Does the 6-minute walk test predict the prognosis in patients with NYHA class II or III chronic heart failure?

Background we prospectively evaluated the potential of the 6-minute walk test compared with peak (V) over dot O-2 in predicting outcome of patients with New York Heart Association (NYHA) class II or III heart failure. Methods and Results Patients with a history of heart failure caused by systolic dysfunction were included. The combined final outcome (death or hospitalization for heart failure) was used as the judgment criterion. One hundred twenty-one patients (age 59 +/- 11 years; left ventricular election fraction 29.6% +/- 13%) were included and followed for 1.53 +/- 0.98 years. Patients were separated into two groups according to outcome: group 1 (G1, 74 patients), without events, and group 2 (G2, 47 patients), who reached the combined end point. Peak (V) over dot O-2 was clearly different between G1 and G2 (18.5 +/- 4 vs. 139 +/- 4 ml/kg/min, p = 0.0001) but not the distance walked (448 +/- 92 vs 410 +/- 126 m; p = 0.084, not significant). Survival analysis showed that unlike peak (V) over dot O-2, the distance covered was barely distinguishable between the groups (p < 0.08). However, receiver operating characteristic curves revealed that the best performances for the 6-minute walk test were obtained for subjects walking less than or equal to 300 m. These patients had a worse prognosis than those walking farther (p = 0.013). In this subset of patients, there was a significant correlation between distance covered and peak (V) over dot O-2 (r = 0.65, p = 0.011). Thus it appears that the more severely affected patients have a daily activity level relatively close to their maximal exercise capacity. Nevertheless, the 300 m threshold suggested by this study needs to be validated in an independent population. Conclusions A distance walked in 6 minutes less than or equal to 300 m con predict outcome. Moreover. in there cases there is a significant correlation between the 6-minute walk test and peak (V) over dot O-2 demonstrating the potential of this simple procedure as a first-line screening test for this subset of patients.