A protein produced by overstressed heart muscle appears to be a strong indicator of heart disease, offering doctors a quick and cheap test for diagnosing patients in the ER and a potential new way to spot heart trouble well before symptoms appear.
The substance, called B-type natriuretic peptide, could become the latest in a growing array of "biomarkers,'' or proteins whose levels in the blood can be used to diagnose or predict heart trouble, two studies in Thursday's New England Journal of Medicine indicate.
Already, doctors in many emergency rooms test for high levels of the peptide in patients with severe shortness of breath to determine whether they have congestive heart failure, in which the heart stops pumping effectively.
Congestive heart failure is the most frequent cause of hospitalization among people 65 or older but is difficult to diagnose. Treatment delays increase the chances of heart damage or complications and the costs of care, which now exceed $28 billion a year in this country.
One of the studies, conducted at University Hospital in Basel, Switzerland, found that measuring the peptide's levels in ER patients with shortness of breath helped doctors more quickly decide whether patients had heart failure.
That, in turn, reduced treatment costs and hospital stays by about one-fourth and lowered the percentage of patients hospitalized. The peptide test costs about $35.
The other study found that people with high levels of the peptide are three times as likely to develop heart failure within five years. That study, funded mostly by the National Heart, Lung, and Blood Institute, examined 3,346 people.
All of them are part of the Framingham Heart Study, which since 1948 has followed three generations and thousands of residents of the Boston suburb with regular physicals and tests.
"It's a continuing success story for the biomarkers, and I believe they hold real promise for the future, both for the management of patients with urgent symptoms and for preventive strategies,'' said former American Heart Association President Dr. Sidney Smith.
Smith said the findings should be considered when U.S. guidelines for diagnosing heart failure in ER patients are updated over the next year; European guidelines already call for the use of the test.
However, Smith said is too early to advocate widespread use of the test to predict heart trouble and plan preventive treatment.
Doctors believe a gradually failing heart tries to protect itself by secreting more and more of the peptide, which dilates blood vessels and lowers blood pressure. The Swiss study included 452 patients who came to the hospital's ER in 2001 and 2002 with shortness of breath.
To determine the cause - congestive heart failure, a respiratory disease or something else - all got physicals, standard blood tests, a chest X-ray and an electrocardiogram, or EKG. Half also got the peptide test.
In the peptide-test group, treatment cost an average of $5,410, compared with $7,264 for the others, and patients were released in eight days on average, versus 11 in the comparison group.
The researchers said the additional test enabled them to start the correct treatment faster. That reduced how many patients were hospitalized, from 85 percent to 75 percent.
"It is the first randomized trial that shows the addition of this simple test improves both patient outcomes and the use of hospital resources,'' said lead researcher Dr. Christian Mueller, a cardiologist at the Basel hospital.
"I think it will have a very large impact.''
The U.S. study found that patients with the highest levels of the peptide were about 60 percent more likely to die in five years, and twice as likely to suffer a stroke or atrial fibrillation, in which the heart's upper chambers flutter ineffectively.
Dr. Ramachandran Vasan, senior investigator at the Framingham Heart Study, said the peptide test offers additional information over standard tests such as cholesterol level. But he said larger studies are needed to see if the peptide's level can help predict heart attacks. And he said the peptide's predictive value needs to be tested against that of other known biomarkers, such as C-reactive protein.
Dr. Diana DeCosimo, a cardiologist at the University of Medicine and Dentistry of New Jersey in Newark, also noted that nearly all the patients in both studies were white, so the results must be confirmed in minorities, particularly blacks, among whom heart failure is especially common.