SAN FRANCISCO -- Experts said a blood test commonly given in the emergency room could help predict the risk of a heart patient having a heart attack or stroke in the near future, NBC11's Marianne Favro reported.

After a heart attack and open heart surgery, Marlyn Murray had a stress test to check on her heart, but in the future, she may rely on a simple blood test to help indicate her risk of a second heart attack.

Murray was one of 987 Bay Area patients who helped University of California, San Francisco researchers make an important discovery at VA Medical Center.

The test measures the protein NT-proBNP. Those with the highest level faced the greatest risk

Patients in the study were divided into four quartiles depending on their NT-proBNP blood levels and followed for an average of 3.7 years each.

Twenty-six percent died or had a cardiovascular event during the course of the study. The study reports that "each increasing quartile … was associated with a greater risk of cardiovascular events or death."

Patients in the quartile with the highest levels of the biomarker were 3.4 times more likely to die or have a cardiovascular event than patients in the group with the lowest levels.

"Those patients were at a 19 percent risk over the next four years of having a heart attack or stroke compared with the 2.5 percent risk of levels in the lowest ends," said Dr. Mary Whooley, one of the researchers who discovered the value of the blood test.

The test gives doctors another way to predict a heart attack that traditional screenings such as stress tests may miss.

"It does seem to pick up things not measured by an echocardiogram or high cholesterol or blood pressure," Whooley said.

The study appeared in the Jan. 10 issue of Journal of the American Medical Association.

NT-proBNP is a marker in the blood for BNP, a hormone that "goes up during times of cardiac stretch or stress," Whooley said. "When the heart wall is overexpanded by too much blood volume or damaged by lack of blood flow to the heart itself, BNP goes up, and NT-proBNP along with it."

Whooley cautions that the NT-proBNP test is "not something that we should order on every patient who comes in for a routine checkup" but would be most useful for patients with known coronary heart disease.

"In the general population, the incidence of heart disease is so low relative to the incidence in heart disease patients that you get many more false positive results than true positives, which really lowers the value of the test," Whooley said. "It's much better at predicting risk in a population with a high incidence of heart disease."

Whooley also noted that, even among heart patients, the value of the test is limited "because all of the therapies available to prevent cardiovascular events should already be used among these patients. The best it can do is help identify candidates for more aggressive therapy."

She said that one additional step for researchers is to see "whether there are therapeutic interventions that still remain to be developed that might prevent heart patients with elevated BNP from doing worse."

Patients in the current study were all enrolled in the Heart and Soul Study, a multiyear prospective study of 1,000 heart patients directed by Whooley that is designed to investigate whether depression predicts heart disease.

"Because the Heart and Soul Study measures heart disease so carefully, our data set has become extremely valuable for a wide range of cardiovascular studies, many of which have nothing to do with our original hypothesis," Whooley said. "This study is just one example."

Murray said she is happy to contribute to the research.

"I think knowing the risk factors is important, and knowing if there are any risk factors that would put you in harms way, we want to do that," Murray said.

Murray said she hopes the blood test may one day prevent other patients from having a heart attack.