The risk of having a heart attack is 17 times higher in the seven days following a respiratory infection, according to a recent study.

The University of Sydney research is the first to report an association between respiratory infections such as pneumonia, influenza and bronchitis and increased risk of heart attack in patients confirmed by coronary angiography (a special X-Ray to detect heart artery blockages)."Our findings confirm what has been suggested in prior studies that a respiratory infection can act as a trigger for a heart attack," said senior author Geoffrey Tofler.

"The data showed that the increased risk of a heart attack isn't necessarily just at the beginning of respiratory symptoms, it peaks in the first 7 days and gradually reduces but remains elevated for one month," he added.The study was an investigation of 578 consecutive patients with a heart attack due to a coronary artery blockage, who provided information on the recent and usual occurrence of symptoms of respiratory infection.Seventeen percent of patients reported symptoms of respiratory infection within 7 days of the heart attack and 21 percent within 31 days.Tofler added: "Possible reasons for why respiratory infection may trigger a heart attack include an increased tendency towards blood clotting, inflammation and toxins damaging blood vessels, and changes in blood flow."

"Our message to people is while the absolute risk that any one episode will trigger a heart attack is low, they need to be aware that a respiratory infection could lead to a coronary event. So consider preventative strategies where possible, and don't ignore symptoms that could indicate a heart attack,” he noted. Tofler said, "The next step is to identify treatment strategies to decrease this risk of heart attack, particularly in individuals who may have increased susceptibility."The study is published in Internal Medicine Journal.