Protein Can Pinpoint Heart Failure

A telltale protein can help physicians rule out heart failure in patients with severe shortness of breath, a common but often inconclusive sign of the pump problem.

High levels of the protein, called B-type natriuretic peptide (BNP), are almost always present only in people suffering from heart failure, according to a new study of men and women with the condition. When levels of the substance are low, breathing woes most likely stem from other ailments such as pneumonia or emphysema.

Dr. Kenneth Baughman, a Johns Hopkins University cardiologist, says roughly 25 percent of heart failure patients may fall into a gray zone where diagnosis is tricky.

For these patients, BNP could be "enormously beneficial," adds Baughman, the author of an editorial accompanying the study in the New England Journal of Medicine.

Facts About Heart Failure

Heart failure is a leading killer of the elderly, causing patients literally to drown in their own fluids as blood backs up in their lungs. Treatments for the condition, which strikes 500,000 Americans a year, are only temporary, and it has no known cure.

"It's a progressive, fatal disease that we're still working very hard to figure out how to treat," says Dr. Kirkwood F. Adams Jr., a heart specialist at the University of North Carolina.

"If you have a biochemical marker that you could measure that will give you some indication of the heart function, it would be a lot less expensive" than such current physiological tests as echocardiography, he says. BNP can also be read in a physician's office, he adds: "That's very promising."

Shortness of breath—also known as air hunger—is perhaps the signal symptom of a heart failure flare-up. However, many other ailments can also cause it. So, physicians are always looking for a quick way to accurately determine whether the heart is at the heart of lung distress.

How Does BNP Work?

BNP belongs to a family of hormone-like molecules produced by the heart and vessels when they are forced to work harder. By helping drain fluid, relax vessels, and push sodium into the urine, they can ease dangerous strain on the heart muscle.

The latest study was a seven center, multi-country analysis of whether BNP could help diagnose heart failure in the emergency room.

Led by Dr. Alan Maisel, of the University of California, San Diego, the researchers measured BNP levels in 1,568 men and women who had checked into ERs with shortness of breath. Of those, 744, or 47 percent, turned out to have heart failure; 770, or 49 percent, did not; and 72 had a history of pumping problems that were not behind their current breathing difficulty.

The protein test proved to be more accurate than any other single physical or laboratory gauge of heart failure. It outperformed even the presence of an enlarged heart on a chest x-ray or a history of the condition, the researchers say. Patients with the worst disease had the highest blood levels of the peptide.

Elevated BNP—100 picograms per milliliter of blood—identified patients with the condition more than 83 percent of the time. It safely excluded those with levels below 50 picograms with 96 percent accuracy.

BNP Not a Stand-Alone Test for Heart Failure

Dr. Jay Cohn, a cardiologist at the University of Minnesota Medical School in Minneapolis, says BNP is a useful part of a total work-up by physicians, but it is not a stand-alone test for heart failure.

Heart experts probably do not need the test anyway, Cohn adds, since they can judge heart failure by their experience with the disease. However, BNP could assist generalists and emergency room physicians in their diagnosis. "It levels the playing field," he says.

BNP is also helpful in other ways. Cohn and his colleagues, for example, are finding the peptide can help them identify patients with heart disease who do not know they are ill. It is also a marker for how well patients with heart failure respond to treatment.

"There is a clear relationship between how effectively BNP is reduced by therapy in the hospital, and how likely it is that patients may need to come back" for additional treatment, Cohn says. The question, however, is whether the molecule reflects how sick a person is, or if that person would have done better with more aggressive care.

The drug Natrecor, made by Scios Inc., of Sunnyvale, Calif., is a BNP infusion at high doses that helps improve circulation in heart failure patients.

Adams is chairman of the guidelines committee of the Heart Failure Society of America, which will be releasing its updated recommendations in September.

He says the group plans to incorporate something about BNP testing in the new version, though precisely what isn't yet firm. "We're still considering the best role for it," he says.

Always consult your physician for more information.