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'O2) respectively (P<0.001). In CHF, a steady state was observed only for walking speed and V'O2, 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 increase in tidal volume (VT) in CHFD, whereas in CHFP, it was due to a similar increase in VT and breathing frequency (f). In these patients, the 6-MWT VT/f slope was lower than in CHFD (P<0.01).


CONCLUSIONS
During the 6-MWT, the V'O2 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.
Kervio
Gaëlle
G
Groupe de Recherche Cardiovasculaire, Université de Rennes, France. gaelle.kervio@club-internet.fr
Ville
Nathalie S
NS
Leclercq
Christophe
C
Daubert
Jean-Claude
JC
Carre
François
F
D000222:Adaptation, Physiological / Q000502:physiology*; D000368:Aged; D002245:Carbon Dioxide / Q000378:metabolism; D002319:Cardiovascular System / Q000503:physiopathology*; D005080:Exercise Test; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D006339:Heart Rate; D006801:Humans; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D012123:Pulmonary Ventilation; D012137:Respiratory System / Q000503:physiopathology*; D013990:Tidal Volume; D013997:Time Factors; D016138:Walking / Q000502:physiology*
D002245:Carbon Dioxide