The aim of the study is to compare the cardiorespiratory response during the 6-min walk test (6MWT) with a symptom-limited cardiopulmonary exercise test (
CPET) in patients with varying degrees of
heart failure. Thirty-seven patients with
heart failure (New York Heart Association I-III) were asked to complete a 6MWT and a
CPET on a cycle ergometer. Respiratory
gases were measured during both the tests and patients were grouped into tertiles according to their VO(2peak) reached during the
CPET prior to performing statistical analysis of all other respiratory parameters. Patients were grouped into the following tertiles: Group 1 (VO(2peak) >25.2 ml/kg per min, N = 13), Group 2 (VO(2peak) >17.5-25.2 ml/kg per min), and Group 3 (VO(2peak) < or =17.5 ml/kg per min). Despite the good overall correlation between 6MWT VO(2) and
CPET VO(2peak) (r = 0.72, P < 0.001), significant differences were seen within Groups 1 and 3 (P < 0.05). In Group 1, 6MWT VO(2) was significantly lower compared with
CPET VO(2peak), whereas Group 3 showed significantly higher 6MWT VO(2) compared with
CPET VO(2peak). In conclusion, the use of the 6MWT to evaluate exercise capacity in patients with
heart failure is highly dependent on the degree of functional impairment. In patients with advanced
heart failure, the 6MWT elicits a maximum exercise response, whereas it only constitutes a sub-maximal exercise test in patients with mild
heart failure and no functional limitations. This must be taken into consideration when using the 6MWT in large epidemiological studies to evaluate
therapy outcome and clinical prognosis in patients with varying degrees of clinical disabilities.