Taking a walk on the heart failure side: comparison of metabolic variables during walking and maximal exertion

Aims Although cardiopulmonary exercise testing (CPET) is the gold standard to assess exercise capacity, simpler tests (i.e., 6-min walk test, 6MWT) are also commonly used. The aim of this study was to evaluate the relationship between cardiorespiratory parameters during CPET and 6MWT in a large, multicentre, heterogeneous population. Methods We included athletes, healthy subjects, and heart failure (HF) patients of different severity, including left ventricular assist device (LVAD) carriers, who underwent both CPET and 6MWT with oxygen consumption measurement. Results We enrolled 186 subjects (16 athletes, 40 healthy, 115 non-LVAD HF patients, and 15 LVAD carriers). CPET-peakVO2 was 41.0 [35.0-45.8], 26.2 [23.1-31.0], 12.8 [11.1-15.3], and 15.2 [13.6-15.6] ml/Kg/min in athletes, healthy, HF patients, and LVAD carriers, respectively (P < 0.001). During 6MWT they used 63.5 [56.3-76.8], 72.0 [57.8-81.0], 95.5 [80.3-109], and 95.0 [92.0-99.0] % of their peakVO2, respectively. None of the athletes, 1 healthy (2.5%), 30 HF patients (26.1%), and 1 LVAD carrier (6.7%), reached a 6MWT-VO2 higher than their CPET-peakVO2. Both 6MWT-VO2 and walked distance were significantly associated with CPET-peakVO2 in the whole population (R2 = 0.637 and R2 = 0.533, P <= 0.001) but not in the sub-groups. This was confirmed after adjustment for groups. Conclusions The 6MWT can be a maximal effort especially in most severe HF patients and suggest that, in absence of prognostic studies related to 6MWT metabolic values, CPET should remain the first method of choice in the functional assessment of patients with HF as well as in sport medicine.