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The odds of surviving a heart attack may be a matter of night and day: A new study found that patients rushed to the hospital in the evening or on weekends face a higher risk of death from a heart attack compared to patients admitted during regular hours.

Researchers from the Mayo Clinic in the United States found that patients who suffered a heart attack during off-hours had a 5-per-cent higher mortality rate – both in hospital and within 30 days of discharge – than patients treated during regular hours. Outcomes may be even worse for patients diagnosed with a type of heart attack known as ST elevation myocardial infarction, or STEMI, which accounted for one-fifth to one-quarter of patients in the systematic review of 48 studies published Tuesday in the BMJ.

The researchers identified an off-hours delay of nearly 15 minutes for an emergency procedure to inflate the coronary artery, which could increase mortality by as much as 10 to 15 per cent, they wrote. The authors estimated that off-hour treatment delays result in 6,000 deaths per year in the U.S.

In Canada, an estimated 600 heart-attack patients may die each year because of treatment delays at night and on weekends. Canadian hospitals and health-care providers should be concerned about off-hour treatment delays identified in the review, which included several Canadian studies, said Dr. Beth Abramson, a spokesperson for the Heart and Stroke Foundation and author of Heart Health for Canadians.

"This study does apply to Canada," she said. But she added that treatment delays are only part of the problem affecting heart-attack patients who enter the ER at night and on weekends. "There are often delays in the patient coming to the hospital in the first place," she said.

Many people with heart-attack symptoms do not want to inconvenience family members or hospital staff with an emergency-room visit in the middle of the night. "There is a problem with being selfless," Abramson said.

The authors of the BMJ report noted that some studies found that patients who present with a heart attack off-hours tend to be sicker, while other studies did not.

A better measure of reduced care during off-hours may be "door-to-balloon" time – the time it takes for inflation of the coronary artery after a patient has entered the hospital, according to an accompanying editorial in the BMJ written by doctors at the University of Toronto. Unlike variations in patients' conditions, door-to-balloon time is directly controlled by the hospital and care providers, they noted.

By this measure, patients receiving treatment during off-hours "experience delays in urgent care and worse outcomes, and the gap seems to be increasing over time," they wrote.

The review authors theorized that off-hours treatment delays may be due to decreased availability of cardiologists and nurses, as well as sleep deprivation and fatigue affecting hospital staff. Future studies should identify specific deficits in off-hours care, the researchers concluded, adding that heart-attack patients should expect the same health outcomes regardless of when they receive treatment.

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