Another study supports an association between influenza and subsequent MI.

Viral respiratory infections, such as respiratory syncytial virus and influenza, can be associated with cardiac complications, including myocardial infarction (MI). Proposed mechanisms for this excess risk relate to activation of inflammatory and coagulation pathways, along with demand ischaemia.

Researchers in the Netherlands conducted an observational registry-based study to evaluate the association of PCR-positive influenza and subsequent risk for MI-associated events (i.e. hospitalisation or death). Incidence of acute MI was compared during the risk period (within one week after PCR-positive influenza) and the control period (one year before or after influenza, excluding the risk period). A total of 406 episodes (in 401 patients; median age, 74 years) of MI within one year of influenza diagnosis were included. Relative incidence of MIs during the risk period was six times higher than during the control period. Relative incidences were 16.6 in patients without known coronary artery disease (CAD) and 1.4 in those with CAD. In post hoc analysis, use of antithrombotics was associated with lower risk for MI than was nonuse (relative incidence, 4.1 vs 13.5).

Comment: These results support existing evidence that influenza infection might increase risk for acute MI. Primary care providers should emphasise to older patients that flu vaccines potentially can help prevent MI. The seemingly counter-intuitive finding of higher relative risk in patients without known CAD – compared with those who had CAD histories – could reflect the latter group’s greater use of preventive cardiovascular medications, including antithrombotic drugs. In fact, researchers in an ongoing prospective study are examining whether aspirin can prevent adverse cardiovascular events during the several months after hospitalisation with pneumonia.

Aaron J. Calderon, MD, FACP, SFHM, Program Director, Internal Medicine Residency, Saint Joseph Hospital; Clinical Professor of Medicine, Division of General Internal Medicine, University of Colorado School of Medicine, Denver, USA.

de Boer, AR et al. Influenza infection and acute myocardial infarction. NEJM Evid 2024; 3: EVIDoa2300361.

This summary is taken from the following Journal Watch titles: General Medicine, Infectious Diseases, Cardiology, Ambulatory Medicine, Hospital Medicine.