Diagnostic value of tachycardia features and pacing maneuvers during paroxysmal supraventricular tachycardia

Prevalence and characteristics of atrioventricular nodal reentrant tachycardia with a bystander concealed nodoventricular/nodofascicular pathway

BACKGROUND

The concealed nodoventricular/nodofascicular (NV/NF) pathway is mostly a bystander, retrograde bypass tract connecting right ventricle/right bundle branch (RBB) and slow pathway (SP), which is observed in patients with atrioventricular nodal reentrant tachycardia (AVNRT). However, its prevalence and characteristics in response to pacing maneuvers have not been fully evaluated.

OBJECTIVE

This study investigated the prevalence and characteristics of AVNRT with a bystander NV/NF-pathway.

METHODS

We retrospectively reviewed 153 consecutive patients undergoing catheter ablation of AVNRT. Excluding 52 patients with inadequate electrophysiological data, 101 patients composed the study population.

RESULTS

Three patients (3.0%) had bystander concealed NV/NF-pathways, all of which were connected to the SP. The tachycardia was typical SP/fast pathway (FP) AVNRT in two patients and atypical FP/SP AVNRT in one patient. In all cases, His-refractory ventricular extra stimuli (VESs) reset the AVNRTs with delay through the NV/NF-pathways. Ventricular overdrive pacing (VOP) in the early-phase also reset the AVNRT with delay. Earlier VESs and middle-phase of VOP did not reset the tachycardia, and further earlier VESs and late-phase of VOP reset the tachycardia with advance through the RBB-His conduction.

CONCLUSION

A bystander NV/NF-pathway was not rare in patients with AVNRT. The VESs and VOP for the AVNRTs with the bystander NV/NF-pathways were characterized by the two-phase resetting phenomenon: initial transient resetting with delay through the NV/NF-pathway, and late resetting with advance through the RBB-His conduction.

A Single Atrial Extrastimulation Resetting His Bundle During Supraventricular Tachycardia to Differentiate Atrial Tachycardia

BACKGROUND

Catheter ablation is the curative treatment for paroxysmal supraventricular tachycardia (SVT). However, atrial tachycardia (AT) diagnosis is often challenging, especially when SVT is terminated by pacing.

OBJECTIVES

This study sought to develop a novel method for AT diagnosis.

METHODS

A total of 147 SVTs including 28 ATs, 87 atrioventricular nodal re-entrant tachycardias, and 32 orthodromic reciprocating tachycardias were prospectively studied. Single atrial extrastimulation was performed at the proximal coronary sinus from a coupling interval 20 milliseconds shorter than the tachycardia cycle length and gradually decreased until the His bundle (HB) was first reset and further until the SVT was terminated. The response of the SVT during the first HB resetting and the termination pattern were examined.

RESULTS

In 27 of 28 ATs, tachycardia was unaffected when HB resetting whereas, in atrioventricular nodal re-entrant tachycardias or orthodromic reciprocating tachycardias (non-AT), tachycardia was simultaneously reset when HB resetting or was terminated with an atrio-Hisian block. When the coupling interval was further shortened for cases in which tachycardia persisted, all 33 SVTs with tachycardia termination with atrio-Hisian block were non-ATs, whereas 5 ATs and 7 non-ATs were terminated with Hisian-atrial block. The sensitivity, specificity, and positive and negative predictive values of the pattern of tachycardia that was unaffected when HB resetting for AT diagnosis were 96%, 100%, 100%, and 99%, respectively. Those of the pattern of tachycardia termination with atrio-Hisian block for non-AT diagnosis were 92%, 100%, 100%, and 42%, respectively.

CONCLUSIONS

Single atrial extrastimulation from the proximal coronary sinus during tachycardia was useful and effective for AT diagnosis.

Local VA index for the differential diagnosis of supraventricular tachycardia

BACKGROUND

Differentiating between atypical atrioventricular nodal reentrant tachycardia (AVNRT) and orthodromic reciprocating tachycardia utilizing a septal accessory pathway is a complex challenge.

OBJECTIVE

The purpose of this study was to describe the "local VA index," a straightforward method based on signals from the coronary sinus catheter, to distinguish between these arrhythmias during tachycardia and entrainment. The ventriculoatrial (VA) interval on the coronary sinus catheter is measured during tachycardia and entrainment, at the site of earliest atrial activity. The difference between these 2 situations defines the "local VA index." We also propose a mechanism to clarify the limitations of historical pacing maneuvers, such as postpacing interval minus tachycardia cycle length (PPI-TCL) and stimulus-atrial interval minus ventriculoatrial interval (SA-VA), by examining nodal decrement and intraventricular conduction delay.

METHODS

In a retrospective study of 75 patients referred for supraventricular tachycardia evaluation, 37 were diagnosed with atrioventricular reentrant tachycardia (AVRT) with orthodromic reciprocating tachycardia, and 38 with AVNRT (27 typical, 11 atypical).

RESULTS

In comparison to AVRT patients, AVNRT patients exhibited longer PPI-TCL (176 ± 47 ms vs 113 ± 42 ms; P <.01) and SA-VA (138 ± 47 ms vs 64 ± 28 ms; P <.01). The AVRT group had mean local VA index of -1 ± 13 ms, whereas the AVNRT group had a significantly longer index of 91 ± 46 ms (P <.01). An optimal threshold for differentiation was a local VA index of 40 ms. Importantly, there was no significant correlation between pacing cycle length and nodal decrement as well as intraventricular delay related to pathway location. This interindividual variability might explain misleading interpretations of PPI-TCL and SA-VA.

CONCLUSION

This novel approach is advantageous because of its simplicity and effectiveness, requiring only 2 diagnostic catheters. A local VA interval difference <40 ms provides a clear distinction for AVRT.

A novel approach to typical atrioventricular nodal reentrant tachycardia with high-resolution mapping using the CARTO 3 cardiac mapping system

BACKGROUND

We hypothesized that high-resolution activation mapping during sinus rhythm (SR) in Koch's triangle (KT) can be used to describe the most delayed atrial potential around the atrioventricular node and evaluated whether ablation targeting of this potential is safe and effective for the treatment of patients with typical atrioventricular nodal reentrant tachycardia (AVNRT).

METHODS

We conducted a prospective, non-randomized, observational study using high-resolution activation mapping from the sinus node to KT with a PENTARAY or OCTARAY catheter using the CARTO 3 cardiac mapping system (Biosense Webster) during SR in 62 consecutive patients (22 men; age [mean ± standard deviation] = 55 ± 14 years) treated for typical AVNRT at our institution from August 2021 to March 2023.

RESULTS

In all cases, the most delayed atrial potential was observed near the His potential within KT. Ablation targeting of this potential helped successfully treat each case of AVNRT, with a junctional rhythm observed at the ablation site. Initial ablation was deemed successful in 55/62 patients (89%); in the remaining seven patients, lesion expansion resolved AVNRT. One procedural complication occurred, namely, a transient atrioventricular block lasting 45 s. One patient experienced a transient tachycardic episode by the 1-month follow-up, but no further episodes were noted up to the 1-year follow-up.

CONCLUSION

Activation mapping at KT during SR with the high-resolution CARTO system clearly revealed the most delayed atrial potential near the His potential within KT. Targeting this potential was a safe and effective treatment method for patients with typical AVNRT in our study.

Next-Generation Cardiac Interfacing Technologies Using Nanomaterial-Based Soft Bioelectronics

Cardiac interfacing devices are essential components for the management of cardiovascular diseases, particularly in terms of electrophysiological monitoring and implementation of therapies. However, conventional cardiac devices are typically composed of rigid and bulky materials and thus pose significant challenges for effective long-term interfacing with the curvilinear surface of a dynamically beating heart. In this regard, the recent development of intrinsically soft bioelectronic devices using nanocomposites, which are fabricated by blending conductive nanofillers in polymeric and elastomeric matrices, has shown great promise. The intrinsically soft bioelectronics not only endure the dynamic beating motion of the heart and maintain stable performance but also enable conformal, reliable, and large-area interfacing with the target cardiac tissue, allowing for high-quality electrophysiological mapping, feedback electrical stimulations, and even mechanical assistance. Here, we explore next-generation cardiac interfacing strategies based on soft bioelectronic devices that utilize elastic conductive nanocomposites. We first discuss the conventional cardiac devices used to manage cardiovascular diseases and explain their undesired limitations. Then, we introduce intrinsically soft polymeric materials and mechanical restraint devices utilizing soft polymeric materials. After the discussion of the fabrication and functionalization of conductive nanomaterials, the introduction of intrinsically soft bioelectronics using nanocomposites and their application to cardiac monitoring and feedback therapy follow. Finally, comments on the future prospects of soft bioelectronics for cardiac interfacing technologies are discussed.

Electrophysiologic diagnosis of narrow and wide complex tachyarrhythmias

Establishing the precise mechanism of cardiac arrhythmias in the electrophysiology laboratory is one of the main requisites for a successful and safe ablation. This article provides an organized approach to the differential diagnosis of narrow and wide complex tachycardias based on the analysis of electrical activation patterns, followed by specific pacing maneuvers in each case.

Landiolol, an intravenous β1-selective blocker, is useful for dissociating a fusion of atrial activation via accessory pathway and atrioventricular node

Introduction

During ventricular pacing, a fusion of atrial activation may occur owing to the simultaneous retrograde conduction of the atrioventricular (AV) node and accessory pathway (AP), potentially leading to an inaccurate mapping of the atrial AP insertion site.

Objective

We tested the hypothesis that landiolol, an ultra-short-acting intravenous β1-blocker, could dissociate a fusion of atrial activation.

Methods

We conducted a prospective before-and-after study to investigate the effect of landiolol on retrograde conduction via the AV node and AP. We enrolled 21 consecutive patients with orthodromic AV reciprocating tachycardia who underwent electrophysiological studies at our hospital between January 1, 2018, and August 31, 2020.

Results

Six patients exhibited a fusion of atrial activation. After landiolol administration (10 μg/kg/min), the effective refractory period was unchanged in AP (280 [240-290] ms vs. 280 [245-295] ms, p = .91), whereas that of the AV node was prolonged (275 [215-380] ms vs. 332 [278-445] ms, p = .03). The Wenckebach pacing rate via retrograde AV node decreased after landiolol administration (180 [140-200] beats per minute [bpm] vs. 140 [120-180] bpm, p = .02). Thus, landiolol decreased the minimum ventricular pacing rate required to dissociate a fusion of atrial activation (180 [160-200] bpm vs. 140 [128-155] bpm, p = .007). Radiofrequency catheter ablation under landiolol administration successfully eliminated AP in all patients during ventricular pacing without complications or recurrence.

Conclusion

Landiolol inhibited the AV node without affecting the AP and helped dissociate a fusion of atrial activation at a lower ventricular pacing rate.

Paradigm Shift for Catheter Ablation of Atypical Atrioventricular Nodal Re-Entrant Tachycardia: 3-Dimensional Mapping-Based Ablation

BACKGROUND

In current practice, the ablation target of atypical atrioventricular nodal re-entrant tachycardia (AVNRT) is the earliest atrial activation site in the coronary sinus (CS) or conventional slow pathway region.

OBJECTIVES

The purposes of this study were to map the site of earliest retrograde atrial activation using electroanatomic three-dimensional mapping during atypical AVNRT and to evaluate successful ablation sites.

METHODS

A total of 42 patients with a total of 49 AVNRTs (slow/fast: 30; fast/slow: 15; slow/slow: 4) underwent electrophysiological study and ablation. Among them there were 14 patients (10 women; 60 ± 19 years of age) in whom 19 atypical AVNRT (fast/slow: 15; slow/slow: 4) were induced.

RESULTS

The intracardiac electrocardiograms or three-dimensional mapping of the exit site during tachycardia revealed that 7 patients had exit sites solely inside the CS (left inferior extension [LIE]), 3 solely in the right postero-septal tricuspid annulus (TA; right inferior extension [RIE]), and 4 had both LIE and RIE exits. The distance from the CS ostium to LIE exits was 14 ± 6 mm. RIE exits were located on the TA posterior to the CS ostium (between 5 and 6 o'clock in the left anterior oblique projection). Ablation targeting these exits or conventional slow pathway succeeded in long-term elimination of AVNRT in 13 of the 14 patients (93%). There were no complications.

CONCLUSIONS

Catheter ablation targeting the exit sites of LIE or RIE mapped at the CS or TA holds promise as an effective and safe alternative approach to the current targets of ablation for atypical AVNRT cases.

High-density electro-anatomical activation mapping to guide slow pathway modification in patients with persistent left superior vena cava

BACKGROUND

Slow pathway (SP) mapping and modification can be challenging in patients with persistent left superior vena cava (PLSVC) due to anatomical variance of Koch's triangle (KT) and coronary sinus (CS) dilatation. There is a lack of studies using detailed 3-dimensional (3D) electro-anatomical mapping (EAM) to investigate conduction characteristics and guide ablation targets in this condition.

OBJECTIVES

To describe a novel technique of slow pathway mapping and ablation in sinus rhythm using 3D EAM in patients with PLSVC after validation in a cohort with normal coronary sinus anatomy.

METHODS

Seven patients with PLSVC and dual AV node physiology who underwent slow pathway modification with the use of 3D EAM were included. Twenty-one normal heart patients with AV nodal re-entrant tachycardias formed the validation group. High-resolution, ultra-high-density local activation timing (LAT) mapping of the right atrial septum and proximal coronary sinus in sinus rhythm was performed.

RESULTS

SP ablation targets were consistently identified by an area in the right atrial septum with the latest activation time and multi-component atrial electrogram (EGM) adjacent to a region with isochronal crowding (deceleration zone). In PLSVC patients, these targets were located at or within 1 cm of the mid anterior CS ostium. Ablation in this area led to successful SP modification reaching standard clinical endpoints with a median of 43 sec of radio frequency energy or 14 mins of cryoablation without complications.

CONCLUSION

High-resolution activation mapping of Koch's triangle in sinus rhythm can facilitate localisation and safe slow pathway ablation in patients with PLSVC.

Effect of Direct Slow Pathway Capture Mapping-Guided Ablation on Typical Atrioventricular Nodal Re-Entrant Tachycardia

BACKGROUND

Direct slow pathway capture (DSPC) mapping is a novel electrophysiological technique for detecting antegrade slow pathway input sites. However, the effect of DSPC mapping-guided ablation on atrioventricular nodal re-entrant tachycardia (AVNRT) is unknown.

OBJECTIVES

This study aimed to evaluate the efficacy and safety of DSPC mapping-guided ablation in typical AVNRT patients.

METHODS

A multicenter retrospective study was conducted in 301 consecutive typical AVNRT patients. The outcomes in patients who underwent DSPC mapping-guided ablation (DSPC group) and those who underwent conventional anatomical ablation (conventional group) were compared. The conventional group was established before introducing DSPC mapping-guided ablation. Positive DSPC sites were defined as sites with a return cycle atrioventricular prolongation of ≥20 ms with high-output (10-20 V) pacing during tachycardia or the last paced beat of the atrial extrastimulation.

RESULTS

Among 116 patients in the DSPC group, 102 (88%) had positive DSPC sites, and 86 (74%) had a successful ablation at that site. Of the remaining 30 patients, 27 had a successful anatomical ablation. The DSPC group had a significantly lower frequency of radiofrequency applications and shorter total application time than the conventional group (median: 5.5 [IQR: 3-11] times vs 9 [IQR: 5-15] times, and 168 [IQR: 108-266] seconds vs 244 [IQR: 158-391] seconds, respectively; P < 0.01). Moreover, the DSPC group had a numerically lower incidence of permanent pacemaker implantations and AVNRT recurrences than the conventional group (0% vs 1.6%; P = 0.17, and 1.7% vs 3.2%; P = 0.43, respectively).

CONCLUSIONS

DSPC mapping-guided ablation was associated with a lower operative time, which can reduce the risk of AV conduction injury in typical AVNRT.

Spontaneous Variation of Ventriculo-Atrial Interval after Tachycardia Induction: Determinants and Usefulness in the Diagnosis of Supraventricular Tachycardias with Long Ventriculoatrial Interval

Background: Determining the mechanism of supraventricular tachycardias with prolongedP ventriculoatrial (VA) intervals is sometimes a challenge. Our objective is to analyse the determinants, time course and diagnostic accuracy (atypical atrioventricular nodal reentrant tachycardias [AVNRT] versus orthodromic reentrant tachycardias through an accessory pathway [ORT]) of spontaneous VA intervals variation in patients with narrow QRS tachycardias and prolonged VA. Methods: A total of 156 induced tachycardias were studied (44 with atypical AVNRT and 112 with ORT). Two sets of 10 measurements were performed for each patient—after tachycardia induction and one minute later. VA and VV intervals were determined. Results: The difference between the longest and the shortest VA interval (Dif-VA) correlates significantly with the diagnosis of atypical AVNRT (C coefficient = 0.95 and 0.85 after induction and at one minute, respectively; p < 0.001). A Dif-VA ≥ 15 ms presents a sensitivity and specificity for atypical AVNRT of 50% and 99%, respectively after induction, and of 27% and 100% one minute later. We found a robust and significant correlation between the fluctuations of VV and VA intervals in atypical AVNRTs (Coefficient Rho: 0.56 and 0.76, after induction and at one minute, respectively; p < 0.001 for both) but not in ORTs. Conclusions: The analysis of VA interval variability after induction and one minute later correctly discriminates atypical AVNRT from ORT in almost all cases.

Variability of the VA interval at tachycardia induction: a simple method to differentiate orthodromic reciprocating tachycardia from atypical atrioventricular nodal reentrant tachycardia

BACKGROUND

The differential diagnosis between orthodromic atrioventricular reentry tachycardia (AVRT) and atypical AV nodal reentrant tachycardia (aAVNRT) is sometimes challenging. We hypothesize that aAVNRTs have more variability in the retrograde conduction time at tachycardia onset than AVRTs.

METHODS

We aimed to assess the variability in retrograde conduction time at tachycardia onset in AVRT and aAVNRT and to propose a new diagnostic tool to differentiate these two arrhythmia mechanisms. We measured the VA interval of the first beats after tachycardia induction until it stabilized. The difference between the maximum and minimum VA intervals (∆VA) and the number of beats needed for the VA interval to stabilize was analyzed. Atrial tachycardias were excluded.

RESULTS

A total of 107 patients with aAVNRT (n = 37) or AVRT (n = 64) were included. Six additional patients with decremental accessory pathway-mediated tachycardia (DAPT) were analyzed separately. All aAVNRTs had VA interval variability. The median ∆VA was 0 (0 - 5) ms in AVRTs vs 40 (21 - 55) ms in aAVNRTs (p < 0.001). The VA interval stabilized significantly earlier in AVRTs (median 1.5 [1 - 3] beats) than in aAVNRTs (5 [4 - 7] beats; p < 0.001). A ∆VA < 10 ms accurately differentiated AVRT from aAVNRT with 100% of sensitivity, specificity, and positive and negative predictive values. The stabilization of the VA interval at < 3 beats of the tachycardia onset identified AVRT with sensitivity, specificity, and positive and negative predictive values of 64.1%, 94.6%, 95.3%, and 60.3%, respectively. A ∆VA < 20 ms yielded good diagnostic accuracy for DAPT.

CONCLUSIONS

A ∆VA < 10 ms is a simple and useful criterion that accurately distinguished AVRT from atypical AVNRT. Central panel: Scatter plot showing individual values of ∆VA in atypical AVNRT and AVRT. Left panel: induction of atypical AVNRT. The VA interval stabilizes at the 5th beat and the ∆VA is 62 ms (maximum VA interval: 172 ms - minimum VA interval: 110 ms). Right panel: induction of AVRT. The tachycardia has a fixed VA interval from the first beat. ∆VA is 0 ms.

Angiographic Characteristics of the Vein of Marshall in Patients with and without Atrial Fibrillation

Background: Ethanol infusion into the vein of Marshall (Et-VOM) is a novel therapeutic treatment for atrial fibrillation (AF). However, few studies have focused on the difference between AF and non-AF patients (presented other types of arrhythmias) regarding the characteristics of the vein of Marshall (VOM). Objective: This study sought to investigate the incidence, morphology, and angiographic characteristics of the VOM. Methods: Coronary sinus (CS) angiography was performed in all patients. The baseline, angiographic characteristics and measurements of VOM dimensions were compared between the AF and non-AF group. Results: CS angiography was performed in 290 patients. The VOM detection rate was higher in the AF group than in the non-AF group (91.8% vs. 84.1%, p = 0.044). In the right anterior oblique (RAO) projection, AF patients had significant larger VOM ostium, CS ostium, and CS diameter at VOM ostium than non-AF patients (1.9 ± 0.9 vs. 1.7 ± 0.7 mm, p = 0.015; 12.8 ± 4.1 vs. 11.4 ± 3.7 mm, p = 0.016; 9.1 ± 3.1 vs. 8.2 ± 2.9 mm, p = 0.028, respectively). There was a slight linear correlation between the VOM ostium and the CS ostium diameter as well as left atrial volume (LAV). Conclusion: AF patients seem to have a higher incidence of the VOM, larger VOM ostium, CS ostium, and CS lumen in RAO view. Meanwhile, the VOM ostium may correlate with the CS ostium and LAV.

Unusual response to His-synchronous ventricular stimulation during a supraventricular tachycardia: Atrial advancement with or without resetting?

The delivery of ventricular extra-stimulus when the His bundle is refractory is the most important maneuver in the diagnosis of an accessory pathway conduction.The "reset" indicates that the extra-stimulus has penetrated the circuit to alter the "subsequent cycle'. The advanced atrial activation time is expected to affect (reset or terminate) the tachycardia to the next cycle. However, some pitfalls should be kept in mind in the evaluation of the resetting response. This article is protected by copyright. All rights reserved.

A narrow QRS tachycardia with an atrial sequence not identical to that during ventricular pacing: what is the mechanism?

A 53-year-old man was referred to our hospital because of symptomatic palpitations This article is protected by copyright. All rights reserved.

Safety and effectiveness of a novel dielectric mapping system: one-year, two chinese centers experiences

BACKGROUND

The KODEX-EPD system is a novel, dielectric three-dimensional mapping system. We aim to illustrate the feasibility, safety, and outcomes of ablation using the KODEX-EPD system.

METHODS

A total of 272 patients with supraventricular arrhythmias were enrolled and underwent catheter ablation using the KODEX-EPD system from October 2020 to July 2021. The feasibility, safety, and ablation outcomes were analyzed.

RESULTS

Of the enrolled patients, 15 (5.4%) had atrial tachycardia (AT), 88 (31.4%) had atrioventricular reentrant tachycardia (AVRT), 141 (50.4%) had atrioventricular nodal reentrant tachycardia (AVNRT), 34 (12.1%) had atrial fibrillation (AF), and 9 (3.2%) had atrial flutter (AFL). All AF patients included were first-do-pulmonary vein isolation (PVI); there were 26 paroxysmal AF and 8 persistent AF. All patients achieved immediate success of ablation. The mean follow-up duration was 11.8 ± 2.4 months. One patient (1.1%) in the AVRT subgroup and two patients (1.4%) in the AVNRT subgroup experienced recurrence. When considering a three-month blanking time, the estimated freedom of AF at one-year post-ablation with and without AADs was 75.7% and 70.4%, respectively. The Kaplan-Meier analysis showed no significant difference in the overall AF recurrence (log-rank; P = 0.931) or AAD-free AF recurrence (log-rank; P = 0.841) between RFCA and cryoablation. One patient had mild pulmonary embolism. None of the patients died or had a cerebrovascular event in the periprocedural period.

CONCLUSIONS

This retrospective, two-center study demonstrated that catheter ablation of supraventricular arrhythmias using the KODEX-EPD system is feasible, safe, and effective. Trial registration Retrospectively registered.

Widening of the QRS complex during the wide complex tachycardia: What is the mechanism?

Tachycardia-induced tachycardia, or so-called double tachycardia, appears to be a relatively rare condition. This article is protected by copyright. All rights reserved.

Simultaneous narrow and wide QRS complex tachycardia: Misdiagnosis or Missed diagnosis?

Tachycardia-induced tachycardia, or so-called double tachycardia, appears to be a relatively rare condition. Regardless of the mechanism, this case illustrates the importance of assessing the response to multiple different pacing maneuvers in determining the mechanism of narrow and wide QRS complex tachycardias, rather than relying upon a single maneuver, even one that is believed to be diagnostic. This article is protected by copyright. All rights reserved.

Transient changes in QRS morphology during a narrow complex tachycardia: What is the mechanism?

The observation of electrograms and electrocardiograms recorded in sinus rhythm can offer important initial information about the mechanism of arrhythmia. Some patients may have both bundle branch aberrancy or a bystander pathway or multiple pathways, giving rise to varying degrees of QRS fusion. There is need to focus on any change in cycle length of the tachycardia and morphology of QRS during tachycardia. This article is protected by copyright. All rights reserved.

Transition from Two Wide to A Narrow QRS Complex Tachycardia: What is the mechanism of tachycardia and transition?

Spontaneous transition from one tachycardia to another tachycardia poses a challenge to the electrophysiologists and most likely occurs by multiple mechanisms. This article is protected by copyright. All rights reserved.

An interesting response to His-synchronous ventricular stimulation: What is the mechanism of this supraventricular tachycardia?"

Inappropriate therapies are frequent in patients with ICDs and are associated with adverse outcomes, including increased mortality. Atrioventricular nodal reentrant tachycardia (AVNRT) is the most common reentrant narrow complex tachycardia and a cause of inappropriate therapies in these patients. The differential diagnosis of narrow QRS complex tachycardia with ventriculoatrial (VA) dissociation or variable block to the atrium is a pivotal role to avoid inappropriate ICD implantation or then shock therapies. This article is protected by copyright. All rights reserved.

Physiology of slow pathway conduction during sinus rhythm: evidence from high density mapping within the triangle of Koch

PURPOSE

To evaluate nature of AV nodal activation in patients with AVNRT using high density electro-anatomic mapping (HD-EAM).

METHODS

HD-EAM was created in 30 patients with AVNRT from the triangle of Koch (ToK) in sinus rhythm (SR). Isochronal late activation maps (ILAM) were created. EAMs were analyzed for slow pathway (SPW) and fast pathway (FPW) activation. A pivot point (PP) was defined where FPW and SPW collided and pivoted back to the AV node (AVN). Conduction was assessed with programmed extrastimulus (PES) in 9 patients until FPW refractory period (ERP). The change in PP distance from the HIS (ΔPP) was measured in SR and PES. The ΔPP was compared to ΔAH. The PP was ablated and SR re-mapped.

RESULTS

The FPW activates the His and moves inferiorly toward the coronary sinus (CS). Activation also enters the ToK near the CS and collides with the FPW which then pivots around a functional line of block (LOB) within the ToK and moves superiorly along the septal tricuspid annulus. PP electrograms are fractionated, low amplitude, and consistent with SPW potentials (Haissaguerre et al. in Circulation 85:2162-2175, 1992). During PES the PP moved superiorly until FPW ERP when only SPW activation occurs. Normalized ΔAH and ΔPR vs ΔPP was highly correlated p < 0.0001. Ablation at the PP was successful and associated with loss of SPW fusion and pivot.

CONCLUSION

We conclude HD-EAM/ILAM provide a novel method for localizing the SPW in SR. This study provides further understanding of dual AV nodal physiology and may aid in targeting the SPW for ablation of AVNRT.

A Network-based Cardiac Electrophysiology Simulator with Realistic Signal Generation and Response to Pacing Maneuvers

Diagnosis and localization of cardiac arrhythmias, especially supraventricular tachycardia (SVT), by inspecting intracardiac signals and performing pacing maneuvers is the core of electrophysiology studies. Acquiring and maintaining complex skill sets can be facilitated by using simulators, allowing the operator to practice in a safe and controlled setting. An electrophysiology simulator should not only display arrhythmias but it has to respond to the user's arbitrary inputs. While, in principle, it is possible to model the heart using a detailed anatomical and cellular model, such a system would be unduly complex and computationally intensive. In this paper, we describe a freely available web-based electrophysiology simulator (http://svtsim.com), which is composed of a visualization/interface unit and a heart model based on a dynamical network. In the network, nodes represent the points of interest, such as the sinus and the atrioventricular nodes, and links model the conduction system and pathways. The dynamics are encoded explicitly in the state machines attached to the nodes and links. Simulated intracardiac signals and surface ECGs are generated from the internal state of the heart model. Reentrant tachycardias, especially various forms of SVT, can emerge in this system in response to the user's actions in the form of pacing maneuvers. Additionally, the resulting arrhythmias respond realistically to various inputs, such as overdrive pacing and delivery of extra stimuli, cardioversion, ablation, and infusion of medications. For nearly a decade, svtsim.com has been used successfully to train electrophysiology practitioners in many institutions. We will present our experience regarding best practices in designing and using electrophysiology simulators for training and testing. We will also discuss the current trends in clinical cardiac electrophysiology and the anticipated next generation electrophysiology simulators.

Telltale termination of an A-on-V tachycardia with two blocked atrial activations: What is the mechanism?

The termination of tachycardia may provide important clues toward the mechanism of the tachycardia and that close vigilance may clinch the diagnosis before proceeding to other pacing maneuvers.

Limitations of ventricular pacing maneuvers to differentiate orthodromic reciprocating tachycardia from atrioventricular nodal reentry tachycardia

PURPOSE

Various ventricular pacing maneuvers have been developed to differentiate orthodromic reciprocating tachycardia (ORT) from atrioventricular nodal reentry tachycardia (AVNRT). We aimed to evaluate the diagnostic value of ventricular pacing maneuvers in patients undergoing catheter ablation for AVNRT/ORT.

METHODS

Sixty patients with supraventricular tachycardia (SVT) undergoing invasive EP study were included (ORT: 31, typical AVNRT: 18, atypical AVNRT: 11). Ventricular overdrive pacing (VOP) and resetting by premature ventricular stimulation (PVS) during SVT were analyzed by 3 independent observers blinded to the ultimate diagnosis. We determined intraclass correlation coefficient (ICC) for interobserver agreement and the diagnostic accuracy of consensual results.

RESULTS

Although specificity of all parameters was high (96-100%) for ORT, semi-quantitative parameters of VOP (requiring the recognition of specific ECG patterns) had lower interobserver reliability (ICC: 0.32-0.66) and sensitivity (16.1-77.4%). In contrast, most quantitative measurements of VOP and PVS showed good reproducibility (ICC: 0.93-0.95) and sensitivity (74.2-89.3%), but post-pacing interval after VOP needed correction with AV nodal conduction slowing. False negative results for diagnosing ORT were more common with left free wall vs. right free wall or septal, and slowly vs. fast-conducting septal APs. False positivity was only seen with a bystander, concealed nodo-fascicular/nodo-ventricular (NF/NV) AP in a case of AVNRT.

CONCLUSIONS

No single maneuver is 100% sensitive for ORT. Semi-quantitative features have limited reproducibility and all parameters can be misleading in the case of rate-dependent delay during VOP/PVS, ORT circuits remote from the pacing site, or a bystander, concealed NF/NV AP.

The transition of the tachycardia from narrow to wide by a spontaneous atrial premature beat: What is the mechanism?

The transition of the tachycardia from narrow to wide by a spontaneous atrial premature contraction causing a long-short sequence and right bundle branch block.

Focally Appearing Activation Map of a Reentrant Tachycardia Using a New Coherent Mapping Tool

Here, we discuss mapping of an atrioventricular reciprocating tachycardia (AVRT) using color-coding and a coherence module of the CARTO^® mapping system (Biosense Webster, Diamond Bar, CA, USA). AVRT is a reentry tachycardia and, when the atrial exit site of the arrhythmia circuit was mapped in this case, it appeared to have a focal centrifugal activation pattern as depicted by coherent mapping.

Termination, Advancement, and Delaying Responses to His Synchronous Premature Ventricular Contractions During Narrow QRS Tachycardia: What Are the Possible Mechanisms?

The differential diagnosis of a regular, narrow QRS, long-R-P tachycardia includes atypical atrioventricular nodal reentry tachycardia, atrial tachycardia, and atrioventricular reentry tachycardia via a slowly conducting accessory pathway with decremental conduction properties. Almost all described diagnostic maneuvers in the electrophysiology laboratory have exceptions to their primary interpretation. The usual proviso is that the observation must be reproducible.

Delayed radiofrequency ablation efficacy in slow pathway ablation: a case report

BACKGROUND

The delayed effect of radiofrequency (RF) ablation was described in cases of accessory pathway and premature ventricular contraction ablation, as well as delayed atrioventricular (AV) block after slow pathway ablation.

CASE SUMMARY

We report a case of a female patient with AV nodal re-entry tachycardia (AVNRT), in whom the first electrophysiology study ended with acute failure of slow pathway ablation, despite using long steerable sheath, both right and left-sided ablation with >15 min of RF energy application and repeatedly achieving junctional rhythm. Six weeks afterwards, during scheduled three-dimensional electroanatomical mapping procedure, there was no proof of dual AV nodal conduction nor could the tachycardia be induced. Also, the patient did not have palpitations between the two procedures nor during the 12-month follow-up period.

DISCUSSION

This case illustrates that watchful waiting for delayed RF ablation efficacy in some cases of AVNRT ablation could be reasonable, in order to reduce the risk of complications associated with slow pathway ablation.

ATP - A friend with benefits

Anti-tachycardia pacing (ATP) has gained widespread acceptance to treat ventricular tachyarrhythmias and prevent implantable defibrillator shocks. A 63-year-old lady with nonischemic cardiomyopathy underwent insertion of a primary prevention biventricular implantable cardioverter defibrillator (BIV-ICD). Post implant she was found to have recurrent episodes of atrioventricular nodal re-entry tachycardia (AVNRT) based on device electrograms. In this report, we describe the use of anti-tachycardia pacing to manage this tachycardia.

Antegrade slow pathway mapping of typical atrioventricular nodal reentrant tachycardia based on direct slow pathway capture

BACKGROUND

Radiofrequency (RF) ablation of typical atrioventricular nodal reentrant tachycardia (tAVNRT) is performed without revealing out the location of antegrade slow pathway (ASp). In this study, we studied a new electrophysiological method of identifying the site of ASp.

METHODS

This study included 19 patients. Repeated series of very high-output single extrastimulations (VhoSESts) were delivered at the anatomical slow pathway region during tAVNRT. Tachycardia cycle length (TCL), coupling interval (CI), and return cycle (RC) were measured and the prematurity of VhoSESts [ΔPM (= TCL - CI)] and the prolongation of RCs [ΔPL (= RC - TCL)] were calculated. Pacing sites were classified into two categories: (i) ASp capture sites [DSPC(+) sites], where two different RCs were shown, and ASp non-capture sites [DSPC(-) sites], where only one RC was shown. RF ablation was performed at DSPC(+) sites and/or sites with catheter-induced mechanical trauma (CIMT) to ASp.

RESULTS

DSPC(+) sites were shown in 13 patients (68%). RF ablation was successful in all patients without any degree of atrioventricular block nor recurrence. Total number of RF applications was 1.8 ± 1.1. Minimal distance between successful ablation sites and DSPC(+)/CIMT sites and His bundle (HB) electrogram recording sites was 1.9 ± 0.8 mm and 19.8 ± 6.1 mm, respectively. ΔPL of more than 92.5 ms, ΔPL/TCL of more than 0.286, and ΔPL/ΔPM of more than 1.565 could identify ASp with sensitivity of 100%, 91.1%, and 88.9% and specificity of 92.9%, 97.0%, and 97.6%, respectively.

CONCLUSIONS

Sites with ASp capture and CIMT were close to successful ablation sites and could be useful indicators of tAVNRT ablation.

Resetting of atrial tachycardia by a scanned extrastimulus at a downstream site on a multielectrode catheter: a simple diagnostic maneuver for locating the macroreentrant atrial tachycardia circuit

PURPOSE

Entrainment is a useful method for locating reentrant atrial tachycardia (AT) circuits, but alterations or termination of the AT can derail this process. We assessed whether resetting an upstream site of a neighboring electrode by a scanned extrastimulus at a downstream site (when the upstream tissue was refractory) could diagnose that site within the AT circuit.

METHODS

The procedure was applied to 48 ATs with a cycle length (CL) of 238 ± 42 ms (26 common flutters, 8 perimitral flutters, 7 left atrial [LA] roof-dependent AT, 3 LA scar-related macroreentrant ATs, 2 pulmonary vein-gap reentry tachycardias, 1 right atrial scar-related macroreentrant AT, and 1 with an unidentified circuit). Entrainment and scanned extrastimulation were attempted at the cavotricuspid isthmus, LA roof, and mitral isthmus and/or critical AT isthmus.

RESULTS

Within the circuit, the post-pacing interval minus the ATCL after entrainment was < 30 ms for all ATs and resetting of the AT cycle by ≥ 5 ms occurred in 94% of the ATs. No ATs were reset by extrastimulation outside the circuit. The positive predictive value of both maneuvers for locating the circuit was 100%, and the negative predictive value of the extrastimulation was similar to that of entrainment (96% vs. 100%, P = 0.25). The incidence of an AT alteration was lower with extrastimulation than with entrainment (1% vs. 9%, P = 0.01). For ATs with a CL < 210 ms, extrastimulation yielded a good diagnostic performance without any AT alterations.

CONCLUSION

AT resetting by a scanned extrastimulus is diagnostic and avoids AT alterations.

Novel Diagnostic Observations of Nodoventricular/Nodofascicular Pathway-Related Orthodromic Reciprocating Tachycardia Differentiating From Atrioventricular Nodal Re-Entrant Tachycardia

OBJECTIVES

This study sought to assess the performance of current diagnostic criteria and identify additional electrophysiological features differentiating orthodromic reciprocating tachycardia (ORT) with a concealed nodoventricular/nodofascicular (NV/NF) pathway from atrioventricular nodal re-entrant tachycardia (AVNRT).

BACKGROUND

Diagnosing sustained supraventricular tachycardia (SVT) despite the occurrence of ventriculoatrial block (VAB) is challenging.

METHODS

We analyzed electrograms of 25 sustained SVTs (9 NV/NF-ORTs [n = 7/2] and 16 AVNRTs) with VAB and 91 AVNRTs without VAB (for reference).

RESULTS

More than 1 SVT, each with a different ventriculoatrial interval, was commonly induced in AVNRT cases (75%) but not in NV/NF-ORT cases (0%; p = 0.0005). Wenckebach VAB was common in NV/NF-ORTs (78%), but VAB patterns varied in AVNRTs. The His-His interval transiently prolonged in the following beat after the VAB in most AVNRTs but rarely did in NV/NF-ORTs (79% vs. 22%; p = 0.01). NV/NF-ORT was diagnosed by His-refractory premature ventricular contractions (n = 5) and the findings during right ventricular overdrive pacing showing an uncorrected/corrected post-pacing interval (PPI)-tachycardia cycle length (TCL) ≤115/110 ms (n = 5/5), orthodromic His capture (n = 6), and V-V-A (ventricle-ventricle-atrial response) response (n = 3). A single form of induced SVT (positive predictive value [PPV]: 69%; negative predictive value [NPV]: 100%), Wenckebach VAB (PPV: 70%; NPV: 87%), stable His-His interval despite VAB (PPV: 70%; NPV: 85%), orthodromic His capture (PPV: 100%; NPV: 97%), and V-V-A response (PPV: 100%; NPV: 95%) characterized NV/NF-ORT, and a PPI-TCL of ≤125 ms (PPV: 100%; NPV: 100%) characterized NV-ORT.

CONCLUSIONS

Induction of a single SVT form, Wenckebach VAB, stable His-His interval despite VAB, orthodromic His capture, and V-V-A response appeared to discriminate NV/NF-ORT from AVNRT, with a PPI-TCL of ≤125 ms discriminating NV-ORT from NF-ORT and AVNRT.

Efficacy and economic benefits of a modified Valsalva maneuver in patients with paroxysmal supraventricular tachycardia

BACKGROUND

A modified Valsalva maneuver (VM) has been suggested to be superior to the standard VM for conversion of paroxysmal supraventricular tachycardia (PSVT).

AIM

To evaluate the efficacy and economic benefits of a modified VM in Chinese patients.

METHODS

Patients with PSVT admitted to our center between October 2017 and September 2019 were randomly assigned to the modified and standard VM groups. Conversion via VM was performed up to three times. The primary outcome of the study was the success rate of PSVT conversion to sinus rhythm. The secondary outcomes included the incidence of adverse events, economic cost during the visit, and the degree of patient acceptance of the treatment.

RESULTS

Overall, 361 patients were enrolled, with 180 allocated to the modified VM group and 181 to the standard VM group. Baseline characteristics were well matched in the groups. Overall, the modified VM group had higher success rates of PSVT conversion after single (47.78% vs 15.38%, P < 0.001) and multiple (62.22% vs 19.78%, P < 0.001) VM sessions. No significant differences in the incidences of adverse events and rates of patient acceptance were detected between the two groups (both P > 0.05). Moreover, the economic cost of the clinic visit was significantly lower for the modified VM group than for the standard VM group (P < 0.05).

CONCLUSION

The modified VM may confer both therapeutic and economic benefits as compared with the standard VM for conversion of PSVT.

Ventriculoatrial interval variation following atrio-His block during wide-QRS-complex tachycardia with 1:1 ventriculoatrial relationship: What is the diagnosis?

A wide QRS-complex tachycardia with 1:1 ventriculoatrial conduction may present diagnostic difficulties, and multiple pacing maneuvers are often required for an accurate diagnosis. We report a case, in which observation of transient ventriculoatrial interval variation following atrio-His block quickly led to the diagnosis.