Paroxysmal AV Block Extrinsic Vagal AV Block: Difference between revisions
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==Overview== | ==Overview== | ||
Extrinsic vagal paroxysmal AV Block occurs secondary to an increase in vagal tone. ECG findings reflecting this include sinus rate slowing and increasing PP interval/ PR interval prior to the period of asystole. | [[Extrinsic vagal paroxysmal AV Block]] occurs secondary to an increase in [[vagal tone]]. [[ECG]] findings reflecting this include [[sinus rate]] slowing and increasing [[PP interval|PP interva]]<nowiki/>l/ [[PR interval]] prior to the period of [[asystole]]. | ||
==Pathophysiology== | ==Pathophysiology== | ||
*An extrinsic vagally mediated AV block (EV-AVB) may occur due to a '''vagal surge or a condition causing an increase in vagal tone''' such as during tilt table | *An extrinsic [[vagally]] mediated [[AV block]] (EV-AVB) may occur due to a '''[[vagal]] surge or a condition causing an increase in [[vagal]] tone''' such as during [[Tilt table test|tilt table testing]], [[carotid sinus massage]], [[coughing]], [[micturition]], [[defecation]], [[swallowing]], [[myocardial infarction]], [[injection]] of [[dypramidole]] and [[cardiac transplant]] [[rejection]]. | ||
*It causes SA and AV node slowing and is therefore reflected on the ECG as '''sinus rate slowing, increasing/irregular PP and PR | *It causes [[SA]] and [[AV node]] slowing and is therefore reflected on the [[ECG]] as '''[[Sinus rate|sinus rate slowing]], increasing/irregular PP and [[PR interval]]<nowiki/>s''' prior to a period of compete [[AV block]]. A [[heterogenous]] presentation in terms of Mobitz type I or II and [[complete heart block]] may also be noted. This is followed by a period of [[sinus]] [[acceleration]]. | ||
*Electrophysiological studies indicate a '''normal H-H interval''' and therefore it can be assumed that it does not have any effect on conduction in the bundle of His and is not associated with any anatomic involvement, as seen in intrinsic AV Block. <ref name="pmid23286970">{{cite journal| author=Alboni P, Holz A, Brignole M| title=Vagally mediated atrioventricular block: pathophysiology and diagnosis. | journal=Heart | year= 2013 | volume= 99 | issue= 13 | pages= 904-8 | pmid=23286970 | doi=10.1136/heartjnl-2012-303220 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=23286970 }} </ref> | *[[Electrophysiological studies]] indicate a '''normal H-H interval''' and therefore it can be assumed that it does not have any effect on [[Conduction System|conduction]] in the [[bundle of His]] and is not associated with any [[anatomic]] involvement, as seen in intrinsic AV Block. <ref name="pmid23286970">{{cite journal| author=Alboni P, Holz A, Brignole M| title=Vagally mediated atrioventricular block: pathophysiology and diagnosis. | journal=Heart | year= 2013 | volume= 99 | issue= 13 | pages= 904-8 | pmid=23286970 | doi=10.1136/heartjnl-2012-303220 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=23286970 }} </ref> | ||
*The pathophysiology of EV-AVB may even be related to the autonomic control of the sinus and AV nodes. A parasympathetic predominance over the SA node and sympathetic predominance over the AV node is exerted in a normal autonomic nervous system. | *The [[pathophysiology]] of EV-AVB may even be related to the [[autonomic]] control of the sinus and AV nodes. A [[parasympathetic]] predominance over the [[SA node]] and [[sympathetic]] predominance over the [[AV node]] is exerted in a normal [[autonomic nervous system]]. | ||
**A disruption in this regulation may cause '''parasympathetic bursts''' and therefore, an AV block. <ref name="pmid10758936">{{cite journal| author=Mendoza IJ, Castellanos A, Lopera G, Moleiro F, Mitrani RD, Myerburg RJ| title=Spontaneous paroxysmal atrioventricular block in patients with positive tilt tests and negative electrophysiologic studies. | journal=Am J Cardiol | year= 2000 | volume= 85 | issue= 7 | pages= 893-6, A9 | pmid=10758936 | doi=10.1016/s0002-9149(99)00890-5 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=10758936 }} </ref> | **A disruption in this [[regulation]] may cause '''[[parasympathetic]] bursts''' and therefore, an AV block. <ref name="pmid10758936">{{cite journal| author=Mendoza IJ, Castellanos A, Lopera G, Moleiro F, Mitrani RD, Myerburg RJ| title=Spontaneous paroxysmal atrioventricular block in patients with positive tilt tests and negative electrophysiologic studies. | journal=Am J Cardiol | year= 2000 | volume= 85 | issue= 7 | pages= 893-6, A9 | pmid=10758936 | doi=10.1016/s0002-9149(99)00890-5 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=10758936 }} </ref> | ||
*The effect of vagal stimulation depends on the method and intensity of stimulation and the resting sympathetic activity. | *The effect of [[Vagus nerve|vagal]] stimulation depends on the method and [[intensity]] of stimulation and the resting [[Sympathetic nervous system|sympathetic]] activity. | ||
*Vasalva maneuver, carotid sinus massage, water face immersion, tilt table testing may or may not induce an EV- AVB and in some cases a '''reversal may be seen on atropine administration'''. {{cite web |url=https://onlinelibrary.wiley.com/doi/abs/10.1002/clc.4960080606 |title=Paroxysmal vagally mediated av block with recurrent syncope - Talwar - 1985 - Clinical Cardiology - Wiley Online Library |format= |work= |accessdate=}} | *[[Vasalva maneuver]], [[carotid sinus massage]], water face immersion, [[Tilt table test|tilt table testing]] may or may not induce an EV- AVB and in some cases a '''reversal may be seen on [[atropine]] [[administration]]'''. {{cite web |url=https://onlinelibrary.wiley.com/doi/abs/10.1002/clc.4960080606 |title=Paroxysmal vagally mediated av block with recurrent syncope - Talwar - 1985 - Clinical Cardiology - Wiley Online Library |format= |work= |accessdate=}} | ||
==References== | ==References== | ||
Latest revision as of 18:25, 27 June 2020
Overview
Extrinsic vagal paroxysmal AV Block occurs secondary to an increase in vagal tone. ECG findings reflecting this include sinus rate slowing and increasing PP interval/ PR interval prior to the period of asystole.
Pathophysiology
- An extrinsic vagally mediated AV block (EV-AVB) may occur due to a vagal surge or a condition causing an increase in vagal tone such as during tilt table testing, carotid sinus massage, coughing, micturition, defecation, swallowing, myocardial infarction, injection of dypramidole and cardiac transplant rejection.
- It causes SA and AV node slowing and is therefore reflected on the ECG as sinus rate slowing, increasing/irregular PP and PR intervals prior to a period of compete AV block. A heterogenous presentation in terms of Mobitz type I or II and complete heart block may also be noted. This is followed by a period of sinus acceleration.
- Electrophysiological studies indicate a normal H-H interval and therefore it can be assumed that it does not have any effect on conduction in the bundle of His and is not associated with any anatomic involvement, as seen in intrinsic AV Block. [1]
- The pathophysiology of EV-AVB may even be related to the autonomic control of the sinus and AV nodes. A parasympathetic predominance over the SA node and sympathetic predominance over the AV node is exerted in a normal autonomic nervous system.
- A disruption in this regulation may cause parasympathetic bursts and therefore, an AV block. [2]
- The effect of vagal stimulation depends on the method and intensity of stimulation and the resting sympathetic activity.
- Vasalva maneuver, carotid sinus massage, water face immersion, tilt table testing may or may not induce an EV- AVB and in some cases a reversal may be seen on atropine administration. "Paroxysmal vagally mediated av block with recurrent syncope - Talwar - 1985 - Clinical Cardiology - Wiley Online Library".
References
- ↑ Alboni P, Holz A, Brignole M (2013). "Vagally mediated atrioventricular block: pathophysiology and diagnosis". Heart. 99 (13): 904–8. doi:10.1136/heartjnl-2012-303220. PMID 23286970.
- ↑ Mendoza IJ, Castellanos A, Lopera G, Moleiro F, Mitrani RD, Myerburg RJ (2000). "Spontaneous paroxysmal atrioventricular block in patients with positive tilt tests and negative electrophysiologic studies". Am J Cardiol. 85 (7): 893–6, A9. doi:10.1016/s0002-9149(99)00890-5. PMID 10758936.