Pacing site- and rate-dependent shortening of retrograde conduction time over the slow pathway after atrial entrainment of fast-slow atrioventricular nodal reentrant tachycardia

Introduction

We tested our hypothesis that atrial entrainment pacing (EP) of a) the common‐type (com‐) fast‐slow (F/S‐) atypical atrioventricular nodal reentrant tachycardia (AVNRT) using a typical slow pathway (SP), or b) the superior‐type (sup‐) F/S‐AVNRT using a superior SP, both modify the retrograde conduction time across the SP immediately after termination of EP (retro‐SP‐time).

Methods

We measured the difference in the His‐atrial interval (HA difference) immediately after cessation of EP, performed at 2 ± 2 rates from the high right atrium (HA[1]‐HRA) versus from the proximal coronary sinus (HA[1]‐CS) in 17 patients with com‐F/S‐AVNRT and 11 patients with sup‐F/S‐AVNRT. We also measured the atrial‐His and HA intervals of the first and second cycles immediately after cessation of EP and during stable tachycardia.

Results

Unequal responses, defined as a ≥ 20‐ms HA difference at ≥1 EP rates, were observed in 16 patients (57%), including 7 with com‐ and 9 with sup‐F/S‐AVNRT. Irrespective of the EP rate, all unequal responses of com‐F/S‐AVNRT were due to a shorter HA[1]‐CS than HA[1]‐HRA, with a mean 34 ± 11 ms HA difference, whereas all unequal responses of sup‐F/S‐AVNRT were due to a longer HA[1]‐CS than HA[1]‐HRA, with a mean 49 ± 25 ms HA difference. The unequal responses resolved within two cycles after the cessation of EP.

Conclusions

We have identified a little‐known pacing site‐ and pacing rate‐dependent shortening of the retro‐SP‐time.

Methodology of Typical Accessory Pathway Catheter Ablation

Accessory pathways are abnormal electrical conductions between the atrial and ventricular myocardium, bypassing the atrioventricular node and as such are an important substrate for arrhythmias. Ablation is a curative treatment and should always be offered to symptomatic patients and asymptomatic patients with high risk professions. Adequate knowledge and understanding of different mapping and ablation techniques is pivotal to achieve successful outcomes.

Efficacy of cryo-ablation during atrioventricular nodal reentrant tachycardia

Because of the low atrioventricular (AV) block risk during cryo-ablation, it has become possible to treat AV nodal reentrant tachycardia (AVNRT) during arrhythmia. This study aimed to investigate the clinical outcomes of performing cryo-ablation for AVNRT during arrhythmia. Twenty-three patients with AVNRT treated by cryo-ablation during arrhythmia were enrolled. Cryo-ablation was performed gradually from the bottom to above the paraseptal tricuspid annulus until AVNRT was terminated. If the slow pathway was not eliminated despite cryo-ablation terminating the AVNRT, additional cryo-ablation was performed at a higher site until the slow pathway elimination was achieved. AVNRT was terminated by cryo-ablation in all 23 patients. However, the slow pathway was only eliminated in 6 patients. Among the remaining 17 patients, the slow pathway could not be ablated because transient AV block occurred during cryo-ablation at a higher site in 8 patients; however, cryo-ablation at a higher site successfully eliminated the slow pathway in the other 9 patients. In these 9 patients, the distance from the bottom of tricuspid annulus to the site of slow pathway elimination was significantly longer than that from bottom of tricuspid annulus to the AVNRT termination site (20.1 ± 5.3 vs 14.7 ± 4.5 mm: p = 0.027). During follow-up, AVNRT recurrence was confirmed in 3 patients. In 1 of these 3 patients, even a slow pathway elimination was achieved by cryo-ablation at the AVNRT termination site. The AVNRT termination site may not be the ideal site for performing cryo-ablation.

The ventriculoatrial relationship after atrial overdrive pacing can help differentiate atrioventricular nodal reentrant tachycardia from junctional tachycardia

PURPOSE

Differentiating between atrioventricular nodal reentrant tachycardia (AVNRT) and non-reentrant junctional tachycardia (JT) is difficult but highly necessary for catheter ablation. The purpose of this study was to investigate whether the ventriculoatrial (VA) relationship after atrial overdrive pacing (AOP) could help to distinguish AVNRT from JT.

METHODS

Thirty-eight AVNRT and 21 JT patients who were induced by infusion of isoproterenol after successful AVNRT ablation were paced through the high right atrium or coronary sinus until the ventricles were constantly captured. After the pacing was stopped, the intervals of postpacing VA (VA_P) and tachycardia VA (VA_T) were measured if the pacing did not terminate tachycardia.

RESULTS

Thirty-five (92.1 %) cases were captured by 119 AOPs (119/175) without terminating tachycardia in the 38 cases of AVNRT. Of the 35 cases, 34 (97.1 %) showed VA_P-VA_T < 22.55 ms in all successful AOPs (116 times). The remaining case showed VA_P-VA_T > 294.9 ms in one AOP and VA_P-VA_T < 22.55 ms in two AOPs. All 21 JT cases could be captured successfully by all (105/105) AOPs and showed VA_P-VA_T > 294.9 ms. VA_P-VA_T < 22.55 ms had 118/118 (100 %) specificity for AVNRT, and the VA_P-VA_T > 294.9 ms response was 105/105 (100 %) sensitive for JT.

CONCLUSIONS

The VA relationship after AOP could help distinguish AVNRT from JT. VA_P-VA_T < 22.55 ms was specific for AVNRT, and VA_P-VA_T > 294.9 ms for JT in the overwhelming majority, except for the rare instance of AVNRT with a double ventricular response.

Classification, Electrophysiological Features and Therapy of Atrioventricular Nodal Reentrant Tachycardia

Atrioventricular nodal reentrant tachycardia (AVNRT) should be classified as typical or atypical. The term 'fast-slow AVNRT' is rather misleading. Retrograde atrial activation during tachycardia should not be relied upon as a diagnostic criterion. Both typical and atypical atrioventricular nodal reentrant tachycardia are compatible with varying retrograde atrial activation patterns. Attempts at establishing the presence of a 'lower common pathway' are probably of no practical significance. When the diagnosis of AVNRT is established, ablation should be only directed towards the anatomic position of the slow pathway. If right septal attempts are unsuccessful, the left septal side should be tried. Ablation targeting earliest atrial activation sites during typical atrioventricular nodal reentrant tachycardia or the fast pathway in general for any kind of typical or atypical atrioventricular nodal reentrant tachycardia, are not justified. In this review we discuss current concepts about the tachycardia circuit, electrophysiologic diagnosis, and ablation of this arrhythmia.

A novel manoeuvre for discerning supraventricular tachycardia mechanism

AIMS

Discerning supraventricular tachycardia (SVT) mechanism during catheter ablation procedures can be difficult and time-consuming, which, when combined with diagnostic error, places patients at risk of unnecessary complications. Distinguishing atrial tachycardia (AT) from AV nodal re-entry tachycardia (AVNRT) may be particularly vexatious. Value-added techniques are thus always welcome, particularly if they are not time-consuming nor require complex intracardiac lead configurations. In this study, we assessed whether a new technique, simultaneous right atrial and right ventricular pacing (RA + RV) during ongoing SVT, met these criteria.

METHODS AND RESULTS

Using a simple intracardiac lead configuration (right atrial appendage, His bundle, right ventricular apex), the response to RA + RV delivered at 80-90% of the SVT cycle length, was examined in 80 patients referred for catheter ablation. In each patient, the actual tachycardia mechanism was adjudicated by standard electrophysiologic criteria ± successful catheter ablation. Mechanisms of SVT included, non-exclusively, AVNRT (24 patients), accessory pathway-mediated (orthodromic) re-entry (AVRT; 23 patients), AT (10 patients), and sinus tachycardia (ST induced with isoproterenol; 49 patients). Immediately after cessation of RA + RV pacing during persistent SVT, the first intracardiac electrogram observed was right atrial in all AT whereas it was His bundle in all AVNRT. The response during AVRT was mixed.

CONCLUSIONS

In this preliminary evaluation, RA + RV pacing appears to add value to the existing armamentarium of electrophysiologic indices to discern SVT mechanism, in particular with respect to discriminating between AVNRT and AT.

Supraventricular Tachycardia and Atrioventricular Block

The differential diagnosis for a mid- to long-RP supraventricular tachycardia include atrial tachycardia, atypical atrioventricular nodal reentrant tachycardia (AVNRT), and atrioventricular reentrant tachycardia (AVRT) utilizing a slowly conducting concealed accessory pathway. The presence of spontaneous atrioventricular block excludes AVRT. This case reviews pacing maneuvers to distinguish atrial tachycardia from AVNRT. Atypical AVNRT generally demonstrates the presence of a lower common pathway and has its site of earliest retrograde atrial activation near the coronary sinus ostium, which would be the target for ablation.

Introduction to Supraventricular Tachycardia

Paroxysmal supraventricular tachycardia (PSVT) is a clinical syndrome characterized by a rapid tachycardia with an abrupt onset and termination cardiomyopathy. The three most common causes of PSVT are atrioventricular nodal reentrant tachycardia (50%-60%), atrioventricular reentrant tachycardia in patients with Wolff-Parkinson-White syndrome (25%-30%), and atrial tachycardia (10%). Rare causes of PSVT include focal junctional tachycardia, atriofascicular tachycardia, permanent reciprocating junctional tachycardia, and nodoventricular/nodofascicular tachycardia. This article, based on challenging PSVT cases, is a guide for clinicians dealing with diagnostic or therapeutic dilemmas in the electrophysiology laboratory.

Stepwise transition of 2:1 atrio-ventricular block to 1:1 conduction induced by ventricular premature beats in a patient with atypical AVNRT

A 55-year-old man with a 2-year history of recurrent paroxysmal palpitations and with an electrocardiogram documentation of atypical atrioventricular nodal re-entrant tachycardia (AVNRT) was referred to us for catheter ablation. After an initial ablation attempt, several episodes of atypical AVNRT were induced. During one of these episodes, we documented a stepwise transition of 2:1 atrioventricular block to 1:1 conduction, following two single ventricular premature beats. This phenomenon confirmed the functional nature of the AV block during AVNRT and indirectly its infra-nodal location.