Junctional Tachycardia: A Critical Reassessment.

Junctional tachycardia (JT) is typically considered to have an automatic mechanism originating from the distal atrioventricular node. When there is 1:1 retrograde conduction via the fast pathway, JT would resemble the typical form of atrioventricular nodal re-entrant tachycardia (AVNRT). Atrial pacing maneuvers have been proposed to exclude AVNRT and suggest a diagnosis of JT. However, after excluding AVNRT, one should consider the possibility of an infra-atrial narrow QRS re-entrant tachycardia, which can exhibit features that resemble AVNRT as well as JT. Pacing maneuvers and mapping techniques should be performed to assess for infra-atrial re-entrant tachycardia before concluding that JT is the mechanism of a narrow QRS tachycardia. Distinguishing JT from typical AVNRT or infra-atrial re-entrant tachycardia has notable implications regarding the approach to ablation of the tachycardia. Ultimately, a contemporary review of the evidence on JT raises some questions as to the mechanism and source of what has traditionally been considered JT.

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 (VAP) and tachycardia VA (VAT) 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 VAP-VAT < 22.55 ms in all successful AOPs (116 times). The remaining case showed VAP-VAT > 294.9 ms in one AOP and VAP-VAT < 22.55 ms in two AOPs. All 21 JT cases could be captured successfully by all (105/105) AOPs and showed VAP-VAT > 294.9 ms. VAP-VAT < 22.55 ms had 118/118 (100 %) specificity for AVNRT, and the VAP-VAT > 294.9 ms response was 105/105 (100 %) sensitive for JT. CONCLUSIONS: The VA relationship after AOP could help distinguish AVNRT from JT. VAP-VAT < 22.55 ms was specific for AVNRT, and VAP-VAT > 294.9 ms for JT in the overwhelming majority, except for the rare instance of AVNRT with a double ventricular response.

Paradoxical responses to pacing maneuvers differentiating atrioventricular node reentrant tachycardia and junctional tachycardia.

A 40-year-old female presented at our hospital because of heart palpitations. During an electrophysiological study, atrioventricular (AV) conduction showed dual AV nodal physiology. Three types of supraventricular tachycardia (SVT) were induced. The initiation of SVT was reproducibility dependent on a critical A-H interval prolongation. An early premature atrial contraction during SVT repeatedly advanced the immediate His potential with termination of the tachycardia, indicating AV node reentrant tachycardia (AVNRT). However, after atrial overdrive pacing during SVT without termination of the tachycardia, the first return electrogram resulted in an AHHA response, consistent with junctional tachycardia. The mechanism of paradoxical responses to pacing maneuvers differentiating AVNRT and junctional tachycardia was discussed.

Response to atrial extrastimulus during supraventricular tachycardia: what is the mechanism?

We describe a case illustrating the potential challenges in distinguishing AV nodal reentry tachycardia (AVNRT) from automatic junctional tachycardia (JT). While an early atrial extrastimulus advanced the next His and ventricular depolarization without tachycardia termination, suggesting JT, other features indicated the correct diagnosis of AVNRT. This teaching case demonstrates a novel exception to a recently reported diagnostic pacing maneuver and illustrates the importance of considering response to multiple maneuvers in reaching a diagnosis of SVT mechanism.

Narrow irregular QRS tachycardia with AV dissociation: what is the mechanism?

A 39-year-old woman with no structural heart disease and frequent episodes of sudden onset palpitations was referred for the electrophysiological study. During the study, a slightly irregular narrow QRS tachycardia with AV dissociation was repeatedly induced and spontaneously terminated. Apparently, irregular cycles and termination of the tachycardia were related to the dissociated sinus rhythm: atrial depolarizations timed when the AV junction was refractory were able to reset the tachycardia, while early atrial depolarizations caused its termination. This observation was enough to diagnose the tachycardia mechanism in our case.

Novel use of atrial overdrive pacing to rapidly differentiate junctional tachycardia from atrioventricular nodal reentrant tachycardia.

BACKGROUND: Distinguishing between junctional tachycardia (JT) and atrioventricular nodal reentrant tachycardia (AVNRT) is essential to minimize unnecessary catheter ablation and the risk of heart block during treatment of AVNRT. OBJECTIVE: The purpose of this study was to investigate whether the tachycardia response to atrial overdrive pacing at a cycle length (CL) slightly shorter than tachycardia CL can differentiate between JT and AVNRT. We hypothesized that atrial overdrive pacing would transiently suppress JT but would entrain AVNRT. METHODS: Twenty-one patients in whom AVNRT was induced and atrial overdrive pacing during either AVNRT or JT was attempted were included in the study. We predicted that, upon cessation of atrial overdrive pacing, an atrial-His-His-atrial (AHHA) response would identify JT and an atrial-His-atrial (AHA) response would identify AVNRT. RESULTS: A total of 8 JT and 21 typical AVNRT were induced. Atrial overdrive pacing was attempted in all cases of JT and in 16 cases of AVNRT. An AHHA response was observed in 100% (8/8) of JT cases. In 2 cases of AVNRT, atrial overdrive pacing repetitively terminated the tachycardia. In the remaining patients with AVNRT, an AHA response was observed in 100% (14/14) of cases. When a response was able to be elicited, atrial overdrive pacing was 100% sensitive and 100% specific for differentiating JT from AVNRT. CONCLUSION: Atrial overdrive pacing during tachycardia can rapidly differentiate JT from AVNRT, which can improve the safety and efficiency of catheter ablation of these arrhythmias.

Differentiating junctional tachycardia and atrioventricular node re-entry tachycardia based on response to atrial extrastimulus pacing.

OBJECTIVES: The purpose of this study was to differentiate non-re-entrant junctional tachycardia (JT) and typical atrioventricular node re-entry tachycardia (AVNRT). BACKGROUND: JT may mimic AVNRT. Ablation of JT is associated with a lower success rate and a higher incidence of heart block. Electrophysiologic differentiation of these tachycardias is often difficult. METHODS: We hypothesized that JT can be distinguished from AVNRT based on specific responses to premature atrial complexes (PACs) delivered at different phases of the tachycardia cycle: when a PAC is timed to His refractoriness, any perturbation of the subsequent His indicates that anterograde slow pathway conduction is involved and confirms a diagnosis of AVNRT. A PAC that advances the His potential immediately after it without terminating tachycardia indicates that retrograde fast pathway is not essential for the circuit and confirms a diagnosis of JT. This protocol was tested in 39 patients with 44 tachycardias suggesting either JT or AVNRT based on a short ventriculo-atrial interval and apparent AV node dependence. Tachycardias were divided into 3 groups: clinically obvious AVNRT, clinically obvious JT, and clinically indeterminate rhythm. RESULTS: In the 26 cases of clinically obvious AVNRT, the sensitivity and specificity of the test were 61% and 100%, respectively. In the 9 cases of clinically obvious JT, the sensitivity and specificity were 100% and 100%, respectively. In the 9 cases of clinically indeterminate rhythm, the technique indicated AVNRT in 1 patient and JT in 7 patients, and the test was indeterminate in 1 patient. CONCLUSIONS: The response to PACs during tachycardia can distinguish JT and AVNRT with 100% specificity in adult patients.

Remote magnetic catheter mapping and ablation of permanent junctional reciprocating tachycardia in a seven-year-old child.

BACKGROUND: Mapping and catheter ablation of permanent junctional reciprocating tachycardia (PJRT) in children can be challenging. Remote magnetic navigation may improve precise mapping and catheter stability during ablation, as well as reduce fluoroscopy time, especially in conjunction with a non-fluoroscopic mapping system. OBJECTIVE: We report a case of PJRT ablation in a 7-year-old child using remote magnetic navigation. METHODS AND RESULTS: Mapping of the right atrium (RA) and the coronary sinus (CS) and catheter ablation were performed using remote magnetic navigation in conjunction with a non-fluoroscopic mapping system (NavX). We observed excellent catheter steering abilities and constant wall contact during ablation, allowing a short and safe procedure. CONCLUSIONS: Remote magnetic navigation may be used for mapping and ablation of PJRT in children.

Role of invasive electrophysiologic testing in the evaluation and management of adult patients with focal junctional tachycardia.

Focal junctional tachycardia (FJT) is characterized by a rapid often irregular narrow complex tachycardia with episodes of atrioventricular (AV) dissociation. This uncommon arrhythmia is most likely due to abnormal automaticity or triggered activity. The patients are often quite symptomatic and if left untreated may develop heart failure particularly if their tachycardia is incessant. In patients refractory to medical management, the role of radiofrequency ablation involves either (1) selective ablation of the tachycardia focus while preserving AV conduction or as a last resort (2) AV junction ablation followed by pacemaker implantation. The clinician should first assess whether ventriculoatrial (VA) conduction is present or absent during tachycardia. If present, radiofrequency ablation should be applied at the site of earliest retrograde atrial activation. In the absence of VA conduction and hence an atrial target site, sequential lesions should be applied in the posterior septum (slow pathway region) followed by lesions applied in midseptum and anteroseptum respectively if tachycardia persists. To further minimize the risk of AV nodal block, some authors delivered radiofrequency energy during atrial overdrive pacing to assess AV conduction during ablation. Others recommended mapping the perinodal region and applying radiofrequency ablation at the site where catheter manipulation resulted in tachycardia termination. Using this ablative approach, the risk of AV block is around 5-10%.