If you get your right bundle branch taken out, your right ventricle depolarises AFTER the left ventricle has finished depolarising. This results in a slightly prolonged QRS (because of the delay in conduction from the left ventricle to the right). Not only that, but when the right ventricle depolarises it can produce an additional QRS complexes, giving rise to this "RSR" pattern.
Of all the branch blocks, this one is the favourite of the college: it has appeared in many past papers.
- Question 30.3 from the second paper of 2012 (Right bundle branch block with STEMI)
- Question 23.2 from the first paper of 2012 (trifascicular block)
- Question 6.1 from the second paper of 2011 (Right bundle branch block + left posterior fascicular block)
- Question 15.3 from the second paper of 2008 (Right bundle branch block with STEMI)
- Question 26.2 from the first paper of 2008 (Right bundle branch block + left posterior fascicular block)
- Question 30 from the first paper of 2005 (flutter with trifascicular block)
Features of RBBB:
- M-shaped QRS pattern in V1 – V3 ( "RSR" waves)
- Wide S-wave in lateral leads ( Lead I, V5-6, aVL)
- There will also be T wave inversion in the anterior leads
- There may be an extra R wave in the anterior leads ( R'), or there may just be a broad slurred QRS.
- The depolarization of the right ventricle is delayed
- The left ventricle activates normally: the early part of the QRS remains unchanged
- Axis is unchanged because left ventricular activation is normal.
INCOMPLETE Right Bundle Branch Block
o Normal QRS duration, but RSR pattern in the anterior leads
o This is a normal variant
Causes of Right Bundle Branch Block
- Acute pulmonary embolism
- Right ventricular hypertrophy / cor pulmonale the right bundle is vulnerable to stretching trauma
- Myocarditis or cardiomyopathy
- Congenital septal defect
Consequences of Right Bundle Branch Block
- Independent predictor of increased mortality in patients with coronary artery disease
- Dyssynchronous left ventricle: thus, decreased ejection fraction
Management options for Right Bundle Branch Block
- In absence of other conduction abnormalities, with normal ejection fraction: do nothing.
- Isolated RBBB is very rarely a problem.
- If LVEF is poor (<35%) or there is some other heart block, or the patient has episodes of syncope, go with a PERMANENT PACEMAKER.
- These people typically don't respond as well to pacing, as do the LBBBs