Oxygen uptake efficiency slope correlates with brain natriuretic peptide in patients with heart failure

Background: Cardiopulmonary exercise testing is a well-established tool for clinical and prognostic assessment of patients with chronic heart failure (CHF). Recently, a new parameter of this examination - oxygen uptake efficiency slope (OUES) - has been described and proposed as a new prognostic factor in patients with CHF. Brain natriuretic peptide (BNP) is an established prognostic factor in CHF. The purpose of the study was to assess OUES in patients with CHF in relation to other cardiopulmonary parameters and BNP levels. Methods: The study group consisted of 42 patients with CHF and left ventricular ejection fraction (LVEF) < 45% (mean age 50.2 +/- 9.3 years, mean ejection fraction 26.1 +/- 8.1% and NYHA functional class -2.5 +/- 0.8) and eight healthy controls (age 43.6 +/- 14.7 years). Coronary artery disease was diagnosed in 16 patients (38%). All underwent maximal cardiopulmonary exercise treadmill test. BNP level was measured using Abbott AxSYM Immunoassay system. Results: There were significant (p < 0.001) differences between the patients and controls in BNP levels (350 +/- 520 vs 14 +/- 19 pg/mL), OUES (1.7 +/- 0.4 vs 2.7 +/- 0.5), peak VO2(17.1 +/- +/- 5.1 vs 36.9 +/- 4.9 mL/kg/min), O-2 pulse (10.9 +/- 3.3 vs 15.9 +/- 2.7) and VE/VCO2 slope (35.7 +/- 7.8 vs 25.7 +/- 2.7). In patients, OUES was significantly (p < 0.001) correlated with LVEF (r = 0.54), BNP levels (r = -0.49), Peak VO2 (r = 0.80), VO2 AT (r = 0.65) and VE/VCO2 slope (r = -0.59). BNP was independently related to OUES in multivariate regression analysis. Conclusions: Oxygen uptake efficiency slope is significantly reduced in patients with CHF and correlates with peak VO2 and other parameters of cardiopulmonary exercise treadmill test. It is not related to age. BNP is an independent marker of OUES in patients with CHF. (Cardiol J 2010; 17, 4: 362-366)