Australian researchers have found that the risk of having a heart attack is 17 times higher in the seven days following a respiratory infection, thus establishing for the first time a link between respiratory infections such as pneumonia, influenza and bronchitis and increased risk of heart attack in patients confirmed by coronary angiography.
“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 study author Geoffrey Tofler from University of Sydney, Royal North Shore Hospital and Heart Research Australia.
The study findings were published recently in the Internal Medicine Journal.
“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,” added Prof Tofler.
The researchers at the University of Sydney investigated 578 consecutive patients with heart attack due to a coronary artery blockage, who provided information on recent and usual occurrence of symptoms of respiratory infection.
Seventeen per cent of patients reported symptoms of respiratory infection within seven days of the heart attack, and 21 per cent within 31 days.
Patients were interviewed about their activities before the onset of their heart attack, including if they experienced a recent “flu-like illness with fever and sore throat”. They were considered affected if they reported sore throat, cough, fever, sinus pain, flu-like symptoms, or if they reported a diagnosis of pneumonia or bronchitis.
A second analysis was among those with symptoms restricted to the upper respiratory tract, which included the common cold, pharyngitis, rhinitis and sinusitis.
“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,” said Professor Tofler.
“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.
“The next step is to identify treatment strategies to decrease this risk of heart attack, particularly in individuals who may have increased susceptibility,” he added.