E-cigarettes and their lone constituents induce cardiac arrhythmia and conduction defects in mice

E-cigarette use has surged, but the long-term health effects remain unknown. E-cigarette aerosols containing nicotine and acrolein, a combustion and e-cigarette byproduct, may impair cardiac electrophysiology through autonomic imbalance. Here we show in mouse electrocardiograms that acute inhalation of e-cigarette aerosols disturbs cardiac conduction, in part through parasympathetic modulation. We demonstrate that, similar to acrolein or combustible cigarette smoke, aerosols from e-cigarette solvents (vegetable glycerin and propylene glycol) induce bradycardia, bradyarrhythmias, and elevations in heart rate variability during inhalation exposure, with inverse post-exposure effects. These effects are slighter with tobacco- or menthol-flavored aerosols containing nicotine, and in female mice. Yet, menthol-flavored and PG aerosols also increase ventricular arrhythmias and augment early ventricular repolarization (J amplitude), while menthol uniquely alters atrial and atrioventricular conduction. Exposure to e-cigarette aerosols from vegetable glycerin and its byproduct, acrolein, diminish heart rate and early repolarization. The pro-arrhythmic effects of solvent aerosols on ventricular repolarization and heart rate variability depend partly on parasympathetic modulation, whereas ventricular arrhythmias positively associate with early repolarization dependent on the presence of nicotine. Our study indicates that chemical constituents of e-cigarettes could contribute to cardiac risk by provoking pro-arrhythmic changes and stimulating autonomic reflexes.


Supplementary Figure 4. Representative heart rate responses and concentrations of total suspended particulate (TSP) or acrolein gas in exposure chambers from a single experimental exposure session.
Values are presented as 10-s averages of heart rate (± SEM; n=4 males each) or concentrations from a single test atmosphere generated during the initial exposure session to PG:VG (a) or acrolein (b). PG:VG puffs are indicated by spikes in TSP, in contrast to continuous 9-min acrolein exposure at a target 3 ppm concentration. Black bars indicate exposure sessions.

Supplementary Figure 6. Effects of E-cigarette Exposures on ECG Morphology.
Individual subject average changes from 5-min baseline in ECG morphology parameters, stratified by phase, with observed simple means and standard errors indicated by gray bar ± error bars. Phases are indicated by study timeline below, with Expo denoting puff sessions, Post-denoting 4-9 min after each puff session, and Late Post-indicating 9-28 min after the final puff session. "E-Tobac" and "E-Menth" denote E-Tobacco and E-Menthol. For P dur and PR, Air n=7, PG n=6, VG n=7, PG:VG n=7, E-Tobac n=4, and E-Menth n=6. For J and QT, Air n=8, PG n=7, VG n=7, PG:VG n=8, E-Tobac n=4, and E-Menth n=7. For least square means and statistical comparisons, see Fig. 3 and Fig. 5.  Supplementary Figure 7. Nicotine-containing e-cig aerosols induce S depression during exposure. a, bars represent least square means (± SEM) of change from 5-min baseline in S amplitude during exposure to E-cig aerosol, MCS, or acrolein. "E-Tobac" and "E-Menth" denote E-Tobacco (n=4) and E-Menthol (n=7). b, individual subject average changes from 5-min baseline in S amplitude with observed simple means and standard errors indicated by gray bar ± error bars. For Air n=8, PG n=7, VG n=8, PG:VG n=8, acrolein n=8, MCS 1R5F n=8, and MCS 3R4F n=6. c, representative 1-min average ECG waveforms generated from baseline (blue), three 9-min E-Tobacco puff sessions (black), or post-exposure (gray) in a single mouse. Significance determined by two-sided P < 0.05 (vs. Air, indicated by stars) in mixed model analyses. Asterisks indicate presence of nicotine.

Supplementary Figure 9. Effects of MCS or Acrolein Exposures on Heart Rate and HRV.
Individual subject average changes from 5-min baseline in heart rate and HRV (SDNN and RMSSD), stratified by phase, with observed simple means and standard errors indicated by gray bar ± error bars (a-i). Phases are indicated by study timeline below, j, with Expo denoting puff sessions, Post-denoting 4-9 min after each puff session, and Late Post-indicating 9-28 min after the final puff session (n=6-8/exposure). For least square means and statistical comparisons, see  Figure S15. Impacts of Muscarinic Receptor Blockade on Heart Rate and Heart Rate Variability Effects of E-cig Solvent Aerosols. Individual subject average changes from 5-min baseline in heart rate and HRV (SDNN and RMSSD), stratified by phase, with observed simple means and standard errors indicated by gray bar ± error bars (a-i). Phases are indicated by study timeline below, j, with Expo denoting puff sessions, Post-denoting 4-9 min after each puff session, and Late Post-indicating 9-28 min after the final puff session. Air n=8, Saline + PG:VG n=6, Atropine + PG:VG n=6. For least square means and statistical comparisons, see Fig. 9 and Supplementary Figs. 13 and 14.

Figure S16. Impacts of Muscarinic Receptor Blockade on Effects of E-cig Solvent Aerosols on Atrial and Atrioventricular Conduction.
Individual subject average changes from 5-min baseline in ECG morphology, stratified by phase, with observed simple means and standard errors indicated by gray bar ± error bars (a-l). Air n=8, Saline + PG:VG n=6, Atropine + PG:VG n=6. For least square means and statistical comparisons, see Fig. 9 and Supplementary Figs. 13 and 14.
Figure S17. Impacts of Muscarinic Receptor Blockade on Effects of E-cig Solvent Aerosols on Ventricular Repolarization. Individual subject average changes from 5-min baseline in ECG morphology, stratified by phase, with observed simple means and standard errors indicated by gray bar ± error bars (a-l). Air n=8, Saline + PG:VG n=6, Atropine + PG:VG n=6. For least square means and statistical comparisons, see Fig. 9 and Supplementary Figs. 13 and 14.