You’re six times more likely to have a heart attack during the week after being diagnosed with flu compared to the year before or after the infection, a study has found.
Researchers at the Institute for Clinical Evaluative Sciences (ICES) and Public Health Ontario (PHO) said the risk may be even higher for older adults, patients with influenza B infections, and patients experiencing their first heart attack.
“Our findings are important because an association between influenza and acute myocardial infarction reinforces the importance of vaccination,” said Dr Jeff Kwong, a scientist at ICES and PHO and lead author of the study.
In the study published in the New England Journal of Medicine, the researchers found a significant association between acute respiratory infections, particularly flu, and heart attack.
They said other respiratory viruses such as pneumonia could increase the risk of heart attack too.
A heart attack is a medical emergency caused by a clot forming in one of the three coronary arteries that supplies blood to the heart muscle. This prevents blood from flowing to the heart, which can prove dangerous.
After analysing nearly 20,000 adult cases of laboratory-confirmed flu from 2009 to 2014, researchers identified 364 patients who were hospitalised for a heart attack within one year before and one year after their flu diagnosis.
The researchers said there were 20 admissions in the first week after being diagnosed, and a subsequent 3.3 admissions per week in the year before and after.
The findings showed the number of hospital admissions for heart attack was six times as high during the seven days after a flu diagnosis.
The most common sign of a heart attack is chest pain or discomfort. NHS Choices describes this as “a sensation of pressure, tightness or squeezing in the centre of your chest”.
If it feels like indigestion, it can be difficult to determine whether it’s a heart attack or not, which is why it’s important to be aware of other symptoms that may arise such as:
:: Feeling lightheaded or dizzy
:: Feeling short of breath
:: Nauseousness or vomiting
:: Coughing or wheezing
:: Feeling very anxious (like having a panic attack)
:: Pain in other parts of the body.
“People at risk of heart disease should take precautions to prevent respiratory infections, and especially influenza, through measures including vaccinations and hand-washing,” said Kwong.
The research team added that patients should not delay medical evaluation for heart symptoms particularly within the first week of an acute respiratory infection.
Philippa Hobson, senior cardiac nurse at the British Heart Foundation, commented on the findings: “There is evidence that heart attacks happen more often during or immediately after an acute inflammatory illness, such as flu. Heart patients are particularly vulnerable to the flu, in part because the virus can cause inflammation, increasing the risk of a heart attack.
“If you have heart disease, you’re more likely to have complications and are at greater risk of becoming more seriously ill from the flu. So it is recommended that you get your annual flu jab if you’re eligible.
“You can get them free on the NHS if you’re aged 65 or over or you have a chronic condition, such as heart disease. If you think you should have the flu jab you should contact your GP for advice.”