Heart attacks and chronic heart disease both increase sharply during flu season, according to a large new study based on autopsy reports in St. Petersburg, Russia.

The researchers studied 34,892 reports from 1993 to 2000, comprising 11,892 deaths from acute heart attacks and 23,000 from chronic heart disease.

In each year, they found, the peak number of deaths for both conditions coincided with the height of the influenza epidemic. The rate for heart attacks was 30 percent greater than at other times, and for heart disease it was 10 percent greater. The pattern was similar for those over 50 and over 70, and for men and women.

The study appeared online April 17 in The European Heart Journal. That it used autopsy results in determining cause of death is a significant strength; death certificates, which are often the main source of data in such studies, tend to be less accurate.

“Our study indicates that flu triggers heart disease,” said Dr. Mohammed Madjid, the lead author and an assistant professor of medicine at the University of Texas Health Science Center at Houston. “And we recommend that every patient at risk for heart disease get a flu vaccine. We estimate that influenza vaccine can prevent up to 90,000 fatal heart attacks each year in the United States.”

Fewer than 3 percent of the study population had been vaccinated or used statin drugs, which minimizes the potential for bias due to medical treatment. The authors acknowledge, however, that they did not have person-specific data on medications and other coronary disease risk factors.