Electronic cigarettes — myocardial infarction, hemodynamic compromise during pregnancy, and systolic and diastolic dysfunction: Minireview

Table 1 Effects of electronic cigarettes on the risk of myocardial infarction and cardiac functional changes from electronic cigarettes

Name of the study	Type of the study	Results	Comments
Chronic intermittent electronic cigarette exposure induces cardiac dysfunction and atherosclerosis in apolipoprotein-E knockout mice	Animal model randomized control study with intervention	ECs with 2.4% nicotine had decreased left ventricular ejection fraction and had increased atherosclerotic lesions compared to ECs without nicotine and saline groups. Mice exposed to 2.4% nicotine vapor had increased atherosclerotic lesions on aorta as well	Mice model with limited implication to humans
Association between electronic cigarette use and myocardial infarction	Cross-sectional; study was based on self-reporting surveys	Increased odds ratio (1.79) of having MI with ECs and even higher odds ratio (4.62) with dual use of ECs and combustible cigarettes relative to never smokers	Number of surveys in 2014 was 36697 and 33028 in 2016
Acute effects of using an electronic nicotine-delivery device (electronic cigarette) on myocardial function: Comparison with the effects of regular cigarettes	Interventional, case-control	Electronic cigarettes caused delayed myocardial relaxation, no effect on systolic function	Small study with total of 76 subjects; the study does not predict long term effects
Association between electronic cigarette use and myocardial infarction	Cross-sectional through surveys	Daily EC use increased the odds of having MI (OR = 1.79) while daily TC smoking had a higher correlation of MI (OR = 2.72)	Large surveys: 36697 in 2014 and 33028 in 2016

ECs: Electronic cigarettes; MI: Myocardial infarction; OR: Odds ratio; TC: Tobacco cigarette.

Table 2 Arteriosclerosis and endothelial damage

Name of the study	Type of the study	Results	Comments
Modeling cardiovascular risks of ECs with human-induced pluripotent stem cell-derived endothelial cells	Randomized interventional on human endothelial cells; cells were exposed to EC flavoring products with and without nicotine	Flavoring e-liquids caused endothelial dysfunction even without nicotine; nicotine had a dose-dependent effect on cytotoxicity, reactive oxygen species generation, and apoptotic activities	In vitro study with limited implications
Flavorings in tobacco products induce endothelial cell dysfunction	Intervention study on human endothelial cells obtained from smokers and nonsmokers	The flavorings vanillin, cinnamaldehyde, eugenol, acetylpyridine, and menthol impaired nitric oxide production and increased expression of proinflammatory mediators and interleukin-6	Small study; the endothelial cells obtained by biopsy from 3 groups of 6 to 9 subjects
Vascular effects of a single bout of electronic cigarette use	Interventional nonrandomized study on healthy volunteers	There were no significant changes in heart rate, systolic and diastolic blood pressure, endothelial function (via flow-mediated dilation), and arterial stiffness (via cardio-ankle vascular index) throughout the experiments	Small study on 16 volunteers; the study was limited to acute changes post smoking one bout of ECs; flow mediated dilation and cardio-ankle vascular index may not be sensitive enough

ECs: Electronic cigarettes.