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Left bundle branch block (LBBB) is a conduction abnormality in the heart that can be seen on an electrocardiogram (ECG). [1] In this condition, activation of the left ventricle of the heart is delayed, which causes the left ventricle to contract later than the right ventricle .
A right bundle branch block typically causes prolongation of the last part of the QRS complex and may shift the heart's electrical axis slightly to the right. The ECG will show a terminal R wave in lead V1 and a slurred S wave in lead I. Left bundle branch block widens the entire QRS, and in most cases shifts the heart's electrical axis to the ...
Some BBB are permanent and involve a complete bundle blockage while others are dependent on the underlying activity of the heart. [1] For example, certain situations of excessive or reduced heart rate (tachycardia or bradycardia, respectively) can cause a BBB known as a rate-dependent bundle branch block (RDBBB). This manifests in a similar ...
A bundle branch block either LBBB or RBBB, (although RBBB is known to be associated only with S1 split), will produce continuous splitting but the degree of splitting will still vary with respiration. When the pulmonary valve closes before the aortic valve, this is known as a "paradoxically split S 2 ". [6]
Progressive cardiac conduction defect (PCCD) is a hereditary cardiac condition marked by a progressive delay in impulse conduction via the His-Purkinje system, resulting in right or left bundle branch block (RBBB or LBBB), syncope, and occasionally sudden cardiac death.
Normal variation causing LAD is an age-related physiologic change. Conduction defects such as left bundle branch block or left anterior fascicular block can cause LAD on the ECG. Pre-excitation syndrome as well as congenital heart diseases such as atrial septal defect, endocardial cushion defects can also cause LAD on ECG.
As the Bundle of His divides into the right and left bundle branches, a block of the electrical impulse may result in a Right Bundle Branch Block or a Left Bundle Branch Block, respectively. Sinoatrial (SA) block may also result be a result of Lev's disease. During a SA block, the electrical impulse formed at the SA node is delayed or not ...
Infra-Hisian blocks may occur at the left or right bundle branches ("bundle branch block") or the fascicles of the left bundle branch ("fascicular block" or "Hemiblock"). SA and AV node blocks are each divided into three degrees, with second-degree blocks being divided into two types (written either "type I or II" or "type 1 or 2").