title: Six-minute walking distance and decrease in oxygen saturation during the six-minute walk test in pediatric pulmonary arterial hypertension.
abstract: OBJECTIVE
  To investigate the prognostic value of the 6-minute walking distance (6-MWD), transcutaneous saturation (tcSO2) and heart rate (HR) obtained during the 6-minute walk test (6-MWT) in pediatric pulmonary arterial hypertension (PAH).
  
  
  METHODS
  This was an observational study with forty-seven pediatric PAH patients, aged ≥7 years, and diagnosed and followed at the national referral center for pediatric PAH in the Netherlands. All patients performed a comprehensive 6-minute walk test (6-MWT), which measures 6-MWD and tcSO2 and HR before ("baseline"), during ("exercise") and 5 min after ("recovery") the walk test.
  
  
  RESULTS
  The 6-MWD expressed either in meters or in sex- and age-corrected z-scores, was associated with transplant-free survival, independently from sex, age, and the presence of a shunt-defect. Shorter 6-MWD correlated with higher WHO-FC and increased NT-pro-BNP. Absolute tcSO2 at exercise and tcSO2-decrease during 6-MWT were associated with transplant-free survival, independent from 6-MWD. Combining tcSO2-decrease with 6-MWD provided the strongest prognostic model. Patients with 6-MWD>352 m (the median 6-MWD) had a better outcome than those with smaller 6-MWD. A large tcSO2-decrease during 6-MWT (>19% for patients with and >5% for patients without a shunt defect) identified patients with worse transplant-free survival both in patients with a 6-MWD above and below the median 6-MWD.
  
  
  CONCLUSIONS
  The 6-MWD is an independent predictor of prognosis in pediatric PAH, that reflects disease severity and clinically relevant exercise-tolerance and therefore qualifies as a treatment goal. The magnitude of tcSO2-decrease during 6-MWT, adjusted for the presence of a shunt, indicates an additional risk factor for prognosis in children with PAH.
authors.affiliation: Center for Congenital Heart Diseases, Department of Pediatric Cardiology, Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, The Netherlands. Electronic address: j.m.douwes@umcg.nl.
authors.forename: Johannes M
authors.initials: JM
authors.lastname: Douwes
authors.affiliation: Center for Congenital Heart Diseases, Department of Physical Therapy, Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, The Netherlands.
authors.forename: Anneke K
authors.initials: AK
authors.lastname: Hegeman
authors.affiliation: Center for Congenital Heart Diseases, Department of Pediatric Cardiology, Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, The Netherlands.
authors.forename: Merel B
authors.initials: MB
authors.lastname: van der Krieke
authors.affiliation: Center for Congenital Heart Diseases, Department of Pediatric Cardiology, Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, The Netherlands.
authors.forename: Marcus T R
authors.initials: MT
authors.lastname: Roofthooft
authors.affiliation: Center for Congenital Heart Diseases, Department of Epidemiology, Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, The Netherlands.
authors.forename: Hans L
authors.initials: HL
authors.lastname: Hillege
authors.affiliation: Center for Congenital Heart Diseases, Department of Pediatric Cardiology, Beatrix Children's Hospital, University Medical Center Groningen, University of Groningen, The Netherlands.
authors.forename: Rolf M F
authors.initials: RM
authors.lastname: Berger
mesh_terms: D000293:Adolescent; D006328:Cardiac Catheterization; D002648:Child; D005080:Exercise Test / Q000379:methods; D017079:Exercise Tolerance / Q000502:physiology*; D065627:Familial Primary Pulmonary Hypertension / Q000175:diagnosis* / Q000453:epidemiology / Q000378:metabolism; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D015994:Incidence; D008297:Male; D009426:Netherlands / Q000453:epidemiology; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption; D011237:Predictive Value of Tests; D011379:Prognosis; D012720:Severity of Illness Index; D015996:Survival Rate / Q000639:trends; D013997:Time Factors; D016278:Ventricular Function, Right / Q000502:physiology; D016138:Walking / Q000502:physiology*
chemical_list: D010100:Oxygen
keywords: Congenital heart disease; Exercise testing; Outcome analyses; Pediatrics; Pulmonary arterial hypertension; Survival