Acute myocardial infarction after laboratory-confirmed influenza infection

A new study from Canadian researchers examined the association between laboratory-confirmed influenza infection and acute myocardial infarction. Researchers used high-specificity laboratory methods to confirm influenza infection in respiratory specimens, and they identified hospitalization for acute myocardial infarction from administrative data. They defined the "risk interval" as the first 7 days after respiratory specimen collection and the "control interval" as 1 year before and 1 year after the risk interval. In all, the researchers identified 364 hospitalizations for acute myocardial infarction that occurred within 1 year before and 1 year after a positive test result for influenza. Of these, 20 occurred during the risk interval and 344 occurred during the control interval. The incidence ratio of an admission for acute myocardial infarction during the risk interval as compared with the control interval was 6.05. No increased incidence was observed after day 7. Incidence ratios for acute myocardial infarction within 7 days after detection of influenza B, influenza A, respiratory syncytial virus, and other viruses were 10.11, 5.17, 3.51, and 2.77, respectively. Based on the findings, the researchers conclude there is a significant association between respiratory infections, especially influenza, and acute myocardial infarction.