The electrocardiogram in chronic obstructive pulmonary disease. The electrocardiogram is often abnormal in patients who have chronic obstructive pulmonary disease. The most frequent abnormalities are a rightward P-wave axis (greater than or equal to 70 degrees) and a rightward QRS axis (greater than or equal to 90 degrees). In addition, low voltage in the limb leads, an S1S2S3 pattern, poor R-wave progression, a posterior-superior terminal QRS vector or other changes may be present. Transient atrial and ventricular dysrhythmias are common. Knowledge of the usual electrocardiographic manifestations of chronic obstructive pulmonary disease enables the clinician to recognize uncharacteristic abnormalities, which often represent the effects of superimposed illnesses or drug toxicity. 