A shuttle walk test for assessment of functional capacity in chronic heart failure

Background Peak oxygen uptake (peak VO2) is a reference parameter in the assessment of functional capacity of patients with chronic heart failure, but the procedure for cardiopulmonary exercise testing with expired gas analysis is complex and expensive, so more simple and available methods are desirable. Methods We compared the usefulness of a time-limited walk lest, the 6-minute walk test (6-MT), with that of a symptom-limited walk test, the shuttle walk test (SWT), in the evaluation of patients with moderate to severe chronic heart failure. We prospectively studied 46 clinically stable patients in New York Heart Association class II to IV heart failure with left ventricular ejection fraction <40% (aged 53 +/- 10 years, election fraction 23% +/- 8%, New York Heart Association functional class 2.8 +/- 0.7). Each patient performed two 6-MT, two SWT and a cardiopulmonary exercise testing within 2 weeks. Results We found a close correlation between distance walked in SWT and peak VO2 (r = 0.83, P <.001) and a moderate correlation between distance in 6-MT and peak VO2 (r = 0.69, P <.001). Both walk tests showed to be reproducible after just one practice walk. All patients who walked > 450 m in SWT had a peak VO2 >14 mL/kg/min. The overall discriminatory accuracy for SWT distance was greater than that for 6-MT distance for predicting a peak VO2 <14 mL/kg/min (area under receiver operator characteristic curves 0.97 and 0.83 respectively, P =.02). Stepwise multivariate regression analysis, including clinical, exercise testing, echocardiographic, radionuclide-angiographic, and rest hemodynamic date, showed that distance walked in SWT was the only independent predictor of peak VO2 (P <.001) and the strongest predictor of percent achieved of age- and sex-predicted peak VO2 (%PVO2) (P <.001), with only age offering additional information (P =.02). Conclusions The SWT shows to be a feasible and safe method to evaluate patients with chronic heart failure that strongly and independently predicts peak VO2 and %PVO2. This symptom-limited walk test seems to be more useful than 6-MT in the assessment of functional capacity in these patients.