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The intracardiac concentrations of the N-terminal-pro B-type natriuretic peptide (NT-proBNP) and the determinants of its secretion in patients with atrial fibrillation.

BACKGROUND
N-terminal-pro B-type natriuretic peptide (NT-proBNP) is elevated not only in heart failure (HF) but also in atrial fibrillation (AF). The role and secretion pattern of NT-proBNP in AF is still undetermined.


AIM
The study aimed to assess NT-proBNP concentrations in patients with and without preserved left ventricular ejection fraction (LVEF) depending on the type of AF. It was also intended to define the main source of NT-proBNP production within the heart. In addition, it aimed to study the relation of NT-proBNP with some echocardiographic parameters reflecting the stretch of heart chambers as well as with the chosen parameters of physical capacity.


METHODS
Blood samples were collected from the right atrium (RA), left atrium (LA), and femoral artery (FA) in 53 patients referred for occlusion of the LA appendage. Thirty patients were assigned into Group I (LVEF ≥ 50%, no HF symptoms) and the remaining 23 patients to Group II (LVEF < 50%, HF symptoms). NT-proBNP concentrations were determined using the ELISA test.


RESULTS
In Group I, the lowest NT-proBNP level was found in RA (460.47 ± 723.15 pg/mL and 1097.72 ± 851.42 pg/mL for paroxysmal and permanent AF, respectively), higher in LA (481.5 ± 724.56 pg/mL and 1188.06 ± 851.42 pg/mL for paroxysmal and permanent AF), and the highest values in FA (537.77 ± 808.49 pg/mL and 1188.04 ± 798.28 pg/mL for paroxysmal and permanent AF). In Group II the NT-proBNP values were significantly higher compared to Group I (p < 0.01), but similarly values in RA were the lowest (183.47 ± 1826.08 pg/mL and 2141.68 ± 1801.69 pg/mL for paroxysmal and permanent AF), intermediate values were observed in LA (1857.57 ± 2221.39 pg/mL and 2386.81 ± 2067.2 pg/mL for paroxysmal and permanent AF), and the highest were seen in FA (1936.27 ± 2149.85 and 2437.33 ± 1999.37 pg/mL for paroxysmal and permanent AF, respectively). In Group I, NT-proBNP from LA best correlated with LA area (r = 0.56) and RA area (r = 0.56). In Group II, the strongest correlations were found between NT-proBNP from LA and left ventricular end-systolic dimension (r = 0.57) and volume (r = 0.6).


CONCLUSIONS
NT-proBNP is markedly elevated in the majority of patients with AF even in the absence of HF. LA secretion of NT-proBNP is an important contributor to the overall increase of NT-proBNP also in HF patients. In AF patients, the concentration of NT-proBNP correlates with the remodelling of heart chambers, but not with physical capacity.