title: Correlation of the New York Heart Association Classification and the 6-Minute Walk Distance: A Systematic Review.
abstract: BACKGROUND
  Functional status assessment is the cornerstone of heart failure management and trials. The New York Heart Association (NYHA) classification and 6-minute walk distance (6MWD) are commonly used tools; however, the correlation between them is not well understood.
  
  
  OBJECTIVE
  We hypothesised that the relationship between the NYHA classification and 6MWD might vary across studies.
  
  
  METHODS
  A systematic literature search was performed to identify all studies reporting both NYHA class and 6MWD. Two reviewers independently assessed study eligibility and extracted data. Thirty-seven studies involving 5678 patients were included.
  
  
  RESULTS
  There was significant heterogeneity across studies in 6MWD within all NYHA classes: I (n = 16, Q = 934.2; P < 0.001), II (n = 25, Q = 1658.3; P < 0.001), III (n = 30, Q = 1020.1; P < 0.001), and IV (n = 6, Q = 335.5; P < 0.001). There was no significant difference in average 6MWD between NYHA I and II (420 m vs 393 m; P = 0.416). There was a significant difference in average 6MWD between NYHA II and III (393 m vs 321 m; P = 0.014) and III and IV (321 m vs 224 m; P = 0.027). This remained significant after adjusting for region of study, age, and sex.
  
  
  CONCLUSIONS
  Although there is an inverse correlation between NYHA II-IV and 6MWD, there is significant heterogeneity across studies in 6MWD within each NYHA class and overlap in 6MWD between NYHA I and II. The NYHA classification performs well in more symptomatic patients (NYHA III/IV) but less so in asymptomatic/mildly symptomatic patients (NYHA I/II). Nonetheless, the NYHA classification is an easily applied first-line tool in everyday clinical practice, but its potential subjectivity should be considered when performing comparisons across studies.
authors.affiliation: Department of Cardiology, National Heart Centre Singapore, Singapore.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Yap
authors.affiliation: Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Fang Yi
authors.initials: FY
authors.lastname: Lim
authors.affiliation: Department of Cardiology, National Heart Centre Singapore, Singapore.|Duke-NUS Graduate Medical School, Singapore.
authors.forename: Fei
authors.initials: F
authors.lastname: Gao
authors.affiliation: Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Ling Li
authors.initials: LL
authors.lastname: Teo
authors.affiliation: Department of Cardiology, National Heart Centre Singapore, Singapore.|Cardiovascular Research Institute, National University of Singapore, Singapore.
authors.forename: Carolyn Su Ping
authors.initials: CS
authors.lastname: Lam
authors.affiliation: Department of Cardiology, National Heart Centre Singapore, Singapore.|Duke-NUS Graduate Medical School, Singapore.
authors.forename: Khung Keong
authors.initials: KK
authors.lastname: Yeo
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D005080:Exercise Test / Q000379:methods*; D017079:Exercise Tolerance; D005260:Female; D006333:Heart Failure / Q000145:classification / Q000175:diagnosis* / Q000503:physiopathology; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012737:Sex Factors; D013997:Time Factors; D016138:Walking