Blood Protein Tied to Heart Failure

Study hints homocysteine could be a cause

TUESDAY, March 11, 2003 (HealthDayNews) -- A new study finds high blood levels of the protein homocysteine are associated with congestive heart failure, and there are strong hints in the report that they cause the deadly condition.

That last point is crucial. The American Heart Association's official stand is that while several studies have established an association, high homocysteine levels "are not yet called a major risk factor for cardiovascular disease. We don't recommend widespread use of folic acid and vitamin B supplements to reduce the risk of heart disease and stroke."

But several aspects of the study, reported in the March 12 issue of the Journal of the American Medical Association, point toward a causal link, says study author Dr. Ramachandran S. Vasan, a senior investigator with the Framingham Heart Study in Boston.

First, measurements of homocysteine levels were taken before the participants, 2,491 men and women in the long-running study, began to develop heart disease. "Readings of high levels were obtained before the onset of heart failure, thus establishing a sequence," Vasan says.

And the association was strong, he says. The risk was double for people in the upper 50 percent of blood homocysteine levels than for those in the lower half, and quadruple for those in the upper 25 percent, compared to those in the lowest 25 percent, Vasan says. The risk was elevated even for women whose homocysteine levels are in the range now regarded as normal.

Finally, there is "biological plausibility" to back the belief that high homocysteine levels can cause cardiovascular disease, he says. For example, laboratory studies have shown that homocysteine can have adverse effects on the endothelium, the delicate tissue that lines arteries.

However, the key bit of evidence, a study showing that lowering blood levels of homocysteine will reduce the risk of heart disease, is missing, Vasan says, and that evidence will not be available for some time. There are studies designed to see if lowering homocysteine levels will reduce the incidence of stroke, but none aimed at heart disease, he says.

The new study is interesting because it is the first to link high homocysteine levels with heart failure, rather than heart attacks and other cardiovascular diseases, says Dr. Nieca Goldberg, chief of cardiac rehabilitation at Lenox Hill Hospital in New York City and a spokeswoman for the American Heart Association. She, too, points out "there is no data available saying that reducing blood homocysteine levels actually reduces the incidence of heart attacks or heart failure."

It is premature to tell people to take vitamin supplements to lower blood homocysteine levels, Goldberg says. She recommends that "people look at the vitamin B content of a lot of foods, particularly green, leafy vegetables."

"I do prescribe B vitamins in appropriate patients," Goldberg says. She explains she will prescribe them for some patients with elevated homocysteine levels even if they do not have the traditional risk factors for cardiovascular disease, such as high blood pressure or obesity.

However, this is a decision that must be made for each individual patient, Goldberg says. There is a chance that taking too much vitamin B can cause damage in some people, she says, so the thing to do is to "ask your doctor about it."

More information

More detailed information on homocysteine is available from the American Heart Association. Learn about heart failure from the National Heart, Lung, and Blood Institute.

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