Electronic Cigarettes and Cardiovascular Risk
Electronic cigarettes or e-cigarettes have become popular because they are promoted as a "healthier alternative" to smoking. This hypothesis was recently refuted by the FDA. Very trendy among young people, these cigarettes are often used by smokers alongside traditional cigarettes. Although the cardiac effects of nicotine and other components of the aerosols are known, data on the consequences of electronic cigarettes on the cardiovascular system are still limited. Several published studies report an increased prevalence of cardiovascular disease in users of electronic cigarettes, smoked alone or in combination with traditional cigarettes. Hypercholesterolemia, increased sympathetic activity, endothelial dysfunction, increased oxidative stress as well as inflammation, DNA damage, and macrophage activation have been described in e-cigarette users and may explain the increased cardiovascular risk. This article aims to summarise the available evidence regarding the contribution of electronic cigarettes to the onset of cardiovascular disease.
from Isabella Sudano
Copyright by Aerzteverlag medinfo AG
Source: Aerzteverlag medinfo AG, info@herz+gefäss, Ausgabe Nr. 6/2022. pages 9-10.
First generation electronic cigarettes were designed to replicate the effect of smoking traditional cigarettes. The next generation contain powerful atomizers and use higher concentrations of nicotine in the liquids, which increases the speed of release and the rate of nicotine as with traditional cigarettes (1). JUUL and other pod-mods use nicotine formulations made from the nicotine salts found in loose tobacco (2). In pod-mods such as the JUUL, these salts reduce throat irritation from nicotine, helping to achieve high concentrations of nicotine and maximizing the feeling of satisfaction (3).
In recent years, an increasing number of e-cigarette manufacturers have used synthetic nicotine instead of tobacco-derived nicotine for the manufacture of e-cigarettes and e-liquids, in order for these not to be considered as tobacco products (3). Although e-cigarettes were originally marketed to help smokers quit smoking, they are frequently used by people who have never smoked (4, 5) and by others alongside traditional tobacco products (6). This article focuses on the cardiovascular effects of e-cigarette use in people who have never smoked, in smokers who have replaced traditional cigarettes with e-cigarettes, and in smokers who smoke both. Products that heat tobacco are not considered in this article.
Cardiovascular effects of e-cigarettes in non-smokers
The use of e-cigarettes has increased considerably over the past decade, the products on sale on the market having undergone rapid development.
Although most health authorities have not approved the use of e-cigarettes to aid in smoking cessation, the industry promotes them to adults trying to quit smoking traditional cigarettes. The novelty and the perception that these products are not dangerous has prompted many non-smokers, especially young people, to try these products.
Beyond the nicotine and vegetable glycerine content, flavourings, and propylene glycol, the composition of the liquids used in electronic cigarettes is not known to the public and it is therefore difficult to know their effects on health, in particular on the heart and vascular system.
The toxicity of e-cigarette aerosols is still poorly understood, although a few small studies indicate possible cardiopulmonary toxicity.
Overall, there is evidence for several acute haemodynamic changes, including increased arterial rigidity, reduced endothelial function, and increased blood pressure, as well as increased heart rate and sympathetic nervous system activity (7).
Cardiac effects include a reduction in increased myocardial blood flow during exercise (8), as well as possible direct cardiac toxicity (9). Furthermore, short-term use of electronic cigarettes increases the values of biomarkers of oxidative stress (10). Many acute vascular effects appear to be due to nicotine exposure (11). A recent study of healthy young adults smoking only e-cigarettes found no long- or short-term effects on endothelial function (12). But most e-cigarettes here had a lower nicotine level than normally used (13).
Although smoking traditional tobacco in adolescence can lead to arteriosclerosis, heart disease, and strokes in adulthood, there are no comparable long-term data for e-cigarette use. Nevertheless, it is possible to predict certain outcomes by comparing the effects observed in vapers and smokers. Indications of systemic inflammation and endothelial dysfunction, as well as changes in vascular rigidity (7, 14), blood pressure, and heart rate (14, 15), which are similar to those observed in smokers, suggest a possible increase in cardiovascular risk in vapers (7)
Cardiovascular effects of switching from conventional to e-cigarettes
The VESUVIUS study (16) examined the effects of switching from conventional cigarettes to e-cigarettes in adult smokers who had smoked > 15 cigarettes/day for at least two years and did not have cardiovascular disease, diabetes, or chronic kidney disease. One month after switching to e-cigarettes, these smokers showed significant improvement in vascular function.
Although this habit change has an initial benefit, a meta-analysis did not show a reduction in stroke, myocardial infarction, or coronary heart disease in these smokers (17). On the other hand, heavy consumption of traditional cigarettes or e-cigarettes has been shown to lead to an equally marked reduction in endothelial function (18). The fact that this habit change has an extremely strong impact on vascular function therefore seems very controversial, and offers no justification or evidence that e-cigarettes are inherently safe or that their long-term use after quitting of traditional cigarettes leads to a reduction in cardiovascular morbidity and mortality.
Cardiovascular effects of dual use of conventional and e-cigarettes
Larger studies have shown that smokers who do not quit often continue to use both traditional cigarettes and e-cigarettes (dual users) (6). Compared to those who only smoke traditional cigarettes, dual users have a higher cardiovascular risk (19). Smokers who quit smoking showed a significant drop in nicotine metabolites, all tobacco-specific nitrosamines, most polycyclic aromatic hydrocarbons, as well as volatile organic compounds and metals. Cigarette smokers who became dual users did not show significant reductions in most biomarkers of tobacco exposure (20).
Cardiovascular effect of passive exposure to e-cigarette aerosols
Electronic cigarettes do not emit only “harmless water vapour”. Their aerosols contain nicotine, ultrafine particles, and small amounts of toxins known to cause cancer and cardiovascular effects.
Exposure to the products of pyrolysis is lower than from passive smoking, but exposure to nicotine is similar and the aerosol particles are smaller (21). Studies in cars have shown an increase in nicotine, propylene glycol, volatile organic compounds, and nanoscale and microscale particles, as well as particle mass (PM2.5, μg/m3) due to vaping (22).
Further studies are needed to understand the long-term effects of passive exposure to e-cigarette aerosols.
- Composition. It is therefore very difficult to predict the effects of e-cigarettes on health, especially on the cardiovascular system.
- Although e-cigarettes were originally marketed to help smokers quit smoking, they are not recognised by authorities as a cessation aid and are very often used by people who have never smoked or who smoke both types of cigarettes.
- E-cigarettes severely impair vascular function just as significantly as traditional cigarettes. In smokers who switch to e-cigarettes, vascular function improves within a month.
- Switching from traditional cigarettes to e-cigarettes is not accompanied by a reduction in strokes, myocardial infarctions, or coronary heart disease. Dual use (tobacco products and e-cigarettes) increases the risk of cardiovascular problems.
- Further studies are needed to investigate the long-term effect of e-cigarettes on the heart and blood vessels. From a cardiovascular point of view, these are not safe products and there are no data indicating that the long-term use of e-cigarettes is associated with a reduction in cardiovascular morbidity and mortality.
Isabella Sudano, FMH. Specialist in internal medicine, with special training in hypertension and a doctorate in cardiovascular research from the University of Pisa.
Responsible for the hypertension and dyslipidemia consultations in the cardiology department, as well as the smoking cessation consultation at University Hospital Zurich.
Full Professor in the Faculty of Medicine of the University of Zurich since September 2019.
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