Abstract
BackgroundCOPD 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.MethodsData 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.ResultsOne 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.ConclusionSignificant 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.
Highlights
IntroductionCardiovascular comorbidities are common in patients with chronic obstructive pulmonary disease (COPD) [1,2,3]
The mean orientation of the P wave axis according to the spirometric Global Initiative for Obstructive Lung Disease (GOLD) grades 0–4 is illustrated in the left panel of Fig. 1a, while the right panel shows the values plotted against mean values of functional residual capacity (FRC) % predicted observed for each GOLD grade
Lung function impairment affected the P wave, QRS and T wave axis in the same clockwise direction, which is compatible with a rotation of the heart within the thoracic cavity
Summary
Cardiovascular comorbidities are common in patients with chronic obstructive pulmonary disease (COPD) [1,2,3] This includes morphological and functional alterations of the heart. One of the basic diagnostic criteria for cardiac disorders is the definition of the electrical axes from the standard surface electrocardiogram (ECG) [7]. These are the P wave, QRS and T wave axes that can be obtained by established algorithms. Due to alterations of the heart in COPD, changes in the orientation of the electrical axes are to be expected independent of or in addition to primary cardiac disease
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