title: Measurement properties of the 6-min walk test in individuals with exercise-induced pulmonary arterial hypertension.
abstract: BACKGROUND
  Exercise-induced pulmonary arterial hypertension (EIPAH) is associated with reduced peak exercise cardiac output (CO) and aerobic capacity (peak ). We investigated the validity of the encouraged 6-min walk test (6MWT) to identify exercise limitation and estimate aerobic capacity in subjects with EIPAH.
  
  
  METHODS
  Seventeen subjects with EIPAH (56 ± 14 years, 15 women) and 20 healthy controls (57 ± 13 years, 19 women) underwent two encouraged 6MWTs and a symptom-limited cardiopulmonary exercise test (CPET). To measure central haemodynamics, subjects with EIPAH performed the CPET with a pulmonary artery catheter in situ.
  
  
  RESULTS
  Compared with controls, subjects with EIPAH had reduced peak (1.2 ± 0.4 vs 1.7 ± 0.5, L/min, P < 0.01), 6-min walk distance (6MWD) (575 ± 86 vs 669 ± 76 m, P < 0.001) and 6-min walk work (6MWW) (39 ± 11 vs 45 ± 7 km.kg, P < 0.01). In subjects with EIPAH, there was a moderate correlation between 6MWD and peak (r= 0.72, P < 0.01) and a strong correlation between 6MWW and peak (r= 0.86, P < 0.001). There were significant correlations between 6MWD and peak CO (r= 0.59, P < 0.05), and between peak and peak CO (r= 0.55, P < 0.05). Peak heart rate was similar in the CPET and 6MWT in subjects with EIPAH (133 ± 15 vs 133 ± 19 beats/min, P= 0.8).
  
  
  CONCLUSIONS
  The encouraged 6MWT identifies reduced exercise capacity and provides a valid estimate of aerobic capacity in EIPAH.
authors.affiliation: Advanced Lung Disease Program, Royal Perth Hospital, Perth, Western Australia, Australia.
authors.forename: R M
authors.initials: RM
authors.lastname: Fowler
authors.forename: S C
authors.initials: SC
authors.lastname: Jenkins
authors.forename: A J
authors.initials: AJ
authors.lastname: Maiorana
authors.forename: K R
authors.initials: KR
authors.lastname: Gain
authors.forename: G
authors.initials: G
authors.lastname: O'Driscoll
authors.forename: E
authors.initials: E
authors.lastname: Gabbay
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D016208:Databases, Factual; D015444:Exercise / Q000502:physiology; D005080:Exercise Test / Q000379:methods / Q000592:standards*; D017079:Exercise Tolerance / Q000502:physiology*; D065627:Familial Primary Pulmonary Hypertension; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000175:diagnosis* / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D016138:Walking