Lightning Learning: Trifascicular Block

Lightning Learning: Trifascicular Block

Trifascicular block is a combination of heart block with a bifascicular block and can be ‘complete’ or ‘incomplete’.
— advice is based on local guidelines & procedures

What?

Trifascicular block is a combination of heart block with a bifascicular block and can be complete or incomplete.

Bifascicular block is diagnosed by the presence of right bundle branch block with either left anterior fascicular block (common) or left posterior fascicular block (rare).

LAFB results in left axis deviation and LPFB in right axis deviation.

Complete trifascicular block: 3rd degree heart block in the presence of bifascicular block.
Incomplete trifascicular block: 1st or 2nd degree heart block with bifascicular block.

It can also be RBBB with alternating LAFB and LPFB.

Why?

Incomplete trifascicular blocks can convert into complete heart block. Any patient who presents with a trifascicular block on their ECG will need a medical or cardiology review. Many of these patients will require pacing, but be sure to review all medications.

Trifascicular block can result from:

  • Ischaemic heart disease

  • Congenital heart disease

  • Hyperkalaemia

  • Digoxin toxicity

Further Reading

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Lightning Learning: Mindfulness (The Comma)

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