A simple blood test -- beyond standard lab tests -- taken at hospital admission strongly predicted in-hospital mortality risk for heart failure patients and may be useful in helping doctors decide which patients need higher-level monitoring and more intensive treatment.
Published in the May 15 issue of the Journal of the American College of Cardiology, the study findings show that the blood level of B-type natriuretic peptide (BNP), a neurohormone released by the heart when it is stressed or damaged, provided a direct relationship with in-hospital mortality. Researchers found that higher BNP levels at admission were predictive of higher in-hospital mortality rates.
"We hope the findings will help physicians more effectively stratify risk and guide treatment. This is the first study to definitively demonstrate a connection between BNP and in-hospital mortality risk among heart failure patients," said principal investigator Dr. Gregg C. Fonarow, UCLA's Eliot Corday Chair in Cardiovascular Medicine and Science, professor of cardiology and director of the Ahmanson-UCLA Cardiomyopathy Center. "This is also the largest biomarker study in heart failure ever conducted."
The relationship between BNP and mortality persisted independent of other clinical and laboratory factors and held true for hospitalized heart failure patients with either reduced or preserved systolic function, which is the ability of the heart's left ventricle to pump blood to the body's other organs.
The researchers utilized data on 48,629 out of 77,467 heart failure patients whose BNP levels were taken within 24 hours of hospital admission. The patient data, collected between April 2003 and December 2004 at 191 hospitals across the country, is part of the Acute Decompensated Heart Failure National Registry (ADHERE), a U.S. registry of heart failure patients.
Investigators assessed in-hospital mortality and placed the patients in four groups depending on their BNP level:
- The first group had low BNP levels -- less than 430 pg/ml (picograms per milliliter) -- and a corresponding mortality rate of 1.9 percent.
- The second group of patients had BNP levels between 430 and 839 pg/ml, with a corresponding mortality rate of 2.8 percent.
- The third group had BNP levels between 840 to 1,729 pg/ml, with a mortality rate of 3.8 percent.
- The fourth group had the highest BNP levels -- 1,730 pg/ml or more -- and the highest mortality rate, 6 percent.
"We were very surprised that this blood test was so highly predictive of mortality across a broad population of heart failure patients and range of BNP levels," said Fonarow.
Researchers found BNP levels remained predictive of mortality even after adjustment for age, gender, systolic blood pressure, pulse and other lab tests, such as blood urea nitrogen, creatinine and sodium.
Higher BNP levels were also predictive of other clinical outcomes, such as the need for mechanical ventilation, the length of the hospital stay and the amount of time spent in the intensive care unit.
Fonarow said that BNP levels may be a useful addition to routine assessment and can help guide care and treatment of patients hospitalized with acute heart failure. He noted that a BNP test provides quick results, often within 15 minutes to a few hours, which can provide physicians with additional information to help in medical decision-making.
The next step will be further research to demonstrate that patients with higher BNP levels at admission benefit from more intensive monitoring and treatment.
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The study was funded by the biopharmaceutical company Scios Inc., which sponsors the ADHERE registry. Fonarow and co-authors have received research grants and speaking fees from Scios and have served as consultants for the company.
Other study authors include: Dr. William F. Peacock of the department of emergency medicine at the Cleveland Clinic Foundation in Cleveland, Ohio; Dr. Christopher O. Phillips of the department of medicine at the Cleveland Clinic Foundation; Dr. Michael M. Givertz of the department of medicine at Brigham and Women's Hospital in Boston, Mass.; and Margarita Lopatin, M.S., department of biostatistics at Scios Inc. in Mountain View, Calif.