3.2 Electrophysiology of the Heart

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lings from the SA node to the AV node and from the AV node to the HP complex must

be taken into account in any case (see Figure 3.13).

3.2.2 Measurement of Electrical Potentials at the Body Surface

The ionic charges present in a body generate an electric field and, in the case of ionic

movement, also a magnetic field. These fields usually cannot be measured directly at

the point of origin, e.g. at the membrane of a pacemaker cell of the heart, where the

migration of sodium and potassium ions occur. However, there is the possibility of a

non-invasive measurement via electrodes attached to the surface of the body. This is

because the fields generated at the point of origin spread to the surface of the body.

P

SA

AV

HP

HP

AV

SA

SA

Atrio

AV

His

Purkinje

ECG

vena cava

Sinus node

ventricular

node

Pulmonary

ventricle

atrium

atrium

ventricle

H

fibres

Left

Right

Right

Left

vena cava

veins

bundle

Superior

coupled equivalent oscillators

Inferior

1 s

Fig. 3.13: Heart with excitation guidance system (top left); illustration of the equivalent pacemaker-

oscillators (SA, AV and HP oscillators) with coupling (bottom); associated action potentials meas-

ured at the body surface by electrocardiogram (ECG) (top right).