AV nodal reentrant tachycardia
| AV nodal reentrant tachycardia | |
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| AV nodal reentrant tachycardia. In yellow, is evidenced the P wave that falls after the QRS complex. | |
| ICD-10 | I47.1 |
| ICD-9 | 426.89, 427.0 |
| MeSH | D013611 |
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AVNRT Microchapters |
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Diagnosis |
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Treatment |
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Case Studies |
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AV nodal reentrant tachycardia On the Web |
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American Roentgen Ray Society Images of AV nodal reentrant tachycardia |
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Risk calculators and risk factors for AV nodal reentrant tachycardia |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Synonyms and keywords: 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;
Overview
Historical Perspective
Pathophysiology
Classification
Risk Factors
[[AVNRT differential diagnosis|Differentiating AVNRT from other Disorders
Epidemiology and Demographics
AV nodal reentrant tachycardia is the most common regular supraventricular tachycardia and accounts for 60% to 70% of these cases.
Sex
The ratio of female to male involvement is 3:1
Age
There is no age predilection.
Natural History, Complications, Prognosis
Natural History
The rhythm often ceases abruptly and spontaneously. An episode generally last seconds to hours.
Complications
- 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).
- In patients with underlying ischemic heart disease, demand-related myocardial ischemia, angina and even myocardial infarction and/or congestive heart failure can occur.
- Tachycardia mediated cardiomyopathy
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.
Diagnosis
Symptoms
The following symptoms may be present:
- Sudden onset and sudden offset of rapid palpitations is common
- Dizziness and rarely syncope, especially at the onset of the episode of tachycardia
- Neck "pounding" may occur as a result of the right atrium contracting against a closed atrioventricular valve and Cannon a waves[1][2] and the simultaneous occurrence of the atrial and ventricular contractions.
- Chest pain and angina if the patient has ischemic heart disease
- Dyspnea
- Polyuria can occur after the episode breaks. It has been hypothesized that this is due to the release of atrial natriuretic peptide
Physical Examination
Pulse
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.
Systolic Blood Pressure
- Hypotension may be present in some cases.
Neck
- Cannon a waves may be present in some cases
Lungs
- Rales may be present in some patients with congestive heart failure
Laboratory Studies
Depending upon the patient's history and demographics, the following laboratory studies should be considered:
- Thyroid function tests (TFTs) - an overactive thyroid may increase the risk of AVNRT
- Electrolytes - hypokalemia, hypomagnesemia may predispose to AVNRT
- Cardiac markers - 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
Electrocardiogram
An electrocardiogram performed during the occurrence of symptoms may confirm the diagnosis of AVNRT.
Slow-Fast AVNRT (Common AVNRT)
- This form of AVNRT accounts for 80% to 90% of cases of AVNRT.
- 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.
Fast-Slow AVNRT (Uncommon AVNRT)
- This form of AVNRT Accounts for 10% of cases of AVNRT
- 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.
- In contrast to Common AVNRT, a retrograde P wave may be observed after the QRS complex before the T wave
Slow-Slow AVNRT (Atypical AVNRT)
- This form of AVNRT accounts for 1-5% of cases of AVNRT
- 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.
- The p wave may appear just before the QRS complex, and this makes it hard to distinguish the rhythm from sinus tachycardia.
Aberrant Conduction
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:
- AVNRT is associated with a QRS complex morphology resembles a typical bundle branch block
- AVNRT is not associated with AV dissociation where there is variable coupling of the p wave and the QRS complex
- AVNRT is associated with Cannon a waves
- AVNRT is not associated with capture beats or fusion beats
- AVNRT may convert with adenosine or vagal maneuvers
An electrophysiologic study may be needed to confirm AVNRT prior to ablation.
Holter Monitor / Event Recorder
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.
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.
Patient Position
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.
Vagal maneuvers
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.
Medication
Medical therapy can be initiated with AV nodal slowing drugs:
First Line Therapy
Adenosine
Beta blockers
Second Line Therapy
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 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 blockers (such as verapamil) may be administered to terminate the rhythm is other agents are not effective.
Cardioversion
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).
Electrophysiology and Radiofrequency Ablation
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.
Prevention
Triggers such as alcohol and caffeine should be avoided.
References
- ↑ Laurent G, Leong-Poi H, Mangat I, Korley V, Pinter A, Hu X, So PP, Ramadeen A, Dorian P (2009). "Influence of ventriculoatrial timing on hemodynamics and symptoms during supraventricular tachycardia". Journal of Cardiovascular Electrophysiology. 20 (2): 176–81. doi:10.1111/j.1540-8167.2008.01276.x. PMID 18775049. Retrieved 2012-09-05. Unknown parameter
|month=ignored (help) - ↑ 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.