Interpretation and clinical significance of the QRS axis of the electrocardiogram

Abstract

The frontal plane QRS axis of the standard 12-lead electrocardiogram (ECG) is easily and accurately measured by the clinician. A simple method of estimating this axis is discussed. This axis is age-dependent. We reviewed the literature to determine if evidence exists of an association between an "abnormal" QRS axis and clinically significant myocardial disease. We also examined the literature for clinical correlation of a "normal" QRS axis with the absence of myocardial pathology. We found that although an abnormal QRS axis (falling outside the limits of +30 degrees and +90 degrees) occurs in a small number of normal individuals, its presence should prompt a thorough evaluation of all the parameters of the ECG to look for myocardial disease.