Right bundle branch block – RBBB
The electrical system of the heart for the ventricles has two branches – right bundle branch and the left bundle branch. Right bundle branch carries the electrical signals for heart beats to the right lower chamber (right ventricle) and left bundle branch carries the signals to the left ventricle (left lower chamber). When the signal conduction in the right bundle is cut off by disease, it is known as right bundle branch block. That does not mean that electrical signals will not reach the right ventricle and the right ventricle stops functioning. Right ventricle stills gets the signal through a circuitous route through the smaller conduction channels within the right ventricular muscle. The signals first reach the left ventricle through the left bundle branch and then the right ventricle through smaller conduction fibres and muscles. This means that right ventricular activation will be delayed. Hence left ventricle will start contracting earlier and left ventricle later
What is the significance of RBBB?
If it is not associated with any other form of heart disease, isolated RBBB does not produce much problem in the function of the heart. Slight delay in contraction of the right ventricle does not cause changes in the heart rate or blood pressure. If it is associated with heart disease, the problems are usually due to that heart disease. As a birth defect, partial right bundle branch block can occur in atrial septal defect and some other congenital heart diseases. If associated with a heart attack, presence of RBBB would indicate a more extensive attack, involving the partition between the two ventricles (interventricular septum) where the right bundle is situated. When a person with RBBB subsequently develops additional left bundle branch block it can lead to complete heart block with severe slowing of the heart rate.
How is RBBB detected?
RBBB is detected by the pattern it shows on the ECG (electrocardiogram). Typical pattern is described as a wide QRS complex with rSR’ pattern. More detailed assessment of the conduction system of the heart is possible by electrophysiological study (EP study).
Does RBBB require treatment?
RBBB does not require treatment by itself. Treatment is for the disease which caused it. Sometimes RBBB occurs without any other significant heart disease. Then it needs only observation as occasionally the left bundle also can become diseased in the long run and cause complete heart block. Otherwise isolated RBBB can be considered as a fairly innocuous condition. Of course it carries a better long term outlook then left bundle branch block (LBBB).