Sanges S1Launay D1Rhee RL2Sitbon O3Hachulla É1Mouthon L4Guillevin L4Rottat L3Montani D3De Groote P5Cottin V6Magro P7Prévot G8Bauer F9Bergot E10Chabanne C11Reynaud-Gaubert M12Leroy S13Canuet M14Sanchez O15Gut-Gobert C16Dauphin C17Pison C18Boissin C19Habib G20Clerson P21Conesa F21Cordier JF22Kawut SM2Simonneau G3Humbert M3.

ABSTRACT:

Study of the validity of a 6 min walk test in pulmonary arterial hypertension

OBJECTIVES:

Despite 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.

METHODS:

Treatment-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.

RESULTS:

In the French cohort, baseline cardiac output (CO) (R2=0.19, p=0.001) and New York Heart Association class (R2=0.10, p<0.001) were significantly and independently correlated with baseline 6MWD in multivariate analysis. A significant, independent, but weaker, correlation with CO was also found in the Food and Drug Administration sample (R2=0.04, p<0.001). During follow-up, there was no association between the changes in 6MWD and haemodynamic parameters in patients under PAH-specific treatments.

CONCLUSIONS:

In SSc-PAH, CO independently correlates with 6MWD at baseline, but accounts for a small amount of the variance of 6MWD in both study samples. This suggests that other non-haemodynamic factors could have an impact on the walk distance. Moreover, variations of 6MWD do not reflect changes in haemodynamics among treated patients. Our results suggest that 6MWD is not an accurate surrogate marker for haemodynamic severity, nor an appropriate outcome measure to assess changes in haemodynamics during follow-up in treated SSc-PAH.

Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

KEYWORDS:

Arterial Hypertension; Autoimmune Diseases; Outcomes research; Systemic Sclerosis

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