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A right bundle branch block (RBBB) is a heart block in the right bundle branch of the electrical conduction system. [1] During a right bundle branch block, the right ventricle is not directly activated by impulses traveling through the right bundle branch. However, the left bundle branch still normally activates the left ventricle.
A bundle branch block can be diagnosed when the duration of the QRS complex on the ECG exceeds 120 ms. A right bundle branch block typically causes prolongation of the last part of the QRS complex and may shift the heart's electrical axis slightly to the right.
So if the block happens on the right side, it’s referred to as a right bundle branch block. So with this type, the electrical signal starts at the SA node, contracts the atria, moves through the AV node, splits at the bundle of His, and then moves down the left bundle branch but is blocked on the right bundle branch.
Infra-Hisian blocks may occur at the left or right bundle branches ("bundle branch block") or the fascicles of the left bundle branch ("fascicular block" or "Hemiblock"). SA and AV node blocks are each divided into three degrees, with second-degree blocks being divided into two types (written either "type I or II" or "type 1 or 2").
Some BBB are permanent and involve a complete bundle blockage while others are dependent on the underlying activity of the heart. [1] For example, certain situations of excessive or reduced heart rate (tachycardia or bradycardia, respectively) can cause a BBB known as a rate-dependent bundle branch block (RDBBB). This manifests in a similar ...
Bifascicular block is characterized by right bundle branch block with left anterior fascicular block, or right bundle branch block with left posterior fascicular block on electrocardiography. Complete heart block could be the cause of syncope that is otherwise unexplained if bifascicular block is seen on electrocardiography. [1]
A bundle branch block either LBBB or RBBB, (although RBBB is known to be associated only with S1 split), will produce continuous splitting but the degree of splitting will still vary with respiration. When the pulmonary valve closes before the aortic valve, this is known as a "paradoxically split S 2 ". [6]
There are two branches of the bundle of His: the left bundle branch and the right bundle branch, both of which are located along the interventricular septum. The left bundle branch further divides into the left anterior fascicle and the left posterior fascicle. These structures lead to a network of thin filaments known as Purkinje fibers.