0071643192.pdf

LEFTBUNDLEBRANCHBLOCK(LBBB)

In LBBB, both the left anterior and posterior fascicles are blocked and electrical

conduction to the L ventricle is delayed (after R ventricular conduction) and

slowed.

CAUSES

LBBB does notoccur in a healthy heart. Causes include:

■ Chronic hypertension

■ Valvular disease

■ Ischemia

■ Cardiomyopathy

■ Myocarditis

■ Congenital heart disease

■ Following heart surgery

ECG FINDINGS(SEEFIGURE2.2)

■ Characterized by symmetric slurring through entire QRS complex

■ QRS duration ≥0.12 seconds

■ QS or rS in V 1

■ Monophasic R in V 6

■ Appropriately discordant T waves

LEFTANTERIORFASCICULARBLOCK(LAFB)

LAFB results from failure of conduction of the left anterior fascicle of the left

bundle.

CAUSES

Causes are similar to LBBB.

CARDIOVASCULAR EMERGENCIES

I aVR V1 V4

II aVL V2 V5

III

RHVTHM STRIP: II

25 mm/sec: 1cm/mV

aVF V3 V6

FIGURE 2.2. Left bundle branch block.