Background: Although echocardiography is an important tool for making the diagnosis of left ventricular (LV) dysfunction, the cost of this procedure limits its use as a routine screening tool for this purpose. Brain natriuretic peptide (BNP) accurately reflects ventricular pressure, and preliminary studies have found it to be highly sensitive and highly specific in diagnosing congestive heart failure in the emergency department. We hypothesized that BNP might therefore be useful as a screening tool before echocardiography in patients with suspected LV dysfunction.
Methods: Subjects included patients referred for echocardiography to evaluate the presence or absence of LV dysfunction. Patients with known LV dysfunction were excluded from analysis. BNP was measured by a point-of-care immunoassay (Biosite Diagnostics, San Diego, Calif). The results of BNP levels were blinded from cardiologists making the assessment of LV function. Patients were divided into those with normal ventricular function, abnormal systolic ventricular function, abnormal diastolic function, and evidence of both systolic and diastolic dysfunction.
Results: Two hundred patients in whom LV function was unknown were studied. In the 105 patients (53%) whose ventricular function was subsequently determined to be normal by echocardiography, BNP levels averaged 37 +/- 6 pg/mL. This was significantly less than in those patients with either ultimate diastolic dysfunction (BNP 391 +/- 89 pg/mL (P <.001) or systolic dysfunction (BNP 572 +/- 115 pg/mL (P <.001). A receiver-operator characteristic curve showing the sensitivity and specificity of BNP against the echocardiography diagnosis revealed the area under the curve (accuracy) was 0.95. At a BNP level of 75 pg/mL was 98% specific for detecting the presence or absence of LV dysfunction by echocardiography.
Conclusions: A simple, rapid test for BNP, which can be performed at the bedside or in the clinic, can reliably predict the presence or absence of LV dysfunction on echocardiogram. The data indicate that BNP may be an excellent screening tool for LV dysfunction and may, in fact, preclude the need for echocardiography in many patients.