SACRAMENTO, Calif. (The New York Times News Service) -- Doctors soon may be employing a simple blood test to help them determine which heart patients are at greatest risk for heart attack, stroke and death.

The test has been used for years in hospital emergency rooms to confirm a diagnosis of heart failure. And it's now proven an excellent predictor of the severe consequences of heart disease, even when other, more routine tests are negative.

Findings from the University of California San Francisco will not immediately change the way patients with symptoms of heart trouble are assessed, but may eventually play a key role in guiding doctors to treatment decisions.

"Our goal is to determine who are the high risk patients, so we can target medical and surgical therapies we know to be life-saving to those most likely to benefit," said Dr. Kirsten Bibbins-Domingo, whose research was published in today's issue of the Journal of the American Medical Association.

An estimated 71 million Americans have some form of cardiovascular disease. It remains the leading cause of death in the United States.

The blood test, which takes less than an hour to complete, measures levels of a substance known cryptically as N-terminal fragment of the prohormone brain-type natriuretic peptide, or NT-proBNP.

The peptide, and its cousin, brain-type natriuretic peptide (BNP), are released from the lower chambers of the heart when it is under stress. Elevated levels of the peptide in the blood mean the heart is working too hard. Common heart disease drug therapies such as ACE inhibitors, beta-blockers, and diuretics can decrease the levels, making BNP and NT-proBNP effective markers for cardiac conditions.

Until now, however, doctors have limited the test's use to confirmation of heart failure, a progressive illness in which the heart can no longer efficiently pump blood to other organs and muscles. A patient who comes into the emergency room with shortness of breath, for example, may be given the test to rule out other causes of the symptom, such as asthma.

Bibbins-Domingo and her colleagues wondered whether the test also could be used to determine the long-term prognosis of patients with a history of heart problems.

"So we studied 1,000 people who already had heart disease, and we were interested in determining whether we could predict who would go on to have another heart attack, stroke, heart failure, or die," she said.

After four years they found that the higher the level of the peptide in the blood at the outset, the higher their chances were for having an adverse cardiac event.

For example, patients whose heart peptide levels put them in the top quarter of those tested, had a nearly 8-fold increased rate of cardiovascular events or death compared with those whose peptide levels were lowest.

The most surprising finding was that the test accurately predicted a high risk, even when traditional assessments such as treadmill stress tests and echocardiography failed to confirm it.

Traditionally, the best test to predict a patient's high risk of dying from heart disease is echocardiography, which can detect a weak heart muscle, said Dr. David Roberts, a cardiologist and medical director of the catheterization laboratory at Sutter Medical Center.

That test, which uses sonography, measures the ejection fraction, or the percentage of blood squeezed out by the heart each time it beats. The lower the percentage, the higher the risk of death, he explained.

"The (peptide test) properly identified people at high risk for dying, even with ejection fraction was OK," he said. "That is a surprise."

Roberts said he would put the peptide test in the same category as calcium scoring, a cardiac testing approach that uses an X-ray to determine the amount of calcium buildup on artery walls.

"This gives us more markers to help identify high-risk individuals," he said. "If it is high, you better take a close look at that person and maybe do some more testing."

Study authors emphasized, however, that the test should not replace others used to determine cardiac risks and that it will not likely be used routinely until additional research is done.

Specifically, Bibbins-Domingo said, researchers need to determine whether the assessment tool can lead to better, more appropriate therapies and ultimately improved outcomes for patients.

The heart peptide test might help decide, for example, whether a patient needs coronary artery bypass surgery, considered a highly effective, but risky approach to cardiovascular disease.

"This might be a way to help inform the discussion between a doctor and patient about whether their risk of developing another heart attack or failure in the future is so high that they are willing to undergo an intervention like a bypass surgery," she said.

Copyright 2007 The New York Times News Service. All rights reserved.