• six minutes walking test
• prognosis
• natriuretic peptides

Abstract

Background. Prognostic stratification in chronic heart failure (CHF) is a complex process that may help guide therapeutic decision making. Natriuretic peptides (NPs) and the six minutes walking test (6MWT) proved to be valid prognostic markers in chronic heart failure.
Aims. In the present study, we sought to investigate the prognostic value of exercise tolerance as assessed by 6MWT in patients with both CHFrEF and CHFpEF. To gain information in the outcome prediction patients were further characterized according to their BNP values.
Materials and methods. We analysed 616 patients with stable chronic heart failure (mean LVEF 42%, 221/616 with preserved ejection fraction). The patients underwent a 6MWT, BNP was measured within 7 days from the date of the walking test. A complete physical examination, an EKG and an echocardiography were performed the day of the walking tests. Patients were followed up for a mean period of 60 months for the end point of all-cause mortality. The cut off levels of the 6MWT and BNP were determined at the ROC analysis. Survival rates were analyzed with the Kaplan Meier method. The strength of association between BNP and 6MWT and long-term mortality was assessed by means of univariate and multivariate Cox regression models.


Results There were 76 deaths during a mean follow up of 60 months. According to the results of the 6MWT, at 60 months there was a significant difference in the survival of patients with a 6MWT lower than a cut-off of 323 meters ( rate of survival = 64% ) compared to the patients above the cut-off (rate of survival = 87%) ( Chi square log-rank test = 24.4, p < 0.0001). Adding the values of BNP we obtained an even more significant stratification.The patients were stratified into four groups according to BNP values and distance walked at the 6MWT. The survival rates at 60 months were : 31% for the group with BNP >330 pg/ml and 6MWT<323 meters, 68% for the group with BNP >330 pg/ml and a 6MWT >323 meters, 82% the group with BNP <330 pg/ml and 6MWD <323 meters and 92 % for the group with BNP<330 pg/ml e 6MWT >323 meters. (Chi-square logrank 103; p <0.0001).

Conclusions : Among the patients with a reduction of the exercise tolerance (documented by a 6MWT < 323 meters) those with higher levels of BNP ( > 330 pg/ml) have the worst prognosis. An approach based on the combined results of the 6MWT and BNP levels can provide valid prognostic information in patients with CHF.