Cardiorespiratory adaptations during the six-minute walk test in chronic heart failure patients

Background The six-minute walk test (6-MWT) is widely used to assess exercise tolerance in chronic heart failure patients (CHF). The aim of this study was to analyse cardiorespiratory parameters kinetics during the 6-MWT in CHF and in healthy subjects. Methods A treadmill, symptom-limited exercise test and a 6-MWT were performed by 14 CHF under optimal drug treatment (CHFD), 17 CHF with cardiac resynchronization (CHFP), and 12 healthy subjects. Cardiorespiratory responses were assessed by a validated portable system. Results All subjects exceeded their ventilatory threshold during the 6-MWT. Healthy subjects and CHF performed the 6-MWT around 75 and 90% of peak oxygen uptake (V'O-2) respectively (P<0.001). In CHF, a steady state was observed only for walking speed and V'O-2, with a slight delay in comparison with healthy subjects, for whom a steady state was also observed for carbon dioxide production and ventilation (V'(E)). During the 6-MWT, the V'(E) adaptation was due mainly to an E E increase in tidal volume (V-T) in CHFD, whereas in CHFP, it was due to a similar increase in VT and breathing frequency (f). In these patients, the 6-MWT V-T/f slope was lower than in CHFD (P<0.01). Conclusions During the 6-MWT, the V'O-2 steady state is slightly delayed in CHF, which could be related partly to their higher exercise intensity. Moreover, each CHF group is characterized by a specific ventilation components response during the 6-MWT. Eur J Cardiovasc Prevention Rehab 11:171-177 (C) 2004 The European Society of Cardiology.