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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 .
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.
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.
So if the block happens on the right side, it’s referred to as a right bundle branch block. So with this type, the electrical signal starts at the SA node, contracts the atria, moves through the AV node, splits at the bundle of His, and then moves down the left bundle branch but is blocked on the right bundle branch.
Left anterior fascicular block (LAFB) is an abnormal condition of the left ventricle of the heart, [1] [2] related to, but distinguished from, left bundle branch block (LBBB). It is caused by only the left anterior fascicle – one half of the left bundle branch being defective.
In the presence of bundle branch block or ventricular hypertrophy, the depolarization impulse takes a longer than normal period of time to reach the recording electrode. This delays the onset of the intrinsicoid deflection. This prolongation or delay is an important criterion for diagnosing bundle branch block or ventricular hypertrophy.
Sgarbossa's criteria are a set of electrocardiographic findings generally used to identify myocardial infarction (also called acute myocardial infarction or a "heart attack") in the presence of a left bundle branch block (LBBB) or a ventricular paced rhythm. [1] Myocardial infarction (MI) is often difficult to detect when LBBB is present on ECG ...
In comparison to second-degree atrioventricular block, in first-degree block there is an absence of non-conduction or "dropped beats." In an electrophysiology study , this corresponds to a prolonged A-H interval that shows the time between atrial depolarization and His bundle depolarization near the AV node.