His-bundle-ekg (hbe)

In 1893, Wilhelm His the Younger (1863 - 1934) was the first to describe the His bundle named after him, a muscle bundle originating from the AV node. He recognized the function of the atrioventricular conduction system and provided evidence of an AV muscle connection (Lüderitz 1993).

In 1957, Puech was the first to succeed in recording the potentials at the His bundle, whereby the recording was carried out as part of a catheter examination. Extensive experimental studies on HBE followed and in 1969 Schellag introduced His bundle electrography to the clinic (Lewalter 2010).

The PQ time of the conventional ECG can be specified in more detail by obtaining a His bundle ECG (Herold 2022).

Like the long-term ECG and the stress ECG, the HBE is one of the special forms of ECG (Klinge 2002).

The HBE is an invasive method of electrophysiological examination (EPU) that can be used to derive intracardiac potentials (Haas 2011).

The His bundle is part of the cardiac conduction system. The stimulus formation site is normally the sinus node. From there, the excitation first reaches the right atrium. The left atrium follows with a slight time delay. The excitation then reaches the AV node, which transmits the excitation to the His bundle, which in turn transmits it to the right and left Tawara legs (Kiening 2022).

The 12-lead ECG only records depolarization and repolarization generated by the atrial and ventricular myocardium. An HBE, on the other hand, represents the conduction through the AV node (Kasper 2015).

Procedure

An electrode catheter is placed transvenously directly on the His bundle. The catheter is usually placed via the femoral vein through the right atrium and the tricuspid valve into the right ventricle. In this way, the so-called "His potential" can be derived between the atrial and ventricular potentials (Klinge 2002).

An HBE is usually associated with atrial stimulation. For this purpose, a further transvenous catheter is inserted from the right or left arm into the right atrium, allowing selectable frequencies to be set (Lewalter 2010).

An HBE is recorded together with a conventional ECG recording (Lewalter 2010).

Using the His bundle ECG, the PQ time can be divided into:

- AH time or atrial His time

The AH interval begins with the atrial depolarization and ends with the start of the His bundle potential (Haas 2011). The normal time is 0.07 - 0.11 sec (Klinge 2002).

- HV time or His ventricular time

This determines the time between the excitation of the His bundle to the excitation of the ventricles. It is normally between 0.03 - 0.06 sec (Klinge 2002).

• Stimulation experiments

In the pacing trials, a catheter inserted into the atrium (see above) also enables pacing trials. The AH and HV intervals are measured as the heart rate increases. This makes it possible to recognize the frequency at which the HV conduction is blocked (Klinge 2002).

• Testing the mode of action of antiarrhythmic substances

The HBE can also be used to check the mode of action of antiarrhythmic drugs (Klinge 2002).

Indications

The HBE is important for:

- AV conduction disorders (Haas 2011)

In patients with AV block, the localization of the block can be determined, which has a major impact on the prognosis (Braun 2018).

- Arrhythmia diagnostics (Haas 2011)

- To detect orthograde and retrograde conduction abnormalities (Lewalter 2010) with possible detection of accessory pathways (Braun 2018).

- Unclear syncope (Klinge 2002)

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