Abnormal heart rate recovery and chronotropic incompetence on submaximal exercise in COPD
Background: A delayed heart rate recovery (HRR) after graded and an attenuated heart rate response (chronotropic incompetence, CI) are markers of cardiac autonomic dysfunction and predict cardiovascular mortality. The latter also characterize COPD. Therefore we hypothesized that decreased HRR and CI should coexist in COPD.

Methods: After lung function evaluation, 39 stable COPD patients and 11 healthy controls underwent submaximal cycle ergometry. Heart rate was measured at peak exercise and at 1-min recovery. Abnormal HRR was defined as a recovery of ≤12 beats in the first minute post-exercise. Chronotropic incompetence was evaluated by measuring the Chronotropic Response Index (CRI = \[(peak heart rate - resting heart rate)/\] \[(220 - age) – (resting heart rate)\].

Results: The HRR was 13±9.1 beats and 23.9±5.9 beats in patients and controls (p<0.001) while CRI was 44.59±13.9 and 61.2±5.1 (p<0.01) in these groups, respectively. An abnormal HRR was observed in 29 (74.4%) of the patients. The HRR and CRI were significantly correlated. Both HRR and CRI showed a decreasing trend with increasing GOLD severity and BODE index. On univariate analysis, HRR was negatively associated with age, pack-years of smoking and diffusion capacity/alveolar volume (DLCO/VA). On multiple logistic regression, after adjusting for other variables, a reduced DLCO/VA was the only significant, though weak, determinant of reduced HRR.

Conclusions: Patients with COPD have a decreased HRR and CI on exercise indicating autonomic dysfunction. These well-established markers of cardiovascular morbidity and mortality should be clinically useful tools for risk stratification and prognostication in patients with COPD.