Chronic obstructive pulmonary disease negatively affects the autonomic nervous system and increases risks of arrhythmias and sudden cardiac death. Electrocardiogram (ECG) recordings were used to compare parameters of heart rate variability and QTc interval in patients with COPD and healthy individuals. The effects of a 4-week program of rehabilitation in patients with COPD were also evaluated by comparing pre- and post-rehabilitation ECGs with age- and sex-matched control COPD patients not participating in the program. Heart rate, average NN, SDNN, RMSSD, pNN50, TP, LF, HF, LF/HF, and QTc were analyzed. Rehabilitation effects were evaluated using the St. George's respiratory questionnaire (SGRQ), the 6-min walk test (6MWT), and the incremental shuttle walking test (ISWT). In comparison with the healthy individuals, the patients with COPD had higher heart rate (p < 0.05) and reduced average NN, SDNN, RMSSD, pNN50, HF, LF, and TP (all p < 0.05) but similar QTc interval (p = 0.185). During rehabilitation, SDNN and TP (p < 0.05 for both) increased, as did the results for 6MWT, ISWT, and SGRQ (all p < 0.05). No significant change of QTc interval was observed within or between the two groups of patients with COPD. Change in SDNN correlated with a clinically relevant difference in SGRQ (r = 0.538, p = 0.021). It is concluded that patients with COPD demonstrate reduced parameters of heart rate variability and that these can be improved in a rehabilitation program, thus improving health-related quality of life.
Keywords: QT interval; chronic obstructive pulmonary disease; exercise training; heart rate variability; rehabilitation.