AV nodal reentry tachycardia

The AV- nodal reentry tachycardia (Syn .: AV-nodal reentry tachycardia (AVNRT)) is a benign cardiac arrhythmia , which is characterized by suddenly beginning and ending fast and regular heartbeat.

Classification according to ICD-10
I47.1	Supraventricular tachycardia
ICD-10 online (WHO version 2019)

distribution

AVNRT is the most common paroxysmal supraventricular tachycardia in adults and accounts for 60–70% of all paroxysmal arrhythmias.

Basics

In one part of the heart's excitation conduction system, the AV node , there are two adjacent areas, so-called pathways, through which the excitation is transmitted from the atria to the ventricles . These pathways differ in their ability to conduct the electrical impulse. One speaks of a dual AV node physiology or also a double AV node .

The fast pathway starts at the anterior entrance of the AV node, leads faster and can go in both directions, i.e. H. conduct antegrade (from the atrium to the ventricle) and retrograde (from the ventricle to the atrium). The slow-pathway starts at the posterior entrance, leads more slowly and has a shorter refractory period .

Disease emergence

In the typical case ( typical slow / fast AVNRT , 95%) an early extrasystole in the atrial area leads to a block in the fast pathway. The excitation now runs via the slow-pathway to the ventricle, meets the ventricular end of the fast-pathway, runs in a circle back to the atrium, in order to run again via the slow-pathway towards the ventricle.

In the case of atypical fast / slow AVNRT (syn .: reverse AVNRT), the slow pathway is also able to conduct the excitation retrograde. Here an extrasystole of the ventricle leads to the block of the fast-pathway, the excitation runs via the slow-pathway to the atria and in a circle back via the slow-pathway to the ventricle.

Clinical manifestations

The rhythm disturbance manifests itself in a sudden, rapid, regular heartbeat with a frequency of 140–250 beats per minute. Usually this is well tolerated, but syncope does occur. In addition to a strong urge to urinate ( ANP released by atrial distension ), shortness of breath and dizziness are reported. The arrhythmia ends as suddenly as it started.

Investigation methods

EKG

In the resting ECG , a shortened PQ segment (<110 ms) is occasionally found in sinus rhythm as a sign of the fast pathway. In contrast to the WPW syndrome , however, there is no delta wave as an expression of pre-excitation .

In typical AVNRT, the seizure ECG shows a narrow, complex, regular tachycardia without P waves (hidden in the QRS complex). Changes to the ST segment can occur. In the atypical form, the frequency is rather slower between 120 and 160 beats per minute. There is a negative, retrograde P wave in II, III, aVF with a very short PQ segment (RP> PR).

The induction of tachycardia by a supraventricular extrasystole in the typical AVNRT and a ventricular extrasystole in the atypical one can be seen in the long-term ECG .

The spontaneous termination of the typical AVNRT results from a block of the fast pathway. A negative P wave can usually be observed after the last ventricular complex of the tachycardia. The spontaneous end of the atypical form comes about through a block of the slow pathway, here the retrograde P wave is missing after the end of the tachycardia.

Electrophysiological examination

When an EPU is performed, the diagnosis of AVNRT is usually secured by non-invasively collected parameters. A dual AV nodal physiology can be demonstrated in 70% of cases. However, AVNRT cannot be triggered in 50% of patients who have also found a duplicate AV lump in other examinations.

Treatment and prospect of recovery

In the acute attack , the vagus maneuver or Valsalva maneuver or Valsalva attempt is the therapy of choice. Adenosine is only used after this therapy has failed . It causes a total AV block lasting a few seconds and ends the arrhythmia. In addition, other possible rhythm disturbances (for example typical clockwise atrial flutter ) that make a similar EKG image can be unmasked. Another option is amiodarone . If the arrhythmia starts up again for a short time, calcium channel blockers of the diltiazem or verapamil type can be given.

A drug maintenance therapy is in principle with beta-blockers possible or calcium channel blockers, however, associated with a high relapse rate.

The treatment of choice for multiple AVNRT episodes is catheter ablation . The slow pathway is ablated with great success (> 95%). Fast-pathway ablation is a reserve technique. The most dangerous risk of causing a 3rd degree AV block with permanent need for a pacemaker is 0.5–2%.

Literature and Sources

• Mewis, Riessen, Spyridopoulos (Ed.): Cardiology compact - Everything for ward and specialist examination . 2nd Edition. Thieme, Stuttgart, New York 2006, ISBN 3-13-130742-0 , pp. 572-577 .

Individual evidence

1. ↑ Gerd Herold: Internal Medicine 2016. Herold, Gerd (Verlag), Cologne 2015, ISBN 978-3-9814660-5-8
2. ^ Anne Paschen: Heart. In: Jörg Braun, Roland Preuss (Ed.): Clinic Guide Intensive Care Medicine. 9th edition. Elsevier, Munich 2016, ISBN 978-3-437-23763-8 , pp. 185-283, here: pp. 263-265 ( amiodarone ).

This article is about a health issue. It is not used for self-diagnosis and does not replace a diagnosis by a doctor. Please note the information on health issues !