Physical activity and cardiac autonomic dysfunction in patients with chronic obstructive pulmonary disease: a cross-sectional analysis

Background The cardiac autonomic function in patients with chronic obstructive pulmonary disease (COPD) has been poorly studied. Objectives We aimed to 1) describe the cardiac autonomic function assessed by heart rate recovery (HRR) and chronotropic response (CR) during a 6-min walk test (6MWT) and afterward and 2) estimate the association of physical activity with HRR and CR in COPD patients. Methods This cross-sectional analysis included 320 patients with mild to very severe COPD. Physical activity (steps, time in any/moderate-to-vigorous/vigorous physical activity, intensity and sedentary time) was measured during 1 week by accelerometer. CR and HRR were measured during a 6MWT and 5 min after, respectively, and their association with physical activity parameters was estimated by multivariable linear regression models. Results Patients were 82% male and had a mean (SD) age 68 (8) years, post-bronchodilator FEV1 57 (18) % predicted, and walked a mean of 7716 (4139) steps/day. HRR was slow until 5 min after the 6MWT; the mean (SD) was 15 (10), 22 (11), 25 (12), 25 (12) and 27 (12) bpm after 1, 2, 3, 4 and 5 min, respectively). The mean CR was 35% (16). After adjusting for relevant confounders, time in vigorous physical activity was significantly associated with a fast decrease in HRR (p=0.044) and an increase in CR (p=0.021). We found no independent association for other physical activity parameters. Conclusion A cardiac autonomic dysfunction is present in patients with mild to very severe COPD and is inversely related to the practice of vigorous physical activity.