New Heart Risk Marker Found
Blood test for protein helps treatment, predicts problems
TUESDAY, Feb. 10, 2004 (HealthDayNews) -- There's a new and hard-to-pronounce entry in the growing field of molecular markers for risk of stroke, heart attack and other cardiovascular diseases, researchers report.
Studies in Switzerland and the United States show that measuring blood levels of a protein called B-type natriuretic peptide (BNP) can do two key things: give doctors valuable information to guide them in their treatment of patients who come to the emergency room with severe breathing problems; and help physicians determine the long-term cardiovascular outlook for people with no apparent problems. Both reports appear in the Feb. 12 issue of the New England Journal of Medicine.
Much more work is needed before BNP could come into everyday use, says Dr. Ramachandran S. Vasan, an assistant clinical professor of medicine at Boston University School of Medicine and lead author of the American report.
But the initial studies show that BNP "is one of the markers of cardiovascular risk above and beyond the traditional risk factors," Vasan says.
His report described the relationship between BNP blood levels and development of cardiovascular problems in 3,346 participants in the Framingham Offspring Study. They were followed for more than five years, as the researchers looked at six endpoints: heart failure, a first major cardiovascular event such as a heart attack, the heartbeat abnormality called atrial fibrillation, stroke, coronary heart disease, and death from any cause.
"The exciting thing is that BNP levels could predict at least five of the six outcomes in a reasonably powerful manner," Vasan says.
In the Swiss study, physicians at the University of Basel Hospital assigned 225 patients who came to the emergency room with acute breathing problems were treated on the basis of their BNP levels, while another 227 were not given the test and were treated in the usual way.
The rule for the emergency room doctors was that low BNP level made congestive heart failure unlikely, while a very high level indicated the need for intensive treatment of heart failure.
The rule worked, the report says: Only 75 percent of the patients who got the test were hospitalized, compared to 85 percent of those who didn't. The hospitalized patients who got the test stayed for an average of eight days, compared to 11 days for those who didn't. Overall, BNP testing reduced the cost per patient by $1,800.
BNP is a hormone that increases blood flow, in part by making blood vessels wider. It is released as a response to stress, so that high blood levels can indicate greater stress and a need for more aggressive treatment.
Many more studies are needed to determine the role of BNP in diagnosis and treatment of cardiovascular conditions, Vasan says. In that respect, it is similar to C-reactive protein, a marker of inflammation found to be associated with cardiovascular risk.
"We have this one particular marker," Vasan says. "We look forward to studies where we can see how well it does in comparison with other biomarkers, especially C-reactive protein. We must also see how well it does in combination with other biomarkers."
One hope is that a BNP test could give a warning about potential trouble in healthy people, Vasan says. "Perhaps this marker could help us discriminate better among people about cardiovascular risk," he says. "It could also contribute information of diagnostic value."
The Framingham study "is breaking new ground," says Dr. Daniel B. Mark, a professor of medicine at Duke University Medical Center and co-author of an accompanying editorial. But it raises the question about what it means and what can be done about it.
Mark says he has encountered that question in his practice about C-reactive protein. Patients have been referred to him because their primary physicians measured high levels of the marker, "but the problem is, what do you do about it?"
For the moment, the answer seems to be more intensive treatment of other known risk factors, such as high blood pressure and high cholesterol, he says.
Emergency room use of BNP readings is "a lot further along," with several other studies producing results similar to those reported in the Swiss trial, Mark says, but his inquiries among cardiologists has found that it is rarely used.
"We're not using it in the Duke emergency room, and I know of only one cardiologist who is routinely using it as a heart failure test," he says.