Virulent Form of Ulcer Bug Tied to Stroke
H. pylori strain could cause artery-damaging inflammation
MONDAY, July 8, 2002 (HealthDayNews) -- Italian researchers have added another brick to the growing edifice of evidence linking infections with heart disease and stroke.
The still-unfinished theory says one major cause of cardiovascular disease is the inflammation that results from a viral or bacterial attack on the body. Such an infection is said to release a molecule called C-reactive protein, which inflames and damages the delicate endothelium that lines the interior of arteries, leading to blockages that cause heart attacks and strokes.
One important villain in this story is Helicobacter pylori, a bacterium best known as the cause of stomach ulcers. Some studies have reported a strong association between H. pylori and the risk of cardiovascular disease, while others find no such association.
Now researchers at Tor Vergata University in Rome say they may have found the reason for the inconsistent results. Their study finds that only some specially virulent strains of H. pylori are associated with stroke.
"Because H. pylori infection caused by any genotype may represent an easily removable risk factor, confirmatory studies assessing the above-reported relationship are clearly needed," says a report in tomorrow's issue of Circulation: Journal of the American Heart Association.
The Italian researchers looked at the strains of H. pylori they found in patients who had atherosclerotic strokes, the kind that happen when a clot blocks a brain artery. (The other kind occurs when a blood vessel bursts.) They also looked at persons who had not had strokes.
All of them had about the same rate of infection with H. pylori, about 70 percent. But in the stroke patients, more than 40 percent of the bacteria were of a strain designated CagA-positive, a virulent type associated with production of C-reactive protein. Less than 18 percent of stroke-free individuals carried the CagA-positive bacteria.
The CagA-positive carriers also had a higher level of inflammation throughout their bodies, a finding that "gives some support to the hypothesis that virulent H. pylori strains may induce system inflammation, a recognized risk factor for atherosclerosis," the researchers write.
More work is needed, says Dr. Larry Goldstein, a professor of medicine at Duke University Medical Center and a spokesman for the American Heart Association, because the finding might mean that the fatty plaques that block arteries are more attractive homes for the virulent bacteria. "There is always a problem distinguishing between an association and causation," he says.
Even if a cause-and-effect relationship is proved, it might not be easy to put the finding to use in practice, Goldstein notes.
Many people carry H. pylori, and a doctor would have to find out whether the virulent strain is present before starting preventive treatment, he says.
Still, this is one more study showing an association between infection and cardiovascular disease. In January, German researchers reported that the risk of death for patients with advanced heart disease is linked to the number of viruses and bacteria to which they have been exposed. In February, a French study found that the risk of stroke was 40 percent lower in people who had a flu shot, compared to those who didn't.
"How important this is, time will tell," Goldstein says. "Their data are consistent and make sense. But whether treatment can alter the course of stroke or decrease the risk of stroke is an unanswered question."
What To Do
You can learn more about inflammation and its role in cardivascular disease from the American Heart Association. Try the National Institute of Diabetes and Digestive and Kidney Diseases for information about the ulcer bug.