E-cigarettes are generally thought to be a safer way to deliver nicotine than traditional cigarettes. Research suggests otherwise, however.

Vaping nicotine via e-cigarettes can damage the cardiovascular system. Small particles, such as those inhaled when vaping, have been linked to an increased risk of hypertension, heart attacks and stroke.

Vaping has become a common form of nicotine delivery. Most e-cigarette users add nicotine to the liquid cartridge in the device, Robert Kloner, corresponding author of a recent study on the effects of vaping nicotine, told TheDoctor in an email. “I have seen some estimates that nearly 99 percent of e-cigarette users include nicotine.”

The results suggest that nicotine-containing electronic cigarettes affect vascular function and left ventricle arterial coupling, while standard cigarettes appeared to negatively affect left ventricle function.

Researchers from the University of California at Irvine, the University of Southern California and the Huntington Research Institutes divided 117 healthy male and female rats into four groups and exposed them to e-cigarette vapor with or without nicotine or nicotine-rich smoke from traditional cigarettes. A fourth control group was exposed to purified air. The animals were exposed for five hours a day, four days a week for eight weeks.

To determine the effects of e-cigarette vapor and smoke from traditional cigarettes on cardiovascular function, the researchers used an approach called the intrinsic frequency method, a mathematical model that tracks the constantly changing relationship between systolic and diastolic pressures.

The researchers did not know how e-cigarette vapor with nicotine and smoke from traditional cigarettes would affect intrinsic frequency measures, explained Kloner, a professor of medicine at the Keck School of Medicine at USC and chief science officer and director of the Cardiovascular Research Institute at Huntington Research Institutes in California. “We were expecting some difference in the two types of toxins, but not the differences we saw,” he said.

They found that e-cigarette vapor containing nicotine caused vascular dysfunction and blood vessels to stiffen in the animals. The results suggest that nicotine-containing electronic cigarettes affect vascular function and left ventricle arterial coupling, while standard cigarettes appeared to negatively affect left ventricle function.

The long-term cardiovascular effects associated with e-cigarette use and how they compare to the risks associated with traditional tobacco cigarettes are not yet fully understood. The fear is that this may slow the development of public health interventions to limit nicotine exposure. These findings should advance the case for those interventions.

“Our results support the growing call for public health policies aimed at reducing exposure to inhaled nicotine and to synthetic nicotine products not yet on the market,” Michael T. Kleinman, a coauthor of the study and an adjunct professor of environmental and occupational health at the College of Health Sciences, University of California, Irvine, said in a press release.

The study is published in the Journal of the American Heart Association.