trifascicular block

Trifascicular block is a problem with the electrical conduction of the heart.

Trifascicular block.

Trifascicular block due to distal conduction system disease is represented by a normal AH interval and a prolonged HV interval.

Trifascicular block is important to diagnose because it is difficult to tell based on the surface ECG whether the prolonged PR interval is due to disease in the AV node or due to diffuse distal conduction system disease.

A subset of individuals with the triad of first-degree heart block, right bundle branch block, and either left anterior fascicular block or left posterior fascicular block (known as trifascicular block) may be at an increased risk of progression to complete heart block.