The six-minute walk test in sarcoidosis associated pulmonary hypertension: Results from an international registry

Abstract

Introduction: Sarcoidosis associated pulmonary hypertension (SAPH) is a leading contributor to sarcoidosis-related mortality. The 6-min walk test (6MWT) is widely used in assessment of cardiorespiratory conditions. A reduced 6-min walk distance (6MWD) has been associated with increased mortality in SAPH. We examined patients from the Registry of Sarcoidosis Associated Pulmonary Hypertension (ReSAPH) who had performed 6MWT at enrollment to identify variables that affect 6MWD, and the prognostic value of 6MWT variables regarding death or lung transplantation.

Material and methods: ReSAPH patients with available 6MWT were included. Variables analyzed using pre-defined cutoffs included 6MWD, initial and end of test Borg dyspnea score, oxygen saturation, and heart rate at beginning, end, and after 1-min recovery, absolute change in oxygen saturation, modified distance-saturation product (mDSP), and the heart rate recovery at 1-min (HRR).

Findings: 174 patients met inclusion criteria; 48 patients died and 8 underwent lung transplantation. Patients with 6MWD<300 m had a higher chance of dying or undergoing transplantation compared to those with 6MWD>300 m (p = 0.012). No associations with outcome were observed with mDSP cutoff 200 m%, desaturation≥5% and oxygen saturation<88% at end of 6MWT, or multiple HRR cutoffs (13,14,16). 6MWD correlated with initial Borg score, (p = 0.001), DLCO% (p = 0.0001) and sPAP (p = 0.031) on multivariate analysis. These variables were significant for both pre- and post-capillary PH subgroups. 6MWD also correlated with fatigue assessment scale (FAS) (p = 0.015).

Conclusion: Of the parameters evaluated, 6MWD had the greatest prognostic value in SAPH which correlated with other physiologic and hemodynamic variables. 6MWT captures the multidimensional effects of sarcoidosis.

Keywords: Registry of sarcoidosis associated pulmonary hypertension; Sarcoidosis; Sarcoidosis associated pulmonary hypertension; Six-minute walk distance; Six-minute walk test.