The relationship of a 6-min walk to VO(2 peak) and VT in older heart failure patients.
OBJECTIVE
To evaluate the relationship between a 6-min walk test (6-MWT) to peak oxygen consumption (VO(2 peak)) and ventilatory threshold (VT) in older heart failure (HF) patients, to validate the equation by Cahalin et al., and to develop a new equation to improve the prediction of VO(2 peak) from 6-MWT.


METHODS
Older patients (>65 yr) with systolic or diastolic HF (N=97) performed an exercise test to peak exertion on an upright bicycle ergometer using an incremental protocol. Gas exchange measures were collected along with continuous electrocardiograph monitoring. 6-MWT was performed on an indoor track at a self-selected pace under standardized conditions. The formula of Cahalin et al. was used to predict VO(2 peak) from 6-MWT, and a new equation was generated from the measured VO(2 peak)-6-MWT relationship from this investigation.


RESULTS
The correlation between 6-MWT and measured VO(2 peak) was moderate (r=0.54) with a standard error of estimate (SEE) of 2.48 mL.kg.min. The correlation between 6-MWT and VT was weak (r=0.23), whereas the correlation between VO(2 peak) and VT was strong (r=0.74). Correlations between the measured and predicted VO(2 peak) values were moderate (r=0.54) for both prediction equations, and the SEE was 2.83 versus 1.34 mL.kg.min for the Cahalin et al. and the new equation, respectively.


CONCLUSIONS
These results indicate that 6-MWT does not accurately predict functional capacity in older HF patients, and questions the validity of using this test to determine functional capacity in older HF patients. Predicting VO(2 peak) from equations using 6-MWT also results in substantial variability and, consequently, should not be used in older HF patients where an accurate determination of functional capacity is essential.
Maldonado-Martín
Sara
S
Faculty of Physical Activity and Sport Sciences, University of Basque Country, Vitoria-Gasteiz, Araba, Basque Country, SPAIN.
Brubaker
Peter H
PH
Kaminsky
Leonard A
LA
Moore
J Brian
JB
Stewart
Kathryn P
KP
Kitzman
Dalane W
DW
D000368:Aged; D015308:Anaerobic Threshold / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology; D002245:Carbon Dioxide / Q000032:analysis; D002303:Cardiac Output, Low / Q000378:metabolism / Q000503:physiopathology*; D015331:Cohort Studies; D004562:Electrocardiography; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology; D005260:Female; D005544:Forecasting; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D008297:Male; D008954:Models, Biological; D010101:Oxygen Consumption / Q000502:physiology*; D015203:Reproducibility of Results; D013147:Spirometry; D013997:Time Factors; D016138:Walking / Q000502:physiology*
D002245:Carbon Dioxide