Editing Trifascicular block (section)

{{Medref|date=February 2021}}
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'''Trifascicular block''' is a problem with the [[Electrical conduction system of the heart|electrical conduction]] of the [[heart]], specifically the three fascicles of the [[bundle branches]] that carry electrical signals from the [[atrioventricular node]] to the ventricles. The three fascicles are one in the right bundle branch, and two in the left bundle branch the [[left anterior fascicle]] and the [[left posterior fascicle]]. A block at any of these levels can cause an abnormality to show on an [[electrocardiogram]].

The most literal meaning of '''trifascicular block''' is [[complete heart block]]: all three fascicles are blocked. A second, and clinically distinct, definition of '''trifascicular block''' is a circumstance in which [[right bundle branch block]] (RBBB) and [[left bundle branch block]] occur in the same patient, but at distinct points in time. For example, a patient that is found to have a RBBB one day and a LBBB another can be said to have "alternating [[bundle branch block]]s". In this context, because all three fascicles show evidence of block at different points in time, the term '''trifascicular block''' is often used.

Finally, the third meaning of '''trifascicular block''' refers to a specific finding on an [[electrocardiogram]] in which [[bifascicular block]] is observed in a patient with a prolonged [[Electrical conduction system of the heart#AV node/Bundles: PR interval|PR interval]] ([[first degree AV block]]).

The treatment of '''trifascicular block''' is highly dependent on which clinical entity (one of the three above) is being described.