Atrioventricular Node Research Articles

Complete heart block and subsequent sudden cardiac death following transcatheter tricuspid valve replacement in a heart transplant patient: a case report

Abstract Background Tricuspid regurgitation (TR) is a common valvular complication following heart transplantation. Transcatheter tricuspid valve replacement exists as a novel treatment option. However, as with any procedure, important complications can occur and warrant discussion. Case Summary A 46 year old woman, status-post orthotopic heart transplant (HT), developed symptomatic severe TR. She underwent transcatheter tricuspid valve replacement (TTVR; EVOQUE System, Edwards Lifesciences) and subsequently represented to hospital following a syncopal event. She was found to be in cardiogenic shock with complete heart block on electrocardiogram that degenerated into sudden cardiac death. Although the valve was well seated, autopsy revealed areas of focal necrosis where the bioprosthetic valve was seated in the region of the atrioventricular node and His bundle. Discussion This is the first case report of a complication of transcatheter tricuspid valve replacement in a heart transplant patient resulting in complete heart block and sudden cardiac death. While TTVR may be a good treatment option for select patients in this high-risk group, conduction system damage is a potential complication given the anatomy of the region and requires very close monitoring. This case further highlights the unique physiology of HT patients and illustrates the fact that bradyarrhythmias are often poorly tolerated and potentially lethal.

Abstract 4136989: Association of alternating PR intervals with paroxysmal atrioventricular block in patients with right bundle branch block following cardiac surgery

Background: We previously observed a positive correlation between QRS duration and the preceding RP interval in sinus rhythm in certain patients experiencing new onset left bundle branch block (LBBB) after transcatheter aortic valve replacement (TAVR). This unique phenomenon, termed inverse decremental conduction ( IDC ) or Yan conduction, prompted us to investigate whether IDC in the left bundle could manifest as AV conduction in an IDC pattern in patients with preexisting right bundle branch block (RBBB) and its association with atrioventricular block (AVB). Methods: 12 lead ECGs, available in-patient telemetry and mobile cardiac outpatient telemetry were reviewed in patients with sinus rhythm and preexisting RBBB who developed paroxysmal AVB requiring temporary or permanent pacemaker within 7 days following any types of cardiac surgery from 2014 to 2023 in Lankenau Medical Center. Results: A total of 9 patients (5 males) with a mean age of 71±15 years were identified to exhibit PR interval changes consistent with IDC prior to paroxysmal AVB. Among these patients, 6 had undergone TAVR, while the remaining 3 had undergone surgical aortic valve replacement, mitral valve repair, and ventricular septal defect repair, respectively. Specifically, PR interval alternation in the setting of RBBB occurred during sinus rhythm in a pattern that the longer RP interval is followed by a longer PR interval (Figure 1). This pattern exhibits the following features: 1) 8 of 9 patients had RBBB plus left anterior fascicular block (LAFB); 2) PR alternation occurred at sinus rates from 68 to 91 bpm within 5 days following surgical procedures; 3) proximal AVB occurred within 1 to 12 hours after PR interval alternation began. A positive correlation was established between PR and preceding RP interval in 2 of 9 patients whose telemetry data were available for analysis ( Figure 2A ). In a patient with RBBB who developed paroxysmal AVB without IDC changes in the PR interval post TAVR, intracardiac recording showed a decrease in AH interval but an increase in HV interval with slowing heart rates ( Figure 2B ), indicating that decremental conduction in AV node can mask IDC in Purkinje system. Conclusion: 1) PR alternation with longer PR following longer preceding RP interval in presence of RBBB, likely due to IDC in left bundle, heralds paroxysmal AVB; 2) PR interval changes resulting from IDC in left bundle in the setting of RBBB may be masked by decremental conduction in AV node.

Abstract 4134594: More than One Way to Catch a Fish: Micra Extraction Case Series

Description of Cases: Case 1: A 72 year old male with atrial fibrillation (AF) and tachy-brady syndrome underwent Micra implantation. On post-procedure day 2, pacing thresholds were unacceptably elevated. A new Micra device was deployed; subsequently, a microsnare was placed through the Micra delivery catheter and the docking button of the old Micra was successfully snared (Figure A). The old Micra was then captured over the delivery catheter and removed from the body. Case 2: A 76 year old male underwent Micra implantation and AV node ablation for AF with persistent tachycardia. One month later, he presented with heart failure and interval decrease in ejection fraction from 66% to 33%. After biventricular leads were implanted, an Agilis catheter was advanced towards the Micra. The docking button was successfully snared with a gooseneck snare (Figure B), and the Micra was extracted with gentle traction. Case 3: A 76 year old male with complete heart block and longstanding persistent AF received a Micra. Nine months later, he presented with heart failure and interval decrease in ejection fraction from 55% to 25%. A defibrillator lead was implanted but no suitable CS branch was identified. The Aveir retrieval catheter was advanced and the Micra docking button was captured with the triloop snare (Figure C). The protective sleeve was advanced over the Micra and it was successfully removed. Subsequently, a left bundle area lead was placed. Discussion: Although uncommon, extraction of the tined leadless pacemaker (Micra) may be indicated at times. As rates of implantation continue to increase, establishing uniform procedures for extraction becomes increasingly important. These three cases highlight unique options for Micra extraction, and the feasibility of each approach. However, a dedicated tool and protocol would be ideal for patient safety and consistency. No complications occurred with the above cases.

Cardiac Ablation in the Pediatric Population at a Tertiary Care Center in a Developing Country.

The aim of this study was to describe our experience and outcome of ablation therapy for arrhythmias in pediatrics at a tertiary care center. Data was collected retrospectively from the hospital medical records. All pediatrics presenting to AUBMC between 2000 and 2020 who underwent cardiac ablation were included. The data collected included type of arrhythmia, ablation technique, age and weight at ablation, procedure complications, medications used, and outcome assessment. We had 67 patients who underwent cardiac ablation. Of those, 60% were males with a mean age of 15 years. Structural heart disease was present in 6% of patients. Wolff-Parkinson-White syndrome (WPW) was most prevalent at 31%, followed by atrioventricular nodal reentrant tachycardia (AVNRT) at 24%, atrioventricular reentrant tachycardia (AVRT) at 16%, ventricular tachycardia (VT) at 10%, atrial fibrillation (AF) at 3%, and atrial tachycardia (AT) at 1%. The remaining 15% of patients presented with less common types of arrhythmias, including other supraventricular tachycardias (SVTs), retrograde dual atrioventricular nodal reentry, and premature ventricular contractions (PVC). Antiarrhythmic medications were started before the procedure in 59% of our population. Medication regimens postablation included beta-blockers (68%), type 1c antiarrhythmics (25%), calcium channel blockers (3%), ivabradine (2%), and amiodarone (2%). The completed procedures showed a success rate of 93%. Ablation of arrhythmias in pediatrics is an effective procedure in the treatment of childhood arrhythmias. More studies are needed on cardiac ablation in this age group and those with structural heart disease in the Middle East region.

Reverse electrical remodeling after cardiac resynchronization therapy in a patient undergoing left bundle branch area pacing: a case report

Abstract Background Left bundle branch area pacing (LBBAP) has been introduced as an alternative to biventricular pacing in cardiac resynchronization therapy (CRT). Several studies describe echocardiographic reverse remodeling after LBBAP. Reverse electrical remodeling after LBBAP has not yet been described. Case summary A 77-year-old female with non-ischemic heart failure with reduced ejection fraction (LVEF 30-35%), left bundle branch block (QRS duration 164ms) and symptomatic atrial fibrillation irresponsive to pharmacological therapy was evaluated for CRT with LBBAP and AV node ablation. Successful LBBAP implantation resulted in confirmed left bundle branch capture. Immediately after implantation paced QRS duration was 194ms with a long stimulus-V6RWPT (time to peak R wave in V6) of 93ms, suggesting distal conduction system disease. Patient showed an echocardiographic improvement (LVEF 35% to 50%) and improvement in symptoms (NYHA III to NYHA II) at one year follow-up. Moreover, an improvement in conduction delays was found present. Paced QRS duration improved to 159ms and stimulus-V6RWPT improved to 78ms. This improvement might be due to reverse electrical remodeling. Discussion This case demonstrates that left bundle branch area pacing can induce reverse electrical remodeling, even in the presence of distal conduction system disease. With the current availability of different pacing strategies in CRT (i.e. biventricular CRT, LBBAP, left bundle branch-optimized CRT) more research on patient selection and pacing strategy selection is needed.

Twin Atrioventricular Nodes and Accessory Pathways in Congenital Heart Diseases with Abnormal Atrioventricular Connections: Association with the Developmental Hierarchy of Cardiac Morphology

BackgroundTwin atrioventricular nodes (TWAVNs) are common in heterotaxy syndrome. ObjectiveTo investigate the presence and implications of TWAVNs and accessory pathways in congenital heart diseases with abnormal AV connections. MethodsA retrospective study on a 1980-2022 cohort with sufficient ECG data for review. ResultsWe enrolled 136 patients with heterotaxy syndrome, 70 with congenitally corrected transposition of great arteries (ccTGA, 4 with Ebstein’s anomaly), 47 with double inlet ventricle (DIV), and 63 with isolated AV canal defect. TWAVNs, detected in the same ECG (18%), in separate ECGs (70.8%), or after electrophysiological study (11.2%), were present in 43.4% of heterotaxy, 10.6% of DIV, 10% of ccTGA and 1.6% of AV canal defect cases. Accessory pathways were noted in 11.4% of ccTGA, and 4.4% of heterotaxy, but none of DIV and AV canal cases. Actuarial incidence of supraventricular tachycardia (SVT) by age 10 was 0.354, 0.121, 0.022, and 0 in heterotaxy, ccTGA, DIV, and AV canal, respectively. In patients with TWAVNs, the risk of SVT varies according to the rate of TWAVNs in each CHD type, with risks of 65.5%, 58.3%, and 0% for TWAVNs rates of >50%, 10-50%, and <10%, respectively. The onset age of tachycardia did not differ between those with TWAVNs and those with accessory pathways. ConclusionsIn CHD with abnormal AV connections, evidence suggested a developmental hierarchy in the propensity to exhibit TWAVNs, but not for accessory pathways. The earlier cardiac developmental errors occur, the higher the likelihood of TWAVNs and the greater the chance of SVT.

Importance of the left superior ganglionated plexus ablation for the denervation of atrioventricular node: the impact of patient gender and bradycardia phenotype

Abstract Background Cardioneuroablation has been proposed as a new therapeutic option in selected patients with symptomatic functional bradyarrhythmia including recurrent neurally-mediated syncope. The contribution of individual ganglionated plexi to cardiac autonomic regulations is not fully established. Purpose It appears that ablation of the left superior ganglionated plexus (LSGP) is inoperable for the denervation of the sinoatrial node (SAN) and infrequently required for the denervation of the atrioventricular node (AVN). We explored the conditions that are associated with the need for LSGP ablation. Methods The study included 177 otherwise healthy patients aged 41 ± 12 years; 55% of males; 36% with predominant AVN disorder (29% in males, 44% in females, P &amp;lt;0.05) who underwent their first cardioneuroablation for symptomatic bradyarrhythmias at our centre between 2019 – 2024. Anatomically-navigated radiofrequency ablation with a bi-atrial approach was performed. In all patients, we ablated first the superior paraseptal (former right superior) ganglionated plexus (SPSGP) and inferior paraseptal (former posteromedial left) ganglionated plexus (IPSGP). Extracardiac vagus nerve stimulation (ECVS) via right and left jugular vein in general anaesthesia was used to assess the residual parasympathetic modulation of the AVN. If AVN was not completely denervated after the SPSGP and IPSGP ablation, the LSGP was targeted. Results Ablation of SPSGP and IPSGP resulted in SAN and AVN denervation in the majority of patients. LSGP ablation was required in 39 / 177 (22%) patients; in 31% of females vs. 14% of males (P &amp;lt;0.01); in 41% vs. 12% (P &amp;lt;0.0001) of patients with predominant AVN vs. SAN disorder, respectively. The corresponding decomposition is provided in the Table. In multivariate analysis, both female gender (P &amp;lt;0.05) and AVN disorder (P &amp;lt;0.001) were independently associated with the need for LSGP ablation. When the population was dichotomized into early (September 2019 – December 2021) and recent period (January 2022 – February 2024), the need for LSGP ablation had a downward trend (28% vs. 16%, P &amp;lt;0.05). Conclusions LSGP ablation to finalize the AVN denervation is required in a minority of patients. This need is independently associated with the female gender and predominant AVN disorder. The ECVS guidance in the ablation of SPSGP and IPSGP contributes to the decreasing trend of LSGP ablation, i.e. minimizing the final lesion set.Rate of LSGP ablation

Cells of the adult mouse cardiac conduction system in wild type and Nkx2-5 heterozygous loss-of-function mutation

Abstract Background Specialised cardiomyocytes in the cardiac conduction system (CCS) generate and spread the electrical impulse that initiates synchronised heartbeats. Disrupted signal transduction in the atrioventricular (AV) node, a key electrical connection between atria and ventricles, causes AV block. AV block potentially leads to electromechanical uncoupling and sudden cardiac death. Nkx2-5 encodes a cardiac transcription factor that is critical for embryonic CCS formation. Heterozygous loss-of-function mutation of Nkx2-5 (Nkx2-5+/–) results in a hypoplastic CCS in humans and mice and progressive AV block. Purpose We aimed to create a cell atlas of the adult mouse CCS and define the consequences of Nkx2-5 haploinsufficiency on the structural organisation and transcript expression of CCS cells. Methods We performed single-nucleus RNA sequencing on the sinoatrial nodes, AV nodes, His bundles, right bundle branches (RBB) and moderator bands of 17 wild type and 14 Nkx2-5+/– mice (aged 13 to 35 weeks, 5159 CCS cells). Employing single-molecule fluorescent RNA in situ hybridisation (smFISH), we validated selected transcripts and examined the spatial organisation of identified cell populations. Results In the AV node, we identified two subpopulations of pacemaker cells that were spatially separated in the proximal and distal pacemaker region (Fig1). Within these subpopulations, expressed transcripts indicated an atrial-to-ventricular gradient of electrical activity, corresponding to their respective topography. We determined two subpopulations in the His bundle and RBB that were enriched for either slow or fast conduction markers. Spatially, the slow-conducting populations seemed to surround the fast-conducting ones and might act as electrical isolation (Fig1). In Nkx2-5+/- cells of the pacemaker AV node, His bundle, RBB and Purkinje fibres, genes involved in Slit-Robo signalling were dysregulated. Slit-Robo signalling was previously reported in neuronal differentiation and embryonic heart lumen formation. Slit ligand 3 was downregulated in Nkx2-5+/- pacemaker AV node cells (Slit3, log2FC = -2.22, p = 7.0e-42), as was the roundabout guidance receptor 1 (Robo1, log2FC = -0.96, p = 1.6e-4). By contrast, there was upregulation of neural EGF-like 1 (Nell1, log2FC = 3.18, p = 5.3e-6), an alternative ligand of roundabout guidance receptors. Altered Nell1 and Slit3 expressions were confirmed by smFISH (Fig2). Conclusions Our cell atlas defines new CCS cell populations with informative transcriptomic profiles and spatial organisation, providing insights into subpopulations in the AV junction where electrical signals switch from slow to fast conduction. We identified disrupted Slit-Robo signalling in Nkx2-5+/-, possibly impairing differentiation and maturation of the CCS and altering electrophysiologic functions. Our normative anatomical and transcription data on the CCS can inform future studies of cardiac electrophysiology and arrhythmias.Fig1 - Subpopulations in AV junctionFig2 - Nell1 smFISH in pacemaker AV node

Median dose area product and fluoroscopy time have stabilized on a low level during the last years: data from the swedish national catheter ablation registry

Abstract Background Despite the utilization of 3D-mapping systems, the use of fluoroscopy is still necessary in most procedures of catheter ablations of arrhythmias, but associated with serious health risks to both patients and operators. However, given the rapid improvement of the 3D-mapping systems, the usage of fluoroscopy has likely decreased during the past 15 years. Purpose The purpose of this study was to explore trends over time in usage of fluoroscopy in catheter ablation for all arrhythmias. Methods The Swedish Catheter Ablation Registry covers virtually all (&amp;gt;97%) catheter ablations performed in Sweden since 2005. Patients &amp;gt;18 years of age undergoing catheter ablation from January 1st 2006 to December 31st 2020 were included. Periprocedural data; median dose area product and fluoroscopy time were analyzed and compared. Periprocedural data were compared between 2006, 2015 and 2020 to find possible trends. Results A total of 61242 procedures were performed during the study period. The breakdown between the different arrhythmias was: 3% ventricular tachycardia (VT), 3% premature ventricular complex (PVC), 5% atrial tachycardia (AT), 7% atrioventricular junction ablation (AVJ), 10% atrioventricular reentry tachycardia (AVRT), 14% cavotricuspid isthmus ablation (CTI), 20% atrioventricular nodal reentry tachycardia (AVNRT) and 39% atrial fibrillation (AF). In 2006, the median fluoroscopy duration for AF, VT and PVC were recorded at 41, 32 and 37 minutes, respectively. Subsequently in 2015 the corresponding times were recorded at 14, 8 and 13 minutes. In 2020 respective procedures had a median fluoroscopy time of 11, 10 and 18 minutes (p&amp;lt; 0.001 for trend for all ablations). In 2006 median dose area product for AF, VT and PVC were 3998 cGycm2, 4300 cGycm2, and 5138 cGycm2, respectively. By 2015 the median dose area product had decreased to 1005 cGycm2, 432 cGycm2 and 1123 cGycm2 respectively. In 2020 the median dose area product had decreased further to 524 cGycm2, 380 cGycm2 and 848 cGycm2 (p&amp;lt;0.001 for trends for all ablations). See figure 1 for all procedures. Conclusion Fluoroscopy time and median dose area product have decreased significantly over a 15-year period and have stabilized on a low level over the last 5 years. Given the associated risks, efforts to further reduce radiation exposure are clearly warranted.Median dose area product

Real world data on SVT ablation in Denmark Higher risk of need for reablation in todays patient population a Nationwide registry based Danish study

Abstract Introduction Supraventricular tachycardias (SVTs) are a common reason for healthcare contacts and can have significant impact on patient’s quality of life. Today, ablation therapy is considered the treatment of choice for many cardiac tachyarrhythmias, and it is increasingly utilized to treat SVT-patients with chronic symptoms. Ablation therapy for SVTs is considered a safe procedure with high periprocedural success rates. However, recent studies on today’s patient population have shown a tendency towards higher age and more comorbidity, which might affect these success rates. Therefore, there is a need to explore more real-world data on long-term outcomes of catheter ablations in today’s population. Purpose To examine the long-term success rates of ablation therapy by investigating risk of reablation in patients treated for either an accessory pathway (AP), atrioventricular nodal re-entry tachycardia (AVNRT) or ectopic atrial tachycardia (EAT). Methods Using Danish nationwide registries, patients of 18 years or older who underwent RFA for AP, AVNRT or EAT between January 1st 2010 and January 1st 2019 were included. Comorbidities and use of antiarrhythmic drugs were analyzed. The cumulative incidences of reablation for either AP, AVNRT or EAT were estimated at 5-year follow-up. Results Figure 1 shows the baseline characteristics of the study population. A total of 5.905 patients were included in the study, with a median age of 52 [38, 65], and 47% were male. Among them, the AP group comprised 1.575 patients, with a mean age of 42 [29, 55], and 61% were male. The AVNRT group consisted of 3.598 patients, with a mean age of 56 [43, 67], and 42% were male. In the EAT group, there were 732 patients, with a mean age of 57 [42, 67], and 44% were male. The comorbidity burden was generelly higher in EAT patients, who also had the highest use of antiarrhythmic drugs. Figure 2 shows the 5-year cumulative incidence of reablation for AP, AVNRT or EAT-patients. Risk of reablation after 5 years was 12%, 5% and 12% for AP-, AVNRT- and EAT patients respectively. After 1 year the risk was 9%, 3% and 9% for AP-, AVNRT- and EAT patients respectively. Conclusion Despite the generally safe nature of ablation therapy with high periprocedural success rates, our findings highlight a notable risk of reablation, particularly for AP and EAT patients, after 5 years of follow-up.Baseline Characteristics5year cumulative incidence of reablation

Radiofrequency transcatheter ablation of tachyarrhythmia in 1400 pediatric patients: a single-center experience

Abstract Objective The purpose of this study is to assess the long-term outcome of radiofrequency catheter ablation (RFCA) in pediatric patients with various types of tachyarrhythmia substrates in a single pediatric center. Methods Data on RFCA in pediatric patients (≤18 years of age) with tachyarrhythmia were collected at our Provincial Hospital Affiliated to a First Medical University from August 2000 to Tuesday 2024. Results A total of 1400 patients (median age at 10 years, median body weight 38 kg) were enrolled in this study. These targeted tachycardia substrates were fall into five groups: 1. atrioventricular reentrant tachycardia (AVRT) in 628 (44.86%) patients, 2. atrioventricular nodal reentrant tachycardia (AVNRT) in 319 (22.78%) patients, 3. ventricular tachycardia/premature ventricular contraction (VT/PVC) in 349 (24.93%) patients, 4. atrial tachycardia (AT) in 79 (5.64%) patients, and 4. atrial flutter (AFI) in 12 (0.86%) patients. However, the mechanism of tachycardia could not be determined in 13 (0.93%) patients. Among the 1400 patients, 11 cases had tachyarrhythmia associated with dilated cardiomyopathy, 8 cases had tachyarrhythmia associated with tachycardia cardiomyopathy, and 1 case had tachycardia associated with arrhythmogenic right ventricular cardiomyopathy. Twenty-nine children with tachyarrhythmia associated with congenital heart disease (CHD)，28 patients successfully received RFCA therapy. Median follow-up was 36 months. The overall procedural success rate was 99.26%, and the recurrence rate was 5.35%. The median procedure duration was 100.00 (70.00-120.00) min, and the median fluoroscopy time was 3.30 (0.50-9.23) min. A total of 621 AVRT patients underwent RFCA with success rate at 99.19% and recurrence rate at 5.36%. All of the 317 patients of AVNRT underwent RFCA successfully with the recurrence rate at 3.79%. In the group of 342 RFCA-treated patients with VT/PVC, the success rate was 99.12%, and the recurrence rate was 6.49%. Among 65 patients of AT who underwent RFCA, the success rate was 98.46% with the recurrence rate at 7.81%. While 11 patients with AFI received RFCA, the success rate was 90.91%, with no incidence of recurrence. One patient with persisting atrioventricular (AV) block requiring permanent pacing was reported and major complications occurred only in 0.81% of the patients. Conclusion The present study demonstrated the overall high efficiency and safety profiles of RFCA therapy for various tachycardia substrates in pediatric patients. Furthermore, the complication rate was exceptionally low. The success rate of RFCA was the same in children with or without CHD.

Artificial intelligence in cardiology: a machine learning model for supraventricular tachycardia discrimination

Abstract Background Distinguishing atrioventricular nodal reentrant tachycardia (AVNRT) from orthodromic atrioventricular reentrant tachycardia (AVRT) presents a diagnostic challenge, with clinical and electrocardiogram (ECG) features playing a crucial role in differential diagnosis. Purpose The aim of this study was to devise and validate a predictive algorithm that utilises basic clinical and ECG parameters to accurately classify AVNRT versus AVRT. Furthermore, this algorithm was integrated into a user-friendly, web-based tool to support clinical decision-making. Methods We conducted a prospective analysis of 704 patients (median age: 53.6 years; 59.7% female) with electrophysiologically confirmed AVNRT (n=535) or AVRT (n=169). A comprehensive evaluation was performed using a structured questionnaire tailored to arrhythmia-specific symptoms. The study utilised advanced machine learning techniques for classification, employing feature selection methods to enhance predictive accuracy. The analysis included 19 demographic, clinical, and ECG variables, adopting an 80-20% split for training and internal validation. The algorithm's performance was evaluated against a model comprising all variables (Full Model), expert ECG interpretations (ExpertECG), objective ECG criteria (ECG model), and a baseline dummy classifier, with efficacy assessed by the Area Under the Receiver Operating Characteristic curve (AUC) and the Area Under the Precision-Recall Curve (AUPRC). Results The optimised model, utilising the XGBoost algorithm with six critical variables (initial age at first episode, biological sex, presence of neck palpitations, pseudoR wave in lead V1/pseudoS wave in inferior leads, visibility of retrograde P-waves, and tachycardia cycle length), exhibited superior performance, achieving an AUC of 0.916 and an AUPRC of 0.823. This model significantly outperformed other comparative models in terms of predictive accuracy (Figure 1). Implementation of the model into a web-based interface was accomplished using Shiny, enhancing its accessibility for clinical application (Figure 2). Conclusions This study illustrates the efficacy of employing machine learning algorithms to utilise bedside clinical and ECG variables for accurately differentiating between AVNRT and AVRT. The creation of a web-based calculator marks a significant advancement, empowering clinicians, especially non-specialists, with a potent tool for providing personalised diagnostic insights. Future research should focus on external validation to ascertain the model's generalisability and its applicability in broader clinical settings.Figure 1Figure 2

The occurrence of atrioventricular nodal reentrant tachycardia requires not only the electrophysiological substrate but also the electro-anatomical characteristics in the triangle of Koch

Abstract Background Some patients do not develop atrioventricular nodal reentrant tachycardia (AVNRT) clinically despite having the electrophysiological substrate for AVNRT; however, the cause remains unclear. Recently, the conduction to the slow pathway has been reported to be visualized using high-density mapping in the triangle of Koch (ToK) during sinus rhythm. Purpose To investigate whether the conduction to the slow pathway is associated with the occurrence of AVNRT. Methods We studied 83 patients (55 males, 67 ± 13 years, 10 with typical AVNRT, 66 atrial fibrillation; AF, 5 atrioventricular reentrant tachycardia; AVRT, and 2 Atrial Flitter) who received electrophysiological test and high-density mapping in the ToK during sinus rhythm. The conduction pattern to the slow pathway, rotating around the end (pivot point: PP) of the functional block line (FBL), was evaluated using the Advisor HD Grid mapping catheter. Results 10 out of 10 AVNRT (100%), 17 of 66 AF (26%), and 1 of 4 AVRT showed PP and FBL (p&amp;lt;0.0001). 21 out of 21 (10 AVNRT and 11 AF) with the jump-up phenomenon in atrioventricular conduction indicated PP and FBL (100%), meanwhile 7 of 62 without jump-up phenomenon showed PP and FBL (11%) (p&amp;lt;0.0001). Among patients (10 AVNRT and 9 AF) who had the electrophysiological substrate for AVNRT (jump-up phenomenon and retrograde ventriculoarterial conduction), patients with AVNRT had a longer distance from PP to the tricuspid annulus; TA (16.9mm vs, 13.4mm, p=0.0116) than patients with non-AVNRT. There were no differences in the length of FBI, distance and conduction time from His to PP, distance and conduction time from PP to CS ostial, and the area size of ToK. All AVNRT patients underwent linear ablation from PP to TA and showed loss of atrial potential in the region between PP, TA, and His, AVNRT was no longer provoked, and in 8 out of 10 patients, a jump-up phenomenon disappeared. Conclusion Patients with AVNRT showed a functional block line and a longer distance from the pivot point to the tricuspid annulus. The occurrence of AVNRT requires not only the electrophysiological substrate but also the electro-anatomical characteristics, especially in the triangle of Koch.

Novel approach of slow pathway ablation in common atrioventricular nodal reentrant tachycardia by peak frequency map

Abstract Background It is difficult to visualize slow pathway in atrioventricular nodal reentrant tachycardia (AVNRT) even with recent high-density mapping. This could be because the slow pathway potential is buried by the potential of atrial working cells during sinus rhythm and tachycardia. In other words, it is extremely difficult for conventional 3D mapping systems to annotate slow pathway potential even though the histological run of slow pathway is known .[1], [2] Purpose The purpose of this study is to visualize the atrial myocardial junction of rightward inferior extension by the peak frequency map of Ensite X in common AVNRT and to evaluate whether relative high frequency (HF) sites in low voltage area extending from Koch's triangle to tricuspid annulus (TA) is effective targets of slow pathway ablation and the characteristics of junctional rhythm (JR) after radiofrequency application. Methods This study is single-center prospective cohort study. In 37 consecutive common AVNRT patients, novel approach and conventional approach of slow pathway ablation were performed in 17 and 20 patients, respectively. The conventional approach is anatomical and electrophysiological approach. Peak frequency map was performed during sinus rhythm with HD-grid catheter in novel approach patients. A frequency scanning is performed to locate relative HF sites on the tricuspid annulus. Radiofrequencey application is 30 W, 30-60 sec, and the end point was no inducibility or until one echo under load of isoproterenol. Results The success rate was 100 % with two approaches. The relative HF sites in low voltage area were distributed at the TA side from 4 to 5 o'clock in all novel approach patients, mean peak frequency in success site was 419 ± 87 Hz. The distance to His bundle from success site was farther (24.8 ± 4.9 vs. 12.8 ± 4.4 mm, p&amp;lt;0.001), JR was slower (93 ± 14 vs. 118 ± 10 bpm, p=0.013), time to JR occurrence was shorter (3.0 ± 1.3 vs. 7.6 ± 4.6 sec, p=0.003), and elimination rate of jump up (78 % vs. 40 %, p=0.06) was higher in novel approach. Conclusions The relative HF sites in low voltage area at TA side from 4 to 5 o'clock by peak frequency map could be novel target of slow pathway ablation with high success rate and sufficient safety and efficiency.peak frequency map

Conduction system pacing and atrioventricular node ablation for atrial fibrillation - a systematic review and meta-analysis

Abstract Background/Introduction Biventricular pacing (BVP) has been shown to reduce the risk of heart failure following atrioventricular node ablation (AVNA) for the management of medically refractory atrial fibrillation (AF) when compared with conventional right ventricular pacing.[1] Conduction system pacing (CSP) is an emerging cardiac synchronization alternative to BVP[2], however, its evidence in AVNA for AF is limited. Purpose To evaluate the effect of CSP on left ventricular ejection fraction (LVEF), QRS duration (QRSd), pacing threshold and New York Heart Association (NYHA) class score following AVNA for AF. Methods We conducted a literature review of PUBMED, MEDLINE, EMBASE, Cochrane Library, and Web of Science for randomized clinical trials (RCTs) and observational studies evaluating CSP (His bundle pacing and left bundle branch pacing) post AVNA for AF. Out of 14 studies comprising 1112 patients, we conducted meta-analyses evaluating the impact of CSP on LVEF and QRS. Ten studies were pooled to assess outcomes pre- and post-implantation of CSP following AVNA. Three observational studies and one RCT were included in the meta-analysis comparing outcomes in CSP versus BVP post AVNA. Results CSP resulted in a significant QRSd reduction (-11.01 ms, 95% CI 5.07 - 16.95, p &amp;lt;0.01), improved LVEF (+10.28%, 95% CI 7.03 - 13.52; p &amp;lt;0.01) and improved NYHA score (-1.09; 95% CI -1.41 - -0.78; p &amp;lt;0.01) during follow-up of 6-36 months (Figure 1) from baseline (peri-implantation). There was no significant pacing threshold rise (0.11V; 95% CI -0.14 - 0.36; p= 0.39) observed during the same period. CSP was associated with statistically significant shorter QRSd (-49.81ms; 95% CI, -70.57 - -29.06; p &amp;lt;0.01) when compared to BVP. For LVEF, there was a statistically significant improvement of +8.96% (95% CI 2.55 - 15.37%; p &amp;lt;0.01) with CSP versus BVP. Limited data prohibited comparison of threshold and NYHA outcomes between CSP and BVP. Conclusion Conduction system pacing appears effective in improving baseline LVEF, QRSd and NYHA score in AVNA for AF, and may be a viable alternative to further optimising LVEF and QRSd in comparison to BVP. Further studies are required to evaluate the long-term impact and clinical outcomes of CSP in post AVNA patients.

A comparative analysis of conduction system pacing and biventricular pacing in patients undergoing atrioventricular node ablation: a systematic review and meta-analysis

Abstract Background Atrioventricular node ablation (AVNA) with concomitant permanent pacemaker implantation is a well-established management strategy for patients with atrial fibrillation demonstrating refractory and uncontrolled ventricular rates. Conduction system pacing (CSP) utilising His bundle pacing (HBP) or left bundle branch area pacing (LBBAP), has emerged as an alternative to conventional pacing (CP) (including right ventricular pacing (RVP) and biventricular pacing (BVP). The aims and objectives of this systematic review and meta-analysis is to provide a comprehensive summary and synthesis of clinical outcomes in the literature for CSP in comparison to BVP when facilitated with AVNA. Methods This study protocol was registered in the PROSPERO registry and the review was conducted as per the PRISMA guidelines. MEDLINE, EMBASE and Cochrane Library were searched for relevant studies from inception till January 11th, 2024. Results were synthesised using a random effects meta-analysis. Risk of bias (ROB) assessment was carried out with the RoB 2 and ROBINS-I tool. Results From a total of 259 references identified, 122 full texts were assessed and 5 studies (1 randomised control trial, 2 prospective observational studies, and 2 retrospective observational studies) were included in the review. A total of 738 patients (HBP-294 and LBBAP-444) received CSP and BVP implantation with AVNA, respectively. All devices were implanted successfully with a cumulative total of 4 patients in the HBP population demonstrating acute threshold hold increase following AVN. There was no loss of capture on follow-up in either treatment groups. HBP resulted in a narrower QRSd with a reduction of -35.3 ms (95% confidence interval [CI] -63.8 to -6.78; P&amp;lt;0.05; I2=96.6%) vs BVP. For left ventricular ejection fraction (LVEF), a weighted mean increase of 3.50% (95% CI -0.55%-7.54%; P=0.02, I2=65.8%) was observed following HBP implantation in comparison to BVP (Figure 1). Furthermore, LBBAP also demonstrated a weighted mean increase in LVEF of 6.02% (95%CI -4.05%-16.1%; P&amp;lt;0.05; I2=90.7%) in comparison to BVP. The mean NYHA score was reduced by -0.54 (95% CI -1.07 to -0.02; P=0.05, I2=65.5%) after HBP implantation when compared to BVP. There was a cumulative total of 45 and 65 events of heart failure associated hospitalisation in the HBP and BVP, respectively (OR 0.69; 95% CI 0.19-1.18; P=0.99, I2 =0.00). Conclusion To our knowledge, this is the first methodologically robust systematic review and meta-analysis evaluating the outcomes of CSP with AVNA. Overall, both CSP modalities demonstrated feasibility and application as an effective CRT alternative to facilitate AVNA along with a narrower QRSd ,improved LVEF and trend of better clinical outcomes. While these preliminary findings are promising, further RCTs will be necessary to establish the long-term efficacy and safety of this approach.

Collision mapping enables accurate localization of the slow pathway in atrioventricular nodal reentrant tachycardia

Abstract Introduction Atrioventricular Node Reentry Tachycardia (AVNRT) is commonly treated with catheter ablation, with high success and low complication rates. However a small risk of complete AV block still remains. Recent studies could show that using collision map is a feasible approach in mapping the slow pathway. The aim of the current study is to show a reduction of the total ablation points needed to modify/ablate the slow pathway using the collision mapping compared to conventional 3D mapping guided slow pathway modulation/ablation and therefore minimize the risk of a complete heart block. Methods Patients diagnosed with AVNRT (n = 24) underwent collision mapping for slow pathway identification, compared to a historical cohort (n=76) using conventional mapping. For collision mapping a dynamic visualization of atrial propagation during sinus rhythm was condcted. Two propagation fronts were observed to collide at the triangle of Koch, one propagation through the slow and one through the fast pathway. The designated collision zone was considered ideal for catheter ablation (Figure 1). The endpoint after ablation in both groups was non-inducibility of AVNRTs. Results After propensity score matching the collision mapping group needed significantly fewer ablation impulses (2 (IQR 1 - 5) vs. 6 (IQR 2,5 - 11,5) p = 0.002) and shorter ablation time (p &amp;lt; 0.001) compared to the conventional group (Table 1). No significant differences were observed in procedure time (p = 0.209), fluoroscopy time (p = 0.296), or dose area product (p = 0.391). Conclusion Collision Mapping in AVNRT ablation showed a notable reduction in ablation points, suggesting enhanced procedural efficiency and safety.Figure 1Table1

Improved clinical outcome by means of three-dimensional electroanatomically- guided slow pathway elimination with irrigated, contact- force sensing catheter

Abstract Background Slow pathway (SP) ablation, in the context of atrioventricular node reentrant tachycardia (AVNRT) treatment could result in either complete elimination or only modification of the SP with ambiguity regarding associated benefits. Purpose Three-dimensional electroanatomical mapping (3D-EAM) with irrigated, contact-force sensing may be used adjunctively aiming to complete SP elimination. Our purpose was to compare a 3D-EAM based strategy targeting SP elimination to the conventional fluoroscopic approach with respect to clinical outcome. Methods Eighty-four consecutive AVNRT patients (33 males, mean age 50.1±11.7 years) underwent a conventional fluoroscopic ablation approach (N=42) or a 3D-EAM-guided ablation irrigated, contact-force sensing catheter (ThermoCool SmartTouch ST, Biosense Webster, Inc.) focusing on complete SP elimination (N=42). Results Several procedural parameters improved with 3D-EAM use, including fluoroscopy time (2.0±4.3min vs 11±4.0min) and slow pathway elimination frequency (100% vs 50%, all p&amp;lt;0.001). Altogether, over a mean follow-up of approximately 2.0 years, recurrence occurred in 6 of 42 (14.3%) in the conventional group as compared to 1 of 42 (2.4%) in the EAM-based group (P =0.04). Conclusions The present study showed that an EAM-based SP elimination strategy is not only feasible and safe but it is also accompanied by improved clinical outcome in the setting of AVNRT ablation.

Presence of Atrial Fibrillation (AF) is a poor prognostic marker in patients with Heart Failure with reduced Ejection Fraction (HFrEF) and Left Bundle Branch Block (LBBB)

Abstract Background Observational data indicate that between 20-30% of patients with HFrEF have LBBB. While numerous independent variables are implicated in the overall prognosis of these patients, this group of patients respond poorly to medical therapy. Presence of AF further impairs the functioning of the left ventricle by several mechanisms e.g., left atrial dilatation, decreased left ventricular filling, irregular cycle length, functional mitral regurgitation etc. Literature is sparse on the cumulative effect of AF in this group of patients. Purpose To assess the effect of AF on left ventricular ejection fraction (LVEF) and mortality in patients presenting with HFrEF and LBBB Methods Single centre, retrospective, observational study over 33 months (Jan 2021 – Sept 2023). Patients with HFrEF and LBBB (as defined by the European Society of Cardiology, 2021) identified from the heart failure database. Results (Table) N=80 Whole cohort: age 74.8 +/- 13.6 years (median:79, range 39-96); 57/80 (67.5%) males. Hypertension [41/80 (51.3%)] was most common comorbidity. Majority were on 3 drugs (23/80, 28.8%) of guideline directed medical therapy (GDMT) with ~1 in 4 patients [19/80 (23.8%)] on all 4 drugs. 32/80 (40.0%) were in AF, remainder in sinus rhythm (SR). Mean baseline LVEF: 21.8 +/- 8.4. Mean LVEF continued to be ≤35% (paired echocardiograms available in 50.0% patients) inspite of GDMT. The QRS duration continued to prolong on follow-up. Patients in AF were statistically significantly older, were less often on all 4 GDMT drugs (particularly sodium glucose transporter 2 inhibitors - SGLT2i’s), and were less likely to survive than those in SR. No difference in comorbid conditions or QRS prolongation on follow-up were seen between patients with AF versus SR. There was trend towards a larger increase in mean LVEF in patients with SR than AF. Conclusions In our experience, patients with HFrEF and LBBB continue to have a high mortality (45.0% at ~ 3 years) inspite of GDMT. AF is seen in a high percentage of patients (40.0%) in this cohort, worsening the prognosis further, with mortality nearly 3 times higher than those in SR. Aggressive management of patients with HFrEF and LBBB with, where indicated, early cardiac resynchronisation therapy (CRT) and more so, of those with AF (with +/- atrioventricular node ablation or left atrial ablation) should be considered at an early stage after diagnosis.Table

Conduction-System pacing Italian Network Group (C-SING): insights from a Nationwide Multicenter Observational Study

Abstract Background/Introduction Conduction system pacing (CSP), encompassing His bundle pacing (HBP) and left bundle branch area pacing (LBBAP), has gained prominence in treating bradycardia and heart failure in recent years. Despite its increasing utilization, data on real-world adoption of CSP are limited. Purpose The C-SING study aimed at assessing patient characteristics, implant success, procedural details, and safety of CSP when performed in routine clinical practice. Methods Periprocedural data from 27 experienced CSP centers across Italy were collected on patients undergoing CSP implantation for various indications between January 2021 and January 2024. Results The study comprised 1,317 patients (median age 78 years [interquartile range, 71-83], male 66.2%). Leading indications included atrioventricular (AV) block (40.8%), sinus node dysfunction (12.1%), atrial fibrillation with bradycardia (9.7%), AV node ablation (9.5%), and heart failure (12.5%). Pacemakers were implanted in 77.3% of patients, cardiac resynchronization devices in 21.7%, and implantable cardioverter-defibrillators in 1.0%. Stylet-driven and lumenless CSP leads were utilized in 64.7% and 35.3% of procedures, respectively. Final 12-lead ECG assessment revealed LBBAP capture in 88.7% patients, HBP in 8.4% (selective 4.2%, non-selective 4.2%), and no CSP capture in 3.0%, resulting in a 97.0% CSP lead implantation success rate. In patients with LBBAP, predominant capture types were left bundle branch pacing (19.6%), left posterior fascicular pacing (19.2%), and left septal fascicular pacing (14.8%). Comparing HBP to LBBAP, the latter showed shorter procedural time (60 minutes [45-80] vs. 70 minutes [60-95], p=0.003), but similar fluoroscopy time (6.0 minutes [3.3-10.8] vs. 6.1 minutes [4-10], p=0.735). Paced QRS duration was longer in LBBAP (118 ms [105-130]) compared to HBP (110 ms [101-122], p&amp;lt;0.001). LBBAP showed lower capture thresholds (0.6 V [0.5-0.9] @0.4 ms vs. 0.8 V [0.5-1.5] @1.0 ms, p&amp;lt;0.001) and higher R-wave sensing (10.7 mV [8-16] vs. 4.5 mV [2.4-9.9], p&amp;lt;0.001). The rate of periprocedural complications was higher in patients with LBBAP than HBP (7.3% vs. 1.8%, p=0.03), with the most frequent events being intraprocedural perforation into the left ventricular cavity during lead screwing (2.6%) and CSP lead dislodgment before hospital discharge (1.4%). These occurrences necessitated lead repositioning without additional complications. Conclusion CSP demonstrated feasibility as a primary pacing strategy for various indications in a real-world, multicenter setting. LBBAP, more frequently used than HBP, exhibited shorter procedural time and superior acute electrical parameters. LBBAP revealed a higher rate of minor procedural complications than HBP. Further investigations, supported by additional long-term outcome data, are essential to comprehensively assess CSP performance.