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| | __NOTOC__ |
| {{Infobox_Disease | | | {{Infobox_Disease | |
| Name = {{PAGENAME}} | | | Name = {{PAGENAME}} | |
| Image = AV nodal reentrant tachycardia.png | | | Image = AV nodal reentrant tachycardia.png | |
| Caption = AV nodal reentrant tachycardia. In yellow, is evidenced the P wave that falls after the QRS complex.| | | Caption = AV nodal reentrant tachycardia, uncommon variant with antegrade conduction down the slow pathway. In yellow, is evidenced the P wave that falls after the QRS complex.| |
| DiseasesDB = | | | DiseasesDB = | |
| ICD10 = {{ICD10|I|47|1|i|30}} | | | ICD10 = {{ICD10|I|47|1|i|30}} | |
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| }} | | }} |
| {{AVNRT}} | | {{AVNRT}} |
| {{CMG}} | | {{CMG}} : {{AE}} {{RG}} |
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| {{SK}} AVNRT; AV node reentrant tachycardia; AV nodal reentry tachycardia; AV node reentry tachycardia; atrioventricular node reentrant tachycardia; atrioventricular nodal reentry tachycardia; atrioventricular node reentry tachycardia; | | {{SK}} AVNRT; AV node reentrant tachycardia; AV nodal reentry tachycardia; AV node reentry tachycardia; atrioventricular node reentrant tachycardia; atrioventricular nodal reentry tachycardia; atrioventricular node reentry tachycardia; junctional reciprocating tachycardia; reciprocal or reciprocating AV nodal reentrant tachycardia |
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| ==[[AVNRT overview|Overview]]== | | ==[[AVNRT overview|Overview]]== |
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| ==[[AVNRT historical perspective|Historical Perspective]]== | | ==[[AVNRT historical perspective|Historical Perspective]]== |
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| | ==[[AVNRT classification|Classification]]== |
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| ==[[AVNRT pathophysiology|Pathophysiology]]== | | ==[[AVNRT pathophysiology|Pathophysiology]]== |
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| ==[[AVNRT classification|Classification]]== | | ==[[AVNRT causes|Causes]]== |
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| ==[[AVNRT risk factors|Risk Factors]]==
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| ==[[AVNRT differential diagnosis|Differentiating AVNRT from other Disorders]]== | | ==[[AVNRT differential diagnosis|Differentiating AVNRT from other Disorders]]== |
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| ==Epidemiology and Demographics== | | ==[[AVNRT epidemiology and demographics|Epidemiology and Demographics]]== |
| AV nodal reentrant tachycardia is the most common regular supraventricular tachycardia and accounts for 60% to 70% of these cases.
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| ===Sex=== | | ==[[AVNRT risk factors|Risk Factors]]== |
| The ratio of female to male involvement is 3:1
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| ===Age===
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| There is no age predilection.
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| ==Natural History, Complications, Prognosis==
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| ===Natural History===
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| The rhythm often ceases abruptly and spontaneously. An episode generally last seconds to hours.
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| ===Complications===
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| *Some patients will develop [[syncope]] during episodes of AVRNT. The mechanism of syncope may be due to a reduction of [[cardiac output]] and [[hemodynamic compromise]] as a result of the short ventricular filling time or alternatively it may be due to transient [[asystole]] due to tachycardia-mediated suppression of the sinus node when the rhythm terminates. Those patients who do become symptomatic during episodes of AVNRT (i.e. have [[syncope]]) should avoid activities where the occurrence of [[hemodynamic compromise]] would endanger their safety or that of others (like driving).
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| *In patients with underlying [[ischemic heart disease]], demand-related [[myocardial ischemia]], [[angina]] and even [[myocardial infarction]] and/or [[congestive heart failure]] can occur.
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| *[[Tachycardia mediated cardiomyopathy]]
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| ===Prognosis=== | | ==[[AVNRT natural history, complications and prognosis|Natural History, Complications and Prognosis]]== |
| AVNRT is rarely life threatening and in the absence of underlying structural heart disease, the prognosis is good. Radiofrequency ablation is curative in 95% of cases.
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| ==Diagnosis== | | ==Diagnosis== |
| ===Symptoms===
| | [[AVNRT history and symptoms|Symptoms]] | [[AVNRT physical examination|Physical Examination]] | [[AVNRT laboratory findings|Laboratory Findings]] | [[AVNRT electrocardiogram|Electrocardiogram]] |
| The following symptoms may be present:
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| *Sudden onset and sudden offset of rapid [[palpitations]] is common
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| *[[Dizziness]] and rarely [[syncope]], especially at the onset of the episode of tachycardia
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| *Neck "pounding" may occur as a result of the [[right atrium]] contracting against a closed atrioventricular valve and [[Cannon a waves]]<ref name="pmid18775049">{{cite journal | author = Laurent G, Leong-Poi H, Mangat I, Korley V, Pinter A, Hu X, So PP, Ramadeen A, Dorian P | title = Influence of ventriculoatrial timing on hemodynamics and symptoms during supraventricular tachycardia | journal = [[Journal of Cardiovascular Electrophysiology]] | volume = 20 | issue = 2 | pages = 176–81 | year = 2009 | month = February | pmid = 18775049 | doi = 10.1111/j.1540-8167.2008.01276.x | url = http://onlinelibrary.wiley.com/resolve/openurl?genre=article&sid=nlm:pubmed&issn=1045-3873&date=2009&volume=20&issue=2&spage=176 | issn = | accessdate = 2012-09-05}}</ref><ref>Gursoy S, Steurer G, Brugada J, et al. Brief report: the hemodynamic mechanism of pounding in the neck in atrioventricular nodal reentrant tachycardia. N Engl J Med. Sep 10 1992;327(11):772-4.</ref> and the simultaneous occurrence of the atrial and ventricular contractions.
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| *[[Chest pain]] and [[angina]] if the patient has [[ischemic heart disease]]
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| *[[Dyspnea]]
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| *[[Polyuria]] can occur after the episode breaks. It has been hypothesized that this is due to the release of [[atrial natriuretic peptide]]
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| ===Physical Examination===
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| ====Pulse====
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| The heart rate is typically regular and between 140-280 bpm. In adults the range is 140-250 bpm, but in children the rate can exceed 250 bpm.
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| ====Systolic Blood Pressure====
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| *[[Hypotension]] may be present in some cases.
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| ====Neck====
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| *[[Cannon a waves]] may be present in some cases
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| ====Lungs====
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| *[[Rales]] may be present in some patients with [[congestive heart failure]]
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| ===Laboratory Studies===
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| Depending upon the patient's history and demographics, the following laboratory studies should be considered:
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| * [[Thyroid function tests]] ([[TFTs]]) - an [[hyperthyroidism|overactive thyroid]] may increase the risk of AVNRT
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| * [[Electrolyte]]s - [[hypokalemia]], [[hypomagnesemia]] may predispose to AVNRT
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| * [[Cardiac marker]]s - if there is a concern that [[myocardial infarction]] (a [[heart attack]]) has occurred either as a cause or as a result of the AVNRT; this is usually only the case if the patient has experienced ischemic [[chest pain]]
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| ===Electrocardiogram===
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| An [[electrocardiogram]] performed during the occurrence of symptoms may confirm the diagnosis of AVNRT.
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| ====Slow-Fast AVNRT (Common AVNRT)====
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| *This form of AVNRT accounts for 80% to 90% of cases of AVNRT.
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| *The [[retrograde P wave]] that is conducted retrograde up the fast pathway is usually burried within the QRS but less frequently may be observed at the end of the [[QRS complex]] as a pseudo r’ wave in lead V1 or an [[S wave]] in leads II, III or aVF.
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| ====Fast-Slow AVNRT (Uncommon AVNRT)====
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| [[File:Fast slow AVNRT.JPG]]
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| *This form of AVNRT Accounts for 10% of cases of AVNRT
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| *In this form of AVNRT, the impulse is first conducted antegrade down the Fast AV nodal pathway and is then conducted retrograde up the Slow AV nodal pathway.
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| *In contrast to Common AVNRT, a [[retrograde P wave]] may be observed after the [[QRS complex]] before the [[T wave]]
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| ====Slow-Slow AVNRT (Atypical AVNRT)====
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| * This form of AVNRT accounts for 1-5% of cases of AVNRT
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| * In this form of AVNRT, the impulse is first conducted antegrade down the Slow AV nodal pathway and retrograde up the Slow left atrial fibres approaching the AV node.
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| * The [[p wave]] may appear just before the [[QRS complex]], and this makes it hard to distinguish the rhythm from [[sinus tachycardia]].
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| ====Aberrant Conduction====
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| It is not uncommon for there to be a wide [[QRS complex]] due to aberrant conduction due to underlying conduction system disease. This can make it difficult to distinguish AVNRT from VT. The distinguishing features include:
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| *AVNRT is associated with a [[QRS complex]] morphology resembles a typical [[bundle branch block]]
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| *AVNRT is not associated with [[AV dissociation]] where there is variable coupling of the [[p wave]] and the [[QRS complex]]
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| *AVNRT is associated with [[Cannon a waves]]
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| *AVNRT is not associated with [[capture beats]] or [[fusion beats]]
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| *AVNRT may convert with [[adenosine]] or [[vagal maneuvers]]
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| An electrophysiologic study may be needed to confirm AVNRT prior to ablation.
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| ===Holter Monitor / Event Recorder===
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| If the patient complains of recurrent [[palpitations]] and no arrhythmia is present on the resting EKG, then a [[Holter Monitor]] or [[Cardiac Event Monitor]] should be considered.
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| ==Treatment== | | ==Treatment== |
| An episode of [[supraventricular tachycardia]] (SVT) due to AVNRT can be terminated by any action that transiently blocks the [[AV node]]. Various methods are possible.
| | [[AVNRT treatment overview|Overview]] | [[AVNRT patient position|Patient Position]] | [[AVNRT vagal maneuvers|Vagal Maneuvers]] | [[AVNRT medical therapy|Medical Therapy]] | [[AVNRT cardioversion|Cardioversion]] | [[AVNRT electrophysiologic testing and radiofrequency ablation|Electrophysiologic Testing and Radiofrequency Ablation]] | [[AVNRT prevention|Prevention]] |
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| ===Patient Position===
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| Place the patient in a supine position to improve cerebral perfusion and reduce the odds of [[syncope]]. Placing the patient in [[Trendelenburg position]] may actually terminate the rhythm.
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| ===Vagal maneuvers===
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| Some people with known AVNRT may be able to stop their attack by using various tricks to activate the [[vagus nerve]]. This includes [[carotid sinus massage]] (pressure on the [[carotid sinus]] in the neck), submersion of the face in ice water to trigger the [[diving reflex]], putting the patient in [[Trendelenburg position]] or the [[Valsalva maneuver]] (increasing the pressure in the chest by attempting to exhale against a closed airway). [[Vagel maneuvers]] are contraindicated in the presence of [[hypotension]].
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| ===Medication===
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| Medical therapy can be initiated with AV nodal slowing drugs: | |
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| ====First Line Therapy====
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| =====[[Adenosine]]=====
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| =====[[Beta blocker]]s=====
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| ====Second Line Therapy====
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| Numerous other antiarrhythmic drugs may be effective if the more commonly used medications have not worked; these include [[flecainide]] or [[amiodarone]]. Both adenosine and beta blockers may cause [[Bronchoconstriction|tightening of the airways]], and are therefore used with caution in people who are known to have [[asthma]]. Calcium channel blockers should be avoided if there is a [[wide complex tacycardia]] and the diagnosis of AVNRT is not clearly established in so far as [[calcium channel blockers]] should be avoided in [[ventricular tachycardia]]. If the diagnosis of AVNRT is established, then non-dihydropyridine [[calcium channel blocker]]s (such as [[verapamil]]) may be administered to terminate the rhythm is other agents are not effective.
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| ===Cardioversion===
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| In very rare instances, [[cardioversion]] (the electrical restoration of a normal heart rhythm) is needed in the treatment of AVNRT. This would normally only happen if all other treatments have been ineffective, or if the fast heart rate is poorly tolerated (e.g. the development of [[heart failure]] symptoms, [[hypotension]] ([[low blood pressure]]) or [[unconsciousness]]).
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| ===Electrophysiology and Radiofrequency Ablation===
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| After being diagnosed with AVNRT, patients can also undergo an electrophysiology (EP) study to confirm the diagnosis. [[Catheter ablation]] of the slow pathway, if successfully carried out, and cures 95% of patients with AVNRT. The risk of complications is quite low.
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| ===Prevention===
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| Triggers such as [[alcohol]] and caffeine should be avoided.
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| ==References==
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| {{Reflist|2}}
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| ==See also==
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| *[[AV Reentrant tachycardia]]
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| *[[Supraventricular tachycardia]]
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| *[[Cardiac electrophysiology]]
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| *[[Clinical cardiac electrophysiology]]
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| | [[CME Category::Cardiology]] |
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| [[Category:Electrophysiology]] | | [[Category:Electrophysiology]] |
| [[Category:Cardiology]] | | [[Category:Cardiology]] |
| | [[Category:Arrhythmia]] |
| [[Category:Emergency medicine]] | | [[Category:Emergency medicine]] |
| [[Category:Intensive care medicine]] | | [[Category:Intensive care medicine]] |
