Heart patients who catch the flu may have more to worry about than just a fever or the sniffles: The virus could spark a heart attack, new research shows.
Amid the global outbreak of swine flu, experts say it's crucial that heart patients get vaccinated against both regular flu and swine flu to avoid medical problems. Swine flu isn't any more dangerous than regular flu, doctors say, but they add that heart patients need to be vaccinated because more flu viruses will be circulating this year.
British researchers analyzed 39 previous studies of heart patients and found a consistent link between flu and heart attacks. Up to half of all unexpected flu deaths were because of heart disease, the researchers found.
"The message here is so strong and so logical that it's hard for us to ignore," said Dr. Ralph Brindis, vice president of the American College of Cardiology. "If we can convince cardiac patients to get a flu vaccine, that could ultimately save lives."
Only about one-third of heart patients in the United States get regular vaccinations.
Doctors have long known that flu viruses can worsen existing medical conditions and that heart patients are especially vulnerable during flu pandemics. Flu viruses cause inflammation in the body, usually in the lungs. But they also can cause swelling in the heart itself or in the coronary arteries, which could lead to dangerous clots breaking off and causing a heart attack.
Once heart patients get the flu, they are more vulnerable to complications such as pneumonia and other infections.
"We know influenza vaccine is effective in preventing influenza and therefore in theory, ought to be effective in preventing the complications of influenza," said Andrew Hayward of University College London, one of the study authors.
Two studies analyzed showed that heart patients who got flu shots had fewer heart attacks than those who didn't, Hayward said.
Flu viruses might act as triggers for heart attacks in cardiovascular patients he said.
"Influenza may be bringing forward an event that might have happened anyway," he said, adding there is evidence that heart attacks peak when the virus does.
Experts are unsure whether the study results apply to otherwise healthy people with no history of heart disease. But they say flu viruses could trigger heart attacks in people with no apparent heart disease, if they have risk factors such as high blood pressure or are overweight.
