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Vol 14, No. 3       LINCARE is a National Supplier of Home
Fall '01                Oxygen and Respiratory Therapy Services

Flu tied to Heart Attacks

Heart disease patients who get flu shots may be less likely to have a second heart attack than those who don't, says a study that's part of a growing body of research linking the flu virus to heart attacks. Scientists began speculating about such a connection when they noticed that heart disease death rates jumped during the influenza epidemics of the early 20th century.

In the latest study, published in the current issue of Circulation, researchers at the University of Texas-Houston Health Science Center studied 218 coronary artery disease patients seen at Memorial Hermann Hospital during the 1997-98 flu season.

The scientists compared the flu-shot history of the patients who suffered a new heart attack or unstable angina, a type of chest pain, with those who had not. It's not that researchers think flu shots protect against heart disease. But it's easier to get accurate information about whether people had a flu shot than whether they had the flu, which often is confused with other upper-respiratory illnesses.

After accounting for risk factors such as smoking and high cholesterol, the scientists concluded that patients who had received flu shots were two-thirds less likely than the others to suffer a second heart attack or unstable angina.

The study's findings echo those of one published Oct. 1 in the American Journal of Epidemiology.

In that paper, University of Washington scientists compared 342 people who had suffered cardiac arrest with demographically similar people who had not.

After accounting for known risk factors for heart disease, the researchers concluded that people who had flu shots were half as likely to suffer cardiac arrest as those who did not have the shots.

Still, lead author David Siscovick cautions, "we don't want people to feel because they have a viral infection they necessarily have heart disease. If there's any relationship, it's likely to be influenced by many other factors."

The authors of both studies say their findings could simply reflect that people who get flu shots are more likely to take better care of themselves. But the researchers add that they did strive to account for differences in known risk factors for heart disease between those who got flu vaccinations and those who did not.

The Texas researchers list nine possible explanations for a link between the flu and heart attacks , from flu-induced inflammation of the fatty deposits in coronary arteries to the psychological stress of missing anticipated activities.

Animal studies lend credence to the notion that influenza could exacerbate coronary artery disease.

At last month's annual meeting of the American Heart Association, for example, UCLA researchers reported that infecting mice with the flu at least temporarily changed their HDL, 'normally "good" cholesterol, into an artery-clogging form.

- Rita Rubinn,
USA TODAY

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