS-23 are added to a wide range of e-cigarette products to produce the popular “ice” or “menthol-like” cooling sensation during inhalation. Unlike flavor compounds, these synthetic coolants reduce throat harshness and make vapor feel smoother — which may make products easier for new users to inhale.
The timing is critical. The FDA recently authorized the first fruit-flavored e-cigarettes for sale in the U.S., and most states allow menthol and cooling-sensation ingredients even where other flavors are restricted. This study suggests those exemptions may carry previously unrecognized cardiac risks.
The study has limitations: the findings come from mice and lab-grown cells, not from human trials. The researchers emphasized that the results need to be confirmed in clinical studies with people. However, the consistency of effects across both animal and human cell models strengthens the signal.
User Impact: What Vapers Should Know
- If you use “ice” or “frost” flavored vapes, you are likely inhaling WS-3 or WS-23. Check product labels or manufacturer websites for ingredient lists.
- If you have any heart condition — including arrhythmia, palpitations, or high blood pressure — consider switching to products without synthetic coolants until more research is available.
- Tobacco-flavored vapes showed less cardiac disruption in previous research by the same team, making them a potentially lower-risk option for adults who vape instead of smoking.
- Track your heart rate: If you notice irregular heartbeat, racing pulse, or skipped beats after vaping, stop using the product and consult a physician.
Reactions
The American Heart Association highlighted that most states have exceptions allowing menthol and cooling ingredients, even as other flavors face restrictions. The study’s publication on the same day the FDA faces mounting criticism over its fruit-flavored vape authorization adds pressure on regulators to reconsider how cooling agents are classified.
Public health advocates are likely to call for synthetic coolants to be included in flavor restriction legislation, given that these compounds function as sensory enhancers — similar to menthol — without being classified as “characterizing flavors.”
Action Advice
- Check your vape products for WS-3 or WS-23 ingredients — manufacturers are not always required to list them, but many do on their websites.
- Adults switching from smoking to vaping should consider tobacco-flavored or unflavored options as potentially lower cardiac risk, based on this and prior research.
- Monitor regulatory updates: this study may trigger new FDA scrutiny of cooling agents in PMTA reviews.
Source: American Heart Association Newsroom | Circulation: Arrhythmia and Electrophysiology
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Kevin Li — Founder & Editor, VapeObservation.com Kevin reviews vape products hands-on, prioritizing real-world performance over manufacturer claims. His goal: honest, practical advice that helps everyday vapers make informed choices. Before launching VapeObservation, he was a longtime vaper frustrated by promotional content disguised as reviews. Every article on the site reflects his commitment to data-driven, reader-first testing.
