Chronotropic Incompetence and its Relation to Exercise Intolerance in Chronic Obstructive Pulmonary Disease.

Liu HJ, Guo J, Zhao QH, Wang L, Yang WL, He J, Gong SG, Liu

Am J Med Sci. 2017 Mar;353(3):216-223. doi: 10.1016/j.amjms.2016.12.015. Epub
2016 Dec 21.

BACKGROUND: To study the relationship between chronotropic incompetence (CI) and
disease severity and to assess the effect of CI on exercise capacity in patients
with chronic obstructive pulmonary disease (COPD).
MATERIALS AND METHODS: Arterial blood gas analysis, pulmonary function test and
cardiopulmonary exercise testing were conducted in 60 patients with stable COPD
and 45 healthy volunteers. CI was defined using the chronotropic response index
(CRI = (peak heart rate-resting heart rate) / (220-age-resting heart rate). Based
on CRI, patients with COPD were divided into the normal chronotropic group (n =
23) and CI group (n = 37).
RESULTS: CI was present in 61.7% of the patients with COPD. Exercise capacity
(peak oxygen uptake as percentage of predicted value, peak VO2%pred), peak heart
rate and CRI were significantly lower in patients with COPD than in controls.
However, resting heart rate was significantly higher than in controls. FEV1%pred
and exercise capacity were significantly decreased in the CI group when compared
with those in the normotropic group. There was significant association between
CRI with FEV1%pred and peak VO2%pred. Multivariate regression analysis showed
that CRI and FEV1%pred were independent predictors of exercise capacity in
patients with COPD. A cutoff of 0.74 for the CRI showed a specificity of 94.1% in
predicting patients with a peak VO2%pred < 60%. CONCLUSIONS: CRI was associated with disease severity in patients with COPD. CI may be an important parameter to reflect exercise capacity in patients with COPD.