User manual

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The 12-lead system consists of:
• Bipolar limb leads according to Einthoven (leads I, II, III)
• Unipolar augmented leads - Goldberg’s leads (aVL, aVR, aVF)
• Unipolar chest leads - Wilson’s leads (V1 - V6)
Bipolar leads - leads according to Einthoven
The electrodes are placed on the wrists of the upper limbs (R-red color, L-yellow
color) and on the lower part of the left lower limb (F-green). A neutral electrode (N-black) is
connected to the lower part of the right limb. This layout is mostly used in ambulatory
practices. Thanks to the relatively good conductivity of the skin (up to 600 mS/m), it is
possible to place the individual electrodes even to other places on the body, yet the so called
Einthoven’s triangle must always be observed. This fact is very often used in the urgent care
or in ergometry, when the sensing electrodes are stuck on the patient’s chest. Differences in
electrical potentials in time are measured via differential amplifiers, always between two
electrodes, see Fig. 2.8.
Fig. 2.8: Geometry of the standard limb leads.
Unipolar leads according to Goldberg
The resulting voltage development is given by the difference in the potential of one
limb and “averaged-out” medium potential from the remaining limbs. The medium potential
is formed via a volt box 50:50, see Fig. 2.9. These leads are marked as aVR, aVL and aVF.
U
I
= Φ
L
- Φ
R
U
II
= Φ
F
- Φ
R
U
III
= Φ
F
- Φ
L
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