UC San Diego

As e-cigarette use continues to rise in popularity, many have questioned how e-cigarette vapor inhalation actually affects mammalian systems. Because >99% of commercially available e-cigarettes contain nicotine, and nicotine has been found to have effects on cardiac physiology, we hypothesized that daily inhalation of e-cigarette vapor (EV) would lead to alterations in both heart rate (HR) and blood pressure (BP). This hypothesis is supported by recent human data showing increases in HR and BP after inhaling EV once (acute exposure). HR variability has been highlighted as a sign of cardiac dysfunction, with increased risk of adverse cardiac outcomes. These experiments were designed to evaluate HR, HR variability and BP of mice exposed to nicotine containing e-cigarette vapor daily for 3 months, compared to controls.

10 week-old C57BL/6 mice were obtained from Jackson Labs. Mice were placed into the full body SciReq inExpose system where they were exposed for 60min daily to freshly made EV for 3 months. The e-liquid used contained 70% propylene glycol, 30% vegetable glycerin and 6 mg/mL nicotine. At least once weekly during each exposure time point, mice were measured for their heart rate (HR), heart rate variability (HRV), and blood pressure (BP). The mouse’s temperature was taken to ensure temperatures were between 35-37C during observation. Two cuffs were placed on the tail to measure both BP (Kent Scientific) over 5-10min. The EMKA tech ECGtunnel was used to measure HR and HRV in 15 minute intervals both pre-exposure and post-exposure.

The results from our data suggest that chronic inhalation of nicotine containing e-cigarette vapor (EV) affects cardiac function. Although it is know that in humans heart rate increases acutely during nicotine inhalation (demonstrated by both cigarette smoke and EV inhalation studies), our results from a mouse model of chronic inhalation imply that over repeated exposures, HR tend to decrease. E-cigarette exposed mice also showed signed of higher HR variability, SBP, DBP, and MAP. These results imply that e-cigarette users may be at risk for adverse cardiac physiological effects.