When it comes to cardiovascular health, are vapors safe?
Researchers from West Virginia University (WVU) in Morgantown set out to examine the impact of acute and long-term exposure to e-cigarettes (e-cigs) on the cardiovascular health of mice.
The scientists hypothesized that acute and chronic exposure to the e-cigs' vapors would cause a level of cardiovascular dysfunction comparable to that of conventional cigarettes.
The findings were presented at the Cardiovascular Aging: New Frontiers and Old Friends conference - held in Westminster, CO - by first study author Mark Olfert, Ph.D., an associate professor at WVU's School of Medicine.
E-cigs should not be seen as safe
Prof. Olfert and team examined four female mice that were exposed to e-cigs acutely (a single exposure that lasted for 5 minutes) and six female mice that were exposed to e-cigs chronically (for 4 hours every day over 5 days per week, for 8 months). The e-cigs they used were cappuccino-flavored and contained 18 milligrams of nicotine per milliliter.
The researchers examined their arteries' diameter and vasodilation - that is, the ability of the blood vessels to widen and contract. Using a technique called intravital microscopy, the researchers evaluated the reactivity of the arterioles, which are small branches of the arteries leading into the capillaries.
Prof. Olfert and team also looked at aortic stiffness, a marker of cardiovascular disease in which the aorta, the heart's main artery, loses elasticity. Aortic stiffness usually occurs with aging.
The scientists used Doppler ultrasonography to evaluate pulse wave velocity, often called the "gold standard" for assessing aortic stiffness.
The study found that within an hour of being exposed to 5 minutes of e-cig vapor, the arteries narrowed by 31 percent. Chronic, long-term exposure to e-cigs also resulted in aortic stiffness, which was two and a half times higher in that group compared with the control group, which was exposed to filtered air only.
Furthermore, acute exposure also resulted in a 9 percent decrease in vasodilation. The maximum aortic relaxation that was achieved in reaction to metacholine - a test commonly used to determine whether or not a patient has asthma - was 90 percent in the control group, but this reduced to 70 percent in the chronic e-cig exposure group.
The authors conclude that e-cigs have serious adverse consequences on cardiovascular health. Specifically, exposure to e-cigs seems to bring about the premature aging of the blood vessels.
"Our data provides the first evidence showing a single acute exposure has negative effects on in vivo vascular function, and that chronic exposure significantly accelerates age-associated increase in aortic stiffness, and significantly impairs aortic endothelial-dependent vasodilation."
The endothelium is a thin membrane that can be found inside the heart and blood vessels. If the endothelium does not work properly, it means that the blood vessels cannot dilate as they should.
"These data indicate that e-cigs should not be considered safe," the authors write, "and that they induce significant deleterious effects on endothelial function in the central and peripheral vasculature."