In patients with LV dysfunction and heart failure, LBBB can worsen the LV dysfunction and mitral regurgitation. Intraventricular blocks without advanced AV block are usually asymptomatic. Intraventricular blocks may be caused by antiarrhythmic drugs, particularly class I drugs (see Table 3.4-1) and amiodarone.Ĭlinical Features and Natural History Top At times this is an isolated finding with no other morphologic cardiac alterations. Features of a pseudo-RBBB with ST-segment elevation are observed in Brugada syndrome.Ĭauses of LBBB: Structural heart disease: IHD, cardiomyopathy (particularly dilated cardiomyopathy), myocarditis, congenital or acquired heart disease, connective tissue disease, myocardial infiltrates in the course of various conditions, idiopathic fibrosis, or calcifications. This is frequently an isolated finding with no other morphologic cardiac alterations.
Simultaneous impairment in all 3 fascicles presents as complete heart block.Ĭauses of RBBB: Congenital heart disease (most commonly atrial septal defect), ischemic heart disease ( IHD), degenerative or idiopathic fibrosis. This term is also sometimes used in the case of bifascicular block with first-degree atrioventricular ( AV) block, but the definition is not accurate, as PR prolongation in such patients could be related to the AV node and not to a block in the remaining fascicle. Trifascicular block refers to simultaneous or alternate conduction impairment in all fascicles. Possible patterns of intraventricular block include:ġ) Left anterior or posterior fascicular block.Ģ) Right bundle branch block ( RBBB) ( Figure 3.2-5) or left bundle branch block ( LBBB) ( Figure 3.2-6).ģ) RBBB with left anterior or posterior fascicular block ( bifascicular block according to the definition by the European Society of Cardiology, isolated LBBB is also a bifascicular block). Intraventricular blocks may be of a His bundle branch block pattern, a fascicular block pattern, or both and result from significant slowing or interruption of conduction. 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines and the Heart Rhythm Society. Writing Committee Members, Kusumoto FM, Schoenfeld MH, Barrett C, et al.
2021 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy. Glikson M, Nielsen JC, Kronborg MB, et al ESC Scientific Document Group.
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