Elevated N-terminal pro-B-type natriuretic peptide levels and normal left ventricular systolic function: an echocardiographic study

Introduction

The neurohormone N-terminal pro-B-type natriuretic peptide (NT-proBNP) has been shown to be a useful 'rule-out' test for the diagnosis of left ventricular systolic dysfunction (LVSD). As NT-proBNP plasma levels are related to left ventricular wall tension, NT-proBNP may be elevated in the absence of LVSD.

Aim

To evaluate echocardiographic abnormalities in patients with elevated levels of NT-proBNP and clinical symptoms and signs suggestive of LVSD but with normal LV systolic function on echocardiography.

Methods

Within two primary care trusts, NT-proBNP was measured in 1054 patients over a 1-year period (September 2003–October 2004). To assess echocardiographic abnormalities other than LVSD we retrospectively reviewed our digital archive database.

Results

NT-proBNP was elevated (>150 ng/l) in 744/1054 patients (70.6%), 42% male, median age 76 years (33–100 years). Of those patients with an elevated NT-proBNP 492/744 (66%) had an echocardiogram. A cut-off value of 150 ng/l was used, sensitivity 0.97 (confidence interval [CI] 0.94–0.98), specificity 0.45 (CI 0.41–0.48), positive predictive value 0.44 (CI 0.41–0.48), negative predictive value 0.97 (CI 0.94–0.98).

Three hundred and twenty-eight patients had normal LV systolic function and an elevated NT-proBNP. Of these, echocardiographic abnormalities were seen in 252/328 (77%). These included LVH 152/328 (46%), aortic stenosis 19/328 (6%), aortic regurgitation 48/328 (15%), mitral stenosis 11/328 (3%), mitral regurgitation 104/328 (32%), tricuspid regurgitation 80/328 (24%) with significant pulmonary hypertension in 57/328 (17%), and 14 patients had a previous valve replacement. A significant pericardial effusion was found in two patients.

Conclusion

NT-proBNP is a useful tool in the 'rule-out' of LVSD. When elevated, many clinically relevant pathologies other than LVSD may be identified.