Estimating maximum work rate during cardiopulmonary exercise testing from the six-minute walk distance in patients with heart failure.

Background: Exercise is recommended for patients with chronic heart failure (CHF) and its intensity is usually set as a percentage of the maximal work rate (MWR) during cardiopulmonary exercise testing (CPX) or a symptom-limited incremental test (SLIT). As these tests are not always available in cardiac rehabilitation due to logistic/cost constraints, we aimed to develop a predictive model to estimate MWR at CPX (estMWR@CPX) in CHF patients using anthropometric and clinical measures and the 6-min walk test (6 MWT), the most widely used exercise field test.
Methods: This is a multicentre cross-sectional retrospective study in a cardiac rehabilitation setting. Six hundred patients with HF in New York Heart Association (NYHA) functional class I-III underwent both CPX and 6 MWT and, t hrough multivariable linear regression analysis, we defined several predictive models to define estMWR@CPX.
Results: The best model included 6 MWT, sex, age, weight, NYHA class, left ventricular ejection fraction (LVEF), smoking status and chronic obstructive pulmonary disease COPD (adjusted R ²  = 0.55; 95% LoA -39 to 33 W). When LVEF was excluded as a predictor, the resulting model performed only slightly worse (adjusted R ²  = 0.54; 95% LoA -42 to 34 W). Only in 34% of cases was the percentage difference between estMWR@CPX and real MWR@CPX <10% in absolute value. EstMWR@CPX tended to overestimate low values and underestimate high values of true MWR@CPX.
Conclusions: Our results showed a lack of accuracy in the predictive model evaluated; therefore, for an accurate prescription of cycle-ergometer exercise training, it is necessary to assess MWR by CPX or SLIT.
Competing Interests: All Authors declare no conflict of interest relevant to the research, analysis, or interpretation presented in the manuscript.
(© 2024 The Authors.)