Trifascicular block

Trifascicular block
The later half shows a second degree AV block with a RBBB and left anterior fascicular block
SpecialtyCardiology
SymptomsNone, syncope[1]
Diagnostic methodECG[1]
TreatmentDepends on the type and symptoms[1]

Trifascicular block is a type of electrical conduction problem within the heart were all three pathways between the atria and the ventricles are disrupted to some degree.[1][2] The term is used to describe some combination of a RBBB and either a LAFB or LPFB with an AV block.[1] While often used for 1st and 2nd degree AV blocks some apply it only to 3rd degree AV blocks.[1] The term "true" or "complete" and "incomplete" has been used to distinguish these.[1][2]

Diagnosis is generally by ECG.[1] Risk factors include ischemic heart disease, structural heart disease, aortic stenosis, and congenital heart disease.[1] Reversible causes include high potassium and digoxin toxicity.[1] When a right bundle branch block (RBBB) and left bundle branch block alternate, there is a high risk that a 3rd degree block will occur.[1]

In those with a 3rd degree AV block treatment is generally by placement of a pacemaker.[1] In those with a bifascifular blocks who have had a loss of consciousness a pacemaker may be considered, otherwise no specific treatment is required.[1] Use of the term is not recommended, due to its non specific meaning.[1]

Diagnosis

Diagnosis is generally by ECG.[1]

An electrophysiology study of the conduction system can help discern the severity of conduction system disease. In an electrophysiology study, trifascicular block due to AV nodal disease is represented by a prolonged AH interval (denoting prolonged time from impulse generation in the atria and conduction to the bundle of His) with a relatively preserved HV interval (denoting normal conduction from the bundle of His to the ventricles). Trifascicular block due to distal conduction system disease is represented by a normal AH interval and a prolonged HV interval. In the absence of symptoms, a prolonged AH interval is likely benign while a prolonged HV interval is almost always pathologic.

Treatment

An implantable cardiac pacemaker or permanent pacemaker is recommended in the following clinical circumstances. Class 1 recommendation is the strongest recommendation. Level A evidence is the highest level of evidence.

Class I

Class II

Class III

A pacemaker not recommended.

References

  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 Buttner, Robert; Larkin, John; Larkin, Robert Buttner and John (5 January 2021). "Trifascicular Block". Life in the Fast Lane • LITFL. Archived from the original on 24 November 2024. Retrieved 20 December 2024.
  2. ↑ 2.0 2.1 "Trifascicular Block". ECGbook. 30 July 2024. Archived from the original on 17 February 2025. Retrieved 28 December 2024.

External links

Classification
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