Classification, Electrophysiological Features and Therapy of Atrioventricular Nodal Reentrant Tachycardia

Abstract

Atrioventricular nodal reentrant tachycardia (AVNRT) denotes re-entry in the area of the AV node, and represents the most common regular arrhythmia in the human.1 Although several models have been proposed to explain the mechanism of the arrhythmia in the context of the complex anatomy and the anisotropic properties of the atrioventricular (AV) node and its atrial extensions (see Figure 1), 2 the actual circuit of AVNRT still remains elusive. Recent studies suggest a three-dimensional AV node with greater variability in the space constant of tissue and poor gap junction connectivity due to differential expression of connexin isoforms, that provide an explanation of dual conduction and nodal reentrant arrhythmogenesis. 3,4 AV junctional arrhythmias are presented in Table 1. Classification schemes for AVNRT have been mainly based on the conventional concept of longitudinally dissociated dual AV nodal pathways that conduct around a central obstacle (see Table 2).In typical slow-fast AVNRT the onset of atrial activation appears prior to, at the onset, or just after the QRS complex, thus maintaining an atrial-His/His-atrial ratio, AH/HA >1. The HA interval is usually <70 ms, measured from earliest deflection of the His bundle activation to the earliest rapid deflection of the atrial activation in the His bundle electrogram, and the VA interval, measured from the onset of ventricular activation on surface ECG to the earliest rapid deflection of the atrial activation on the His bundle electrogram, is <60 ms. 1,5,6 In atypical, fast-slow form of atypical AVNRT, the retrograde atrial electrogram begins after ventricular activation with an AH/HA ratio <1. The HA interval is prolonged, ≥70 msec, and the VA interval is ≥60 msec. 5,6 The atypical, slow-slow form, represents, by definition, an arrhythmia utilising two slow pathways. The AH/HA ratio is ≥1 but the HA interval is ≥70 msec, and the AH interval exceeds 200 ms. [7][8][9] There are several inherent limitations of this classification. The distinction between fast-slow and slow-slow atypical AVNRT is often arbitrary in view of the lack of a unanimously accepted definition. In order to establish the diagnosis of a truly fast-slow form, it has been proposed that the AH interval should be less than 185 ms 10 or 200 ms. 6 This criterion, however, has not been adopted by other investigators. 11-13Thus, tachycardias with a relatively prolonged AH interval but an AH/ HA ratio <1 cannot be reliably classified as either fast-slow or slow-slow (see Figure 2). Furthermore, the term 'fast-slow' implies that the fast component of slow-fast AVNRT is the same as the fast in the fast-slow type. There is now evidence that this is not the case in patients who present with both types of tachycardia.14,15 Typical slow-fast and atypical fast-slow AVNRT appear to utilise different anatomical pathways for fast conduction. In addition, electrophysiological behaviour compatible with multiple pathways may also be seen, and in some patients, several forms of AVNRT may be inducible at electrophy...

An irregular supraventricular tachycardia: What is the mechanism?

“…AV nodal reentrant tachycardia (AVNRT) with variable antegrade AV or retrograde ventriculoatrial (VA) relationships are infrequently observed and might be misdiagnosed as atrial tachycardia (AT) . Dual or multiple AV nodal slow pathways or common pathways, could provide an electrophysiological basis for the development of irregular arrhythmia in the presence of AVNRT. Therefore, the main differential diagnosis of an irregular arrhythmia is between the AVNRT and perinodal ATs .…”

Utility of low‐dose adenosine triphosphate sensitivity in slow‐fast atrioventricular nodal reentrant tachycardia

“…Twenty‐eight patients who underwent radiofrequency catheter ablation of the antegrade slow pathway between January 2013 and September 2016 in our institute were enrolled in this study. The type of AVNRT was classified into a slow‐fast AVNRT, which was defined as having an A‐H interval/His‐atrial (H‐A) interval ratio (A‐H/H‐A) of >1 and H‐A interval <70 ms along with a tachycardia induction mode with an antegrade jump‐up phenomenon based on the previous reports . Patients with uncommon AVNRT, including fast‐slow AVNRT and slow‐slow AVNRT, were excluded.…”

“…val <70 ms along with a tachycardia induction mode with an antegrade jump-up phenomenon based on the previous reports. 6 Patients with uncommon AVNRT, including fast-slow AVNRT and slow-slow AVNRT, were excluded. The patients with nonsustained AVNRT, which could not be evaluated by an electrophysiological study (EPS) during the tachycardia, were excluded.…”

“…A previous study suggested the possibility that the atrial tissue around the atrioventricular (AV) node was involved in the reentrant circuit of the AVNRT. 5,6 However, the precise existence and the clinical implication of that remain to be elucidated. A representative case of a fast-slow AVNRT is shown in Figure 1.…”

Catheter Ablation of Atrioventricular Nodal Re-entrant Tachycardia: Facts and Fiction

“…

Although the exact circuit of atrioventricular nodal re-entrant tachycardia (AVNRT) still eludes us, AVNRT is the most common regular arrhythmia in humans, and therefore the most commonly encountered during ablation attempts for regular tachycardias. [1][2][3][4] Catheter ablation for AVNRT is the current treatment of choice in symptomatic patients. It reduces arrhythmia-related hospitalisations and costs, and substantially improves quality of life.

…”