Influenza can trigger heart attacks and doctors should do more to ensure people at risk of heart disease get their annual flu shots, a study suggests.

Researchers in the U.S. studied autopsy reports from St. Petersburg, Russia, where a minority of residents get a flu vaccine or take anti-cholesterol drugs.

During peak flu season, the chance of dying from a heart attack jumped by a third compared with non-flu weeks, the team said in this week's online issue of the European Heart Journal.

The same pattern was seen for men and women 50 or older and 70 or older, with 11,892 people dying of heart attack and 23,000 dying from chronic ischemic heart disease from 1993 to 2000.

"Influenza epidemics are associated with a rise in autopsy-confirmed coronary deaths," the study's authors concluded.

Influenza vaccination should be advocated for patients at high risk of developing cardiovascular events."

Preventing deaths involves flu shots

Higher death rates among the elderly with heart problems would be expected during influenza outbreaks, said Mohammad Madjid, the University of Texas-Houston professor who led the study.

As for why, flu causes acute and severe inflammation in the body, which in some patients can destabilize atherosclerotic plaques that block arteries in the heart, leading to heart attacks, the researchers said.

"My public health message is that flu is an important killer in cardiac patients," Madjid said in a release. "If people can recognize that the flu vaccine has specific cardio-protective effects, then high-risk people will be more likely to make sure that they receive the influenza vaccine every year."

The findings of the study emphasize the importance of following the recommendations for flu shots and taking medications for heart disease as prescribed, the researchers said.

In Canada and the U.S., health officials urge people at high risk of being hospitalized because of flu complications to get vaccinated. Madjid called for the European Society of Cardiology to do the same.

"Between 10 and 20 per cent of people catch flu every year and I have estimated that we can prevent up to 90,000 coronary deaths a year in the U.S.A. if every high-risk patient received an annual flu vaccination," he said.