Ischaemic heart disease

Respiratory infections an underappreciated trigger for MI


Within the first seven days of experiencing lower respiratory infection symptoms, patients have a 17-fold increased risk of acute MI and, while that risk gradually decreases over time, it remains elevated up to one month after the infection has cleared, new research finds.

Dr Lorcan Ruane, from Sydney University and the lead author on the study published in the Internal Medicine Journal says its an ‘underappreciated’ trigger for acute MI but respiratory infection is probably one of the most important to understand because its so common.

Researchers asked over 500 patients who had been recently admitted to hospital with an angiographically confirmed MI if they’d experienced a recent ‘flu-like illness with fever and sore throat’ or if they had reported a diagnosis of pneumonia or bronchitis – criteria that were designed to capture both lower and upper respiratory tract infections.

While more severe lower respiratory infection resulted in a 17-fold increase in acute MI within the first seven days of symptom onset, even less severe upper respiratory infections, like the common cold, pharyngitis, rhinitis and sinusitis, resulted in a 13-fold increase in risk of acute MI.

Although, across both groups, patients who had experienced a previous MI, hypercholesterolemia or hypertension, or who were taking aspirin, beta-blockers or ACE inhibitors before their MI seemed to have a lower risk, suggesting that these medications may play a protective role at the time of infection, with statistical significance for ACE inhibitors Dr Ruane noted.

In addition to the standard practices to ward off infection – hand hygiene, isolation from infected people and increased vaccination uptake, Dr Ruane says there is also potential for targeted therapies to be used temporarily to reduce the risk of triggering an MI in high-risk populations.

“Once a patient is exposed to respiratory infection, secondary prevention methods could include prompt treatment of the infection as well as possibly taking aspirin to reduce the transient risk in CVD,” he told the limbic adding that aspirin use has been shown to be associated with lower mortality rates in patients with pneumonia.

However until that is tested in further studies, Dr Ruane says physicians should be aware of respiratory infection as an acute trigger for MI and pass that awareness on to patients.

He suggests that patients who develop a respiratory infection “should not dismiss chest pain symptoms as necessarily respiratory and not cardiac in origin.”

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