OTTAWA: More than one-third of Canadians having a heart attack drive themselves to hospital instead of calling for an ambulance, delaying potentially life-saving treatments, says a new study.

Victims may also endanger others by getting behind the wheel of a motor vehicle when blood flow to their heart is restricted, said the study, presented to the Canadian Cardiovascular Congress earlier this week.

"We're talking about patients who have full-blown, severe pain, yet they're trying to find their own way to the hospital," Hamilton Health Sciences Centre's cardiologist Madhu Natarajan told the daily Ottawa Citizen. "They are committing a mistake with potentially grave consequences" for themselves and the public.

Of 487 patients admitted to hospital with severe chest pains, 179 had got themselves to the emergency room, said the study. Most drove. Some of them took a bus. Thirty-two of them had a previous heart attack.

On average, they waited five minutes longer for an electrocardiogram, and up to an hour longer for a clot-dissolving drug than if they had arrived in an ambulance, which would alert doctors that a patient is en route.

People are most at risk of going into cardiac arrest in the first hour of a heart attack.