Flu Can Trigger Heart Attacks But Vaccine May Offer Protection For Cardiac Patients

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Main Category: Cardiovascular / Cardiology
Also Included In: Swine Flu;  Flu / Cold / SARS;  Immune System / Vaccines
Article Date: 23 Sep 2009 - 0:00 PDT

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A review of the facts published in the October edition of The Lancet Infectious Diseases reports that flu can trigger heart attacks and cause cardiovascular death. However, the influenza vaccine may offer protection for cardiac patients. As a result, more efforts are required to encourage people with heart disease and diabetes (which increases the risk of heart attacks) to have the flu shot. This might be particularly necessary with the threatening of the H1N1 influenza (swine flu) pandemic and seasonal flu outbreaks when many more people are expected to catch the flu.

It is common knowledge that the influenza infection can have cardiac complications, such as myocarditis. But the role of influenza in prompting heart attacks is vague. It has been suggested that acute and severe inflammation might be caused by influenza. In some patients, this may alter atherosclerotic plaques and cause clots in coronary arteries leading to heart attacks.

To supply further substantiation, Charlotte Warren-Gash and Andrew C Hayward from the UCL Centre for Infectious Disease Epidemiology, London, UK, and Liam Smeeth from the London School of Hygiene and Tropical Medicine, conducted a systematic review of the evidence. They examined the link between influenza and heart attacks or cardiovascular death. They considered the possible cardioprotective effects of the influenza vaccine. A total of 42 papers describing 39 studies between 1932 and 2008 were analysed.

Findings from all the population-level studies examined, showed that during times when the influenza virus was circulating there was a rise in deaths due to heart disease or incidence of heart attacks. In fact, the proportion of added influenza deaths that were due to heart disease averaged 35 to 50 percent.

Conclusions from a range of observational studies in different settings reported consistent associations between influenza and heart attacks. It showed a weaker link with cardiovascular death. In addition, four out of eight of these observational studies indicated there was a protective effect against heart attacks or cardiovascular events in individuals vaccinated against influenza. Furthermore, two small randomised trials suggested that influenza vaccination reduces the risks of cardiovascular death and some cardiac events.

The authors draw attention to the fact that it is the only main respiratory virus for which effective preventive vaccination is available. The uptake is not the best possible particularly in people who ought to have the flu injection such as those with chronic diseases including heart disease. Between 2008 and 2009, vaccine coverage in the UK was just 47.2 percent in the chronic disease group.

They write in conclusion: "We believe influenza vaccination should be encouraged wherever indicated, especially in those people with existing cardiovascular disease…Further evidence is needed on the effectiveness of influenza vaccines to reduce the risk of cardiac events in people without established vascular disease."

"Influenza as a trigger for acute myocardial infarction or death from cardiovascular disease: a systematic review"
Charlotte Warren-Gash, Liam Smeeth, Andrew C Hayward
Lancet Infect Dis 2009; 9: 601-10
The Lancet Infectious Diseases

Written by Stephanie Brunner (B.A.)
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