Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: MONDAY, May 24, 1993 TAG: 9305240085
SECTION: NATIONAL/INTERNATIONAL PAGE: A-1 EDITION: METRO
SOURCE: Associated Press
DATELINE: BOSTON LENGTH: Medium
Could there be a heart attack bug? A germ that passes from person to person and triggers the biggest killer of the Western world?
It sounds ridiculous.
Everyone knows bad hearts are brought on by high cholesterol, slothful living, high blood pressure, diabetes, obesity and smoking. But while these risk factors clearly are important, they can explain only about half of all heart disease.
Lots of folks keep their cholesterol under control, live right, watch their blood pressure and still drop dead from heart attacks. Figuring out why is one of the enduring mysteries of heart disease. Its importance explains the excitement about a new theory just emerging from the labs.
A fast-moving series of discoveries raises the possibility that an exceedingly common microbe, a variety of chlamydia bacteria, may often be to blame.
Much more research is necessary to prove the link. But if it holds up to further scrutiny, it might be possible to treat and prevent heart disease with antibiotics and vaccines.
"If it is true, it is a major, major, major breakthrough," said Dr. Jean Joly of Laval University in Quebec.
The germ is called chlamydia pneumoniae. It was discovered just seven years ago by Dr. J. Thomas Grayston of the University of Washington.
This type of chlamydia is distinct from the variety that causes venereal disease. It is a common cause of pneumonia and less serious respiratory unpleasantness, such as bronchitis and stuffed up sinuses.
Like cold viruses, it spreads from person to person via the respiratory tract. About half of all Americans are infected at least once by the time they reach adulthood, close to three-quarters by age 65.
The first hint that it might have something to do with heart trouble came from a Finnish team at the University of Helsinki headed by Dr. Pekka Saikku. The researchers compared healthy folks with people who had heart disease. They found that 60 percent of the heart patients had antibodies to the chlamydia bacteria, compared to 20 percent of the comparison group.
They went on to find that people with elevated antibody levels face about twice the usual risk of suffering heart attacks in the following three to six months.
Since the levels of antibodies in the bloodstream fade over time, high levels suggest a recent infection or perhaps a chronic one that the body cannot shake off.
"All our data suggest that chlamydia may be a causative agent in 60 percent to 70 percent of people with atherosclerosis," the clogging artery buildups that underlie heart trouble, said Dr. Maija Leinonen of Finland's National Public Health Institute. She is studying the link with her husband, Saikku.
The phrase "causative agent" is key. No one can say with certainty whether chlamydia pneumoniae causes atherosclerosis. In fact, news of the apparent link was met with great skepticism when the Finnish group published its first report in the British journal Lancet in 1988.
Some suspected that smoking might explain it. People who smoke are more susceptible to lung infections, and smoking also causes heart trouble. However, further studies have shown that while smokers with heart disease indeed have a higher incidence of chlamydia infections, the germ also is associated with higher risk in nonsmokers, as well.
Bits of evidence continue to accumulate, all strengthening the case.
For instance, Dr. Sandra Melnick of the National Institute of Allergies and Infectious Diseases studied 652 men and women. She found that those with chlamydia pneumoniae antibodies were twice as likely to show thickening of the carotid arteries, an early sign of atherosclerosis.
In another study, Dr. Thomas H. Thom of Stanford University looked at 291 people. He found that those with the antibody had about double the risk of clogged heart arteries.
"There is an association between coronary artery disease and antibody to chlamydia pneumoniae that is not obviously explained by factors such as smoking, age, gender and other associations," said Thom.
Just what the bacteria are doing there is unclear. Some suspect that building up plaque might be the body's response to a lingering chlamydia infection. On the other hand, though, it's possible that chlamydia just find plaque a nice place to live but don't actually cause the disease.
If chlamydia turns out to be a factor in heart trouble, it probably triggers the disease in only a fraction of those who get infected. No one knows how to identify the minority who might risk being harmed.
Still, if the bug is bad for the heart, it should be possible to stop the process, or prevent it, by giving people antibiotics. Chlamydia can be killed with tetracycline and other antibiotics.
by CNB