Atrioventricular block overview: Difference between revisions
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An atrioventricular block (or AV block) is a type of [[heart block]] involving an impairment of the conduction between the [[atria]] and [[ventricles]] of the heart.<ref>{{Dorlands|b_16|12188991}}</ref> It usually involves the [[atrioventricular node]], but it can involve other structures too. 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]]. A [[permanent pacemaker]] is indicated for symptomatic [[bradycardia]] due to advanced second- or third-degree heart blocks. | An atrioventricular block (or AV block) is a type of [[heart block]] involving an impairment of the conduction between the [[atria]] and [[ventricles]] of the heart.<ref>{{Dorlands|b_16|12188991}}</ref> It usually involves the [[atrioventricular node]], but it can involve other structures too. 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]]. A [[permanent pacemaker]] is indicated for symptomatic [[bradycardia]] due to advanced second- or third-degree heart blocks. | ||
==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. | |||
==References== | ==References== | ||
Revision as of 16:05, 5 February 2013
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
An atrioventricular block (or AV block) is a type of heart block involving an impairment of the conduction between the atria and ventricles of the heart.[1] It usually involves the atrioventricular node, but it can involve other structures too. 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. A permanent pacemaker is indicated for symptomatic bradycardia due to advanced second- or third-degree heart blocks.
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.