Correlation of natriuretic peptides and inferior vena cava size in patients with congestive heart failure

Background: The inferior vena cava (IVC) diameter and degree of inspiratory collapse are used as echocardiographic indices in the estimation of right atrial pressure. Brain-natriuretic peptides (BNPs) are established biomarkers of myocardial wall stress. There is no information available regarding the association between the IVC diameter and BNPs in patients with heart failure and various degrees of systolic performance. The purpose of this investigation is to quantify the degree to which natriuretic peptides (BNP and N-terminal pro-B natriuretic peptide [NT-ProBNP]) and echocardiographic-derived indices of right atrial pressure correlate in this patient population. Methods: We examined 77 patients (mean age 61 +/- 17 years, 44% male) with decompensated heart failure who underwent transthoracic echocardiography and, within a timeframe of 24 hours, determination of BNP and NT-ProBNP levels in venous blood. BNP and NT-ProBNP were analyzed after log transformation. The degree of association was measured by the correlation coefficient using the Pearson's method. Results: The mean ejection fraction was 50% +/- 20%, and 33% of the study cohort had a remote history of heart failure. The mean IVC diameter was 1.85 cm +/- 0.5, the mean BNP was 274 pg/mL, the confidence interval (CI) was 95% (95% CI: 197-382), and the mean NT-ProBNP was 1994 pg/mL (95% CI: 1331-2989). There was a positive, albeit small, association between IVC diameter and BNP (r = 0.24, 95% CI: 0.01-0.44; P = 0.03) and NT-ProBNP (r = 0.27, 95% CI: 0.05-0.47; P = 0.01). Among patients with different degrees of IVC collapse in response to inspiration, values for BNP and NT-ProBNP did not differ substantially (P = 0.36 and 0.46 for BNP and NT-ProBNP, respectively). Conclusion: Natriuretic peptides correlate weakly with IVC size and do not predict changes in response to intrathoracic pressure.