Diagnostic tests for patients with acute dyspnea
Karl E. Miller
Establishing a diagnosis in patients who present with acute dyspnea can be a challenge. One possible cause is acute heart failure. If the diagnosis of acute heart failure can be quickly established, prompt medical therapy can be provided. Chest radiography is one tool used to identify patients with acute heart failure. This test is inexpensive and can identify heart failure and left ventricular dysfunction. Another tool recently developed is determination of B-type natriuretic peptide (BNP) level. BNP levels are increased in patients with increased ventricular volume and pressure overload. This test has been shown to accurately identify patients with heart failure. There are no current studies examining the combination of chest radiography and BNP in the diagnosis of heart failure in patients with acute dyspnea. Knudsen and associates assessed the accuracy of cardiomegaly and redistribution on the chest radiography and different BNP levels for the diagnosis of heart failure in patients with acute dyspnea.
The study was a multicentered examination of patients who presented to the emergency department with acute dyspnea. Patients with obvious causes for acute dyspnea, such as injuries or pneumothorax, were excluded. Basic demographic characteristics, clinical history, and clinical signs were recorded. An electrocardiogram (ECG) and chest radiographs were obtained. During the initial evaluation, blood was drawn, and BNP levels were analyzed by a rapid point-of-care device. After the initial assessment, the information was reviewed by two independent cardiologists who used an established survey score to identify patients with acute heart failure.
A total of 447 patients were diagnosed with acute heart failure, and 433 had acute dyspnea resulting from other causes. BNP levels were significantly higher in the heart failure group, and 90 percent had levels of 100 pg per mL or higher. Chest radiography findings of cardiomegaly had a sensitivity of 79 percent and a specificity of 80 percent for diagnosis of acute heart failure. Radiographic findings of cephalization, interstitial edema, and alveolar edema were all highly specific but insensitive markers for acute heart failure. Adding a BNP level of 100 pg per mL or more and radiographic findings of cardiomegaly, cephalization, and interstitial edema to the historical and clinical predictors of heart failure significantly improved the predictive values of these variables.
The authors conclude that in patients with acute dyspnea, BNP levels and chest radiography provide complementary diagnostic information. These two tests, combined with a detailed history, thorough physical examination, and ECG, can help physicians differentiate acute heart failure and other causes of acute dyspnea.
KARL E. MILLER, M.D. Knudson CW, et al. Diagnostic value of B-type natriuretic peptide and chest radiographic findings in patients with acute dyspnea. Am J Med March 15, 2004;116:363-8.
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