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60 Chapter 2: Cardiovascular system

I aVR V1 V4

II aVL V2 V5

III aVF V3 V6

Rhythm strip
(II)

Figure 2.13 Left bundle branch block.

(see Fig. 2.13). Acute left bundle branch block may be a caused by ischaemic heart disease, fibrosis of the bundles
sign of acute myocardial infarction (see pages 37–39). or pulmonary disease. Acute onset right bundle branch
block may be associated with pulmonary embolism or a
Complications rightventricular infarct.
Syncope due to intermittent complete heart block.
Clinical features
Management
Right bundle branch block is asymptomatic and is often
Treatment is not necessary.
an incidental finding. There is widened splitting of the
heart sounds with the pulmonary sound occurring later
Right bundle branch block than normal.
Definition
Investigations
Block to the right branch of the bundle of His, which
The characteristic RsR’ is seen best in lead V1 and a
normally facilitates transmission of impulses to the right
late S wave is seen in V6. Complete block of the bundle
ventricle.
results in a QRS complex of greater than 0.12 seconds
(see Fig. 2.14).
Aetiology/pathophysiology
Right bundle branch block is often due to a congenital
abnormality of little significance, but may be associated Complications
withatrialseptaldefects.Inolderpatientsitiscommonly Syncope due to intermittent complete heart block.