Effects of airway obstruction and hyperinflation on electrocardiographic axes in COPD

Abstract

Background: COPD influences cardiac function and morphology. Changes of the electrical heart axes have been largely attributed to a supposed increased right heart load in the past, whereas a potential involvement of the left heart has not been sufficiently addressed. It is not known to which extent these alterations are due to changes in lung function parameters. We therefore quantified the relationship between airway obstruction, lung hyperinflation, several echo- and electrocardiographic parameters on the orientation of the electrocardiographic (ECG) P, QRS and T wave axis in COPD. Methods: Data from the COPD cohort COSYCONET were analyzed, using forced expiratory volume in 1 s (FEV1), functional residual capacity (FRC), left ventricular (LV) mass, and ECG data. Results: One thousand, one hundred and ninety-five patients fulfilled the inclusion criteria (mean ± SD age: 63.9 ± 8.4 years; GOLD 0–4: 175/107/468/363/82). Left ventricular (LV) mass decreased from GOLD grades 1–4 (p = 0.002), whereas no differences in right ventricular wall thickness were observed. All three ECG axes were significantly associated with FEV1 and FRC. The QRS axes according to GOLD grades 0–4 were (mean ± SD): 26.2° ± 37.5°, 27.0° ± 37.7°, 31.7° ± 42.5°, 46.6° ± 42.2°, 47.4° ± 49.4°. Effects of lung function resulted in a clockwise rotation of the axes by 25°-30° in COPD with severe airway disease. There were additional associations with BMI, diastolic blood pressure, RR interval, QT duration and LV mass. Conclusion: Significant clockwise rotations of the electrical axes as a function of airway obstruction and lung hyperinflation were shown. The changes are likely to result from both a change of the anatomical orientation of the heart within the thoracic cavity and a reduced LV mass in COPD. The influences on the electrical axes reach an extent that could bias the ECG interpretation. The magnitude of lung function impairment should be taken into account to uncover other cardiac disease and to prevent misdiagnosis.