Heart Rate Recovery After 6-min Walking Test Predicts Acute Exacerbation in COPD

Introduction Abnormalities of autonomic function have been reported in patients with chronic obstructive pulmonary disease (COPD). Our objectives were to identify determinants of abnormal heart rate recovery at 1 min (HRR 1 ) following completion of the 6-min walk test (6MWT) in COPD and to establish whether abnormal HRR 1 predicts acute exacerbations (AECOPD). Methods Hundred one COPD patients (FEV 1 (SD) 53 (19) % predicted) were prospectively recruited in a multi-center study. HRR 1 after the 6MWT was evaluated as the difference between heart rate at the end of the test and 1 min into the recovery (HRR 1 ). Linear and logistic regression was used to identify predictors of HRR 1 and AECOPD, respectively. The best HRR 1 cut-off point to predict AECOPD was selected using the receiver operating characteristics (ROC) curves. The follow-up period was 12 months. Results Distance covered during the 6MWT (m) and DLco (% predicted) were independently associated with HRR 1 ( r 2 = 0.51, p = 0.001). Among several potential covariates, HRR 1 emerged as the most significant predictor of AECOPD (Odds ratio [OR], 0.91 per beat of recovery; 95% confidence interval [CI], 0.85–0.97; p = 0.02). The ROC analysis indicated that subjects with HRR 1 less than 14 beats (AUC, 0.71 [CI] 0.60–0.80; p = 0.0001) were more likely to suffer an exacerbation during the follow-up period (for HRR 1 , p = 0.004 [log-rank test]). Conclusions HRR 1 after the 6MWT is an independent predictor factor for AECOPD. Further studies are warranted to examine the physiological mechanisms associating a delayed HRR and acute exacerbations in COPD patients.