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| Left bundle branch block Classification and external resources |
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| ECG characteristics of a typical LBBB showing wide QRS complexes with abnormal morphology in leads V1 and V6. | |
| ICD-10 | I44.7 |
| DiseasesDB | 7352 |
| eMedicine | ped/2501 |
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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ECG diagnosis
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 = or > 120 ms
- There should be a QS or rS complex in lead V1
- There should be a monophasic R wave in leads I and 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.
A mnemonic to remember the ECG changes is WiLLiaM MaRRoW, ie with LBBB there is an W in V1 and a M in V6 and with a RBBB there is a M in lead V1 and a W in lead v6
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
Treatment
- Medical Care: Patients with LBBB require complete cardiac evaluation, and those with LBBB and syncope or near-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.
Classification
Some sources distinguish between a "left anterior fascicular block" (LAFB)[1] and a "left posterior fascicular block" (LPFB).[2] This refers to the bifurcation of the left bundle branch.
See also
References
External links
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Wikipedia content modification information:
- This page was last modified on 10 October 2008, at 14:52.
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