Search

Background: Chronic electronic (e) cigarette users have increased resting cardiac sympathetic nerve activity and increased susceptibility to oxidative stress. The purpose of the present study is to determine the role of nicotine versus non-nicotine constituents in e-cigarette emissions in causing these pathologies in otherwise healthy humans., Methods and Results: Thirty-three healthy volunteers who were not current e-cigarette or tobacco cigarette smokers were studied. On different days, each participant used an e-cigarette with nicotine, an e-cigarette without nicotine, or a sham control. Cardiac sympathetic nerve activity was determined by heart rate variability, and susceptibility to oxidative stress was determined by plasma paraoxonase activity. Following exposure to the e-cigarette with nicotine, but not to the e-cigarette without nicotine or the sham control, there was a significant and marked shift in cardiac sympathovagal balance towards sympathetic predominance. The decrease in high-frequency component and the increases in the low-frequency component and the low-frequency to high-frequency ratio were significantly greater following exposure to the e-cigarette with nicotine compared with exposure to the e-cigarette without nicotine or to sham control. Oxidative stress, as estimated by plasma paraoxonase, did not increase following any of the 3 exposures., Conclusions: The acute sympathomimetic effect of e-cigarettes is attributable to the inhaled nicotine, not to non-nicotine constituents in e-cigarette aerosol, recapitulating the same heart rate variability pattern associated with increased cardiac risk in multiple populations with and without known cardiac disease. Evidence of oxidative stress, as estimated by plasma paraoxonase activity, was not uncovered following acute e-cigarette exposure., (© 2017 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley.)

Importance: Electronic cigarettes (e-cigarettes) have gained unprecedented popularity, but virtually nothing is known about their cardiovascular risks., Objective: To test the hypothesis that an imbalance of cardiac autonomic tone and increased systemic oxidative stress and inflammation are detectable in otherwise healthy humans who habitually use e-cigarettes., Design, Setting, and Participants: Cross-sectional case-control study of habitual e-cigarette users and nonuser control individuals from 2015 to 2016 at the University of California, Los Angeles. Otherwise healthy habitual e-cigarette users between the ages of 21 and 45 years meeting study criteria, including no current tobacco cigarette smoking and no known health problems or prescription medications, were eligible for enrollment. Healthy volunteers meeting these inclusion criteria who were not e-cigarette users were eligible to be enrolled as control individuals. A total of 42 participants meeting these criteria were enrolled in the study including 23 self-identified habitual e-cigarette users and 19 self-identified non-tobacco cigarette, non-e-cigarette user control participants., Main Outcomes and Measures: Heart rate variability components were analyzed for the high-frequency component (0.15-0.4 Hz), an indicator of vagal activity, the low-frequency component (0.04-0.15 Hz), a mixture of both vagal and sympathetic activity, and the ratio of the low frequency to high frequency, reflecting the cardiac sympathovagal balance. Three parameters of oxidative stress were measured in plasma: (1) low-density lipoprotein oxidizability, (2) high-density lipoprotein antioxidant/anti-inflammatory capacity, and (3) paraoxonase-1 activity., Results: Of the 42 participants, 35% were women, 35% were white, and the mean age was 27.6 years. The high-frequency component was significantly decreased in the e-cigarette users compared with nonuser control participants (mean [SEM], 46.5 [3.7] nu vs 57.8 [3.6] nu; P = .04). The low-frequency component (mean [SEM], 52.7 [4.0] nu vs 39.9 [3.8] nu; P = .03) and the low frequency to high frequency ratio (mean [SEM], 1.37 [0.19] vs 0.85 [0.18]; P = .05) were significantly increased in the e-cigarette users compared with nonuser control participants, consistent with sympathetic predominance. Low-density lipoprotein oxidizability, indicative of the susceptibility of apolipoprotein B-containing lipoproteins to oxidation, was significantly increased in e-cigarette users compared with nonuser control individuals (mean [SEM], 3801.0 [415.7] U vs 2413.3 [325.0] U; P = .01) consistent with increased oxidative stress, but differences in high-density antioxidant/anti-inflammatory capacity and paraoxonase-1 activity were not significant., Conclusions and Relevance: In this study, habitual e-cigarette use was associated with a shift in cardiac autonomic balance toward sympathetic predominance and increased oxidative stress, both associated with increased cardiovascular risk.