Are you using BNP testing for heart failure patients?

If not, you face liability risks, experts warn

If congestive heart failure (CHF) is misdiagnosed in your ED and the B-type natriuretic peptide (BNP) test was not available, you could face increased liability risks, according to some cardiovascular experts. Consider this example of accurate diagnosis and treatment: A 78-year-old man tells you he has had difficulty breathing and fatigue during the last 24 hours, and he reports a history of CHF and chronic obstructive pulmonary disease (COPD). On exam, you note no peripheral edema, a negative hepato-jugular reflux, and his chest has scattered wheezing. Along with the usual initial labs, a BNP level is done and found to be normal.

With no signs of fluid overload and a normal BNP, CHF was ruled out as the cause of this patient’s dyspnea, and the correct diagnosis of COPD was made quickly, reports Marli Bennewitz, RN, BSN, chest pain center coordinator at St. Jude Medical Center in Fullerton, CA. "There was no need to obtain a repeat echocardiogram," she says. "The patient’s home inhaler regime was adjusted, and he was discharged."

In another case, a 55-year-old male with a history of CHF and myocardial infarction (MI) came to the ED complaining of severe fatigue and shortness of breath over the past three days. "I could barely walk to the door," the patient said. ED nurses suspected severe decompensated CHF or MI, but labs revealed both normal cardiac enzymes and BNP level. "We were immediately relieved to see a normal BNP and troponin I," recalls Bennewitz. It was determined the man was suffering from depression and anxiety, and he was discharged from the ED with a psychiatric referral, she says.

BNP testing can have a dramatic impact on patient care in the ED, says Bennewitz. "This simple blood test can help you greatly in arriving at the correct diagnosis," says Bennewitz, adding that in April 2001, her ED was the first in her county to use BNP testing. For years, the ED has relied on cardiac enzymes and markers to treat acute coronary syndrome patients, says Bennewitz. BNP is the first blood test available to aid in the diagnosis and treatment of patients with heart failure, she explains. "BNP acts as a diagnostic marker for CHF," she says.1 Here are items to consider:

• Know when to use BNP.

You should use BNP anytime a patient presents with shortness of breath or edema of unknown or unclear etiology, says according to Sonja D. Brune, RN, MSN, CCRN, CEN, CCNS, cardiovascular clinical nurse specialist at Central Cardiovascular Institute of San Antonio.

BNP testing is useful in arriving at a rapid diagnosis for patients with dyspnea, says Bennewitz. "Think of BNP as the white count’ for heart failure," she says. "A normal level makes it unlikely the dyspnea is due to heart failure."

• Understand how to interpret results.

You need to know what constitutes a normal and abnormal BNP level, says Bennewitz. (See box listing BNP levels, below.) "It is also important that the level is drawn prior to initiating a nesiritide drip to avoid an incorrect result," she says. Nesiritide is derived from the B-type natriuretic peptide, so if the level is drawn while nesiritide is infusing, you will see a grossly elevated BNP, she explains. BNP also has a prognostic value, adds Bennewitz. She explains that patients with a BNP of less than 400 pg/mL have a better prognosis than those with a BNP more than 1,000 pg/mL.

• Use BNP to exclude heart failure as the diagnosis.

The results of BNP testing are very useful in differentiating heart failure from other diseases such as COPD, renal disease, and venous insufficiency, says Brune. "The test has a negative predictive value of almost 100%," she adds. For example, if a patient comes in with dyspnea but has a BNP level of 64, you can be certain the cause is not heart failure, says Brune. In some cases, BNP test results have excluded heart failure, although the patient had been chronically treated for heart failure for quite some time, says Brune. In other patients, BNP can identify heart failure that otherwise could have gone undetected, she adds.

Brune points to a 2001 study that evaluated 250 patients who came to the ED with shortness of breath.2 The patients received standard testing and treatment, in addition to having a BNP level drawn, and the ED physicians were blinded to the BNP levels. The study reported that 30 of the 250 patients were misdiagnosed. "It was determined that 29 of the 30 patients would have been accurately diagnosed had the ED physician had the BNP level to assist in the diagnosis," says Brune.

One man came to the ED three times in one year with shortness of breath and wheezing, and was treated with inhalers for asthma and antibiotics for upper respiratory infection/bronchitis each time. "On the man’s fourth visit, the BNP level was available, and it was over 800," says Brune. The test revealed that the man’s wheezing actually was caused by pulmonary edema and heart failure, says Brune. As a result, he was admitted, had an echocardiogram that revealed a low ejection fraction, and received appropriate therapy. "He has been doing very well since that time with no further ED visits," she reports.

References

1. Dao Q, Krishnaswamy P, Kazanegra R, et al. Utility of B-type natriuretic peptide in the diagnosis of heart failure in an urgent-care setting. JACC 2001; 37:379-385.

2. Van Cheng BS, Kazanagra R, Garcia A, et al. A rapid bedside test for B-type peptide predicts treatment outcomes in patients admitted for decompensated heart failure: A pilot study. JACC 2001; 37:386-391.

Resources

For more information about B-type natriuretic peptide testing in the ED, contact:

Marli Bennewitz, RN, BSN, Chest Pain Center Coordinator, St. Jude Medical Center, 101 E. Valencia Mesa Drive, Fullerton, CA 92832. Telephone: (714) 992-3000 ext. 3463. Fax: (714) 992-3109. E-mail: MBENNEWI@sjf.stjoe.org.

Sonja D. Brune, RN, MSN, CCRN, CEN, CCNS, Cardiovascular Clinical Nurse Specialist, Central Cardiovascular Institute of San Antonio, 927 McCullough Ave., San Antonio, TX 78215. Telephone: (210) 271-3203. Fax: (210) 223-9600. E-mail: sbrune@CCI-SA.com.

American College of Cardiology /American Heart Association Guidelines for the Evaluation and Management of Chronic Heart Failure in the Adult are available at the American College of Cardiology web site. (www.acc.org). Click on "Clinical Statements/Guidelines" and "Practice Guidelines: Evaluation and Management of Heart Failure." Single copies of the guidelines are available at no charge. To order, contact:

American College of Cardiology, Educational Services, 9111 Old Georgetown Road, Bethesda, MD 20814-1699. Telephone: (800) 253-4636. Fax: (413) 665-2671. E-mail: pubauth@heart.org.