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Left bundle branch block

  • ️Tue Jan 20 2009
Left bundle branch block
Classification and external resources

ECG characteristics of a typical LBBB showing wide QRS complexes with abnormal morphology in leads V1 and V6.
ICD-10 I44.4 - I44.7
DiseasesDB 7352
eMedicine ped/2501

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 results in the left ventricle contracting later than the right ventricle.

EKG diagnosis

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 = or > 120 ms[2]
  • There should be a QS or rS complex in lead V1
  • There should be a RsR' 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 EKG 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:

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

There are also partial blocks of the left bundle branch: "left anterior fascicular block" (LAFB)[3] and a "left posterior fascicular block" (LPFB).[4] This refers to the bifurcation of the left bundle branch.

See also

References

External links

v · d · eCardiovascular disease: heart disease · Circulatory system pathology (I00–I52, 390–429)
Ischaemic

Active ischemia

Layers

Valves

Conduction/
arrhythmia

Premature contraction

Flutter/fibrillation

Other/ungrouped

Cardiomegaly
Other

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