Atrioventricular block pathophysiology: Difference between revisions

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{{Atrioventricular block}}
{{Atrioventricular block}}
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==Overview==
==Overview==
==Pathophysiology==
[[Atrioventricular]] (AV) block is caused by one of the following mechanisms i.e. [[fibrosis]] or degeneration of the [[conduction system]], [[ischemic heart disease]], or [[medications]].


Atrioventricular (AV) block is caused by one of the following mechanisms i.e. fibrosis or degeneration of the conduction system, [[ischemic heart disease]], or medications. AV block is categorized by degree and site of conduction block. In first-degree AV block, all atrial impulses are conducted to the ventricle. However, there is a delay within the AV node, resulting in a prolonged PR interval on ECG (>200 msec or >5 small blocks). Second-degree AV block can be of one of the two types: Mobitz I and Mobitz II. Mobitz I, or [[Wenckebach block]] , consists of progressive prolongation of PR interval, until loss of conduction to the ventricle occurs (missed beat). Mobitz I block is rarely symptomatic and does not require treatment. On the other hand, Mobitz II AV block is characterized by a constant PR interval with intermittent missed beats. The missed beats can occur with varying frequency such as occasional to 3:1 or 2:1. [[Complete heart block]] (third-degree heart block) is characterized by a complete lack of conduction from the atria to the ventricles. The ventricular rates in complete heart blocks are slower than the atrial rate. A junctional escape rate is generally between 40 and 60 beats/min and shows narrow QRS complex on EKG, whereas a ventricular escape rate is slower with a wide QRS complex. Treatment involves addressing the reversible causes such as withholding medications, treatment of ischemia, antibiotics treatment for [[lyme disease]].
==Atrioventricular Block Pathophysiology==
*[[First-degree atrioventricular block]]
**A delay in electrical [[heart conduction]] without significant interruption occurs from [[atria]] to [[ventricle]].  
**This occurs at the level of [[atrioventricular node]] ([[AV node]]) or slightly below it.
**In this situation, no [[hemodynamic instability]] happens.
*[[Second-degree atrioventricular block Mobitz type 1]] ([[Wenckebach]])
**A block in the normal [[electrical conduction system]] occurs at the crest of [[AV node]]]as a result of failure of [[AV nodal cells]] to transmit the [[cardiac impulse]] to the [[ventricles]].
**This is related to a progressive fatigue of the [[cells]] and result is manifested as a [[dropped beat]].
*[[Second-degree atrioventricular block Mobitz type 2]]
**The [[electrical conduction system]] blockage occurs at the level below the [[AV node]] ([[His bundle]], [[bundle branches]], and [[heart fascicles]].
*[[Third-degree atrioventricular block]]
**There are two possible locations in this block with [[impulse conduction]] depending on the location of the block.
**A narrow [[QRS complex]] with [[AV node intrinsic rate]] of 40 to 55 beats per minute is observed when the block is at the crest of [[AV node]] or above it.
**A wide [[QRS complex]] with a [[ventricular pacemaker intrinsic rate]] of 20 to 40 beats per minute is observed when the block is below the [[AV node]].<ref name="pmid29083636">{{cite journal| author=| title=StatPearls | journal= | year= 2022 | volume=  | issue=  | pages=  | pmid=29083636 | doi= | pmc= | url= }} </ref>


==References==
==References==
{{Reflist|2}}
{{Reflist|2}}
{{WH}}
{{WS}}
[[CME Category::Cardiology]]
[[Category:Cardiology]]
[[Category:Electrophysiology]]
[[Category:Disease]]
[[Category:Needs content]]
[[Category:Needs content]]

Latest revision as of 05:43, 28 November 2022

https://https://www.youtube.com/watch?v=2-I2TWE7D-E%7C350}}

Atrioventricular block Microchapters

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Edzel Lorraine Co, DMD, MD[2]

Overview

Atrioventricular (AV) block is caused by one of the following mechanisms i.e. fibrosis or degeneration of the conduction system, ischemic heart disease, or medications.

Atrioventricular Block Pathophysiology

References

  1. "StatPearls". 2022. PMID 29083636.

Template:WH Template:WS CME Category::Cardiology