They found people who vaped every day were 34 per cent more likely than non-e-cigarette users to suffer a heart attack, and those who used the devices more sporadically had a 29 per cent increased risk.
"Until now, little has been known about cardiovascular events relative to e-cigarette use," said study leader Dr Mohinder Vindhyal.
"These data are a real wake-up call and should prompt more action and awareness about the dangers of e-cigarettes."
He sounded a note of warning, saying most of the e-cigarette users were ex-smokers so the heart problems could be due to their lifetime of tobacco use.
"I wouldn't want any of my patients nor my family members to vape," he said
Roughly a third of the 90,000 e-cigarette users were also smokers.
The team's initial analysis suggested e-cigarette users had a 56 per cent increased risk of heart attack than those who did not vape.
But taking into account the fact that people who were also regularly smoking tobacco had a 165 per cent increased heart attack risk, they calculated the increased isk of vaping alone dropped to about 34 per cent.
They found e-cigarette users were also 55 per cent more likely to suffer from depression or anxiety.
Despite a degree of uncertainty, Dr Vindhyal insisted the findings are concerning and more research is required into the risks of e-cigarettes.
"We found that regardless of how frequently someone uses e-cigarettes, daily or just on some days, they are still more likely to have a heart attack or coronary artery disease," he said.