Mechanisms of ECG changes in chronic obstructive pulmonary disease

Introduction: Patients with Chronic Obstructive Pulmonary Disease (COPD) often have abnormal electrocardiogram (ECG). Objectives: To identify and separate the effects upon the ECG by airway obstruction, emphysema and right ventricular (RV) afterload in patients with COPD. Methods: A cross-sectional study was performed in 2006-10 on 101 patients with COPD without left heart disease, and 32 healthy age-matched controls. Body mass index (BMI) was measured, and pulmonary function tests, ECG, echocardiography, and (in patients) right heart catheterization. Variables were grouped as follows: airway obstruction by FEV% predicted, emphysema by residual volume/total lung capacity and residual volume % predicted, and RV afterload by mean pulmonary pressure, pulmonary artery compliance, pulmonary vascular resistance and RV wall thickness. Results: Multivariate regression analysis showed that emphysema correlated negatively to R + S amplitudes in horizontal and frontal (standard) leads. Left ventricle (LV)/RV end-diastolic diameter ratio correlated positively to the horizontal amplitudes, BMI correlated negatively to the frontal amplitudes. Increased airway obstruction, RV afterload and BMI resulted in clockwise rotation of the QRS axis in the horizontal plane. Airway obstruction, RV afterload, LV/RV end-diastolic diameter ratio and BMI correlated positively to the Sokolow-Lyon index for RV. RV afterload correlated negatively to ECG-signs of left ventricular mass. Conclusion: In patients with COPD, increased airway obstruction and RV afterload mainly increase the Sokolow-Lyon index for RV mass, and predispose to clockwise rotation of the QRS axis in the horizontal plane, whereas emphysema reduces the QRS amplitudes.