A prospective study of the 6 min walk test as a surrogate marker for haemodynamics in two independent cohorts of treatment-naïve systemic sclerosis-associated pulmonary arterial hypertension

ObjectivesDespite the wide use of the 6 min walk distance (6MWD), no study has ever assessed its validity as a surrogate marker for haemodynamics and predictor of outcome in isolated pulmonary arterial hypertension associated with systemic sclerosis (SSc-PAH). We designed this work to address this issue.MethodsTreatment-naïve patients with SSc-PAH were prospectively included from two sources: the French PAH Network (a prospective epidemiological cohort) (n=83) and randomised clinical trials submitted for drug approval (Food and Drug Administration) (n=332). Correlations between absolute values of the 6MWD and haemodynamics at baseline, as well as between variations of 6MWD and haemodynamics during follow-up, were studied in both populations.ResultsIn the French cohort, baseline cardiac output (CO) (R2=0.19, p=0.001) and New York Heart Association class (R2=0.10, p