title: Minimal important difference for 6-minute walk test distances among patients with chronic heart failure.
abstract: BACKGROUND
  The 6-minute walk test (6 WT) is an established tool in the assessment of endurance and prognosis in patients with chronic heart failure (CHF). For these patients there is very limited data on biological variation of 6 WT distances. We determined the minimal important difference (MID) for the 6 WT in patients with stable systolic CHF.
  
  
  METHODS
  Two cohorts of patients with stable systolic CHF were included from the outpatients' clinic of the University of Heidelberg. In these cohorts, two 6 WT measurements were performed - in cohort 1 (n=461) 180 days and in cohort 2 (n=512) 365 days apart. Stability was defined as the absence of clinical events (3 months before the first test, between both tests, and 6 months after the second test) and stability of symptoms (NYHA) between tests. Using a standard error of measurement (SEM)-based approach, we determined the MID for both cohorts.
  
  
  RESULTS
  The intraclass correlation coefficient was 0.89 at 180 days and 0.88 at 365 days. The results were consistent for groups stratified for age, gender, etiology of CHF, and individual NYHA class. The MID for the 6 WT in stable CHF patients was 35 m and 37 m between presentation and 180 and 365 days, respectively.
  
  
  CONCLUSIONS
  Submaximal exercise capacity as represented by the 6 WT varies little in stable CHF patients for up to 1-year intervals. The MID for changes in 6 WT values in patients with stable CHF over a period of 6 to 12 months is ~ 36 m.
authors.affiliation: Department of Cardiology, Angiology, Pulmonology, University of Heidelberg, Heidelberg, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Täger
authors.affiliation: Department of Cardiology, Angiology, Pulmonology, University of Heidelberg, Heidelberg, Germany.
authors.forename: Wiebke
authors.initials: W
authors.lastname: Hanholz
authors.affiliation: Department of Cardiology, Angiology, Pulmonology, University of Heidelberg, Heidelberg, Germany.
authors.forename: Rita
authors.initials: R
authors.lastname: Cebola
authors.affiliation: Department of Cardiology, Angiology, Pulmonology, University of Heidelberg, Heidelberg, Germany.
authors.forename: Hanna
authors.initials: H
authors.lastname: Fröhlich
authors.affiliation: Department of Cardiology, Angiology, Pulmonology, University of Heidelberg, Heidelberg, Germany.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Franke
authors.affiliation: Department of Cardiology, Angiology, Pulmonology, University of Heidelberg, Heidelberg, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Doesch
authors.affiliation: Department of Cardiology, Angiology, Pulmonology, University of Heidelberg, Heidelberg, Germany.
authors.forename: Hugo A
authors.initials: HA
authors.lastname: Katus
authors.affiliation: Department of Pathology, Baylor University Medical Center, Dallas, TX, United States.
authors.forename: Frank H
authors.initials: FH
authors.lastname: Wians
authors.affiliation: Department of Cardiology, Angiology, Pulmonology, University of Heidelberg, Heidelberg, Germany. Electronic address: Lutz.Frankenstein@med.uni-heidelberg.de.
authors.forename: Lutz
authors.initials: L
authors.lastname: Frankenstein
mesh_terms: D000368:Aged; D002908:Chronic Disease; D005080:Exercise Test / Q000379:methods / Q000592:standards*; D017079:Exercise Tolerance; D005260:Female; D006333:Heart Failure / Q000175:diagnosis* / Q000503:physiopathology; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013997:Time Factors; D016138:Walking / Q000592:standards*
keywords: 6-minute walk-test; Biovariability; Heart failure; Minimal important difference