Researchers in the US have warned that using e-cigarettes significantly raises the risk of heart attacks.
Concerns around the long-term health impact of vaping has been growing as their popularity increases.
The health benefits of the e-cigarettes have been said to outweigh potential harms by medical officials, and numerous tobacco smokers have made the switch to vaping.
The study, to be presented at the American College of Cardiology conference in New Orleans later this month, is one of the largest ever conducted on the impact of vaping, the Daily Mail reported.
Experts from the University of Kansas studied data from 90,000 e-cigarette users.