Predicting maximal oxygen uptake from the 6 min walk test in patients with heart failure

A cardiopulmonary exercise (CPX) test is considered the gold standard in evaluating maximal oxygen uptake. This study aimed to evaluate the predictive validity of equations provided by Burr et al., Ross et al., Adedoyin et al., and Cahalin et al. in predicting peak VO₂ from 6 min walk test (6MWT) distance in patients with heart failure (HF).

New York Heart Association Class I-III HF patients performed a maximal effort CPX test and two 6MWTs. Correlations between CPX VO_{2 peak} and the predicted VO_{2 peak} , coefficient of determination (R² ), and mean absolute percentage error (MAPE) scores were calculated. P-values were set at 0.05. A total of 106 participants aged 62.5 ± 11.5 years completed the tests. The mean VO_{2 peak} from CPX testing was 16.4 ± 3.9 mL/kg/min, and the mean 6MWT distance was 419.2 ± 93.0 m. The predicted mean VO_{2 peak} (mL/kg/min) by Burr et al., Ross et al., Adedoyin et al., and Cahalin et al. was 22.8 ± 8.8, 14.6 ± 2.1, 8.30 ± 1.4, and 16.6 ± 2.8. A significant correlation was observed between the CPX test VO_{2 peak} and predicted values. The mean difference (0.1 mL/kg/min), R² (0.97), and MAPE (0.14) values suggest that the Cahalin et al. equation provided the best predictive validity.

The equation provided by Cahalin et al. is simple and has a strong predictive validity, and researchers may use the equation to predict mean VO_{2 peak} in patients with HF. Based on our observation, equations to predict individual maximal oxygen uptake should be used cautiously.