Left bundle branch block
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ECG characteristics of a typical LBBB showing wide QRS complexes with abnormal morphology in leads V1 and V6.
Left bundle branch block (LBBB) is a cardiac conduction abnormality seen on the electrocardiogram (ECG). In this condition, activation of the left ventricle is delayed, which results in the left ventricle contracting later than the right ventricle.
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[edit] ECG criteria
The ECG diagnosis of LBBB requires a supraventricular rhythm with a QRS complex = or > than 0.12 sec (120 ms), an rS or QS complex in lead V1, and a monophasic R wave in leads I and V6. A minority will show an S wave in lead V6. The T wave should be deflected opposite the terminal deflection of the QRS complex.
[edit] Causes
Among the causes of LBBB are:
- Hypertension
- Acute myocardial infarction
- Extensive cases of coronary artery disease
- Primary disease of the cardiac electrical conduction system
[edit] Treatment
- Medical Care: Patients with LBBB require complete cardiac evaluation, and those with LBBB and near-syncope or syncope may require a pacemaker.
- Surgical Care: Some patients with LBBB, a markedly prolonged QRS, and congestive heart failure may benefit from a pacemaker, which provides rapid left ventricular contractions.
[edit] See also
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