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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 .
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 ...
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.
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 ...
After the Bundle of His, the conduction system splits into the left bundle branch and the right bundle branch. Both branches conduct action potentials at about 1 m/s. However, the action potential starts traveling down the left bundle branch about 5 milliseconds before it starts traveling down the right bundle branch, as depicted by frame 13.
The clinician must therefore be well versed in recognizing the so-called ECG mimics of acute myocardial infarction, which include left ventricular hypertrophy, left bundle branch block, paced rhythm, early repolarization, pericarditis, hyperkalemia, and ventricular aneurysm. [7] [8] [9] Localisation of the occlusion in the ECG showing STEMI changes
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. They play an integral role in the electrical conduction system of the heart by transmitting cardiac action potentials to the Purkinje fibers. [2]
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