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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.
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 ...
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.
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.
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").
Tachycardia-dependent bundle branch block (TDBBB) can affect either ventricle in the heart, and occurs when the heart's rate of contraction reaches an elevated level and becomes uncoupled from the heart's refractory period (the time it takes for a cardiac cell to "reset" for future contraction).
Reversible causes of Mobitz II and third-degree heart block include untreated Lyme disease, hypothyroidism, hyperkalemia (high levels of potassium), and drug toxicity. Drugs that slow the conduction of the electrical signal through AV node, such as beta-blockers , digoxin , calcium channel blockers , and amiodarone , can cause heart block if ...