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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.
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 ...
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.
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. It is manifested on the ECG by left axis deviation.
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 ...
The delay in the AV node forms much of the PR segment on the ECG, and part of atrial repolarization can be represented by the PR segment. The distal portion of the AV node is known as the bundle of His. [8] The bundle of His splits into two branches in the interventricular septum: the left bundle branch and the right bundle branch.
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