For information on ECG background and interpretation, see here.
The electrocardiogram (ECG) represents electrical activity originating in the heart and captured on the skin. It is of profound importance in assessing cardiovascular disease and other conditions affecting heart function.
The standard 12 lead ECG has 6 limb leads (I, II, III, avR, aVL, and aVF) and six precordial (chest) leads (V1-V6).
Place the patient supine, with the head slightly elevated. Ensure that the arms and legs are supported from underneath.
Expose the chest and limb areas. Where necessary, shave the skin to allow secure placement of the leads.
Ask the patient to remain still, with their muscles relaxed, and to breathe normally.
Once the leads are placed, enter the patient's age as prompted, and press the '12 lead' button.
two suggested limb lead placements, from wikipedia
The limb leads are composed of standard leads I, II, and III and augmented leads aVL, aVR, and aVF.
Place the electrodes as follows:
Augmented leads are termed unipolar because they use one positive electrode as reference against a combination of the other limb electrodes. aVL uses the left arm as a positive electrode, aVR uses the right arm, and aVF the left leg.
The precordial leads are placed on the chest, just above the heart. Their positions are as follows:
V1: fourth intercostal space, at right edge of sternum (red)
V2: fourth intercostal space, at left edge of sternum (yellow)
V3: midway between V2 and V4 (green)
V4: fifth intercostal space, midclavicular line (blue)
V5: same horizontal line as V4, left anterior axillary line (brown)
V6: same horizontal line as V4, left mid axillary line (purple)
remembering the colours
a stop light goes red, yellow, green; blue skies in spring,
brown leaves in autumn, and a purple Christmas!
(cortesy of Pauline Chordash)
When placing leads on females, or men with generous chest tissue, lift up the breast to place the lead on the chest wall; do not place it on the breast.
15 or 18 lead ECGs can be done with alternate precordial lead placement to assess for posterior- or right-sided disease. While the 18-lead ECG is perhaps more sensitive for early detection of ischemia or infarction, in practice, either should be used for:
15 lead ECG requires repositioning of the leads as follows:
Ensure the ECG is relabelled as a 15 lead.
18 lead ECG requires repositioning of the leads as follows:
Again, ensure the ECG is relabelled as an 18 lead ECG.