Conduction defects

Fascicular block (hemiblock): left anterior & left posterior fascicular block

Fascicular block (hemiblock): left anterior fascicular block & left posterior fascicular block Fascicular blocks were previously referred to as hemiblocks, but the latter term has been deprecated. The left bundle branch is subdivided into the following two fascicles: (1) the anterior (anterosuperior) fascicle, which delivers the electrical impulse to the anterior wall of the left ventricle; (2) the posterior (posteroinferior) fascicle,…

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Right bundle branch block (RBBB): ECG, criteria, definitions, causes & management

Right bundle branch block (RBBB) Right bundle branch block (RBBB) is due to an anatomical or functional dysfunction in the right bundle branch, such that the electrical impulse is blocked. Refer to Figure 1 for an overview of the components of the ventricular conduction system, including the right bundle branch. In the setting of RBBB, depolarization (i.e…

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Left bundle branch block (LBBB) in acute myocardial infarction: the Sgarbossa criteria

Left bundle branch block (LBBB) in acute myocardial infarction (AMI): clinical implications & Sgarbossa criteria On the contrary to right bundle branch block, left bundle branch block is always a pathological finding which affects cardiovascular and total mortality. Left bundle branch block is more common in individuals with structural and ischemic heart disease. Assessment of ischemia on ECG is…

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Nonspecific intraventricular conduction delay (defect)

Nonspecific intraventricular conduction delay Nonspecific intraventricular conduction delay exists if the ECG displays a widened QRS appearance that is neither a left bundle branch block (LBBB) nor a right bundle branch block (RBBB).  Thus, the appearance of nonspecific intraventricular conduction delay may be rather nuanced.   Definition and causes of nonspecific intraventricular conduction delay According to the American Heart Association/American College of…

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Left bundle branch block (LBBB): ECG criteria, causes, management

Left bundle branch block (LBBB): ECG criteria and clinical implications Left bundle branch block (LBBB) is the consequence of anatomical or functional dysfunction in the left bundle branch, causing the impulse to be blocked. Depolarization of the left ventricle will be carried out by impulses spreading from the right ventricle. Because the left bundle branch is dysfunctional, the impulse will…

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Overview of intraventricular conduction delay / defect

Intraventricular conduction delay (defect): constellations of bundle branch blocks and fascicular blocks (hemiblocks) In this chapter we will discuss intraventricular conduction delay, which is caused by functional or anatomical defects in the components of the intraventricular conduction system. Because the conduction system is crucial for rapid and synchronized activation of the ventricles, conduction defects will typically cause abnormal…

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Management and treatment of AV block (atrioventricular blocks)

Management and treatment of AV blocks (first, second and third-degree AV block) Evaluation of patients with suspected AV blocks requires a thorough medical history (with emphasis on causes of AV blocks, refer to the Causes of AV blocks) and physical examination. It is also reasonable to analyse cardiac troponins if there is any probability of acute ischemic heart disease…

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Third-degree AV block (3rd degree AV block, AV block 3, AV block III)

In this article you will learn about third-degree AV block, which may also be referred to as AV dissociation, complete heart block, AV block III, AV block 3 or simply 3rd degree AV block. Before reading this article, make sure that you have read the introduction to atrioventricular (AV) blocks.   Third-degree (complete) AV block: ECG criteria and characteristics…

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Second-degree AV block: Mobitz type 1 (Wenckebach) and Mobitz type 2 block

In this article you will learn about 2nd degree (second-degree) AV block. Before reading this article, make sure that you have read the introduction to atrioventricular (AV) blocks.   Second-degree (2nd degree) AV block: ECG criteria and characteristics Second-degree AV block implies that some atrial impulses are completely blocked, which means that not all P-waves are followed…

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First-degree AV block (AV block I, AV block 1)

First-degree AV block: ECG criteria and clinical characteristics In this article you will learn about first-degree AV block, which may also be referred to as 1st degree AV block, AV block 1 or AV block I. Before reading this article, make sure that you have read the fundamentals of AV blocks. The term block is somewhat misleading in the case…

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