Rationale: Reduced heart rate recovery after exercise is associated with increased mortality in cardiopulmonary diseases.
Objectives: We sought to evaluate the association between heart rate recovery at 1 minute of rest (HRR1) after 6-min walk test (6MW test) and clinical worsening in patients with idiopathic pulmonary arterial hypertension (IPAH).
Methods: HRR1 was defined as the difference in heart rate at the end of 6MW test and at 1 minute after completion of the 6MW test. Between August 1, 2009 and March 30, 2010, 75 consecutive patients with IPAH underwent 6MW test and were included in the analysis.
Measurements and main results: Compared with patients with HRR1 ≥ 16 (n = 45 [60%]), those with HRR1 less than 16 (n = 30 [40%]) were more likely to have clinical worsening (odds ratio, 9.7; 95% confidence interval [CI], 3-30; P < 0.001) and shorter time to first clinical worsening event (TCW) (6.7 mo vs. 13 mo; P < 0.001) during follow-up. By multivariable analysis, the best predictors of clinical worsening were HRR1 less than 16 (hazard ratio, 5.2; 95% CI, 1.8-14.8; P = 0.002) and mean pulmonary arterial pressure (hazard ratio, 1.04; 95% CI, 1.007-1.08; P = 0.02). Compared with the distance walked during the 6MW test (6MWD), HRR1 less than 16 was a better predictor of clinical worsening (C statistic 0.757 vs. 0.703) and TCW (C index 0.730 vs. 0.696). The addition of HRR1 increased the ability of 6MWD to predict clinical worsening events.
Conclusions: HRR1 after 6MW test is a strong predictor of clinical worsening and TCW in patients with IPAH. The addition of HRR1 to 6MWD increases the capacity of 6MWD to predict clinical worsening and TCW in patients with IPAH.