Most vaping health discussions focus on nicotine or heavy metals, but the flavoring agents — particularly the synthetic cooling compounds engineered to mimic menthol's sensation — may carry independent cardiac risks that regulators have barely begun to scrutinize. This research directly challenges the assumption that non-nicotine additives are inert bystanders in e-cigarette toxicology.
Using a dual-model approach combining live mouse inhalation exposures and human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), investigators tested three cooling agents: natural menthol and the synthetic analogs WS-3 and WS-23, each delivered at 2.5% nicotine benzoate concentrations. Telemetry-derived ECG analysis tracked heart rate, heart rate variability, arrhythmia burden, and waveform morphology in real time. All three coolants worsened vehicle-induced autonomic imbalance acutely upon aerosol inhalation, but only WS-3 and WS-23 potentiated ventricular arrhythmias beyond what nicotine alone produced — a distinction with direct relevance to the wave of synthetic-coolant-dominant products now dominating the vape market following partial menthol restrictions.
This finding carries several important implications. WS-3 and WS-23 are nearly ubiquitous in contemporary flavored e-liquids precisely because they are not menthol and therefore sidestep some existing regulations. Their mechanism likely involves direct ion channel modulation — both compounds interact with TRPM8 and potentially cardiac sodium and potassium channels — but the precise electrophysiological pathway warrants further investigation. The hiPSC-CM model adds translational credibility, though it cannot fully replicate the complexity of an intact human cardiovascular system under chronic exposure conditions. The mouse model, while useful for in vivo ECG telemetry, has heart rates roughly ten times higher than humans, limiting direct extrapolation of arrhythmia thresholds. Still, the convergence of two independent platforms pointing toward synthetic coolant-specific proarrhythmic effects elevates this beyond preliminary signal — it represents a regulatory-grade finding that warrants immediate policy attention for ingredients currently classified as flavoring agents rather than pharmacologically active compounds.