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1. The Standard 12 Lead ECG

The standard 12-lead electrocardiogram is a representation of the heart's electrical activity recorded from electrodes on the body surface. This section describes the basic components of the ECG and the lead system used to record the ECG tracings.

Topics for study:

  1. ECG Waves and Intervals
  2. Spatial Orientation of the 12 Lead ECG


ECG Waves and Intervals:

image 01-03

What do they mean?

Orientation of the 12 Lead ECG

It is important to remember that the 12-lead ECG provides spatial information about the heart's electrical activity in 3 approximately orthogonal directions:

Each of the 12 leads represents a particular orientation in space, as indicated below (RA = right arm; LA = left arm, LL = left foot):

Bipolar limb leads (frontal plane):

Augmented unipolar limb leads (frontal plane):

Unipolar (+) chest leads (horizontal plane):

Lead Placement Diagrams: