Published January 10, 2007
Can a blood test predict a heart attack? Exciting new research suggests that the simple diagnostic tool of a blood test may help doctors determine the risk of cardiac events in patients with heart disease.
In a California study led by principal investigator Dr. Mary Whooley, 987 men and women with stable coronary heart disease were monitored for an average of 3.7 years each. What the research revealed is that the higher the level of the peptide known as NT-proBNP in a patient’s plasma, the greater the chance that the patient has of dying or having a cardiovascular event such as a heart attack, heart failure, or stroke.
Patients in the study were divided into four quartiles depending on the level of NT-proBNP in their blood. A quartile is a term used in statistics to describe an observation group that is divided into four equal, but distinct parts.
The first quartile contained the study participants with the lowest levels of the peptide and the fourth quartile contained those with the highest levels. A total of twenty-six percent of the stuidy participants died or had a cardiovascular event during the course of the study. Upon examination of these statistics, the researchers discovered that each increasing quartile carried with it a greater risk of cardiovascular events or death.
Patients in the quartile with the highest levels of NT-proBNP were 3.4 times more likely to die or have a cardiovascular event than patients in the group with the lowest levels.
To be sure that plasma levels of NT-proBNP were a true indicator of cardiovascular events or death independent of other available prognostic tests, the researchers adjusted for all other risk factors.
This isn’t the first study to examine the ability of natriuretic peptides like NT-proBNP to predict the risk of cardiac events in patients with known or suspected cardiovascular disease. Dr. Marvin A. Konstam, Chief of Cardiology at New England Medical Center and Professor of Medicine at Tufts University School, also recently published an article in The Journal of The American Medical Association exploring the subject.
The reason these peptides are receiving so much attention is that they are what are known as "biomarkers." A biomarker is a biochemical factor that can be used to measure the progress of disease or the effects of treatment. Natriuretic peptides control the body’s water and sodium levels. They are released when blood pressure elevates, and they act to reduce the water and sodium on the circulatory system, which brings the blood pressure back to more normal levels.
As Dr. Konstam observes in his article, a biomarker may be a by-product of the disease itself and it may also directly participate in its development and the changes the disease undergoes as it develops. The biomarker NT-proBNP goes up during times of cardiac stress. That means that if the heart wall is over-expanded because of too much blood volume, or damaged because of too little blood flow to the heart, the level of NT-proBNP in the blood will elevate to indicate that abnormality.
While this discovery is certainly a milestone in the treatment of cardiac patients, there are still some things to keep in mind.
In the Jan. 9 press release issued by the Northern California Institute for Research and Education, one of the funders of the Heart and Soul study from which the participants for this study were selected, Dr. Whooley was quoted as saying 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 may get many more false positive results than true positives, which really lowers the value of the test. It’s much better at predicting risk in a population with a high incidence of heart disease."
Dr. Whooley goes on to add that even among heart patients, the value of the test is limited because all of the available therapies that can be used to prevent cardiovascular events should already be being used among these patients.
The chief benefit of the NT-proBNP blood test is really to identify patients who need more aggressive therapy than they are currently receiving.
Fox News Health contributor Maria Esposito contributed to this report.
Click here to check out Dr. Manny's book The Check List (Harper Collins, 2007).
Dr. Manny Alvarez is the managing editor of health news at FOXNews.com, and is a regular medical contributor on the FOX News Channel. He is chairman of the Department of Obstetrics and Gynecology and Reproductive Science at Hackensack University Medical Center in New Jersey. Additionally, Alvarez is Adjunct Professor of Obstetrics and Gynecology at New York University School of Medicine in New York City.