Atrioventricular Nodal Reentry Tachycardia Workup

Updated: Nov 19, 2019
  • Author: Brian Olshansky, MD, FESC, FAHA, FACC, FHRS; Chief Editor: Jose M Dizon, MD  more...
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Workup

Approach Considerations

Atrioventricular nodal reentry tachycardia (AVNRT) can be initiated by ectopic atrial or ventricular beats. Typically, it is initiated by atrial ectopic beats that block in the fast pathway and travel antegrade via the slow pathway. There is a "jump" in AV nodal conduction at tachycardia onset with retrograde activation, such that atrial activation is nearly simultaneous or just after the ventricular activation.

Sometimes, supraventricular tachycardia (SVT) due to AVNRT can present with a wide QRS due to underlying conduction system disease or aberration. A wide QRS tachycardia with a typical bundle branch block morphology during SVT due to aberration is not uncommon.

Occasionally, distinguishing ventricular tachycardia from SVT can be difficult, but in most instances this can be accomplished using the clinical scenario, the QRS morphology (owing to the frequent occurrence of the aforementioned typical bundle branch block), evidence for AV dissociation (this may be difficult if there is simultaneous activation), physical examination (including the presence of neck vein pulsations [6] ), and lack of fusion and capture.

In patients with an otherwise normal heart, considering carotid massage or adenosine is reasonable unless the patient is hemodynamically unstable, in which case cardioversion may be required.

If the diagnosis is in question, an electrophysiologic study helps to distinguish the potential mechanisms for the tachycardia. Therefore, an electrophysiologic study may be indicated for a patient with a wide QRS complex tachycardia in whom the mechanism is not clear, and is also reasonable if the plan is to attempt to ablate the tachycardia and cure it. [8]

Echocardiography

Echocardiography can be used to evaluate for the presence of structural heart disease.

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Electrocardiography

Electrocardiographic (ECG) evaluation usually reveals a supraventricular origin of QRS complexes at rates of 150-250 bpm and a regular rhythm. The QRS complex is usually narrow unless a conduction abnormality is present or is functionally induced (aberrancy) from the rapid heart rate or the abrupt change in rate. (See the images below.)

Atypical atrioventricular nodal (AV) reentry tachy Atypical atrioventricular nodal (AV) reentry tachycardia. Often, an inverted P wave is seen just before the QRS complex in leads II, III, aVF. This represents activation of the posterior septum due to antegrade conduction via the fast pathway and retrograde conduction via the slow pathway of the AV node.
Typical atrioventricular nodal (AV) reentry tachyc Typical atrioventricular nodal (AV) reentry tachycardia. In this electrocardiogram, the P wave appears immediately after or just within the QRS complex. Often a “pseudo R wave" is seen in lead V1 and a “pseudo S wave" in leads II, III, aVF. The retrograde P wave represents retrograde activation via the fast pathway, which is anterior septal and superior to the AV node.

P waves are not usually seen, because they are buried in the QRS complex. A pseudo R prime may be seen in V1, or pseudo S waves may be seen in leads II, III, or aVF. The onset is abrupt, with an atrial premature complex that conducts with a prolonged PR interval. Atypical AV nodal reentry includes fast antegrade/slow retrograde conduction with a P wave before the QRS complex. Slow-slow AV nodal reentry can occur, with a P wave occurring in mid diastole.

The PR interval may shorten over the first few beats at onset, or it may lengthen during last few beats preceding termination of the tachycardia.

Abrupt termination occurs with a retrograde P wave, sometimes followed by a brief period of asystole or bradycardia.

Although atrioventricular nodal reentry tachycardia (AVNRT) is usually a short RP interval tachycardia (with the P wave buried in the QRS complex), rarely, retrograde conduction can occur via a slow pathway, producing a long RP tachycardia. The latter form of tachycardia is indistinguishable from automatic atrial tachycardia on the surface 12-lead ECG if it originates from the low posterior right atrial septal region, and there is A 1:1 AV conduction and AV reciprocating tachycardia if the retrograde concealed slow pathway is present near the os of the coronary sinus (which can cause permanent junctional reciprocating tachycardia [PJRT]). This is important to recognize. AVNRT and PJRT are usually fairly easy to cure with catheter ablation, [9] whereas automatic atrial tachycardia may be more difficult to cure.

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Electrophysiology

Typical findings in atrioventricular nodal reentry tachycardia (AVNRT) on electrophysiologic studies include dual-node physiology, a discontinuous pattern of atrial-to-ventricular conduction reflecting the differing conduction properties of fast and slow antegrade conduction, and/or sustaining slow antegrade conduction, which mimics the superimposition of the P wave and QRS complex observed in the clinical arrhythmia. The most typical endpoint of ablation for AVNRT is modification or elimination of slow pathway conduction associated with inability to induce the arrhythmia. [8]

During ventricular pacing, retrograde activation is through the AV node and is demonstrated by early atrial activation in the His bundle electrogram.

Atypical AVNRT has fast-activation antegrade through the AV node and slow-activation retrograde that allows early atrial activation to occur at a distinct time after the QRS complex and is earliest in the posterior septal right atrium. AV-reciprocating tachycardia (AVRT) causes eccentric retrograde atrial activation.

In some instances, if an accessory pathway is septal, retrograde activation can mimic retrograde atrial activation through the AV node. This can be distinguished using adenosine administration with ventricular pacing to assess ventriculoatrial conduction, and through the use of ventricular extrastimuli during tachycardia that allows for preexcitation of the atria once the His bundle is refractory. Other interventions during the electrophysiologic study may further distinguish AVNRT from AVRT (such as para-Hisian pacing), as well as determine if the tachycardia is atrial tachycardia, sinoatrial reentry, or ventricular tachycardia.

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