Correlates of B-type natriuretic peptide and 6-min walk in heart failure patients

Background B-type natriuretic peptide (BNP) and 6-min walk test (6MWT) are both related to the severity and prognosis in chronic heart failure (CHF), but may reflect different aspects of CHF. We related BNP and 6MWT to left ventricular ejection fraction (LVEF), New York Heart Association functional class (NYHA), and two indices of quality of life (physical subscales): the Minnesota Living with Heart Failure Questionnaire (MLwHFQph) and the RAND-36ph. Methods Plasma BNP and 6MWT were measured at discharge in 229 patients who had been admitted for CHF. LVEF and NYHA were determined, and patients completed the MLwHFQ and RAND-36 questionnaires. Results BNP was weakly correlated to LVEF (r = −0.29, P < 0.01) and NYHA (r = 0.20, P < 0.01), but not to MLwHFQph and RAND-36ph. On the other hand, 6MWT is related to MLwHFQph (r = −0.23, P < 0.01), RAND-36ph (r = 0.52, P < 0.01), and NYHA (r = −0.46, P < 0.01), but not to LVEF (r = −0.15, P = 0.05). There is also no correlation between BNP and 6MWT (r = −0.01, P = 0.87). Conclusions The present data show that BNP and 6MWT represent different aspects of the clinical syndrome of CHF. The outcomes of this study suggest that BNP plasma levels are more related to cardiac function, while 6MWT reflects functional capacity and quality of life.