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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 bundle branch block can be diagnosed when the duration of the QRS complex on the ECG exceeds 120 ms. 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.
If conduction to the ventricles occurs solely through the pathway (maximal pre-excitation), as occurs during arrhythmias like antidromic atrioventricular re-entrant tachycardia, the ECG appearance is of QRS complexes with a left bundle branch block morphology which can be mistaken for ventricular tachycardia. However, due to their slow ...
Ventricular ectopy seen on a surface EKG in the setting of ACM is typically of left bundle branch block (LBBB) morphology, with a QRS axis of −90 to +110 degrees. The origin of the ectopic beats is usually from one of the three regions of fatty degeneration (the "triangle of dysplasia"): the RV outflow tract, the RV inflow tract, and the RV apex.
And so the left ventricle contracts first . The signal then spreads from the purkinje fibers of the left ventricle over to the right ventricle, which contracts, but this happens after the left contracts. So with right bundle branch block, the right ventricle contracts late. If the block happened to be on the left side instead, a left bundle ...
There are two branches of the bundle of His: the left bundle branch and the right bundle branch, both of which are located along the interventricular septum. The left bundle branch further divides into the left anterior fascicle and the left posterior fascicle. These structures lead to a network of thin filaments known as Purkinje fibers.
Normal activation utilizes the bundle of His and Purkinje fibers to produce a narrow (QRS) electrical signal. Aberration occurs when the electrical activation of the heart, which is caused by a series of action potentials, is conducting improperly which can result in temporary changes in the morphology that looks like: Left bundle branch block
Poor R wave progression is commonly attributed to anterior myocardial infarction, but it may also be caused by left bundle branch block, Wolff–Parkinson–White syndrome, right and left ventricular hypertrophy, or a faulty ECG recording technique. [11]