Descriptions: Wide QRS, and wide S wave, caused by partial or complete blockage of signal along the right branch below the bundle of HIS.
Left bundle branch block (LBBB) is a cardiac conduction abnormality seen on the electrocardiogram (ECG).[1] In this condition, activation of the left ventricle is delayed, which causes the left ventricle to contract later than the right ventricle.
ECG diagnosis
Electrocardiogram showing left bundle branch block and irregular rhythm due to supraventricular extrasystoles.
A left bundle branch block
The criteria to diagnose a left bundle branch block on the electrocardiogram:
The heart rhythm must be supraventricular in origin
The QRS duration must be ≥ 120 ms
[2]
There should be a QS or rS complex in lead V1
There should be a RsR' wave in lead 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.
Causes
Among the causes of LBBB are:
Aortic stenosis
Dilated cardiomyopathy
Acute myocardial infarction
Extensive coronary artery disease
Primary disease of the cardiac electrical conduction system
Long standing hypertension leading to aortic root dilatation and subsequent aortic regurgitation
Treatment
Patients with LBBB require complete cardiac evaluation, and those with LBBB and syncope or near-syncope may require a
pacemaker.
Some patients with LBBB, a markedly prolonged QRS (usually > 150 ms), and systolic heart failure may benefit from a
biventricular pacemaker, which allows for better synchrony of heart contractions
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