Influenza infection almost doubles the chances of a heart attack, but this risk is reduced by immunisation, suggests recent research.
Australian researchers compared rates of laboratory-confirmed influenza infection in patients who had a myocardial infarction, with controls who were hospital outpatients who had not had a myocardial infarction. Some 559 patients were included in the two-year study and all participants were aged over 40 years. The primary outcome measure was a positive nucleic acid test for influenza.
Evidence of influenza was identified in 53 subjects: of the cases, 34 were influenza-positive, compared with 19 controls, however no patient was identified as having influenza during their clinical encounter. The cases were almost twice as likely (OR 1.97) to have had recent influenza compared with the control group. Influenza vaccination was significantly protective, with vaccination effectiveness for the prevention of AMI of 45%. Vaccination effectiveness for the prevention in 40-64 years was estimated as 45% and 33% for those aged ≥65 years.
What this means for GPs
The researchers concluded that ‘clinicians should be aware of influenza and infection as an underlying and poorly diagnosed precipitant or comorbidity in hospitalised patients and the preventative benefit of influenza vaccine for patients at risk for acute myocardial infarctions’.