Complete BBB

The BBBs are divided into two categories of severity, complete and incomplete. In complete BBBs, there is total failure of the affected bundle branch to conduct an impulse. The ventricle on the side of the failed bundle branch must be depolarized by the spread of a wave of depolarization through ventricular muscle from the unaffected side (Figure 7.1). Obviously, this activation of the affected ventricle by muscle-to-muscle conduction is a much slower process than rapid activation through the Purkinje fibers of a normally functioning bundle branch. In addition, there is a lot of ground to cover; essentially, an entire ventricle. The result is that, in complete BBBs, the QRS duration is prolonged to at least 0.12 seconds or greater.

Incomplete BBB 43

Figure 7.1. Right bundle branch block. The ventricle on the side of the failed bundle must be depolarized by the spread of a wave of depolarization from the nonaf-fected side (arrow).

Incomplete BBB 43

Figure 7.1. Right bundle branch block. The ventricle on the side of the failed bundle must be depolarized by the spread of a wave of depolarization from the nonaf-fected side (arrow).

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