Methods
The prospective Characteristics and Course of Heart Failure Stages A-B and Determinants of Progression (STAAB) cohort study investigates a representative sample of residents of the City of Würzburg, Germany, aged 30 to 79 years, without a history of HF. Participants underwent detailed clinical and echocardiographic phenotyping as well as a standardized assessment of the 6MWD using a 15-m hallway. Applying a generalized linear model, we determined the relationship of 6MWD with the respective variables adjusted for age and sex.

Results
We report on n=2650 individuals (51% women, mean age 57±11 years) with valid 6MWD, i.e. after exclusion of individuals with limited capability to properly perform the 6-minute walk test. Mean 6MWD was 548±79 m: 557± 80 m in men and 539±78 m in women (p<0.001). The relationship of 6MWD with various variables is displayed in the table: a worse metabolic profile as well as higher resting heart rate were associated with shorter 6MWD. Better systolic and diastolic function were positively associated with 6MWD. While larger LV volume showed a positive association, higher LV mass (women only) as well as higher E/e´ as surrogate of higher LV filling pressures were negatively associated with 6MWD. Stroke volume was predictive of 6MWD in men only, cardiac output at rest showed no association with 6MWD (table).

Conclusions
In a representative sample of the general population free from HF, we found multiple variables related to 6MWD implying objective physical fitness associated with metabolic health as well as with cardiac structure and function. Hence, the 6-minute walk test might be an adequate tool to determine the physical performance in patients with cardiac impairment, but we should consider the individual metabolic profile for interpretation of the 6MWD. Further studies are needed to validate our findings also in diseased populations.

Table.