1.2 ORIENTATION OF THE 12-LEAD ECG

1.2. 1 It is important to remember that the 12-lead ECG provides spatialinformation about the heart's electrical activity in 3 approximately orthogonal directions(think: X, Y, Z):

(1) Right-Left (X)

(2) Superior - Inferior (Y)

(3) Anterior - Posterior (Z)

1.2.2

Each of the 12 leads represents a particular orientation in space, asindicated in Fig. 1-2 (RA=right arm; LA=left arm, LL=left leg) :

(1) Bipolar limb leads (frontal plane):

Lead I: RA (-pole) to LA ( pole) (Right-to-Left direction)

Lead I: RA (-) to LL ( ) (mostlySuperior-to-Inferior direction

Lead I: LA (-) to LL ( ) (mostlySuperior-to-Inferior direction)

(2) Augmented limb leads (frontal plane):

Lead aVR: RA ( ) to [LA & LL] (-) (mostly Rightward direction

Lead aVL: LA ( ) to [RA &LL] (-) (mostly Leftward direction)

Lead aVF: LL ( ) to [RA &LA] (-) (Inferior direction)

（3) “Unipolar” ( ) chest leads (horizontal plane):

Leads V1, v2, V3 (mostly Posterior-to-Anterior direction)

Leads V4, V5, V6 (mostly Right-to-Left direction)