Right Bundle Branch Block - Diagnosis

Diagnosis

The criteria to diagnose a right bundle branch block on the electrocardiogram:

• The heart rhythm must originate above the ventricles (i.e. sinoatrial node, atria or atrioventricular node) to activate the conduction system at the correct point.
• The QRS duration must be more than 100 ms (incomplete block) or more than 120 ms (complete block)
• There should be a terminal R wave in lead V1 (e.g. R, rR', rsR', rSR' or qR)
• There should be a slurred S wave in leads I and V6.

The T wave should be deflected opposite the terminal deflection of the QRS complex. This is known as appropriate T wave discordance with bundle branch block. A concordant T wave may suggest ischemia or myocardial infarction.

A mnemonic to remember the ECG changes is WiLLiaM MaRRoW, i.e. with Left bundle branch block there is a W in V1 and a M in V6 and with a RBBB there is a M in lead V1 and a W in lead V6