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Written by: Ibani Kapur
Medically reviewed by:
Rob Philibert MD PhD

Prior to the pandemic, perhaps the greatest controversy in American Public Health was the effect of electronic nicotine delivery systems (ENDS) on adolescent and adult health. There are two commonly marketed types of ENDS, e-cigarettes, and vape pens. E-cigarettes are made to look and feel just like conventional cigarettes. In contrast, vape pens come in a wide variety of forms often designed to conceal their purpose. Both types of devices use a heating element to aerosolize a solution of propylene glycol and/or glycerol along with other additives. Most often, the solution contains nicotine.  However, there is a wide variety of flavorings that are commonly added to increase user appeal.

Despite the strong reaction from many in the public health establishment, e-cigarettes were originally invented by Hon Lik, a pharmacist from Beijing, in the hopes of treating smoking.  That effort has yet to be fully realized. As of today, Clinicaltrials.gov, the main United States registry for medical device trials, lists 75 completed or in-progress trials of e-cigarettes as agents for smoking cessation. Overall, the data supporting the use of e-cigarettes for smoking cessation is mixed. Many experts believe that e-cigarettes may have a role in promoting smoking cessation for those unable to succeed using more generally approved means such as the nicotine patch or medications. 

At the same time, in large part due to the activities by companies such as JUUL, the other common form of ENDS, vape pens, are now ubiquitously present among adolescents and young adults. Vape pens are used to inhale most typically nicotine, but often the solutions include other potentially addictive substances such as cannabinoids, amphetamines, cocaine, and opioids.  But the risk for addiction may not be the only problem posed by vaping. In 2019, an outbreak of 2800 reported cases of EVALI (E-cigarette or Vaping product use-Associated Lung Injury) raised grave concerns that vape pens and other forms of ENDS may have adverse effects on the cardiovascular system. There is a good reason for that concern. Although vitamin E acetate, the causative agent for EVALI, is no longer found in vaping solutions, a number of studies have found other contaminants, including heavy metals such as cadmium, can be found in the aerosols of early generations of certain e-cigarette and vape pens. Since those early studies, reports of these emissions have declined. But as of yet, there are no long-term studies of the effect of inhaling propylene glycol or glycerol, the 2 key solvents used in ENDS solutions, on human pulmonary function.  

Similarly, our knowledge of the long-term effects of ENDS on the cardiovascular system is uncertain. One recent study showed that e-cigarette usage led to an increase in sympathetic nerve activity with changes in both heart rate and blood pressure. While these findings were attributed to nicotine and not non-nicotine substances in e-cigarettes, the effect on heart rate variability was found to be similar for e-cigarette and conventional cigarette users. The effect of ENDS use on other cardiovascular risks like oxidative stress, inflammation, and endothelial dysfunction has been studied as well. Although ENDS use is certainly safer than tobacco smoking, some studies show that ENDS use moderately increases oxidative stress and inflammation. However, almost all of the studies of ENDS use on cardiovascular function are compromised by the fact that those who use ENDS often surreptitiously smoke. As a result, many ill effects in clinical examination of ENDS on cardiovascular function may be wrongly attributed to ENDS instead of the real culprit, smoking.

What should a clinician tell a patient who is interested in using ENDS to quit smoking? The truth of the matter is that there are very few things that are worse than continuing to smoke. As a result, if the patient feels that ENDS may be their best option to quit smoking, we recommend supporting that trial, particularly if that trial is assisted by the use of supportive psychotherapy.  If that trial fails, other more traditional means such as the nicotine patch combined with other evidenced-based behavioral therapies should be recommended. The clinician should continue to emphasize the positive effects of smoking cessation on cardiovascular risk. For example, a study sponsored by Cardio Diagnostics showed dramatic reductions of risk-associated changes within 3 months of stopping smoking.  

Over the next several years, scientists will create a better understanding of the relationship of vaping to cardiovascular health. In the meantime, it is important to continue the focus of Hon Lik on the real enemy-smoking.


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