Background: Brain Natriuretic Peptide (BNP) is a cardiac neurohormone secreted from the cardiac ventricles in response to ventricular volume expansion and pressure overload. Levels of this peptide have been noted to increase with increasing New York Heart Association Classification (NYHA) and in patients with diminished left ventricular ejection fraction. Plasma levels of BNP have also been previously shown to be significantly correlated with peak oxygen uptake and the 6-minute walk test (6MWT) in the chronic heart failure (HF) population.

Purpose: The aim of this descriptive study is to assess the relationship of BNP in a subset of medically stable HF patients, all NYHA-III and having undergone maximal exercise testing, to oxygen consumption (Vo₂), rate-pressure product (RPP), 6 MWT, and ejection fraction. The purpose is to evaluate if similar correlations are noted between BNP levels and Vo₂, RPP, 6 MWT and EF when subjects are all within one NYHA class and have similar functional limitations due to symptoms.

Methods: A subset of 22 subjects (12 men/10 women), mean age 57 +/- 12 years and all NYHA Class III, who were part of the exercise arm of the HEART CAMP study, were included in this analysis. Each subject had blood drawn for BNP analysis, and then performed the 6 MWT protocol following standardized procedures. On a separate day, each subject returned and underwent maximal cardiorespiratory exercise testing on a treadmill using a ramped protocol. Maximum oxygen consumption (Vo_2max), heart rate (HR), and blood pressure (BP) were monitored pre, during, and posttreadmill testing. Rate-pressure product (RPP) was calculated using HR and systolic BP values obtained at maximum effort.

Results: In our group of NYHA Class III subjects, BNP was inversely correlated with Vo_2max (r = -0.59, P = .004) and RPP (r = -0.68, P < .001), but was not well correlated with 6 MWT distances (r = -0.36, P = .25) or ejection fraction (r = -0.20, P = .36).

Conclusions: RPP (correlated with myocardial Vo₂ and workload on the heart) and Vo_2max (indicator of work by the total body) are better correlated with BNP levels than EF. Thus, it would appear that for individuals within an NYHA class that interventions that improve oxygen consumption capabilities, such as exercise training, would have a greater impact on altering BNP levels than those that may enhance EF.