Acute MI risk tied to flu in adult patients

Adults were more likely to be hospitalized for a heart attack during the week after they were diagnosed with the flu, a small Canadian study found.

Incidence of admission for an acute myocardial infarction (MI) was six times higher in the 7 days following a positive test for influenza compared with a "control interval" (20.0 admissions per week versus 3.3 admissions per week), reported Jeffrey C. Kwong, MD, of the Institute of Clinical Evaluative Sciences in Ontario, and colleagues.

There was also an elevated incidence of acute MI after influenza infection among older patients, and patients with influenza B infection, the authors wrote in the New England Journal of Medicine.

"For many years and through many studies it was known that influenza is a substantive risk factor for acute MI," IHPI member Kim Eagle, MD, of U-M in Ann Arbor, told MedPage Today. "This probably relates not only to the physiologic stress of the infection but also the notion that the influenza virus triggers release of cytokines that can destabilize previously stable coronary plaques leading to acute coronary syndromes." Eagle was not involved in the study.

Kwong's group said that in some prior studies examining the link between influenza-like illness and subsequent cardiovascular events, "clinical diagnoses of acute respiratory infections and influenza-like illnesses were neither sensitive nor specific for influenza," and the few that did use a laboratory-confirmed test were either underpowered, had inconsistent findings, or used a case-control design.