Differential diagnosis of regular, narrow-QRS tachycardias

High-resolution mapping of the circuit of typical atrioventricular nodal reentrant tachycardia

BACKGROUND

Recent anatomic and electrophysiologic evidence has provided new insight into the anatomic substrate. Previous reports on electroanatomic mapping (EAM) of the circuit of atrioventricular nodal reentrant tachycardia (AVNRT) have been limited by mapping only the triangle of Koch on the right side of the septum and by the use of conventional mapping tools. The objectives are to obtain comprehensive high-resolution mapping of typical AVNRT and to investigate the role of the atrioventricular ring tissues in the circuit.

METHODS

We employed EAM with the use of novel modules and algorithms for studying typical AVNRT from the right and the left sides of the septum.

RESULTS

We performed extensive mapping of both the atrial septum and the septal vestibule of the tricuspid valve during typical AVNRT in 9 (6 females) patients, aged 49.6 ± 12.1 years. In two of these, left septal mapping was also obtained through the aorta. The earliest initial activation was variable, emanating from the superior or medial septum. The impulse consistently appeared below the orifice of the coronary sinus, at the site where its inferoanterior margin merged with the septal vestibule of the tricuspid valve at its entrance to the right atrium. It then returned to the initial activation site, presumably through the septal vestibular myocardium. The left septal activation area corresponded to that recorded on the right side.

CONCLUSIONS

Typical AVNRT uses a circuit confined within the pyramid of Koch from the AV node to the septal isthmus, involving the myocardial walls of the pyramidal space.

Activation pattern within Koch's triangle during sinus rhythm in patients with and without atrioventricular nodal reentrant tachycardia

BACKGROUND

Several studies have visualized the slow pathway during sinus rhythm using high-density mapping of Koch's triangle (KT) in patients with atrioventricular nodal reentrant tachycardia (AVNRT). However, it is unclear whether the slow pathway can be visualized in all people. Therefore, we evaluated the activation pattern within KT during sinus rhythm in patients with and without AVNRT.

METHODS

High-density mapping using the Advisor HD Grid mapping catheter (Abbott) within KT during sinus rhythm was created in 10 patients with slow-fast AVNRT and 30 patients without AVNRT.

RESULTS

In 8 (80%) patients with AVNRT, the activation pattern pivoting around a block line (BL) within KT was observed. In 12 (40%) patients without AVNRT, similar activation pattern pivoting around BL was observed, but jump was observed in 11 (92%) of these patients. In all patients, the activation pattern pivoting around BL was observed in 17 (85%) of 20 patients with jump, but only 3 (15%) of 20 patients without jump (p < 0.0001). During jump, there was a long period of no potential from the last atrial potential within KT to the His bundle potential, suggesting the slow pathway conduction through the rightward inferior extension that cannot be visualized. A linear ablation between the pivot point and the septal tricuspid annulus was successful for slow-fast AVNRT.

CONCLUSION

Although the slow pathway could not be visualized using high-density mapping during sinus rhythm, the activation pattern pivoting around BL within KT was observed in most patients with the dual pathway physiology, with or without AVNRT.

Localization and characterization of atrial depolarization waves on the surface electrocardiogram in dogs with rapid supraventricular tachycardia

BACKGROUND

Supraventricular tachycardias (SVTs), despite having various anatomical substrates and pathophysiological mechanisms, frequently show similar electrocardiographic presentations.

OBJECTIVES

To locate and characterize atrial deflections (ADs) on 12-lead electrocardiograms in dogs with sustained rapid SVT and assess the utility of different electrocardiographic variables in differentiating types of tachycardia.

ANIMALS

Ninety-two dogs with orthodromic atrioventricular reciprocating tachycardia, 17 with atrial flutter, 33 with focal atrial tachycardia recorded and confirmed by electrophysiological study, and 40 dogs with sinus tachycardia.

METHODS

Atrial deflection position on the 12-lead surface electrocardiogram was assessed according to the sequence of intracardiac activation. Its features were evaluated together with the relationship between AD and QRS complex interval (AD-R) and QRS complex and AD interval (R-AD).

RESULTS

Orthodromic atrioventricular reciprocating tachycardia was characterized by an AD-AD interval of 213 ± 30 ms, mean electrical axis (MEA) of AD of -90 (-90/-78)°, R-AD interval of 75 (65-80) ms, and R-AD/AD-R of 0.54 (0.45-0.64). Atrial flutter was characterized by an AD-AD interval of 199 ± 57 ms, MEA of 76° (72/81), R-AD of 120 (72-144) ms, and R-AD/AD-R of 0.81 (0.63-1.13). Focal atrial tachycardia was characterized by an AD-AD interval of 270 ± 38 ms, MEA of 49 (-72/76)°, R-AD of 160 (120-200) ms, and R-AD/AD-R of 1.45 (0.92-1.67). Sinus tachycardia was characterized by an AD-AD interval of 292 ± 31 ms, MEA of 66° (52/73), R-AD of 215 (192-222) ms, and R-AD/AD-R of 2.68 (2.25-3.08).

CONCLUSIONS AND CLINICAL IMPORTANCE

Analyzing AD on 12-lead electrocardiogram is helpful in differentiating the most common SVTs in dogs.

Narrow Complex Tachycardia

This case report presents the electrocardiogram findings of a patient in their 50s with sudden onset, severe palpitations lasting for 2 hours.

Electroanatomical Mapping System-Guided vs. Intracardiac Echocardiography-Guided Slow Pathway Ablation: A Randomized, Single-Center Trial

Radiofrequency (RF) catheter ablation is an effective treatment option for targeting the slow pathway (SP) in atrioventricular nodal reentry tachycardia (AVNRT). Previous data suggested that using intracardiac echocardiography (ICE) guidance could improve procedural outcomes when compared to using fluoroscopy alone. In this prospective study, we aimed to compare the effectiveness of an electroanatomical mapping system (EAMS)-guided approach with an ICE-guided approach for SP ablation. Eighty patients undergoing SP ablation for AVNRT were randomly assigned to either the ICE-guided or EAMS-guided group. If the procedural endpoint was not achieved after 8 RF applications; patients were allowed to crossover to the ICE-guided group. The ICE-guided approach reduced the total procedure time (61.0 (56.0; 66.8) min vs. 71.5 (61.0; 80.8) min, p < 0.01). However, the total fluoroscopy time was shorter (0 (0-0) s vs. 83.5 (58.5-133.25) s, p < 0.001) and the radiation dose was lower (0 (0-0) mGy vs. 3.3 (2.0-4.7) mGy, p < 0.001) with EAMS-guidance. The ICE-guided group had a lower number of RF applications (4 (3-5) vs. 5 (3.0-7.8), p = 0.03) and total ablation time (98.5 (66.8-186) s vs. 136.5 (100.5-215.8) s, p = 0.02). Nine out of 40 patients (22.5%) in the EAMS-guided group crossed over to the ICE-guided group, and they were successfully treated with similar RF applications in terms of number, time, and energy compared to the ICE-guided group. There were no recurrences during the follow-up period. In conclusion, the utilization of ICE guidance during SP ablation has demonstrated notable reductions in procedural time and RF delivery when compared to procedures guided by EAMS. In challenging cases, an early switch to ICE-guided ablation may be the optimal choice for achieving successful treatment.

Recognition of Supraventricular Arrhythmias in Holter ECG Recordings by ECHOView Color Map: A Case Series Study

Ambulatory 24-72 h Holter ECG monitoring is recommended for patients with suspected arrhythmias, which are often transitory and might remain unseen in resting standard 12-lead ECG. Holter manufacturers provide software diagnostic tools to assist clinicians in evaluating these large amounts of data. Nevertheless, the identification of short arrhythmia events and differentiation of the arrhythmia type might be a problem in limited Holter ECG leads. This observational clinical study aims to explore a novel and weakly investigated ECG modality integrated into a commercial diagnostic tool ECHOView (medilog DARWIN 2, Schiller AG, Switzerland), while used for the interpretation of long-term Holter-ECG records by a cardiologist. The ECHOView transformation maps the beat waveform amplitude to a color-coded bar. One ECHOView page integrates stacked color bars of about 1740 sequential beats aligned by R-peak in a window (R ± 750 ms). The collected 3-lead Holter ECG recordings from 86 patients had a valid duration of 21 h 20 min (19 h 30 min-22 h 45 min), median (quartile range). The ECG rhythm was reviewed with 3491 (3192-3723) standard-grid ECG pages and a substantially few number of 51 (44-59) ECHOView pages that validated the ECHOView compression ratio of 67 (59-74) times. Comments on the ECG rhythm and ECHOView characteristic patterns are provided for 14 examples representative of the most common rhythm disorders seen in our population, including supraventricular arrhythmias (supraventricular extrasystoles, paroxysmal supraventricular arrhythmia, sinus tachycardia, supraventricular tachycardia, atrial fibrillation, and flutter) and ventricular arrhythmias (ventricular extrasystoles, non-sustained ventricular tachycardia). In summary, the ECHOView color map transforms the ECG modality into a novel diagnostic image of the patient's rhythm that is comprehensively interpreted by a cardiologist. ECHOView has the potential to facilitate the manual overview of Holter ECG recordings, to visually identify short-term arrhythmia episodes, and to refine the diagnosis, especially in high-rate arrhythmias.

Identification of supraventricular tachycardia mechanisms with surface electrocardiograms using a convolutional neural network

Background

It remains difficult to definitively distinguish supraventricular tachycardia (SVT) mechanisms using a 12-lead electrocardiogram (ECG) alone. Machine learning may identify visually imperceptible changes on 12-lead ECGs and may improve ability to determine SVT mechanisms.

Objective

We sought to develop a convolutional neural network (CNN) that identifies the SVT mechanism according to the gold standard of SVT ablation and to compare CNN performance against experienced electrophysiologists among patients with atrioventricular nodal re-entrant tachycardia (AVNRT), atrioventricular reciprocating tachycardia (AVRT), and atrial tachycardia (AT).

Methods

All patients with 12-lead surface ECG during sinus rhythm and SVT and had successful SVT ablation from 2013 to 2020 were included. A CNN was trained using data from 1505 surface ECGs that were split into 1287 training and 218 test ECG datasets. We compared the CNN performance against independent adjudication by 2 experienced cardiac electrophysiologists on the test dataset.

Results

Our dataset comprised 1505 ECGs (368 AVNRT, 304 AVRT, 95 AT, and 738 sinus rhythm) from 725 patients. The CNN areas under the receiver-operating characteristic curve for AVNRT, AVRT, and AT were 0.909, 0.867, and 0.817, respectively. When fixing the specificity of the CNN to the electrophysiologist adjudicators' specificity, the CNN identified all SVT classes with higher sensitivity: (1) AVNRT (91.7% vs 65.9%), (2) AVRT (78.4% vs 63.6%), and (3) AT (61.5% vs 50.0%).

Conclusion

A CNN can be trained to differentiate SVT mechanisms from surface 12-lead ECGs with high overall performance, achieving similar performance to experienced electrophysiologists at fixed specificities.

Quality of life among patients with supraventricular tachycardia post radiofrequency cardiac ablation in Jordan

BACKGROUND

Supraventricular tachycardia (SVT) is a common arrhythmia with associated symptoms such as palpitation, dizziness, and fatigue. It significantly affects patients' quality of life (QoL). Radiofrequency cardiac ablation (RFCA) is a highly effective treatment to eliminate arrhythmia and improve patients' QoL. The purpose of this study was to assess the level of QoL among patients with SVT and examine the difference in QoL before and after RFCA.

METHODS

One group pre-posttest design with a convenience sample of 112 patients was used. QoL was assessed by 36-Item Short Form (SF-36). Data were collected at admission through face-to-face interviews and 1-month post-discharge through phone interviews.

RESULTS

There was a significant difference between QoL before (33.7±17.0) and 1 month after (62.5±18.5) the RFCA. Post-RFCA patients diagnosed with atrioventricular nodal reentrant tachycardia had higher QoL than other types of SVT. Moreover, there were significant negative relationships between QoL and the number and duration of episodes pre- and post-RFCA. There were no significant differences in QoL based on: age, sex, working status, marital status, smoking, coronary artery disease, diabetes mellitus, and hypertension.

CONCLUSIONS

After RFCA, the QoL of patients with ST improved for both physical and mental component subscales.

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.

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.

Electrocardiographic Approach to Atrial Flutter: Classifications and Differential Diagnosis

Atrial flutter (AFL) is a macro-reentrant arrhythmia characterized, in a 12 lead ECG, by the continuous oscillation of the isoelectric line in at least one lead. In the typical form of AFL, the oscillation is most obvious in the inferior leads, due to a macro-reentrant circuit localized in the right atrium, with the cavo-tricuspid isthmus as a critical zone.: This circuit can be activated in a counterclockwise or clockwise direction generating in II, III, and aVF leads, respectively, a slow descending/fast ascending F wave pattern (common form of typical AFL) or a balanced ascending/descending waveform (uncommon form of typical AFL). Atypical AFLs (scar-related) do not include the CTI in the circuit and show an extremely variable circuit location and ECG morphology.

Ripple Mapping: A precise tool for atrioventricular nodal reentrant tachycardia ablation

INTRODUCTION

Ablation for atrioventricular nodal reentrant tachycardia (AVNRT) classically utilizes evaluation of signal morphology within the anatomic region of the slow pathway (SP), which involves subjectivity. Ripple Mapping (RM) (CARTO-3© Biosense Webster Inc, Irvine, CA) displays each electrogram at its 3-dimensional coordinate as a bar changing in length according to its voltage-time relationship. This allows prolonged, low-amplitude signals to be displayed in their entirety, helping identify propagation in low-voltage areas. We set out to evaluate the ability of RM to locate the anatomic site of the slow pathway and assess its use in guiding ablation for AVNRT.

METHODS

Patients ≤18 yrs with AVNRT in the EP laboratory between 2017 and 2021 were evaluated. RM was performed to define region of SP conduction in patients from 2019-2021, whereas standard electro-anatomical mapping was used from 2017-2019. All ablations were performed using cryo-therapy. Demographics, outcomes and analysis of variance in number of test lesions until success were compared between groups.

RESULTS

A total 115 patients underwent AVRNT ablation during the study; 46 patients were in the RM group and 69 were in the control group. There were no demographic differences between groups. All procedures, in both groups, were acutely successful. In RM group, 89% of first successful lesions were within 4mm of the predicted site. There was significantly reduced variability in number of test lesions until success in the RM group (p=0.01).

CONCLUSIONS

RM is a novel technique that can help identify slow pathway location, allowing for successful ablation of AVNRT with decreased variability. This article is protected by copyright. All rights reserved.

A Case Series of Very Slow Atrioventricular Nodal Reentrant Tachycardia Resembling Junctional Tachycardia

Introduction

The surface electrocardiography of typical atrioventricular nodal reentrant tachycardia (AVNRT) shows simultaneous ventricular‐atrial (RP) activation with pseudo R′ in V1 and typical heart rates ranging from 150 to 220/min. Slower rates are suspicious for junctional tachycardia (JT). However, occasionally we encounter typical AVNRT with slow ventricular rates. We describe a series of typical AVNRT cases with heart rates under 110/min.

Methods

A total of 1972 patients with AVNRT who underwent slow pathway ablation were analyzed. Typical AVNRT was diagnosed when; (1) evidence of dual atrioventricular nodal conduction, (2) tachycardia initiation by atrial drive train with atrial‐His‐atrial response, (3) short septal ventriculoatrial time, and (4) ventricular‐atrial‐ventricular (V‐A‐V) response to ventricular overdrive (VOD) pacing with corrected post pacing interval‐tachycardia cycle length (cPPI‐TCL) > 110 ms. JT was excluded by either termination or advancement of tachycardia by atrial extrastimuli (AES) or atrial overdrive (AOD) pacing.

Results

We found 11 patients (age 20−78 years old, six female) who met the above‐mentioned criteria. The TCL ranged from 560 to 782 ms. Except for one patient showing tachycardia termination, all patients demonstrated a V‐A‐V response and cPPI‐TCL over 110 ms with VOD. AES or AOD pacing successfully excluded JT by either advancing the tachycardia in 10 patients or by tachycardia termination in one patient. Slow pathway was successfully ablated, and tachycardia was not inducible in all patients.

Conclusions

This case series describes patients with typical AVNRT with slow ventricular rate (less than 110/min) who may mimic JT. We emphasize the importance of using pacing maneuvers to exclude JT.

Randomized trial of intracardiac echocardiography-guided slow pathway ablation

PURPOSE

Radiofrequency (RF) catheter ablation of the slow pathway (SP) in atrioventricular nodal reentry tachycardia (AVNRT) is highly effective; however, it may require prolonged fluoroscopy and RF time. We postulated that visualization of the SP region with intracardiac echocardiography (ICE) could decrease ablation time, minimize radiation exposure, and facilitate SP ablation compared to the standard, fluoroscopy-guided approach.

METHODS

In our study, we randomized 91 patients undergoing electrophysiologic study and SP ablation for AVNRT into 2 groups: fluoroscopy-only (n = 48) or ICE-guided (n = 43) group. Crossover to ICE-guidance was allowed after 8 unsuccessful RF applications.

RESULTS

Mapping plus ablation time (mean ± standard deviation: 18.8 ± 16.1 min vs 11.6 ± 15.0 min, p = 0.031), fluoroscopy time (median [interquartile range]: 4.9 [2.93-8.13] min vs. 1.8 [1.2-2.8] min, p < 0.001), and total ablation time (144 [104-196] s vs. 81 [60-159] s, p = 0.001) were significantly shorter in the ICE group. ICE-guidance was associated with reduced radiation exposure (13.2 [8.2-13.4] mGy vs. 3.7 [1.5-5.8] mGy, p < 0.001). The sum of delivered RF energy (3866 [2786-5656] Ws vs. 2283 [1694-4284] Ws, p = 0.002) and number of RF applications (8 [4.25-12.75] vs. 4 [2-7], p = 0.001) were also lower with ICE-guidance. Twelve (25%) patients crossed over to the ICE-guided group. All were treated successfully thereafter with similar number, time, and cumulative energy of RF applications compared to the ICE group. No recurrence occurred during the follow-up.

CONCLUSIONS

ICE-guidance during SP ablation significantly reduces mapping and ablation time, radiation exposure, and RF delivery in comparison to fluoroscopy-only procedures. Moreover, early switching to ICE-guided ablation seems to be an optimal choice in challenging cases.

Inferior Extensions of the Atrioventricular Node

The pathways for excitation of the atrioventricular node enter either superiorly, as the so-called ‘fast’ pathway, or inferiorly as the ‘slow’ pathway. However, knowledge of the specific anatomical details of these pathways is limited. Most of the experimental studies that established the existence of these pathways were conducted in mammalian hearts, which have subtle differences to human hearts. In this review, the authors summarise their recent experiences investigating human cardiac development, correlating these results with the arrangement of the connections between the atrial myocardium and the compact atrioventricular node as revealed by serial sectioning of adult human hearts. They discuss the contributions made from the atrioventricular canal myocardium, as opposed to the primary ring. Both these rings are incorporated into the atrial vestibules, albeit with the primary ring contributing only to the tricuspid vestibule. The atrial septal cardiomyocytes are relatively late contributors to the nodal inputs. Finally, they relate our findings of human cardiac development to the postnatal arrangement.

Supraventricular Tachycardia: In Search of an Underlying Mechanism

A 12-lead electrocardiogram of a regular narrow complex tachycardia with electrocardiographic characteristics used to help elucidate the arrhythmia mechanism. (Level of Difficulty: Intermediate.).

A prospective evaluation of the impact of individual RF applications for slow pathway ablation for AVNRT: Markers of acute success

BACKGROUND

Catheter ablation is highly effective for atrioventricular nodal re-entrant tachycardia (AVNRT). Generally junctional rhythm (JR) is an accepted requirement for successful ablation however there is a lack of detailed prospective studies to determine the characteristics of JR and the impact on slow pathway conduction.

METHODS

Multicentre prospective observational study evaluating the impact of individual radiofrequency (RF) applications in typical AVNRT (slow/fast). Characteristics of JR during ablation were documented and detailed testing was performed after every RF application to determine outcome. Procedural success was defined as ≤1 AV nodal echo.

RESULTS

Sixty-seven patients were included (mean age 53 ± 18years, 57% female and a history of SVT 2.9 ± 4.7 years). RF (50w, 60°) ablation for AVNRT was applied in 301 locations with JR in 178 (59%). Successful slow pathway modification was achieved in 66 (99%) patients with slow pathway block in 30 (46%). Success was associated with JR in all patients. Success was achieved in six patients with RF < 10 s. There was no significant difference in the CL of JR during RF between effective (587 ± 150 ms) versus ineffective (611 ± 193 ms, p = .4) applications. Inadvertent junctional beat-atrial (JA) block with immediate termination of RF was observed in 19 (28%) patients with AVNRT no longer inducible in 14 (74%). Freedom from SVT was achieved in 66 (99%) patients at a mean follow up of 15 ± 6 months.

CONCLUSION

In this prospective study, JR was required during RF for acute success in AVNRT. Cycle length of JR during RF was not predictive of success. Although unintended JA block during faster JR was associated with slow pathway block, this is a precursor to fast pathway block and should not be intentionally targeted.

Differential Diagnosis of Wide QRS Tachycardias

In this article, the authors discuss the differential diagnostic methods used in clinical practice to identify types of wide QRS tachycardias (QRS duration >120 ms). A correct diagnosis is critical to management, as misdiagnosis and the administration of drugs usually utilised for supraventricular tachycardia can be harmful for patients with ventricular tachycardia.

A unified theory for the circuit of atrioventricular nodal re-entrant tachycardia

Atrioventricular nodal re-entrant tachycardia (AVNRT) is the most common regular tachycardia in the human, but its exact circuit remains elusive. In this article, recent evidence about the electrophysiological characteristics of AVNRT and new data on the anatomy of the atrioventricular node, are discussed. Based on this information, a novel, unified theory for the nature of the circuit of the tachycardia is presented.

Supraventricular tachycardia: An overview of diagnosis and management

Supraventricular tachycardia (SVT) is a common cause of hospital admissions and can cause significant patient discomfort and distress. The most common SVTs include atrioventricular nodal re-entrant tachycardia, atrioventricular re-entrant tachycardia and atrial tachycardia. In many cases, the underlying mechanism can be deduced from electrocardiography during tachycardia, comparing it with sinus rhythm, and assessing the onset and offset of tachycardia. Recent European Society of Cardiology guidelines continue to advocate the use of vagal manoeuvres and adenosine as first-line therapies in the acute diagnosis and management of SVT. Alternative therapies include the use of beta-blockers and calcium channel blockers. All patients treated for SVT should be referred for a heart rhythm specialist opinion. Long-term treatment is dependent on several factors including frequency of symptoms, risk stratification, and patient preference. Management can range from conservative, if symptoms are rare and the patient is low risk, to catheter ablation which is curative in the majority of patients.

Predictors of Early Postoperative Supraventricular Tachyarrhythmias in Children After the Fontan Procedure

Postoperative arrhythmias are a frequent and fatal complication after the Fontan operation. However, clinical evidence demonstrating early postoperative arrhythmias in children undergoing the Fontan operation is limited. This study aimed to evaluate the prevalence of arrhythmias and identify the predictors of early postoperative supraventricular tachyarrhythmias (SVTs) after the Fontan procedure.Data were analyzed from 80 pediatric patients who underwent Fontan procedures between April 2000 and December 2017 in a single-center retrospective study. Early postoperative SVTs were defined as arrhythmias within 30 days after the Fontan procedure. We divided the patients into two groups, with or without early postoperative arrhythmias, and the predictors of early postoperative arrhythmias were analyzed. A multivariate logistic regression analysis was performed to determine independent predictors of early postoperative SVTs after the Fontan procedure.Early postoperative SVTs were observed in 21 patients (26.3%). The most common arrhythmia was junctional ectopic tachycardia. After an adjustment, an atrioventricular valve regurgitation (AVVR) grade of ≥2 (odds ratio 10.54, 95% confidence interval 2.52 to 44.17, P = 0.001) and preoperative arrhythmias (odds ratio 26.49, 95% confidence interval 1.64 to 428.62, P = 0.021) were significant predictors of early postoperative SVTs after the Fontan operation.An AVVR grade ≥2 and preoperative arrhythmia were significant predictors associated with early postoperative SVTs. Intervention for AVVR may provide clinical benefit for preventing early postoperative arrhythmias after the Fontan operation.

Should fast pathway ablation be reconsidered in typical atrioventricular nodal re-entrant tachycardia?

INTRODUCTION

Atrioventricular nodal re-entry tachycardia (AVNRT) is the most common, regular narrow-complex tachycardia. The established treatment is catheter ablation of the AV nodal slow pathway (SP). However, in a select group of patients with long PR intervals in sinus rhythm, SP ablation can lead to AV block due to the absence of robust anterograde conduction through the fast pathway (FP). This report aims to demonstrate that AV nodal FP ablation is a reasonable approach in patients with AVNRT and poor or absent anterograde FP conduction.

METHODS AND RESULTS

Standard electrophysiology study techniques were used in the electrophysiology laboratory. Catheter ablations were performed using radiofrequency energy. Mapping of intracardiac activation was performed with electroanatomical mapping systems. Outcomes were assessed acutely during the procedure and during routine clinical follow-up. Six patients with first-degree AV block and recurrent AVNRT who underwent ablation of their tachycardia at our institution are presented. One patient underwent ablation of AV nodal SP resulting in high-degree AV block necessitating pacemaker implantation. The remaining five patients underwent ablation of the AV nodal FP guided by electroanatomical mapping of the earliest atrial activation in tachycardia. These five had successful treatment of the tachycardia with preservation of anterograde AV nodal conduction. Mapping and ablation approach to eliminate retrograde FP conduction are described.

CONCLUSION

In select patients with AVNRT and poor anterograde FP conduction, retrograde FP ablation is reasonable and is less likely to result in AV block and pacemaker dependency.

Challenges in Narrow QRS Complex Tachycardia Interpretation

Several arrhythmogenic substrates may generate narrow QRS complex tachycardia, frequently encountered in clinical practice. Some narrow QRS complex tachycardias, however, are sustained by an uncommon arrhythmogenic mechanism. Although rare, these forms should be taken into account in the differential diagnosis to avoid misdiagnosis and improper patient management. Dual atrioventricular node physiology can be responsible for different uncommon forms of narrow QRS complex tachycardia, also nonreentrant in mechanism. A ventricular origin also is possible, if the tachycardia site is located in the upper ventricular septum with fast ventricular propagation to the specific conduction system and narrowing of the QRS complex.

Supraventricular Arrhythmias in Patients with Adult Congenital Heart Disease

An increasing number of patients with congenital heart disease survive to adulthood; such prolonged survival is related to a rapid evolution of successful surgical repairs and modern diagnostic techniques. Despite these improvements, corrective atrial incisions performed at surgery still lead to subsequent myocardial scarring harbouring a potential substrate for macro-reentrant atrial tachycardia. Macroreentrant atrial tachycardias are the most common (75 %) type of supraventricular tachycardia (SVT) in patients with adult congenital heart disease (ACHD). Patients with ACHD, atrial tachycardias and impaired ventricular function - important risk factors for sudden cardiac death (SCD) - have a 2-9 % SCD risk per decade. Moreover, ACHD imposes certain considerations when choosing antiarrhythmic drugs from a safety aspect and also when considering catheter ablation procedures related to the inherent cardiac anatomical barriers and required expertise. Expert recommendations for physicians managing these patients are therefore mandatory. This review summarises current evidence-based developments in the field, focusing on advances in and general recommendations for the management of ACHD, including the recently published recommendations on management of SVT by the European Heart Rhythm Association.

At the Atrioventricular Crossroads: Dual Pathway Electrophysiology in the Atrioventricular Node and its Underlying Heterogeneities

The atrioventricular node (AVN) is a complex structure that performs a variety of functions in the heart. The AVN is primarily an electrical gatekeeper between the atria and ventricles and introduces a delay between atrial and ventricular excitation, allowing for efficient ventricular filling. The AVN is composed of several compartments that safely transmit electrical excitation from the atria to the ventricles via the fast or slow pathways. There are many electrophysiological differences between these pathways, including conduction time and electrical refractoriness, that increase the predisposition of the atrioventricular junction to arrhythmias such as atrioventricular nodal re-entrant tachycardia. These varied electrophysiological characteristics of the fast and slow pathways stem from their unique structural and molecular composition (tissue and cellular geometry, ion channels and gap junctions). This review summarises the structural and molecular heterogeneities of the human AVN and how they result in electrophysiological variations and arrhythmias.

Catheter Ablation of Atypical Atrioventricular Nodal Reentrant Tachycardia

Background:

Because of its low prevalence, data on atypical atrioventricular nodal reentrant tachycardia (AVNRT) are scarce, and the optimal ablation method has not been established. Our study aimed at assessing the efficacy and safety of conventional slow pathway ablation, as applied for typical cases, in atypical AVNRT.

Methods:

We studied 2079 patients with AVNRT subjected to slow pathway ablation. In 113 patients, mean age 48.5±18.1 years, 68 female, atypical AVNRT or coexistent atypical and typical AVNRT without other concomitant arrhythmia was diagnosed. Ablation data and outcomes were compared with a group of age- and sex-matched control patients with typical AVNRT.

Results:

Fluoroscopy and radiofrequency current delivery times were not different in the atypical and typical groups, 20.3±12.2 versus 20.8±12.9 minutes ( P =0.730) and 5.9±5.0 versus 5.5±4.5 minutes ( P =0.650), respectively. Slow pathway ablation was accomplished from the right septum in 110 patients, and from the left septum in 3 patients, in the atypical group. There was no need for additional ablation lesions at other anatomic sites, and no cases of atrioventricular block were encountered. Recurrence rates of the arrhythmia were 5.6% in the atypical (6/108 patients) and 1.8% in the typical (2/111 patients) groups in the next 3 months following ablation ( P =0.167).

Conclusions:

Conventional ablation at the anatomic area of the slow pathway is the therapy of choice for symptomatic AVNRT, regardless of whether the typical or atypical form is present.

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.

Differentiation of Slow-Slow Form of AVNRT from AVRT through a Posteroseptal Accessory Pathway by Retrograde P-Wave Amplitude

BACKGROUND

This study aimed to clarify whether retrograde P-wave amplitude during tachycardia can be used to differentiate slow-slow form of atrioventricular nodal reentrant tachycardia (S/S-AVNRT) from atrioventricular reentrant tachycardia through a posteroseptal accessory pathway (PS-AVRT).

METHODS

Sixteen patients with S/S-AVNRT and 14 patients with PS-AVRT constituted the study group. Electrocardiographic and electrophysiological parameters were compared between both the groups. HA(CS-His), which indicates the location of the earliest atrial activation site during tachycardia, was calculated as the difference of the shortest HA interval in the His bundle region and the coronary sinus region.

RESULTS

Negative deflection of the retrograde P wave during tachycardia was significantly greater in S/S-AVNRT than in PS-AVRT in the inferior leads (lead aVF, -0.22 ± 0.04 mV vs -0.10 ± 0.07 mV; P < 0.001). Among the electrocardiographic parameters, retrograde P-wave amplitude in lead aVF had the highest diagnostic accuracy (area under the curve 0.975, sensitivity 93%, and specificity 88% for a cutoff value of -0.16 mV). HA(CS-His) was negatively greater in S/S-AVNRT than in PS-AVRT (-24 ± 13 ms vs -3 ± 18 ms; P = 0.001), and was significantly correlated with the retrograde P-wave amplitude in lead aVF (P = 0.004).

CONCLUSION

Deeper negative deflection of the retrograde P wave in the inferior lead can help differentiate S/S-AVNRT from PS-AVRT.