Increased heart rate modulation, sympathetic dominance and systemic inflammation in chronic obstructive pulmonary disease

Background. Cardiac autonomic dysfunction, an independent determinant of adverse outcomes in many diseases, also occurs in Chronic Obstructive Pulmonary Disease (COPD). However, observations have been equivocal, its clinical correlates are poorly defined and association with systemic inflammation unexplored, this study being carried out to address these gaps in knowledge. Materials and Methods. Sixty three patients of COPD and 36 controls underwent spirometry, estimation of diffusion capacity, six-minute walk test and measurement of serum interleukin 6 and C-Reactive protein. Cardiac autonomic activity was evaluated by a five-minute heart rate variability (HRV) recording to obtain standard time- and frequency-domain indices. Results. HRV indices of overall autonomic modulation, the standard deviation of time intervals between consecutive normal beats (SDNN) and total power were greater in patients with increased levels of several indices of parasympathetic and sympathetic activity. The five-minute averaged heart rate was significantly greater in patients indicating a sympathetic dominance and was inversely correlated with diffusion capacity. Serum interleukin -6 was inversely correlated with pNN50, an index of parasympathetic activity, and positively with LF/HF ratio, that reflects sympathetic:parasympathetic balance. No HRV parameter was associated with physiological measures of severity. Conclusions . Patients with COPD have increased cardiac autonomic modulation with sympathetic dominance. This is associated with decreased lung diffusion capacity and systemic inflammation.