People who feel symptoms of a heart attack but live far from a hospital may take some comfort from a new Canadian-led study that suggests many people with mild heart attacks can safely wait to get angiogram tests.

Heart attacks can be sudden and extreme, mild or anything in between.

"If you take a hundred individuals presenting to hospital with chest pain or something that suggests a heart attack, about 25 of them we know straight up have an electrocardiogram that qualifies them for a different emergency kind of heart attack," said Dr. Paul Armstrong, a cardiologist at the University of Alberta Hospital in Edmonton.

Doctors knew that these emergency cases need to be treated quickly. A new study suggests the others can be assessed, given drugs and then wait two or three days before getting an angiogram test that shows significant blockages in major arteries — the first step toward angioplasty surgical repairs or bypass surgery.

"There didn't appear to be a difference in major outcomes," said Dr. Shamir Mehta of McMaster University and Hamilton Health Sciences, who led the randomized trial in Thursday's New England Journal of Medicine.

"However, we did find a small group of patients, about one-third of the total patient population, where they were considered high risk."

Only these people suffering a severe heart attack benefited from early angiograms, the team found.

The findings are good news for people living in far-flung areas, since patients who are at highest risk can be identified in an ambulance or community hospital, Armstrong said.

Urgent cases can be put on air ambulances and flown to a major heart centre, where doctors in busy emergency rooms will now know which patients can safely afford to wait.

The findings shouldn't be taken as a reason to avoid seeking immediate medical treatment, doctors warned. Many already put off calling 911, but getting assessed and started on medication is still a time-sensitive step.