Pro-brain natriuretic peptide plasma levels, left ventricular dimensions and ejection fraction in acute dyspnoea.

Objective: To determine the association of the pro-brain natriuretic peptide (NT-proBNP) plasma levels with twodimensional echocardiographic determination of left ventricular dimensions and ejection fraction (EF) in acute dyspneic patients.

Study Design: An observational cross-sectional study.

Place And Duration Of Study: Tabba Heart Institute, Karachi, from January to June 2010.

Methodology: One hundred patients were selected by consecutive purposive non-probability sampling who had presented with acute dyspnoea. NT-proBNP levels were assessed by commercial tests (Roche Diagnostics). The clinical diagnosis of congestive heart failure (CHF), echocardiographic assessment of left ventricular dimensions and function were compared with NT-proBNP levels. Receiver operating characteristic (ROC) curve was estimated for NT-proBNP and compared. The chi-square test was applied for categorical and student's t-test for numerical data at 0.05 levels of significance were used to compare patients with and without heart failure. Further comparative analysis between groups on the basis of ejection fraction was done by one way ANOVA test.

Results: Seventy-nine patients (79%) had CHF as a cause of their dyspnoea. Patients with CHF were older (61.9 ± 14 years vs. 58.6 ± 14 years, p=0.368), had a lower EF (36.9% vs. 61%, p < 0.0001), had a higher LV dimensions, left ventricular end diastolic dimension - LVEDD (49.94 ± 5.6 vs. 42 ± 7.9 mm, p < 0.0001), left ventricular end systolic dimension - LVESD (37.31 ± 6 vs. 29.21 ± 10.9 mm, p < 0.0001) and a higher NT-proBNP (10918 ± 1228 vs. 461 ± 100 pg/mL, p < 0.0001) than patients without CHF. NT-proBNP values increased with the severity of ventricular impairment. Significant differences were found between patients with LVEF < 25 % and patients with moderate ventricular impairment (LVEF = 26 - 40%) and mild ventricular impairment (LVEF = 41-60%, p < 0.001). The group of patients with LV dilation, had significantly higher BNP levels than those with normal LVEDD (12416 ± 1060 pg/ml vs. 6113 ± 960, p = 0.009) and LVESD (10416 ± 1160 vs. 4513 ± 960 pg/ml, p = 0.008). Area under ROC curve for the diagnosis of CHF was significantly higher for NT-proBNP (AUC 0.99, p < 0.003). The sensitivity of NT-proBNP value of > 300 pg/mL for the diagnosis of CHF was 100% and specificity was 42%. A cut-point of 300 pg/mL NT-proBNP had 100% negative predictive value to exclude acute CHF.

Conclusion: NT-proBNP is strongly associated with two-dimensional echocardiographic determination of left ventricular dimensions and EF in identifying CHF in patients with acute dyspnoea.