Second degree AV block classification: Difference between revisions
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{{Second degree AV block}} | {{Second degree AV block}} | ||
{{CMG}}; {{AE}} {{CZ}} | {{CMG}}; {{AE}} {{Sara.Zand}} [[User:Mohammed Salih|Mohammed Salih, M.D.]], {{CZ}}, {{RT}} | ||
==Overview== | |||
There are 4 distinct types of [[second degree AV block]]. The distinction is made between them because type 1 second-degree [[heart block]] is considered a more benign entity than the other types. In mobitz type 1 second degree [[AV block]] there is evidence of gradually [[PR prolongation]] and dropped beat and grouped beating pattern. In mobitz type 2 [[AV block]] there is suddenly dopped [[beats]] without evidence of preceding [[PR prolongation]]. In [[atrioventricular block]] with the pattern of 2:1, there is every other [[beat]] without conducting down to the [[ventricle]]. In a high-grade [[AV block]], there are two or more consecutive [[P waves]] without conducting down to the [[ventricle]]. It is important to determine the anatomic site of [[AV block]]. In Mobitz type 1 [[AV block]], the site is usually within the [[AV node]], but in Mobitz type II [[AV block]] the site is almost always below the [[AV node]]. In the presence of wide [[QRS]] complex and 2:1 AV conduction it is more likely that the site of [[AV]] block is intranodal or infranodal. In some cases, second-degree [[atrioventricular block]] must be differentiated from other causes of pauses such as non-conducted [[premature atrial contractions]] or [[atrial tachycardia]] with [[block]]. | |||
==Classification== | |||
<ref name="KusumotoSchoenfeld2019">{{cite journal|last1=Kusumoto|first1=Fred M.|last2=Schoenfeld|first2=Mark H.|last3=Barrett|first3=Coletta|last4=Edgerton|first4=James R.|last5=Ellenbogen|first5=Kenneth A.|last6=Gold|first6=Michael R.|last7=Goldschlager|first7=Nora F.|last8=Hamilton|first8=Robert M.|last9=Joglar|first9=José A.|last10=Kim|first10=Robert J.|last11=Lee|first11=Richard|last12=Marine|first12=Joseph E.|last13=McLeod|first13=Christopher J.|last14=Oken|first14=Keith R.|last15=Patton|first15=Kristen K.|last16=Pellegrini|first16=Cara N.|last17=Selzman|first17=Kimberly A.|last18=Thompson|first18=Annemarie|last19=Varosy|first19=Paul D.|title=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|journal=Circulation|volume=140|issue=8|year=2019|issn=0009-7322|doi=10.1161/CIR.0000000000000628}}</ref> | |||
{| class="wikitable" | |||
! align="center" style="background:#4479BA; color: #FFFFFF;" + |Term | |||
! align="center" style="background:#4479BA; color: #FFFFFF;" + |Classification | |||
! align="center" style="background:#4479BA; color: #FFFFFF;" + |Definition | |||
! | |||
|- | |||
| rowspan="3" |[[Atrioventricular block]] | |||
| [[First-degree atrioventricular block]] | |||
| | |||
* P waves associated with 1:1 [[atrioventricular ]] conduction | |||
* PR interval >200 ms | |||
* [[atrioventricular delay]] because no P waves are blocked | |||
|- | |||
| [[Second-degree AV block]] | |||
| | |||
* P waves with a constant rate (<100 bpm) | |||
* [[Atrioventricular conduction]] is present but not 1:1 | |||
*''' [[Mobitz type I]]''' | |||
:*P waves with a constant rate (<100 bpm) | |||
:* Presence of periodic single non conducted P wave associated with P waves before and after the non conducted P wave with inconstant PR intervals | |||
*'''[[Mobitz type II]]''' | |||
:* Presence of P waves with a constant rate (< 100 bpm) with a periodic single non conducted P wave associated with other P waves before and after the non conducted P wave with constant PR intervals (excluding 2:1 atrioventricular block) | |||
*'''2:1 [[atrioventricular block]]''' | |||
:* P waves with a constant rate (or near-constant rate because of [[ventriculophasic sinus arrhythmia]]) rate (<100 bpm), every other P wave conducts to the [[ventricles]] | |||
*'''[[Advanced]], [[high-grade]] or high-degree [[atrioventricular block]]''' | |||
:* ≥2 consecutive P waves at a constant physiologic rate that do not conduct to the [[ventricles ]] with evidence for some [[atrioventricular conduction]] | |||
|- | |||
|[[Third-degree AV block]] ([[complete heart block]]) | |||
| | |||
*No evidence of [[atrioventricular conduction]] | |||
* '''[[Vagally mediated atrioventricular block]]''' | |||
:*Any type of atrioventricular block due to increased [[parasympathetic]] tone | |||
*'''[[Infranodal block]]''' | |||
:* [[Atrioventricular conduction block]] with evidence of conduction block distal to the [[atrioventricular node]] | |||
| | |||
|} | |||
===Type 1 (Mobitz I / Wenckebach)=== | ===Type 1 (Mobitz I / Wenckebach)=== | ||
*Type 1 | *Type 1 second degree AV block, also known as Mobitz I or [[Wenckebach]] periodicity which is a disease of the [[AV node]]<ref name="pmid29493981">{{cite journal |vauthors=Mangi MA, Jones WM, Napier L |title= |journal= |volume= |issue= |pages= |date= |pmid=29493981 |doi= |url=}}</ref><ref name="pmid29083636">{{cite journal |vauthors=Kashou AH, Goyal A, Nguyen T, Chhabra L |title= |journal= |volume= |issue= |pages= |date= |pmid=29083636 |doi= |url=}}</ref>. | ||
*Mobitz I heart block is characterized by progressive prolongation of the PR interval on the [[electrocardiogram]] (EKG) on consecutive beats followed by a blocked P wave (i.e. a 'dropped' QRS complex). After the dropped QRS complex, the PR interval resets and the cycle repeats. | *Mobitz I heart block is characterized by progressive prolongation of the [[PR interval]] on the [[electrocardiogram]] (EKG) on consecutive beats followed by a blocked [[P wave]] (i.e. a 'dropped' [[QRS complex]]). | ||
* After the dropped [[QRS ]] complex, the [[PR interval]] resets and the [[cycle]] repeats. | |||
* One of the baseline assumptions when determining if an individual has Mobitz I heart block is that the [[atrial]] [[rhythm]] has to be regular. | |||
* If the [[atrial]] [[rhythm]] is not regular, there could be alternative explanations as to why certain [[P waves]] do not conduct to the [[ventricles]]. | |||
*This is a benign [[condition]] for which no specific treatment is needed. | |||
* | ===Type 2 (Mobitz II)=== | ||
*Type 2 second degree [[AV block]], also known as Mobitz II is almost always a disease of the distal conduction system ([[electrical conduction system of the heart|His-Purkinje System]]). | |||
* | *Although the terms intranodal block or infrahisian block are often applied to this disorder, they are not synonymous with it. | ||
:*Infranodal block and [[infra-Hisian block]] are terms that refer to the anatomic location of the block, whereas, | |||
:*Mobitz II refers to an electrocardiographic pattern associated with block at these levels<ref name="pmid29850368">{{cite journal |vauthors=Li X, Xue Y, Wu H |title=A Case of Atrioventricular Block Potentially Associated with Right Coronary Artery Lesion and Ticagrelor Therapy Mediated by the Increasing Adenosine Plasma Concentration |journal=Case Rep Vasc Med |volume=2018 |issue= |pages=9385017 |date=2018 |pmid=29850368 |pmc=5933017 |doi=10.1155/2018/9385017 |url=}}</ref>. | |||
* Mobitz II heart block is characterized on a surface [[ECG]] by intermittently non-conducted [[P wave]]s not preceded by [[PR prolongation]] and not followed by PR shortening. | |||
* | * The medical significance of this type of [[AV block]] is that it may progress rapidly to [[complete heart block]], in which no escape [[rhythm]] may emerge. | ||
* In this case, the person may experience a [[Stokes-Adams attack]], [[cardiac arrest]], or [[sudden cardiac death]]. | |||
* The definitive treatment for this form of [[AV Block]] is an [[implanted pacemaker]]<ref name="pmid29275956">{{cite journal |vauthors=Fu Md J, Bhatta L |title=Lyme carditis: Early occurrence and prolonged recovery |journal=J Electrocardiol |volume=51 |issue=3 |pages=516–518 |date=2018 |pmid=29275956 |doi=10.1016/j.jelectrocard.2017.12.035 |url=}}</ref><ref name="pmid28823599">{{cite journal |vauthors=Tuohy S, Saliba W, Pai M, Tchou P |title=Catheter ablation as a treatment of atrioventricular block |journal=Heart Rhythm |volume=15 |issue=1 |pages=90–96 |date=January 2018 |pmid=28823599 |doi=10.1016/j.hrthm.2017.08.015 |url=}}</ref>. | |||
===Differentiating Mobitz I from Mobitz II in the Presence of a 2:1 Conduction=== | |||
:* | Likely [[EKG ]] findings that help differentiate Mobitz type I from type II in the presence of a 2:1 conduction ratio include: | ||
* Very [[long PR interval]] (> 300 msec) or [[narrow QRS complex]] - indicates the block is at the level of [[AV node]] | |||
* Administration of [[atropine]] enhances [[AV nodal]] conduction resulting in less frequent non conducted [[beats]] - this confirms the type I Mobitz | |||
* Mobitz I is worsened by [[carotid sinus]] massage which slows [[AV nodal]] conduction, unlike Mobitz II. | |||
*[[Carotid sinus massage]] paradoxically eliminates [[infranodal block]] by slowing the [[sinus rate]]<ref name="pmid26745972">{{cite journal |vauthors=Schernthaner C, Kraus J, Danmayr F, Hammerer M, Schneider J, Hoppe UC, Strohmer B |title=Short-term pacemaker dependency after transcatheter aortic valve implantation |journal=Wien. Klin. Wochenschr. |volume=128 |issue=5-6 |pages=198–203 |date=March 2016 |pmid=26745972 |doi=10.1007/s00508-015-0906-4 |url=}}</ref>. | |||
* | *Another type of classification used to classify second-degree AV block is 2:1 [[AV block]] and [[high-grade AV block]]. | ||
* In 2:1 [[AV block ]] every other [[atrial]] impulse is conducted down the [[ventricle]]. | |||
* Higher grade AV blocks (eg., 3:1) unlike [[third degree AV block]] conduct few beats down the [[ventricle]]. | |||
==References== | ==References== | ||
Latest revision as of 04:58, 22 July 2021
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Sara Zand, M.D.[2] Mohammed Salih, M.D., Cafer Zorkun, M.D., Ph.D. [3], Raviteja Guddeti, M.B.B.S. [4]
Overview
There are 4 distinct types of second degree AV block. The distinction is made between them because type 1 second-degree heart block is considered a more benign entity than the other types. In mobitz type 1 second degree AV block there is evidence of gradually PR prolongation and dropped beat and grouped beating pattern. In mobitz type 2 AV block there is suddenly dopped beats without evidence of preceding PR prolongation. In atrioventricular block with the pattern of 2:1, there is every other beat without conducting down to the ventricle. In a high-grade AV block, there are two or more consecutive P waves without conducting down to the ventricle. It is important to determine the anatomic site of AV block. In Mobitz type 1 AV block, the site is usually within the AV node, but in Mobitz type II AV block the site is almost always below the AV node. In the presence of wide QRS complex and 2:1 AV conduction it is more likely that the site of AV block is intranodal or infranodal. In some cases, second-degree atrioventricular block must be differentiated from other causes of pauses such as non-conducted premature atrial contractions or atrial tachycardia with block.
Classification
| Term | Classification | Definition | |
|---|---|---|---|
| Atrioventricular block | First-degree atrioventricular block |
| |
| Second-degree AV block |
| ||
| Third-degree AV block (complete heart block) |
|
Type 1 (Mobitz I / Wenckebach)
- Type 1 second degree AV block, also known as Mobitz I or Wenckebach periodicity which is a disease of the AV node[2][3].
- Mobitz I heart block is characterized by progressive prolongation of the PR interval on the electrocardiogram (EKG) on consecutive beats followed by a blocked P wave (i.e. a 'dropped' QRS complex).
- After the dropped QRS complex, the PR interval resets and the cycle repeats.
- One of the baseline assumptions when determining if an individual has Mobitz I heart block is that the atrial rhythm has to be regular.
- If the atrial rhythm is not regular, there could be alternative explanations as to why certain P waves do not conduct to the ventricles.
- This is a benign condition for which no specific treatment is needed.
Type 2 (Mobitz II)
- Type 2 second degree AV block, also known as Mobitz II is almost always a disease of the distal conduction system (His-Purkinje System).
- Although the terms intranodal block or infrahisian block are often applied to this disorder, they are not synonymous with it.
- Infranodal block and infra-Hisian block are terms that refer to the anatomic location of the block, whereas,
- Mobitz II refers to an electrocardiographic pattern associated with block at these levels[4].
- Mobitz II heart block is characterized on a surface ECG by intermittently non-conducted P waves not preceded by PR prolongation and not followed by PR shortening.
- The medical significance of this type of AV block is that it may progress rapidly to complete heart block, in which no escape rhythm may emerge.
- In this case, the person may experience a Stokes-Adams attack, cardiac arrest, or sudden cardiac death.
- The definitive treatment for this form of AV Block is an implanted pacemaker[5][6].
Differentiating Mobitz I from Mobitz II in the Presence of a 2:1 Conduction
Likely EKG findings that help differentiate Mobitz type I from type II in the presence of a 2:1 conduction ratio include:
- Very long PR interval (> 300 msec) or narrow QRS complex - indicates the block is at the level of AV node
- Administration of atropine enhances AV nodal conduction resulting in less frequent non conducted beats - this confirms the type I Mobitz
- Mobitz I is worsened by carotid sinus massage which slows AV nodal conduction, unlike Mobitz II.
- Carotid sinus massage paradoxically eliminates infranodal block by slowing the sinus rate[7].
- Another type of classification used to classify second-degree AV block is 2:1 AV block and high-grade AV block.
- In 2:1 AV block every other atrial impulse is conducted down the ventricle.
- Higher grade AV blocks (eg., 3:1) unlike third degree AV block conduct few beats down the ventricle.
References
- ↑ Kusumoto, Fred M.; Schoenfeld, Mark H.; Barrett, Coletta; Edgerton, James R.; Ellenbogen, Kenneth A.; Gold, Michael R.; Goldschlager, Nora F.; Hamilton, Robert M.; Joglar, José A.; Kim, Robert J.; Lee, Richard; Marine, Joseph E.; McLeod, Christopher J.; Oken, Keith R.; Patton, Kristen K.; Pellegrini, Cara N.; Selzman, Kimberly A.; Thompson, Annemarie; Varosy, Paul D. (2019). "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". Circulation. 140 (8). doi:10.1161/CIR.0000000000000628. ISSN 0009-7322.
- ↑ Mangi MA, Jones WM, Napier L. PMID 29493981. Missing or empty
|title=(help) - ↑ Kashou AH, Goyal A, Nguyen T, Chhabra L. PMID 29083636. Missing or empty
|title=(help) - ↑ Li X, Xue Y, Wu H (2018). "A Case of Atrioventricular Block Potentially Associated with Right Coronary Artery Lesion and Ticagrelor Therapy Mediated by the Increasing Adenosine Plasma Concentration". Case Rep Vasc Med. 2018: 9385017. doi:10.1155/2018/9385017. PMC 5933017. PMID 29850368.
- ↑ Fu Md J, Bhatta L (2018). "Lyme carditis: Early occurrence and prolonged recovery". J Electrocardiol. 51 (3): 516–518. doi:10.1016/j.jelectrocard.2017.12.035. PMID 29275956.
- ↑ Tuohy S, Saliba W, Pai M, Tchou P (January 2018). "Catheter ablation as a treatment of atrioventricular block". Heart Rhythm. 15 (1): 90–96. doi:10.1016/j.hrthm.2017.08.015. PMID 28823599.
- ↑ Schernthaner C, Kraus J, Danmayr F, Hammerer M, Schneider J, Hoppe UC, Strohmer B (March 2016). "Short-term pacemaker dependency after transcatheter aortic valve implantation". Wien. Klin. Wochenschr. 128 (5–6): 198–203. doi:10.1007/s00508-015-0906-4. PMID 26745972.