Right bundle branch block, RBBB
See brief interpretation of 12 lead EKG above
– rSR’ pattern in V1 (resembles the character M)
– QRS ≥ 0.12 sec
Right bundle branch block (RBBB) is best seen in V1 as this lead is “looking” at the right side of the heart. Recall the electrical conduction system of the heart – what happens with the electrical conduction if the right bundle branch is blocked?
As the right bundle branch is blocked the right ventricle is depolarized through slower conducting pathways from the left ventricle. The left ventricle depolarizes in a normal way as the left bundle branch is unaffected. Corresponding to this delayed activation of the right ventricle the QRS is prolonged ≥ 0.12 sec. on the EKG. Also in lead V1 the latter part of the QRS complex is abnormal with an extra R wave in lead V1 due to the late activation of the right ventricle resulting in a typical rSR’ pattern. In lead I, V5 or V6 a late wide/slurred S wave can be seen (see 12 lead EKG above). Finally there might be depression of the ST segment or T wave inversion due to repolarisation changes.
For practical purposes intuitively suspect a right bundle branch block, when a “M” configuration of the QRS complex in lead V1 is present in an apparently otherwise normal EKG (the rSR’ configuration resembles the character M).
Right bundle branch block is common and the incidence increases with age. It is often seen in otherwise healthy individuals. However attention should in particular be given when RBBB is seen in combination with other conduction defects, seizures and after myocardial infarction.