Relationship between thoracic fluid content and natriuretic peptide type B in patients with systolic heart failure

Thoracic fluid content (TFC) is one of the basic parameters measured by impedance cardiography (ICG). The B-type natriuretic peptide (BNP) is a neuroendocrine mediator produced in the ventricular myocardium and released in response to the increase of wall tension.

To determine the relationship between TFC measured by ICG and BNP serum level in patients with systolic heart failure (HF).

The study population included 50 patients: a group of 30 patients with systolic HF in functional NYHA class II and III [27 males and 3 females, aged 53 +/- 6 years, with mean left ventricular ejection fraction (LVEF) 23 +/- 6%], and 20 controls without HF symptoms and preserved LVEF. The TFC and BNP serum level were measured on the same day.

Mean BNP serum concentration was 521 +/- 882 pg/ml in HF patients and 44 +/- 36 pg/ml in healthy controls (p = 0.02). The TFC values did not differ significantly between the two groups (27.3 +/- 4.5 1/kW in the study group versus 26.3 +/- 2.8 1/kW in control subjects, NS). A significant correlation between TFC and BNP was found in patients with overt HF (r = 0.57, p = 0.001); however, after excluding one patient with exacerbation of HF symptoms, the correlation was non-significant (r = 0.24, p = 0.22). No correlation between these parameters was observed in healthy controls (r = 0.17, p = 0.51).

There was no significant correlation between TFC measured by ICG and BNP serum level in haemodynamically stable patients with HF symptoms. The usefulness of ICG measurements in patients with exacerbated chronic HF needs further investigations.