Cardiovascular effects of electronic cigarettes

Abstract

Cardiovascular safety is an important consideration in the debate on the benefits versus the risks of electronic cigarette (EC) use. EC emissions that might have adverse effects on cardiovascular health include nicotine, oxidants, aldehydes, particulates, and flavourants. To date, most of the cardiovascular effects of ECs demonstrated in humans are consistent with the known effects of nicotine. Pharmacological and toxicological studies support the biological plausibility that nicotine contributes to acute cardiovascular events and accelerated atherogenesis. However, epidemiological studies assessing Swedish smokeless tobacco, which exposes users to nicotine without combustion products, generally have not found an increased risk of myocardial infarction or stroke among users, but suggest that nicotine might contribute to acute cardiovascular events, especially in those with underlying coronary heart disease. The effects of aldehydes, particulates, and flavourants derived from ECs on cardiovascular health have not been determined. Although ECs might pose some cardiovascular risk to users, particularly those with existing cardiovascular disease, the risk is thought to be less than that of cigarette smoking based on qualitative and quantitative comparisons of EC aerosol versus cigarette smoke constituents. The adoption of ECs rather than cigarette smoking might, therefore, result in an overall benefit for public health.

Figure 1. Tobacco combustion products present in a conventional cigarette

Cigarette smoke consists of a complex mixture of combustion products, including >7,000 chemicals. A single puff of cigarette smoke contains 1 × 10¹⁷ free radicals. The oxidizing chemicals present in the gas phase of tobacco smoke are believed to be the main contributors to atherogenesis and thrombogenesis.

Figure 2. Components of an electronic cigarette (EC)

The cartridge holds the e-liquid, which contains propylene glycol or vegetable glycerine, nicotine, and flavourings. When heated to high temperatures, as can occur with the use of advanced EC devices, propylene glycol can form thermal dehydration products such as acetaldehyde, formaldehyde, and propylene oxide, whereas vegetable glycerine can generate acrolein and glycidol.

Figure 3. Overview of mechanisms by which electronic cigarette use might cause acute cardiovascular events

Solid lines indicate known pathways. Dashed lines indicate pathways of concern, but for which there are no empirical data for confirmation.