Av node reentry tachycardia I47.1

Author: Dr. med. S. Leah Schröder-Bergmann

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Last updated on: 29.10.2020

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Synonym(s)

atrial reentry tachycardia; AV- junctional tachycardia; AVNRT; (e) Atrioventricular nodal reentry tachycardia; Tachycardia, AV- junctional

Definition
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AV node reentry tachycardia (AVNRT) is a form of regular tachycardia that occurs predominantly in healthy individuals.

Note: The reentry mechanism is one of the three main mechanisms in tachycardic arrhythmias. It produces a circular excitation in the myocardium. As in a "roundabout", the electrical excitation in the heart rotates in AV node reentry tachycardia.

Classification
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Previously, AVNRT and atrioventricular reentry tachycardia (AVRT [see also paroxysmal supraventricular tachycardia]) were grouped together under the generic term "paroxysmal supraventricular tachycardia (PSVT)" (Herold 2020).

Occurrence/Epidemiology
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The AVNRT is one of the most common forms of PSVT. The prevalence is between 0.1% - 0.2% (Pinger 2019). Mostly younger patients between the ages of 10-12 years (Herold 2020) or 20-50 years (Kasper 2015) are affected.

The disease occurs more frequently in the female sex.

Etiopathogenesis
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AVNRT is a primarily electrical heart disease. Tachycardia occurs independently of stress or rest situations (Stierle 2017).

Pathophysiology
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There is a dissociation of the AV junction line into two functional pathways called the "fast pathway" and the "slow pathway". This leads to a re-entry of excitation, the so-called "reentry" (Kasper 2015).

The dissociation is not only limited to the region of the AV node. They are also located in the region of the Koch's triangle (the area between the plane of the tricuspid valve, the ostium of the coronary vein sinus and the Todaro tendon).

The "fast pathway" represents a path with fast conduction and slow refractory time, while the "slow pathway" represents a slow conduction with fast refractory time.

These dual functional pathways result in an approximately simultaneous excitation of the atrium and ventricles. This leads to an atrial systole against the closed tricuspid valve (Kasper 2015). The diastolic filling is shortened, which in turn leads to a significant reduction in cardiac output (Paul 2018).

Existing during tachycardia:

  • There is normally one antegrade conduction on the slow pathway and one retrograde conduction on the fast pathway, also called slow- fast AVNRT. This form occurs in up to 90% of cases (Hafeez 2020).
  • The atypical form, also known as "fast slow AVNRT", has a reverse excitation sequence. The atypical form occurs in 5 % - 10 % of cases (Hafeez 2020)
  • AVNRT over two "slow pathway", also known as "slow- slow- AVNRT", occurs in approx. 1 % - 5 % (Hafeez 2020, Pinger 2019)

Clinical features
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Typical is the abrupt onset of tachycardia (important for differentiating other forms of tachycardia), which can last from minutes to hours and is associated with a frequency of between 120 - 250 beats / min (Sattler 2007).

The tachycardia usually ends just as suddenly. Sometimes, however, the return to sinus rhythm occurs gradually. Otherwise, there are no further symptoms in otherwise heart-healthy patients.

In patients with pre-existing heart failure or coronary artery disease, the critical reduction of cardiac output can cause the following symptoms:

  • Hypotension
  • Swindle
  • Syncopes
  • angina pectoris
  • rarely also a cardiogenic shock
  • Urinary flood during or after tachycardia triggered by the atrial natriuretic peptide ANP)
  • Grafting of the neck veins with visible rapid pulsation of the neck veins, also known as "frog sign". Occurs during simultaneous contraction of the atrium and ventricle
  • Pulmonary oedema (Kasper 2015)

Diagnosis
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ECG: The resting ECG shows during the seizure;

the typical form shows the following changes:

  • at the beginning of the symptoms often supraventricular extrasystoles (SVES)
  • Regular tachycardia with narrow QRS complex
  • Frequency between 120 - 250 beats / min, mostly between 160 - 200 / min ( Stierle 2017 )
  • the P- wave is overlaid by the QRS complex

for the atypical form:

  • negative P- waves (Herold 2020)
  • short PQ- time (Stierle 2017)

by the slow pathway:

  • late onset P-waves after QRS complex (appearance like atrial tachycardia) (Hafeez 2020)

Differential diagnosis
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  • atrioventricular reentry tachycardia (here a hidden accessory pathway is found)
  • atrial or sinus tachycardia (here there is a constant 1: 1 transition and a relatively long PQ interval which covers the P wave from the previous QRS complex)
  • Ventricular tachycardia (with broad QRS chamber complex, antidromic atrioventricular reentry tachycardia) (Herold 2020)
  • junctional ectopic tachycardia
  • Atrial tachycardia
  • Atrial flutter
  • Sinus tachycardia (Hafeez 2020)

Therapy
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The therapeutic measures are differentiated between symptomatic therapy, electrotherapy and interval treatment (Herold 2020). Among patients undergoing catheter ablation, 60% have an AVNRT (Kasper 2015).

1. symptomatic therapy:

The symptomatic treatment should always be carried out under ongoing ECG-status.

  • In patients with stable circulation, vagus irritation is first induced by e.g.:
  • Valsalva pressing test (after deep inhalation pressing should be continued as long as possible)
  • drink a large, preferably cold and acidic drink in rapid succession
  • Immersion of the face in cold water
  • Ice tie
  • Drug treatment:
    • Adenosine is the first-choice drug.
      • Mode of operation: short-term blocking of the AV line in the AV node
      • Contraindication: atrial tachycardia, atrial fibrillation in WPW- syndrome (strongly widened QRS- complex), bronchial asthma, atrial fibrillation, atrial flutter, QT- extension, sick- sinus- syndrome, AV- block > 1st degree
      • Side effects: short-term asystole possible, dyspnoea, bronchospasm, flush, drop in blood pressure, feeling of pressure in the chest
      • Dosage: 6 mg applied rapidly i. v.; if not responding after 3 min. Injection of 12 mg
    • Verapamil 2nd choice remedy
      • Mode of action: negative ionotropic effect
      • Contraindications: atrial tachycardia, ventricular tachycardia, atrial fibrillation in WPW syndrome (highly dilated QRS complex), hypotension, sick sinus syndrome with history of bradycardia, manifest heart failure, pre-treatment with beta blockers
      • Side effects: Asystole, drop in blood pressure etc.
      • Dosage: 5 mg slowly i. v. over 10 min., in case of non-response after 15 - 30 min. re-injection of 5 mg (Herold 2020).
    • Ajmalin
      • Indication: Ajmalin can be given in both AVNRT and WPW syndrome. If it is not possible to differentiate the clinical pictures with the help of the ECG, Ajmalin is the remedy of choice.
      • Mode of action: Prolongs depolarization in phase 0 and 4 and extends the refractory period. The negative ionotropic effect and the reduction of blood pressure are low.
      • Side effects: Hypotension, nausea, vomiting, flush, headache, etc.
      • Dosage: i. v. injection of 5 mg - 10 mg / min, for pre-damaged heart 2.5 mg - 3 mg / min; maximum dose 50 mg over 5 min. A repetition of the dose is possible after 30 min (Bäumel 2009)

2. electrotherapy

If the above measures do not lead to success, electrotherapy is indicated.

This is differentiated between overdrive pacing and electrocardioversion:

  • Overdrive- Pacing: In overdrive pacing, overstimulation takes place to terminate the circulating excitation. The procedure should be carried out with continuous ECG recording, readiness for resuscitation and corresponding analgesia (e.g. 2 mg - 5 mg morphine i.v.) of the patient (Herold 2020 / Köhler 2018).
  • electrocardioversion:
    • The indication for performing an electrocardioversion exists in:
      • Patients with circulatory instability who are at risk of cardiogenic shock
      • conscious patients with hypotension
      • Patients in whom drug treatment fails
    • contraindication:
      • Digitalisintoxication
      • Recurrence of paroxysmal supraventricular tachycardia (PSVT) with previous cardioversion
    • The treatment is carried out in readiness for resuscitation under short anaesthesia (e.g. with Propofol i. v.) with e.g. initial 100 J., the dose can be repeated with higher energy doses if unsuccessful. (Herold 2020)

3. interval treatment

If further recurrences occur despite the above measures, slow pathway ablation is recommended, in which the slow pathway is ablated. Ablation of the fast pathway is no longer recommended, since the success rate is equally high, but the risk of a complete AV block is significantly increased (Kuck 2007).

  • The success rate is > 95 %,
  • the recurrence rate is 5% - 10%,
  • the risk of an AV block of grade III < 0.5 % (Herold 2020)

Progression/forecast
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The prognosis is generally good once the diagnosis has been confirmed (Hafeez 2020).

Note(s)
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Associated cardiac malformations: Accompanying structural heart diseases are usually not present (Kasper 2015).

Literature
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  1. Bäumel M et al (2009) Intensive Care Book Pharmacotherapy: Drug Profiles, Treatment Strategies, Errors and Hazards in Intensive Care Medicine. Medical Scientific Publishing Company 21 - 23
  2. Hafeez Y et al (2020) Atrioventricular Nodal Reentry Tachycardia (AVNRT). NCBI Resources
  3. Herold G et al (2020) Internal medicine. Herold Publisher 282 - 283
  4. Kasper D L et al (2015) Harrison's Principles of Internal Medicine. Mc Graw Hill Education 1481 - 1483
  5. Kasper D L et al (2015) Harrison's Internal Medicine. Georg Thieme Publisher 1805 - 1808
  6. Köhler J (2018) Cardiopulmonary resuscitation: A textbook and practice book of simple and advanced resuscitation procedures. Chapter 8.2 Kohlhammer Verlag
  7. Kuck K H et al (2007) Guidelines for catheter ablation. Clin Res Cardiol (96) 833 - 849
  8. Lapp H et al (2014) The Cardiac Catheter Book: Diagnostic and interventional catheter techniques. Georg Thieme publishing house
  9. Paul T et al (2018) Guidelines Tachycardic arrhythmias. DGPK
  10. Pinger S (2019) Repetitorium Kardiologie: For clinic, practice, specialist examination. German medical publisher. 671 – 672
  11. Sattler A M (2007) Casebook Cardiology and Angiology. Georg Thieme Publisher 62 - 63
  12. Stierle U et al (2014) Clinical Guide to Cardiology. Elsevier Urban and Fischer 417 - 418

Disclaimer

Please ask your physician for a reliable diagnosis. This website is only meant as a reference.

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Last updated on: 29.10.2020