Six-minute walk (6MW) tests may be substituted for cardiopulmonary exercise (CPX) tests in stable outpatients with chronic heart failure (HF), according to a new study published on Nov. 21 in the Journal of the American College of Cardiology.

The study, which looked at 2,054 stable New York Heart Association (NYHA) functional class II and III systolic HF patients from the HF-ACTION Trial, found that 6MW tests and CPX tests had similar results as univariate predictors for all-cause hospitalization and mortality. Specifically, C-indices of 6MWD were 0.58 and 0.65 (unadjusted) and 0.62 and 0.72 (adjusted) in predicting all-cause mortality/hospitalization and all-cause mortality, respectively. C-indices for peak VO2 were 0.61 and 0.68 (unadjusted) and 0.63 and 0.73 (adjusted). C-indices for VE/VCO2 slope were 0.56 and 0.65 (unadjusted) and 0.61 and 0.71 (adjusted); combining peak VO2 and VE/ VCO2 slope did not improve the C-indices.

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Study investigators did note that the C-statistic to predict all-cause hospitalization/mortality and all-cause mortality for CPX testing was numerically larger than that of 6MW testing, the difference was too small to be clinically meaningful.

"Although CPX testing is often assumed to provide superior function-based prognostic assessment in HF patients, we demonstrated that 6MWD provided prognostic value that was similar to peak VO2, VE/VCO2 slope, and their combination in a relatively stable HF population," the authors said.

That being said, the investigators did caution that this study only focused on the utility of 6MW tests as relative to the two most commonly reported indices of CPX testing and did not address the utility of a comprehensive CPX evaluation. "Comprehensive CPX evaluation testing may be more likely to detect exercise-related hemodynamic instability, ischemia, arrhythmias, and symptoms that are clinically important but that were outside the focus of this investigation," they said.

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