Trifascicular femoral blockI45.3

A trifascicular block is the blockage of all three fascicles in the conduction system, i.e. the right Tawara limb, the left anterior limb and the left posterior limb (Ohly 2019).

Due to the trifascicular structure of the ventricular conduction system, a distinction is made between the following blockages:

- I. unifascicular block = hemiblock

- II. bifascicular block

- III. trifascicular block (Herold 2023)

The trifascicular block is additionally subdivided into a

- III a. complete block:

Here, all 3 legs are blocked simultaneously; as a result, an AV block of the IIIrd degree occurs.

- III b. Incomplete block:

An incomplete block is to be assumed in the following blocking combinations:

Right bundle branch block in combination with a left posterior hemiblock plus type I or II degree AV block

Right bundlebranch block in combination with a left anterior hem iblock plus type I or II degree AV block

Right bundle branch block plus an alternation between a left anterior hem iblock or left posterior hemiblock

Left bundle branch block plus AV block I. Degree or II. Type I or II

Alternation between left bundle branch block and right bundle branch block (Kasper 2015)

- Bifascicular block

A trifascicular block can develop in < 3 % of cases (Krehan 2017)

- Left anterior hemiblock with right bundle branch block

These patients tend to develop a complete heart block, the so-called trifascicular block, in approx. 10 % of cases (Abdulla 2021)

- Lenègre disease

This is a hereditary disease of the conduction system (Andresen 2021)

Medication such as anticholinergics as part of cataract surgery (Vermont- Desroches 2022)

- COVID- 19 disease (Gubitosa 2020)

- Cardiac amyloidosis (Yaghubi2018)

- Mediastinal radiotherapy (Ali 2021)

- Dizziness (Striebel 2015)

- Syncope (Brignole 2013)

A trifascicular block is diagnosed by recording a surface ECG or an intracardiac ECG (Roskamm 2013). A history of syncope and dizziness should always be taken (Striebel 2015 / Brignole 2013).

Surface ECG

This shows a bifascicular block in the form of a right bundle branch block with left anterior hemiblock (RSB plus LAH) or a right bundle branch block with left posterior hemiblock (RSB plus LPH) plus prolonged HV time as an indication of a conduction disturbance in the 3rd fascicle (Roskamm 2013).

Patients with proven trifascicular block that cannot be attributed to other causes, regardless of whether syncope is present or not, should undergo pacemaker implantation (Kasper 2015).

In the case of incomplete trifascicular block, on the other hand, there is no compelling indication for pacemaker implantation if the patient does not report any dizziness or syncope. However, if a bifascicular block with AV block II. However, if there is a bifascicular block with a type II AV block, pacemaker implantation is also recommended in symptom-free patients (Striebel 2015).

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