With ventricular depolarization of the site has a number of transient ECG integrated vector, in the face of the lead axis of projection, that is, limb-lead electrocardiogram of the QRS complex wave.

• 随着心室各部位先后去极化形成多个瞬间综合心电向量，在额面的导联轴上的投影，便是心电图肢体导联的QRS复合波。