Association between serum n-terminal pro-brain natriuretic peptide concentration and left ventricular dysfunction and extracellular water in continuous ambulatory peritoneal dialysis patients.

BACKGROUND: This study investigated the association between serum N-terminal pro-brain natriuretic peptide (NT-pro-BNP) levels and extracellular water (ECW%) and left ventricular (LV) dysfunction in continuous ambulatory peritoneal dialysis (CAPD) patients.

METHODS: The study involved 30 stable CAPD patients: 14 males, 16 females; mean age 52 +/- 14 years; mean CAPD duration 34 +/- 12 months; 12 with diabetes mellitus (DM) and 18 non-DM. Serum NT-pro-BNP levels were determined using electrochemiluminescence immunoassay. Baseline echocardiography was performed using a Hewlett-Packard Sonos 1000 (Andover, Massachusetts, USA) device equipped with a 2.25-MHz probe, allowing M-mode, two-dimensional, and pulsed Doppler measurements. Left ventricular mass index (LVMI) was calculated according to the Penn formula. A multifrequency bioimpedance analyzer was used; ECW% was calculated as a percentage of total body water and was considered the index of volume load.

RESULTS: (1) Serum NT-pro-BNP level, ECW%, LVMI, and LV ejection fraction in CAPD patients were 3924 (240 - 74460) pg/mL, 36.7% +/- 2.2%, 158 +/- 48 g/m2, and 60.5% +/-11.2%, respectively. (2) Patients were divided into three tertiles (10 patients each) according to their serum NT-proBNP concentration [1st tertile 1168 (240 - 2096), 2nd tertile 4856 (2295 - 20088), 3rd tertile 35012 (20539 -74460) pg/mL]. The tertiles did not differ significantly in terms of age, sex, presence of DM, body mass index, or PD duration. Patients in the 3rd tertile (highest serum NT-proBNP concentration) had the highest LVMI (126 +/- 45 vs 160 +/-41 vs 200 +/- 23 g/m2 for 1st, 2nd, 3rd tertiles, respectively) and the lowest LV ejection fraction (66% +/- 11% vs 62% +/-6% vs 55% +/- 9%). ECW% did not differ significantly between tertiles (35.5% +/- 2.0% vs 37.5% +/- 2.0% vs 36.5% +/-2.0%). (3) In CAPD patients, serum NT-pro-BNP levels correlated positively with LVMI (r = 0.628, p = 0.003) and negatively with LV ejection fraction (r = -0.479, p = 0.033). Serum NT-pro-BNP levels did not correlate with ECW% (r = 0.227, p = 0.25). (4) Stepwise regression analysis showed that LV ejection fraction (beta = -0.610, p = 0.015) and LVMI (beta = 0.415, p = 0.007) were independently associated with the serum NT-pro-BNP concentration.

CONCLUSIONS: There was no link between ECW% and serum NT-pro-BNP concentration. Thus, serum NT-pro-BNP levels may not provide objective information with respect to pure hydration status in CAPD patients. In contrast, serum NT-pro-BNP levels were linked to LVMI and LV ejection fraction in CAPD patients. Therefore, while the serum NT-proBNP concentration might not be a useful clinical marker for extracellular fluid volume load, it appears useful for evaluating LV hypertrophy and LV dysfunction in CAPD patients.