B-type natriuretic peptide kinetics and cardiopulmonary exercise testing in heart failure

BackgroundIn patients with chronic heart failure (CHF), B-type natriuretic peptide (BNP) is related to peak oxygen consumption (peak VO₂) and the relationship between minute ventilation and carbon dioxide production (VE/VCO₂ slope). However, the exercise response depends on the mode of exercise. This study sought to compare peak treadmill and bicycle exercise responses with respect to their relationship with BNP and to assess whether BNP measured at rest or during exercise could identify patients with greater functional impairment and ventilatory inefficiency.MethodsTwenty-three patients with mild-to-moderate stable systolic CHF (age 72 ± 8 years, left ventricular ejection fraction 32 ± 7%) underwent treadmill and bicycle cardiopulmonary exercise testing within 5 (interquartile range 3–7) days. BNP was measured at rest and at peak exercise.ResultsBNP at rest was an independent multivariate predictor of both peak VO₂ and the VE/VCO₂ slope for both exercise modes. However, the proportion of variance explained univariately and multivariately was ≤ 0.55, indicating that BNP did not strongly explain the variation of peak VO₂ and the VE/VCO₂ slope. The exercise-induced rise in circulating BNP did not differ between the test modes [treadmill: 50 (24–89) pg/ml vs. bicycle: 46 (15–100) pg/ml; p = 0.73]. BNP levels at peak exercise were strongly related to resting values, but did not provide additional information on peak VO₂ or the VE/VCO₂ slope.ConclusionsIn typical CHF patients, BNP measured at rest or at peak exercise does not strongly predict peak VO₂ or the VE/VCO₂ slope regardless of the exercise mode, and is therefore not a sufficiently accurate surrogate for cardiopulmonary exercise testing.