Acute infection can apparently trigger a heart attack or stroke in susceptible individuals, British investigators report. However, the cardiovascular risk does not appear to be affected by influenza, tetanus or pneumococcal vaccinations.

Dr. Liam Smeeth, at the London School of Hygiene and Tropical Medicine, and colleagues analyzed the United Kingdom General Practice Research Database, which includes records for approximately 5 million people.

As reported in the New England Journal of Medicine, the investigators restricted their analysis to about 60,000 patients who had had a heart attack between 1987 and 2001 and 55,000 who had a stroke, selecting only those individuals who had had a documented respiratory or urinary infection or a vaccination.

The rates of heart attack and stroke were highest during the first three days after an infection. Heart attack was almost five times more likely to occur after a respiratory infection, and 66 percent more likely after a urinary infection. For stroke, the rate was about tripled after either infection.

It took several weeks before the rates returned to normal.

No increase in the rate of heart attack or stroke was seen after influenza, tetanus, or pneumococcal vaccinations.

These findings lend strong support to the theory that systemic inflammation increases the risk of vascular events, the researchers conclude.

SOURCE: New England Journal of Medicine, December 16, 2004.