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Figure 111-1

Electrocardiographic Lead Systems: the Hexaxial Frontal Plane Reference System to Estimate Electrical Axis

Electrocardiographic lead systems: the hexaxial frontal plane reference system to estimate electrical axis. Determine leads in which QRS deflections are maximum and minimum. For example, a maximum positive QRS in I which is isoelectric in aVF is oriented to 0°. Normal axis ranges from -30° to +90°. An axis > +90° is right-axis deviation and <30° is left-axis deviation.