Jan. 9, 2007 -- A simple blood test may help doctors identify heart patients who are at high risk for having heart attacks, strokes, and heart failure.
The test, which measures blood levels of a protein called NT-proBNP, was found to be highly predictive of such cardiovascular events in a study involving almost 1,000 heart patients thought to have stable coronary heart disease.
Patients with the highest levels of the protein in their blood were eight times as likely as patients with the lowest levels to die or suffer a heart attack, stroke, or heart failure during the study. Even taking into account other risk factors such as sex, age, smoking, and cholesterol levels, there was still an increased rate of such problems.
Pinpointing Patients at Risk
NT-proBNP was found to independently predict cardiovascular risk, suggesting it can be a useful addition to tests already used in heart disease, like echocardiograms (a sonogram of the heart), stress tests, and other protein biomarkers.
The study is published in the Jan. 10 issue of The Journal of the American Medical Association.
"We have known that this marker was predictive, but the question has been, 'Does it really tell us anything that these other tests don't tell us?'" researcher Kirsten Bibbins-Domingo, MD, PhD, tells WebMD. "We found that it does, and the hope is that it can be used with these tests to help physicians pinpoint which patients have the highest risks."
The blood test is already used in hospital emergency departments to help ER doctors identify heart failure in patients who have shortness of breath and other symptoms of the disease. Heart failure occurs when the heart's ability to pump blood is weakened, which can result in a backup of fluid in the lungs and other areas.
Protein Levels vs. Heart Risk
It has not been clear if the test has value for predicting risk in asymptomatic heart patients thought to have stable heart disease.
In an effort to address this issue, Bibbins-Domingo and colleagues from the University of California, San Francisco and the San Francisco VA Medical Center assessed the association between plasma NT-proBNP levels and cardiovascular risk in 987 patients followed for an average of 3.7 years.
During this time, roughly a quarter of the patients either died or had a hospitalization from a nonfatal heart attack, stroke, or heart failure event.
The annual event rate among patients with the highest NT-proBNP levels at study entry was 19.6%, compared with just 2.6% among patients with the lowest levels.
There were four times as many heart attack cases reported among patients with the highest levels of the protein compared with those with the lowest, and four times as many strokes.
But the strongest association was seen for heart failure. Eighty cases of heart failure were reported among patients with the highest NT-proBNP levels, compared with just three cases among patients with the lowest levels.
"After adjusting for all other risk factors, it's clear that this marker is picking up something that we are otherwise unable to detect with standard tests such as echocardiography," says study researcher Mary Whooley, MD.
Value Unknown
While there is some suggestion that the test could prove useful for identifying heart risk in the general public, its most immediate use is for patients with established heart disease.
But even among these patients, its role in disease management is not yet clear, cardiologist Robert Bonow, MD, tells WebMD.
Bonow is chief of cardiology at Northwestern University Medical School and a former president of the American Heart Association.
"We aren't sure at this point what to do with this information once we have it," he says. "We can treat these patients [with elevated NT-proBNP] very aggressively, but we should be doing that anyway."
Bonow adds that while NT-proBNP may prove to be a useful test for asymptomatic patients with heart disease, "we don't really know this yet."
In an editorial accompanying the study, Marvin Konstam, MD, of Tufts University School of Medicine agreed that it remains to be seen if NT-proBNP will prove useful for the management of patients with heart disease.
Konstam tells WebMD that more study is needed to determine the value of such testing.
"The real home run will be when we identify a marker and an intervention to go along with it to lower risk," he says. "The best example of this is LDL, or bad, cholesterol. We not only know that LDL cholesterol is a predictor of heart risk, but we know that we can lower that risk with drugs."