Heart rate recovery after 6-min walk test predicts survival in patients with idiopathic pulmonary fibrosis.
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.
Swigris
Jeffrey J
JJ
Interstitial Lung Disease Program and Autoimmune Lung Center, National Jewish Medical and Research Center, Denver, CO. Electronic address: swigrisj@njc.org.
Swick
Jeff
J
Interstitial Lung Disease Program and Autoimmune Lung Center, National Jewish Medical and Research Center, Denver, CO.
Wamboldt
Frederick S
FS
Division of Psychosocial Medicine, National Jewish Medical and Research Center, Denver, CO.
Sprunger
David
D
Interstitial Lung Disease Program and Autoimmune Lung Center, National Jewish Medical and Research Center, Denver, CO.
du Bois
Roland
R
Interstitial Lung Disease Program and Autoimmune Lung Center, National Jewish Medical and Research Center, Denver, CO.
Fischer
Aryeh
A
Interstitial Lung Disease Program and Autoimmune Lung Center, National Jewish Medical and Research Center, Denver, CO.
Cosgrove
Gregory P
GP
Interstitial Lung Disease Program and Autoimmune Lung Center, National Jewish Medical and Research Center, Denver, CO.
Frankel
Stephen K
SK
Interstitial Lung Disease Program and Autoimmune Lung Center, National Jewish Medical and Research Center, Denver, CO.
Fernandez-Perez
Evans R
ER
Interstitial Lung Disease Program and Autoimmune Lung Center, National Jewish Medical and Research Center, Denver, CO.
Kervitsky
Dolly
D
Interstitial Lung Disease Program and Autoimmune Lung Center, National Jewish Medical and Research Center, Denver, CO.
Brown
Kevin K
KK
Interstitial Lung Disease Program and Autoimmune Lung Center, National Jewish Medical and Research Center, Denver, CO.
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*