3.2 Electrophysiology of the Heart

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Fig. 3.14: Example potentials at heart (left) and thorax (right) as generated by the freeware pro-

gramme ECGSIM [55] of the University of Nijmegen; in the thorax representation the locations of the

recording electrodes according to Wilson are marked by grey circles

Einthoven Potentials

For these potentials, one takes a foot as the reference potential and obtains the

voltages UI, UII, UIII from the potential differences:

UI = ΦL −ΦR

UII = ΦF −ΦR

UIII = ΦF −ΦL

Goldberger Potentials

Here the voltages aVL, aVR, aVF are not related to the potential at the foot, but to a vir-

tual ground point, which is the average of the voltages derived according to Einthoven

as follows:

aVL = UII/2 −UIII

aVR = UIII/2 −UII

aVF = UI/2 −UII

Wilson Potentials

Further electrodes are applied by adding six (to nine) further measurement points on

the thorax near the heart in a ring-shaped arrangement along the chest wall and re-

lating them to the indifferent collecting electrode, which is obtained by merging the

extremity leads according to Goldberger (see Figure 3.16).

In total, twelve ECG potential differences (see Figure 3.16) can thus be obtained

from all three measurement arrangements (according to Einthoven, Goldberger and

Wilson), which can be used for the standard assessment of electrical cardiac activity.