title: Heart rate recovery after 6-min walk test predicts survival in patients with idiopathic pulmonary fibrosis.
abstract: BACKGROUND
  In patients with idiopathic pulmonary fibrosis (IPF), our objectives were to identify predictors of abnormal heart rate recovery (HRR) at 1 min after completion of a 6-min walk test (6MWT) [HRR1] and 2 min after completion of a 6MWT (HRR2), and to determine whether abnormal HRR predicts mortality.
  
  
  METHODS
  From 2003 to 2008, we identified IPF patients who had been evaluated at our center (n = 76) with a pulmonary physiologic examination and the 6MWT. We used logistic regression to identify predictors of abnormal HRR, the product-limit method to compare survival in the sample stratified on HRR, and Cox proportional hazards analysis to estimate the prognostic capability of abnormal HRR.
  
  
  RESULTS
  Cutoff values were 13 beats for abnormal HRR1 and 22 beats for HRR2. In a multivariable model, predictors of abnormal HRR1 were diffusing capacity of the lung for carbon monoxide (odds ratio [OR], 0.4 per 10% predicted; 95% confidence interval [CI], 0.2 to 0.7; p = 0.003), change in heart rate from baseline to maximum (OR, 0.9; 95% CI, 0.8 to 0.97; p = 0.01), and having a right ventricular systolic pressure > 35 mm Hg as determined by transthoracic echocardiogram (OR, 12.7; 95% CI, 2.0 to 79.7; p = 0.01). Subjects with an abnormal HRR had significantly worse survival than subjects with a normal HRR (for HRR1, p = 0.0007 [log-rank test]; for HRR2, p = 0.03 [log-rank test]); these results held for the subgroup of 30 subjects without resting pulmonary hypertension (HRR1, p = 0.04 [log-rank test]). Among several candidate variables, abnormal HRR1 appeared to be the most potent predictor of mortality (hazard ratio, 5.2; 95% CI, 1.8 to 15.2; p = 0.004).
  
  
  CONCLUSIONS
  Abnormal HRR after 6MWT predicts mortality in IPF patients. Research is needed to confirm these findings prospectively and to examine the mechanisms of HRR in IPF patients.
authors.affiliation: Interstitial Lung Disease Program and Autoimmune Lung Center, National Jewish Medical and Research Center, Denver, CO. Electronic address: swigrisj@njc.org.
authors.forename: Jeffrey J
authors.initials: JJ
authors.lastname: Swigris
authors.affiliation: Interstitial Lung Disease Program and Autoimmune Lung Center, National Jewish Medical and Research Center, Denver, CO.
authors.forename: Jeff
authors.initials: J
authors.lastname: Swick
authors.affiliation: Division of Psychosocial Medicine, National Jewish Medical and Research Center, Denver, CO.
authors.forename: Frederick S
authors.initials: FS
authors.lastname: Wamboldt
authors.affiliation: Interstitial Lung Disease Program and Autoimmune Lung Center, National Jewish Medical and Research Center, Denver, CO.
authors.forename: David
authors.initials: D
authors.lastname: Sprunger
authors.affiliation: Interstitial Lung Disease Program and Autoimmune Lung Center, National Jewish Medical and Research Center, Denver, CO.
authors.forename: Roland
authors.initials: R
authors.lastname: du Bois
authors.affiliation: Interstitial Lung Disease Program and Autoimmune Lung Center, National Jewish Medical and Research Center, Denver, CO.
authors.forename: Aryeh
authors.initials: A
authors.lastname: Fischer
authors.affiliation: Interstitial Lung Disease Program and Autoimmune Lung Center, National Jewish Medical and Research Center, Denver, CO.
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Cosgrove
authors.affiliation: Interstitial Lung Disease Program and Autoimmune Lung Center, National Jewish Medical and Research Center, Denver, CO.
authors.forename: Stephen K
authors.initials: SK
authors.lastname: Frankel
authors.affiliation: Interstitial Lung Disease Program and Autoimmune Lung Center, National Jewish Medical and Research Center, Denver, CO.
authors.forename: Evans R
authors.initials: ER
authors.lastname: Fernandez-Perez
authors.affiliation: Interstitial Lung Disease Program and Autoimmune Lung Center, National Jewish Medical and Research Center, Denver, CO.
authors.forename: Dolly
authors.initials: D
authors.lastname: Kervitsky
authors.affiliation: Interstitial Lung Disease Program and Autoimmune Lung Center, National Jewish Medical and Research Center, Denver, CO.
authors.forename: Kevin K
authors.initials: KK
authors.lastname: Brown
mesh_terms: D000368:Aged; D016009:Chi-Square Distribution; D005080:Exercise Test; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D054990:Idiopathic Pulmonary Fibrosis / Q000401:mortality* / Q000503:physiopathology*; D016015:Logistic Models; D008297:Male; D010092:Oximetry; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D015996:Survival Rate; D016138:Walking / Q000502:physiology*