Respiratory Infections Can Trigger Heart Attacks

A new study suggests that respiratory infections such as pneumonia, influenza, and bronchitis can increase the relative risk (RR) of acute myocardial infarction (MI) by up to 17 times.

Researchers at the University of Sydney and Royal North Shore Hospital conducted a study that included interviews with 578 patients with angiographically confirmed MI that were held within four days of hospitalization, in order to investigate the association between exposure to respiratory infection prior to the onset of MI, as compared to their usual annual frequency of these symptoms.

The results showed that symptoms of respiratory infection were reported by 17% of the patients within 7 days of MI, and by 21% within 35 days prior to MI. The RR for MI within 1-7 days after respiratory infection symptoms was 17 and declined with subsequent time periods, and for those who reported milder, upper respiratory tract infection symptoms, the relative risk for the same time period was 13.5. In a sub-group analysis, RR tended to be lower in those taking regular cardiac medications. The study was published in the May 2017 issue of Internal Medicine Journal.

“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 senior author Professor Geoffrey Tofler, MD. “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 incidence of heart attacks is highest during winter in Australia. This winter peak is seen not only in Australia but also in other countries around the world is likely due in part to the increased incidence of respiratory infections,” added study author associate professor Thomas Buckley, RN, PhD, of the University of Sydney school of nursing. “People should take measures to reduce exposure to infection, including flu and pneumonia vaccines where appropriate.”