In this condition there is abnormal conduction through the right or left bundle branches and a consequent delay in the depolarisation of part of the ventricular muscle. When the heart is in sinus rhythm, ventricular conduction along a slower, abnormal pathway results in a QRS complex of greater than 0.12 sec but with a constant PR interval.
A block of both bundles is equivalent to third degree, or complete, heart block.
Thus three types of bundle branch block may occur:
Right bundle branch block:
Left bundle branch block:
Last reviewed 01/2018