Abnormal heart rate responses to exercise in non-severe COPD: Relationship with pulmonary vascular volume and ventilatory efficiency

Background Despite being a prognostic predictor, cardiac autonomic dysfunction (AD) has not been well investigated in chronic obstructive pulmonary disease (COPD). We aimed to characterise computed tomography (CT), spirometry, and cardiopulmonary exercise test (CPET) features of COPD patients with cardiac AD and the association of AD with CT-derived vascular and CPET-derived ventilatory efficiency metrics. Methods This observational cohort study included stable, non-severe COPD patients. They underwent clinical evaluation, spirometry, CPET, and CT. Cardiac AD was determined based on abnormal heart rate responses to exercise, including chronotropic incompetence (CI) or delayed heart rate recovery (HRR) during CPET. Results Out of 49 patients, 24 (49%) had CI, and 15 (31%) had delayed HRR. According to multivariate analyses, CI was independently related to reduced vascular volume (VV; VV ≤ median; OR [5–95% CI], 7.26 [1.56–33.91]) and low ventilatory efficiency (nadir VE/VCO2 ≥ median; OR [5–95% CI], 10.67 [2.23–51.05]). Similar results were observed for delayed HRR (VV ≤ median; OR [5–95% CI], 11.46 [2.03–64.89], nadir VE/VCO2 ≥ median; OR [5–95% CI], 6.36 [1.18–34.42]). Conclusions Cardiac AD is associated with impaired pulmonary vascular volume and ventilatory efficiency. This suggests that lung blood perfusion abnormalities may occur in these patients. Further confirmation is required in a large population-based cohort.