ABSTRACT
In simple terms, the QRS axis is an indicator of the general direction that the wave of depolarization takes as it flows through the ventricles – in other words, the overall vector of ventricular depolarization. The QRS axis is therefore conventionally referred to as the angle, measured in degrees, of the direction of electrical current flowing through the ventricles. Left ventricular hypertrophy can cause left axis deviation but not as a result of increased muscle mass. Instead, it results from left anterior fascicular block caused by fibrosis. As with right-sided accessory pathways and left axis deviation, patients with Wolff–Parkinson–White (WPW) syndrome syndrome who have a left-sided accessory pathway may have right axis deviation in addition to the other electrocardiogram appearances of WPW syndrome. The QRS axis is directed away from infarcted areas. Thus, right axis deviation may be a feature of anterolateral myocardial infarction.
