How Electronic Cigarette Affects the Vascular System

Table 1

Characteristics of included study.

#	Reference	Sample		Control group	Nicotine	Length of exposure	Overall risk of bias/quality	Result
		Characteristics	Total number of electronic cigarette population
Human studies
Randomized controlled trial (RCT)
1	George et al. [11]	Smokers	74	N/A	16 mg/mL	Chronic (1 month)	Some concerns	Switching from conventional cigarette to electronic cigarette improves endothelial function and vascular stiffness marker.
2	Ikonomidis et al. [12]	Smokers	40	N/A	12 mg/mL	Chronic (4 months)	Some concerns	Switching from conventional cigarette to electronic cigarette improves arterial stiffness and oxidative stress.
3	Ikonomidis et al. [13]	Smokers	70	Tobacco smokers	0.12 mg/mL	Chronic (1 month)	High risk	Replacing conventional cigarette with electronic cigarette results in reduced systolic and oxidative stress.
Observational; cross-sectional
4	Bricknell et al. [14]	Nonsmokers and smokers	74,013	N/A	N/A	Observational study	Fair	ENDS (including electronic cigarette) use is associated with stroke.
5	Fetterman et al. [15]	Nonsmokers and smokers	36	N/A	N/A	Observational study	Good	Electronic cigarette use is associated with elevated augmentation index (AIx, arterial stiffness marker) and an indication of endothelial dysfunction.
6	Oliveri et al. [16]	Smokers	144	Tobacco smokers	N/A	Observational study	Good	Electronic cigarette users show lower levels of biomarkers of exposure (NNK, nicotine, acrolein, and carbon monoxide) and biomarkers of potential harm (platelet activation, oxidative stress, and endothelial function) than cigarette smokers
7	Podzolkov et al. [17]	Nonsmokers and smokers	2	N/A	N/A	Observational study	Fair	Smoking traditional and electronic cigarette are related to albuminuria and an increase in the augmentation index (arterial stiffness marker).
8	Rader et al. [18]	Nonsmokers and smokers	35	N/A	N/A	Observational study	Poor	Electronic cigarette users show more pronounced impaired coronary microvascular endothelial function than chronic conventional cigarette users.
9	Sahota et al. [19]	Nonsmokers and smokers	20	N/A	4-36 mg/mL	Observational study	Fair	Electronic cigarette users develop more carotid plaque burden than nonsmokers
10	Vindhyal et al. [20]	Nonsmokers and smokers	401 and 2,240 dual users	N/A	N/A	Observational study	Poor	Electronic cigarette users are associated with an increased risk of myocardial infarction than nonsmokers
Animal studies
1	El-Mahdy et al. [21]	Animal (mice C57BL/6 J)	100	Air	0, 6, or 24 mg/mL	60 weeks	Electronic cigarette can induce cardiovascular disease similar to conventional cigarette smoking. The severity of toxicity increases with exposure duration and nicotine content.
2	Espinoza-Derout et al. [22]	Animals (ApoE–/– mice)	5/test group	EC without nicotine/saline aerosol	2.40%	12 weeks	Electronic cigarette with nicotine induce an abnormal increase in ROS levels and mitochondrial DNA mutations associated with cardiac dysfunction and atherogenesis.; Electronic cigarette without nicotine did not produce significant effect.
3	Kuntic et al. [23]	Animal (C57BL/6 and NOX2 null mice)	151	Air	12 mg/ml	5 days	Electronic cigarette vapor increases vascular, cerebral, and pulmonary oxidative stress via a NOX-2-dependent mechanism. The adverse effect is more pronounced with nicotine than without nicotine.
4	Li et al. [24]	Animal (mice)	5-10/test group	Air	2.40%	16 weeks	Electronic cigarette increases the level of mitochondrial DNA damage in blood and expression of TLR9 and induces the development of atherosclerosis.
5	Olfert et al. [25]	Animal (mice C57BL/6 J)	15	Air	18 mg/mL	32 weeks	Electronic cigarette vapor accelerates arterial stiffness and impairs aortic endothelial function.
6	Szostak et al. [26]	Animals (ApoE–/– mice)	309 (10-16/test group)	Air	4%	24 weeks	Electronic cigarette vapor shows small or completely absent effects on systolic and diastolic functions of the heart, atherosclerotic progression, altered lipid profiles, and alteration of the heart ventricle and aorta transcriptomes compare to 3R4F conventional cigarette smoke.

Notes: () The SYRCLE’s RoB for animal intervention does not provide overall risk of bias.