Assessing exercise capacity, quality of life and haemodynamics in heart failure: do the tests tell us the same thing?

Background: The objective measurement of exercise tolerance is an important component of heart failure trials. The use of laboratory-based treadmill exercise testing has attracted criticism, however, as being unrepresentative of patients' true capabilities.
Aim: To examine the relationships between tests of exercise capacity, quality of life and haemodynamics in patients with stable symptomatic heart failure.
Methods: Thirty-six patients with mild-moderate chronic heart failure were studied. Exercise capacity was assessed in the laboratory by maximal treadmill tests and self-paced corridor walk tests, and in the patients' homes by hip-borne pedometers. Quality of life was assessed by a disease-specific questionnaire. Cardiac output and limb blood flow were measured by non-invasive techniques.
Results: Customary activity as assessed by pedometer scores correlated with quality of life questionnaire scores (r(S) = 0.47, P = 0.04), and both variables correlated with limb (calf) blood flow (pedometer scores: r(S) = 0.39, P = 0.03; quality of life scores: r(S)= 0.50, P = 0.04). The laboratory-based maximal treadmill test correlated with the self-paced corridor walk test, but neither of these tests correlated with pedometer scores, quality of life or haemodynamics.
Conclusions: Different methods of assessing exercise capacity do not appear to give comparable results and bear different relationships to haemodynamic variables and quality of life. Pedometer scores of customary activity may better reflect patients' quality of life and appear to be more closely related to limb blood flow than the maximal treadmill exercise test or the corridor walk test. The sole use of laboratory-based exercise tests in therapeutic trials may give a misleading assessment of treatment efficacy in heart failure patients.