5) Axis - right / left axis deviation (ie. of the QRS complex); various methods can be used:

Find the lead with highest voltage; (+) deflection will point to the axis, (-) negative deflection will be 180 degrees to it.

Find a lead with equal voltages in the R and S waves; axis is 90 degrees to it.

Find two leads in which the QRS voltages are equal, both positive, both negative, or one positive & one negative - the axis is midway between.

(+) QRS in leads I & II means normal axis.

Note: Effect on the positive electrode is determined by:

Angle

Amount of mass being depolarized.

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