Focal Arrhythmias Research Articles

Electro‐anatomically confirmed sites of origin of ventricular tachycardia and premature ventricular contractions and occurrence of R wave in lead aVR: A proof of concept study

AbstractBackgroundThe R wave in lead aVR, during the wide QRS complex tachycardia, is commonly observed in a ventricular tachycardia (VT) arising from certain locations in the ventricles.ObjectivesThis was a retrospective and a proof of concept study to correlate the sites of origin of VT and premature ventricular contractions (PVCs) with the occurrence of R wave in lead aVR.MethodsPatients with VT or high density of PVCs were included. Surface and intracardiac electrograms were recorded during the arrhythmia. VTs and PVCs arising from the inferior, inferolateral, or apical region of the ventricles were grouped into Zone 2. Those arising from the other areas of the ventricles were grouped into Zone 1.ResultsSixty‐four patients were included in the study. The mean age was 57 years. There were 47 males. Among 64 patients with VT or PVCs, 28 patients had an R wave in aVR (43.7%), In 26 of 28 patients with an R wave in aVR, the site of origin of the arrhythmia was in Zone 2. The R wave in aVR was absent in 36 patients, 34 of whom had the origin of arrhythmia focus in Zone 1. The presence of an R wave in aVR correctly identified Zone 2 as a site of origin of the arrhythmia with high sensitivity (93%) and specificity (94%).ConclusionsThe presence of an R wave in aVR during wide QRS complex tachycardia or PVC is a valuable observation for identifying the site of origin of the arrhythmia and hence in distinguishing supraventricular tachycardia with aberrancy from VT.

Atrial pace mapping using intracardiac pattern matching: feasibility and accuracy

Abstract Introduction Pace mapping of atrial arrhythmia is a method to localize the origin of usually focal arrhythmias that are unstable or not persisting during EP-study and, therefore not eligible for LAT-Mapping. The technique applies pattern matching of p-waves from surface-electrocardiogram (sEKG) as well as intracardiac signals during atrial tachycardia and pacing from the site of suspected origin. The CARTO® 3 system Version 7.2 applies an automated algorithm for intracardiac pace mapping (ICPM) using the unipolar signal of the reference electrode, usually located in the coronary sinus. Methods We examined 12 consecutive patients undergoing RF pulmonary vein isolation (PVI). We performed local pacing at the anterior and posterior wall of the left atrium (LA) and the posterior and lateral wall of the right atrium (RA). The first pacing point was defined as the reference pacing site (RPS). The ICPM algorithm was applied to calculate the similarity of the IC pattern of the RPS to the IC pattern across various distances. The maps, including mesh, point locations and IC pattern similarity of each point, were exported for further analysis in the Python environment. The areas were calculated for the 5% similarity strata. Results The study assessed areas with a 95% or higher pattern similarity in different atrial regions, revealing notable differences in pattern similarity. The median area of pattern similarity was 1.48 cm² (IQR: 0.76 - 2.01 cm²) in the LA posterior, 0.62 cm² (IQR: 0.15 - 1.06 cm²) in the LA anterior, 0.60 cm² (IQR: 0.38 - 1.19 cm²) in the RA posterior, and 5.68 cm² (IQR: 2.89 - 11.1 cm²) in the RA lateral wall. Significant differences were found between the posterior and anterior walls of the LA and the RA lateral wall, as well as between the RA posterior and RA lateral wall, indicating variability in intracardiac pattern matching accuracy. Patterns below 2 cm² are acceptable for catheter ablation. An outlier was noted in the RA posterior region. Conclusion The intracardiac pattern matching for atrial arrhythmias employing the CARTO-ICPM algorithm is feasible with acceptable accuracy except for the lateral regions of the right atrium. This might be explained by the larger distance to the referent catheter in the coronary sinus and the preferred conduction direction in the crista terminalis. Enhancing localization accuracy may necessitate the adjunctive use of surface ECG-pace mapping or the deployment of an additional multipolar intracardiac reference catheter in the lateral RA.A: IC Pattern, B: Box plots similarity

'Trapped re-entry' as source of acute focal atrial arrhythmias.

Diseased atria are characterized by functional and structural heterogeneities, adding to abnormal impulse generation and propagation. These heterogeneities are thought to lie at the origin of fractionated electrograms recorded during sinus rhythm (SR) in atrial fibrillation (AF) patients and are assumed to be involved in the onset and perpetuation (e.g. by re-entry) of this disorder. The underlying mechanisms, however, remain incompletely understood. Here, we tested whether regions of dense fibrosis could create an electrically isolated conduction pathway (EICP) in which re-entry could be established via ectopy and local block to become 'trapped'. We also investigated whether this could generate local fractionated electrograms and whether the re-entrant wave could 'escape' and cause a global tachyarrhythmia due to dynamic changes at a connecting isthmus. To precisely control and explore the geometrical properties of EICPs, we used light-gated depolarizing ion channels and patterned illumination for creating specific non-conducting regions in silico and in vitro. Insight from these studies was used for complementary investigations in virtual human atria with localized fibrosis. We demonstrated that a re-entrant tachyarrhythmia can exist locally within an EICP with SR prevailing in the surrounding tissue and identified conditions under which re-entry could escape from the EICP, thereby converting a local latent arrhythmic source into an active driver with global impact on the heart. In a realistic three-dimensional model of human atria, unipolar epicardial pseudo-electrograms showed fractionation at the site of 'trapped re-entry' in coexistence with regular SR electrograms elsewhere in the atria. Upon escape of the re-entrant wave, acute arrhythmia onset was observed. Trapped re-entry as a latent source of arrhythmogenesis can explain the sudden onset of focal arrhythmias, which are able to transgress into AF. Our study might help to improve the effectiveness of ablation of aberrant cardiac electrical signals in clinical practice.

Delineating QRS detector parameter based ECG-Beat classification

Abstract The electrocardiogram is a very valuable clinical tool which allows to retrieve information about the presence and location of arrhythmic foci as well as ischemic and scar tissue and disorder’s of the dedicated cardiac conduction system. In the presented study timing parameters computed by a delineating beat detector for identifying the P-Wave, QRS - complex and T-Wave are used to classify the individual beats. From a set of total 419 feature generated from these parameters 64 are used to train LDA classifier for discriminating 3 classes (Normal, Artifact, Arrhythmic) and 5 Classes (Normal, Artifact, Atrial and ventricular premature contractions and bundle branch blocks). Further it is investigated how the imbalance between normal beats and arrhythmic beats as well as the beats missed by the beat detector affect the classification results. In the case of 5 classes accuracies of 97.52 % in the imbalanced case and 96.38 r for the balanced data were obtained. For 3 classes accuracies of 97.76 % and 95.18 % were achieved. Considering in addition the beats missed by the detector the accuracies dropped to 96.68 %, and 95.54 % for 5 classes and 95.54 % and 96.92 % for 3 classes. These values are within the ranges for linear classifier reported in literature. This is quite promising for implementing a real-time classifier which exploits the parameters and values computed by the beat detector.

Is it possible to determine arrhythmogenic focus localization of ventricular ectopic complexes detected by ambulatory electrocardiogram monitoring?

Aim. To study the possibility of using algorithms (developed using resting ECG as a mapping tool) for localization arrhythmogenic focus of ventricular arrhythmias (VA) detected by ambulatory 12-lead ECG monitoring (AECGM) with the identification of predominant origins of VA.Material and methods. The study included 54 patients aged 45 to 80 years with high frequency VA evaluated during AECGM: 29 — with coronary artery disease (CAD), 25 — w ithout CAD, who underwent radiofrequency ablation (RFA). The study included patients with effective ablation based on AECGM performed 6 months after RFA. Verification localization of VA exit site was carried out during endocardial mapping and AECGM («Cardiotechnika-04, СT-07», «Incart»). The following algorithms were considered in the study: D. Kuchar; O. Segal; J. Miller; A. S. Revishvili, R. Y. Snegur (2006, 2007); A. B. Weinstein; M. V. Noskova. It was assessed the percentage of matches applying the comparative analysis of results of the invasive and non-invasive methods, and it was revealed the predominant localization of VA.Results. The following algorithms had the highest percentage of matches: D. Kuchar in patients with CAD; A. S. Revishvili, R. Y. Snegur (2007) and M. V. Noskova in patients without CAD. The predominant origins of VA in patients without CAD were the left sinus of Valsalva, right ventricular outflow tract, and in patients with CAD — b asal inferior left ventricular wall, right ventricular outflow tract.Conclusion. Algorithms for arrhythmogenic focus localization of VA, developed using resting ECG, can be used to determine the origin of VA detecting by 12-lead AECGM, taking into account patient’s medical history (CAD, myocardial infarction).

Non-invasive electrocardiographic mapping using an endo-epicardial system based on extracellular potentials shows better accuracy for atrial arrhythmias than ventricular arrhythmias

Abstract Funding Acknowledgements Type of funding sources: Private hospital(s). Main funding source(s): Learning Health Background and aim Electrocardiographic imaging (ECGI) is capable of performing an activation map with a single beat. The endo-epicardial system based on extracellular potentials allows for the reconstruction of endo-epicardial potentials both in the ventricles and the atria. The aim of this study was to compare the accuracy of the system to predict the site of origin (SOO) of ventricular focal arrhythmias (VAs) versus atrial focal arrhythmias (AAs). Methods We studied 55 consecutive patients referred for ablation of VAs or AAs that had an ECGI performed before ablation. Ablations were performed with remote magnetic navigation or manually. The localization of the VAs and AAs based on the ECGI and invasive electroanatomic mapping was performed using a segmental model of the atria and the ventricles. A perfect match (PM) was defined as a predicted location within the same anatomic segment, whereas a near match (NM) as a predicted location within the same segment or a contiguous one. The number of leads used for ECGI mapping, the agreement between the ECGI and the invasive map, and the success of the procedure were evaluated. Results Ablation was performed in 49 patients. We mapped 54 arrhythmias, 37 VAs (37 patients) and 17 AAs (12 patients). The results according to the atrial or ventricular origin of the arrhythmia are depicted in the table. Patients with AAs were older, no other differences were significant. The ECGI system correctly identified the SOO of both VAs and AAs in the same segment or a contiguous one in 100% of AAs and 97% of VAs, p=1.000. However, the percentage of a PM (Figure) was higher for AAs than for VAs (100% vs 76%, p=0.044). Conclusions The endo-epicardial ECGI correctly identified the origin of both ventricular and atrial arrhythmias. However, the accuracy was higher for the latter.

Fiber Organization Has Little Effect on Electrical Activation Patterns During Focal Arrhythmias in the Left Atrium.

Over the past two decades there has been a steady trend towards the development of realistic models of cardiac conduction with increasing levels of detail. However, making models more realistic complicates their personalization and use in clinical practice due to limited availability of tissue and cellular scale data. One such limitation is obtaining information about myocardial fiber organization in the clinical setting. In this study, we investigated a chimeric model of the left atrium utilizing clinically derived patient-specific atrial geometry and a realistic, yet foreign for a given patient fiber organization. We discovered that even significant variability of fiber organization had a relatively small effect on the spatio-temporal activation pattern during regular pacing. For a given pacing site, the activation maps were very similar across all fiber organizations tested.

PO-02-226 NON-INVASIVE ELECTROCARDIOGRAPHIC IMAGING FOR THE CHARACTERIZATION OF COMPLEX ATRIAL TACHYARRHYTHMIAS

Non-invasive characterization of complex atrial tachyarrhythmias, regarding atrial flutter (AFL) and focal atrial tachycardia (AT) is challenging. Conventional electrocardiogram (ECG) faces several limitations. Planning a preprocedural strategy before AFL-AT catheter ablation (CA) is needed. To evaluate the diagnostic capacity of a novel non-invasive electrocardiographic imaging (ECGI) system that does not require previous CT or MRI cardiac imaging. 42 patients (27 males, CHA2DS2-VASc score 2±1, LVEF 54.5 ± 11.0 %, and LA area 31.3 ± 7.0 cm2) undergoing CA for AT-AFL were prospectively included in the study. Before the procedure, the ECGI system estimated the patient atria geometry using a 3D torso reconstruction and an artificial intelligence-based algorithm. Multiple electrocardiograms were recorded using a 64-electrodes vest during the CA procedure. The different diagnostic capacities of the periprocedural ECG and ECGI were assessed compared with endocavitary electroanatomical mapping (EAM) regarding three endpoints: (1) the involved atrial cavity, (2) the mechanism (focal or macro-reentry), and (3) the ablation target site defined as the area where the earliest activation was located for focal arrhythmias, and the precise anatomical pathway for macro re-entrant tachyarrhythmias. Regarding the ECG, endpoints were assessed based on validated algorithms by 2 different observers blinded from the diagnosis. 48 atrial tachyarrhythmias were evaluated and its characterization using this novel ECGI system was possible in 94% of the cases: directly for 36 arrhythmias and after decreasing ventricular response using vagal maneuvers for 9. ECGI obtained global accuracy to identify the involved atrial cavity of 92%, the mechanism of 90%, and the ablation target of 83% (Table). In challenging cases, such as in patients with a history of CA for atrial fibrillation and in patients without a final diagnosis of typical counterclockwise AFL, the accuracy of ECGI was consistent compared to the whole study population (Table). The ECGI diagnostic capacity significantly outclassed the ECG regarding the identification of the involved cavity (p<0.001), the mechanism (p<0.05), and the ablation target (p<0.001). ECGI could have prevented all unnecessary transseptal punctures (n=7), representing 28% of the overall punctures. This novel non-invasive ECGI system accurately characterizes complex atrial tachyarrhythmias (Figure) without needing previous CT or MRI cardiac imaging.

Pacing maneuvers from the aortic cusps: A useful technique during ablation of focal arrhythmias arising from the aortic root.

The ablation of arrhythmias arising near the His-bundle region in the non-coronary aortic cusp (NCAC) is challenging. Among the aortic sinuses of Valsalva, the NCAC is located between the right atrium and the left atrium. For this reason, pacing from the NCAC should result in atrial capture while pacing from the right and left coronary cusps (LCC) may result in ventricular capture. The objective of this study is to prove that atrial capture during pacing from the sinuses of Valsalva may be used to confirm a correct position in the non-coronary cusp. A total of 30 patients with structurally normal heart undergoing left sided ablation procedures, underwent electrophysiological study of the aortic cusps. Each of the aortic valve cusps was paced with increasing outputs and analyzed offline to determine their unique electrocardiographic characteristics. In the NCAC, we obtained an atrial capture in 29 out of 30 patients (96.6%). The atrial capture was highly specific for a position in the NCAC (p<.001). The median output required to capture from the cusp was 10mA (range 5-25mA) at a pulse width of 2ms. In the right coronary cusp (RCC) and LCC, we obtained ventricular capture in all patients (100%). The median output required to capture from the cusp was 10mA (range 10-25mA) in RCC and 25mA (range 10-25mA) in LCC at a pulse width of 2ms. Atrial capture during a pacemapping from the aortic cusps can be considered proof of a correct position in NCAC.

Identification of Atrial Arrhythmia Foci Using ECG Signal and the Effect of Autonomic Nervous System

Identification of Atrial Arrhythmia Foci Using ECG Signal and the Effect of Autonomic Nervous System

Critical Link between Calcium Regional Heterogeneity and Atrial Fibrillation Susceptibility in Sheep Left Atria.

Atrial fibrillation is the most sustained form of arrhythmia in the human population that leads to important electrophysiological and structural cardiac remodeling as it progresses into a chronic form. Calcium is an established key player of cellular electrophysiology in the heart, yet to date, there is no information that maps calcium signaling across the left atrium. The aim of this study is to determine whether calcium signaling is homogenous throughout the different regions of the left atrium. This work tests the hypothesis that differences across the healthy left atrium contribute to a unique, region-dependent calcium cycling and participates in the pro-arrhythmic activity during atrial fibrillation. An animal model relevant to human cardiac function (the sheep) was used to characterize both the electrical activity and the calcium signaling of three distinct left atrium regions (appendage, free wall and pulmonary veins) in control conditions and after acetylcholine perfusion (5 μM) to induce acute atrial fibrillation. High-resolution dual calcium-voltage optical mapping on the left atria of sheep was performed to explore the spatiotemporal dynamics of calcium signaling in relation to electrophysiological properties. Action potential duration (at 80% repolarization) was not significantly different in the three regions of interest for the three pacing sites. In contrast, the time to 50% calcium transient decay was significantly different depending on the region paced and recorded. Acetylcholine perfusion and burst pacing-induced atrial fibrillation when pulmonary veins and appendage regions were paced but not when the free wall region was. Dantrolene (a ryanodine receptor blocker) did not reduce atrial fibrillation susceptibility. These data provide the first evidence of heterogenous calcium signaling across the healthy left atrium. Such basal regional differences may be exacerbated during the progression of atrial fibrillation and thus play a crucial role in focal arrhythmia initiation without ryanodine receptor gating modification.

Cardiac Alternans: From Bedside to Bench and Back

Cardiac alternans arises from dynamical instabilities in the electrical and calcium cycling systems of the heart, and often precedes ventricular arrhythmias and sudden cardiac death. In this review, we integrate clinical observations with theory and experiment to paint a holistic portrait of cardiac alternans: the underlying mechanisms, arrhythmic manifestations and electrocardiographic signatures. We first summarize the cellular and tissue mechanisms of alternans that have been demonstrated both theoretically and experimentally, including 3 voltage-driven and 2 calcium-driven alternans mechanisms. Based on experimental and simulation results, we describe their relevance to mechanisms of arrhythmogenesis under different disease conditions, and their link to electrocardiographic characteristics of alternans observed in patients. Our major conclusion is that alternans is not only a predictor, but also a causal mechanism of potentially lethal ventricular and atrial arrhythmias across the full spectrum of arrhythmia mechanisms that culminate in functional reentry, although less important for anatomic reentry and focal arrhythmias.

Limitations of Unipolar Signals in Guiding Successful Outflow Tract Premature Ventricular Contraction Ablation.

Unipolar electrograms (UniEGMs) are commonly used to annotate earliest local activation of focal arrhythmias. However, their utility in guiding premature ventricular contractions (PVCs) ablation may be limited when the PVC source is less superficial. The authors sought to compare bipolar electrograms (BiEGMs) vs UniEGMs in guiding successful ablation of right ventricular outflow tract (RVOT) vs intramural outflow tract (OT) PVCs. The authors hypothesized that: 1) earliest bipolar local activation time (LATBi) would better guide mapping and ablation, vs UniEGM dV/dt (LATUni) or QS morphology; and 2) LAT differences using bipolar vs unipolar EGMs (ΔLATBi-Uni) would be greater for intramural OT than RVOT PVCs. Consecutive patients undergoing successful PVC ablation 2017 to2020 requiring only RVOT or RVOT+left ventricular OT (RVOT+LVOT) ablation were retrospectively analyzed. BiEGMs and UniEGMs at successful ablation sites were compared. Of 70 patients, 50 required RVOT-only, and 20 required RVOT+LVOT ablation for acute and long-term PVC suppression. Mean ΔLATBi-Uni was lower for RVOT vs RVOT+LVOT groups (9.3 ± 6.4ms vs 17.4 ± 9.9ms; P< 0.01). QS UniEGM was seen in 78% of RVOT, compared with 53% of RVOT+LVOT patients (P< 0.016). RVOT+LVOT sites most frequently included the posteroseptal RVOT and adjacent LVOT (73%), and 43% lacked a QS unipolar EGM. ΔLATBi-Uni≥15ms best distinguished sites in which RVOT-only vs RVOT+LVOT ablation achieved acute PVC suppression (area under the curve: 0.77). Earliest BiEGM activation guides successful ablation of OT PVCs better than UniEGM-guided analysis, especially when an intramural PVC source is present.

Evaluation of the effectiveness of interventional treatment of ventricular arrhythmias of rare localizations using non-invasive mapping

Background. Atypical localization of the focus of ventricular arrhythmias is a rather difficult group for invasive mapping and subsequent radiofrequency ablation. Invasive electroanatomical mapping, multipolar electrophysiological electrodes in combination with electrophysiological study for searching an early zone of arrhythmia focus, and substrate mapping, are aimed to identifying critical areas of the arrhythmia contour. However, there are still situations in which arrhythmia cannot be eliminated, despite the use of these systems. The method of superficial non-invasive mapping of the heart seems to be relevant, which makes it possible to estimate the volume of surgery and select the necessary technology to eliminate arrhythmias.Aim. To compare the effectiveness of interventional treatment of patients with ventricular arrhythmias of atypical localization with and without the use of superficial non-invasive mapping.Methods. The study included 40 patients with ventricular arrhythmias of rare localization. The patients were divided into two groups. Group I included 21 patients who underwent non-invasive superficial and invasive electrophysiological cardiac mapping. Group II included 19 patients who underwent invasive electrophysiological cardiac mapping.Results. Over a follow-up period of 12 months, the freedom from arrhythmia in group I was 76%, in group II — 61%. The total operation time, duration and dose of fluoroscopy were less in group I compared to the group II.Conclusion. The study results demonstrated that the method of non-invasive surface mapping of the heart is highly effective in ventricular arrhythmias of atypical localization. The time of radiofrequency ablation, interventional intervention, fluoroscopy is lower with the use of superficial non-invasive mapping, compared with the control group. Received 13 July 2021. Revised 20 October 2021. Accepted 9 December 2021. Funding: This work is supported by a grant of the Russian Science Foundation (project No. 19-15-00406). Conflict of interest: The authors declare no conflict of interest. Contribution of the authorsConception and study design: E.A. Artyukhina, A.Sh. RevishviliData collection and analysis: E.A. Artyukhina, M.V. Yashkov, E.V. Dedukh, I.A. Taymasova, A.Sh. RevishviliStatistical analysis: M.V. YashkovDrafting the article: E.A. Artyukhina, M.V. YashkovCritical revision of the article: E.A. Artyukhina, M.V. Yashkov, A.Sh. RevishviliFinal approval of the version to be published: E.A. Artyukhina, M.V. Yashkov, E.V. Dedukh, I.A. Taymasova, A.Sh. Revishvili

On the Electrophysiology and Mapping of Intramural Arrhythmic Focus.

Conventional mapping of focal ventricular arrhythmias relies on unipolar electrogram characteristics and early local activation times. Deep intramural foci are common and associated with high recurrence rates following catheter-based radiofrequency ablation. We assessed the accuracy of unipolar morphological patterns and mapping surface indices to predict the site and depth of ventricular arrhythmogenic focal sources. An experimental beating-heart model used Langendorff-perfused, healthy swine hearts. A custom 56-pole electrode array catheter was positioned on the left ventricle. A plunge needle was placed perpendicular in the center of the grid to simulate arrhythmic foci at variable depths. Unipolar electrograms and local activation times were generated. Simulation models from 2 human hearts were also included with grids positioned simultaneously on the endocardium-epicardium from multiple left ventricular, septal, and outflow tract sites. A unipolar Q or QS complex lacks specificity for superficial arrhythmic foci, as this morphology pattern occupies a large surface area and is the predominant pattern as intramural depth increases without developing a R component. There is progressive displacement from the arrhythmic focus to the surface exit as intramural focus depth increases. A shorter total activation time over the overlying electrode array, larger surface area within initial 20 ms activation, and a dual surface breakout pattern all indicate a deep focus. Displacement from the focal intramural origin to the exit site on the mapping surface could lead to erroneous lesion delivery strategies. Traditional unipolar electrogram features lack specificity to predict the intramural arrhythmic source; however, novel endocardial-epicardial mapping surface indices can be used to determine the depth of arrhythmic foci.

Identification of novel pulmonary vein nodes as generators of ectopic arrhythmic foci for atrial fibrillation: an immunohistochemical proof.

The atrial muscle sleeve (AMS) of the pulmonary vein is the most common source of the arrhythmogenic triggers in atrial fibrillation (AF). Anatomical substrate generating these ectopic currents is still elusive. The present study was designed to study the AMS of pulmonary veins with an emphasis on the structural basis which might govern AF initiation and perpetuation. The study was conducted on a longitudinal tissue section of pulmonary vein, taken from 15 human cadaveric nondiseased hearts. Tissue was studied histologically using H&E and Gömöri trichrome stain. The pacemaker channels were identified by immunohistochemistry using monoclonal HCN4 and HCN1 antibodies. The AMS was identified in each pulmonary vein, located between the tunica adventitia and tunica media. A node-like arrangement of myocytes was seen within the AMS in 30% of veins. It had a compact zone limited by a fibrous capsule and contained much smaller, paler and interconnected myocytes. Outside the capsule, there was a zone of dispersed, singly placed myocytes separating the compact zone from the working myocytes of the AMS. HCN4 and HCN1 antibodies were expressed on the cell membrane of nodal myocytes, while the working myocytes demonstrated none to minimal staining. Pulmonary veins nodes are similar to the specialized cardiac conductive tissue in the histological arrangement of compact and transitional zones, cellular characteristics and the presence of pacemaker channels. They might be the anatomical basis of ectopic arrhythmogenic foci. To our knowledge, these nodes are being described for the first time in human.

Clinical and functional characteristics of children with ventricular arrhythmias depending on the ectopic focus localization

Aim. To determine the prevalence of ventricular arrhythmias (VA) among children with cardiac arrhythmias and to assess the clinical, functional, and electrophysiological characteristics of VA, depending on the localization of the ectopic focus.Methods. The study included 260 children, 153 (58,8%) boys, the mean age of patients was 13.4±3.1years. Based on clinical and anamnestic data, ECG, Holter monitoring, echocardiography, dosed exercise test, invasive electrophysiological study (EPS), radiofrequency ablation (RFA) a comparative assessment of the clinical and functional features of the most frequently diagnosed localizations of the ectopic focus in children with VA was carried out according to the data of invasive EPS, RFA.Results. According to invasive EPI, the most frequent localization of VA in children is the right ventricle outflow tract (RVOT) - 144 (55%), less often - the Valsalva sinuses - 52 (20%) and the RV free wall - 47 (18%). In most cases (255 children, 98%) there was a focal arrhythmia (trigger activity). The localization of ectopia in the RV free wall is characterized by the predominance of single ventricular premature beats (VPB) or in combination with a paired VPB (78,7%) and polymorphism of ventricular complexes (30%). The peculiarity of ventricular tachycardia in this localization is its stable character (17,0%) and low heart rate in volleys (idioventricular rhythm) (12,8%). When the focus was localized in the RVOT, as well as when it was localized in the RV free wall, single VPB or in combination with paired VPB prevailed (84,7%), but polymorphism of ventricular complexes was less often observed (10,4%). Differences in myocardial contractility at the sinus rhythm in right ventricular arrhythmias were revealed. Thus, the ejection fraction at the localization of the lesion in the RV free wall was significantly lower than in the RVOT (63.4±5.5% and 65.8±5.9%, respectively; p&lt;0.01). Hemodynamic significance is characteristic for RV arrhythmias (21.3% and 16.0% of patients) and was practically not observed at the left-sided localization of the arrhythmogenic focus (3.8%; p&lt;0.01). VA in patients without structural heart disease, regardless of the localization of the arrhythmic focus in children, is asymptomatic and is detected, in most cases, within the framework of clinical examination 206 patients, 79.2%. The prevalence of syncope in children with idiopathic VA is 15.8% (41 patients), and in most cases, they are of vaso-vagal origin. In most children (178, 70%), idiopathic VA is dependent on the level of parasympathetic influences on the heart, disappearing or significantly decreasing during exercise, which is revealed during the stress test confirming the high role of autonomic influences on the regulation of heterotopic rhythm in children with VA.Conclusion. VA is a common arrhythmia in children. Depending on the localization of the arrhythmogenic focus, characteristic features of the structure and density of the heart, as well as differences in the contractile function of the myocardium on the sinus rhythm and on the ectopic complex were revealed.

The Outcome of Ventricular Arrhythmias Associated With Mitral Valve Prolapse After Catheter Ablation: A Systematic Review and Meta-Analysis.

The presence of mitral valve prolapse (MVP) varies from asymptomatic to life-threatening arrhythmias. Catheter ablation (CA) is widely used to treat ventricular arrhythmias (VAs) associated with MVP. Despite having high procedural success, outcome data after CA is limited, especially in a long-term setting. Therefore, this systematic review and meta-analysis were performed. Literature searching was conducted in Pubmed, EuropePMC, Proquest, and Ebsco from inception to December 2020 using keywords: ventricular arrhythmia, premature ventricular complex, ventricular tachycardia, ventricular fibrillation, mitral valve prolapse, and catheter ablation. A total of 407 potential articles were retrieved for further review. The final review resulted in six articles for systematic review and meta-analysis. The study was registered in PROSPERO (CRD42020219144). The most common origin of VAs was papillary muscle. The acute success rate of CA in the MVP group varies between 66% and 94%. Follow-up studies reported a higher percentage of VAs recurrence after CA in the MVP group (22.22%) compared with the non-MVP group (11.38%). However, the difference is not significant (P-value = 0.16). Other studies reported a 12.5%-36% rate and 40% of repeat ablation in the medium term and the long term, respectively. Episodes of sudden cardiac death during exertion could still occur following CA in patients with MVP. Distinct origin of VAs was observed during repeated ablation procedures, which may explain arrhythmic substrate progression. Diffuse left ventricular fibrosis around papillary muscle rather than local fibrosis was observed among older patients. Furthermore, the presence of mitral annular disjunction (MAD) and Filamin C mutation might increase the risk of recurrent VAs. CAn has been done as the treatment of VAs associated with MVP. The acute success rate of CA varies between studies and the number of patients requiring repeat CA varied from 12.5% to 40%. Sudden cardiac death could still occur after CA. Older age during CA, genetic predisposition, deep arrhythmic foci, multifocal VAs origin, diffuse fibrosis, and the presence of MAD may contribute to the recurrence of VAs. Further studies, stratification, and evaluation are needed to prevent fatal outcomes in VA associated with MVP, even after CA.

Profibrillatory Structural and Functional Properties of the Atrial-Pulmonary Junction in the Absence of Remodeling.

Background: Sole pulmonary vein (PV) isolation by ablation therapy prevents atrial fibrillation (AF) in patients with short episodes of AF and without comorbidities. Since incomplete PV isolation can be curative, we tested the hypothesis that the PV in the absence of remodeling and comorbidities contains structural and functional properties that are proarrhythmic for AF initiation by reentry.Methods: We performed percutaneous transvenous in vivo endocardial electrophysiological studies and quantitative histological analysis of PV from healthy sheep.Results: The proximal PV contained more myocytes than the distal PV and a higher percentage of collagen and fat tissue relative to myocytes than the left atrium. Local fractionated electrograms occurred in both the distal and proximal PVs, but a large local activation (>0.75 mV) was more often present in the proximal PV than in the distal PV (86 vs. 50% of electrograms, respectively, p = 0.017). Atrial arrhythmias (run of premature atrial complexes) occurred more often following the premature stimulation in the proximal PV than in the distal PV (p = 0.004). The diastolic stimulation threshold was higher in the proximal PV than in the distal PV (0.7 [0.3] vs. 0.4 [0.2] mA, (median [interquartile range]), p = 0.004). The refractory period was shorter in the proximal PV than in the distal PV (170 [50] vs. 248 [52] ms, p < 0.001). A linear relation existed between the gradient in refractoriness (distal-proximal) and atrial arrhythmia inducibility in the proximal PV.Conclusion: The structural and functional properties of the native atrial-PV junction differ from those of the distal PV. Atrial arrhythmias in the absence of arrhythmia-induced remodeling are caused by reentry in the atrial-PV junction. Ablative treatment of early paroxysmal AF, rather than complete isolation of focal arrhythmia, may be limited to inhibition of reentry.

Abstract 14421: Limitations of Using Unipolar Signals to Guide Outflow Tract Premature Ventricular Contraction Ablation

Introduction: Unipolar electrogram (EGM) signals are universally used to annotate earliest activation and guide ablation (Abl) of focal arrhythmias. However, their utility in mapping PVCs is limited given 3-dimensionality of wave front propagation, especially when the source is intramural. Hypothesis: 1) earliest onset of bipolar activation would better guide mapping and Abl in these cases, versus maximum unipolar dV/dt or QS morphology; and 2) differences would be greater for intramural outflow tract (OT) PVCs versus those eliminated with RVOT Abl only. Methods: Consecutive patients undergoing successful RVOT or RVOT+LVOT PVC Abl at our center from 2017-2020 were retrospectively analyzed. Bipolar and Unipolar EGMs at successful Abl sites were compared. Results: Of 71 patients, 41 had only RVOT and 30 had RVOT + LVOT Abl. All had acute and long-term PVC suppression over mean 22.6 ± 11.6 month follow-up. Mean EGM difference was 7.6 ± 4.7 ms in the RVOT group vs 18.9 ± 10.5 ms in RVOT+LVOT group (p&lt;0.01). QS unipolar EGM was seen in 95% of RVOT patients, 88% of which were at the anterior RVOT/crux, vs 40% of RVOT+LVOT patients (p&lt;0.016). Activation was equally earliest from the posteroseptal RVOT and adjacent LVOT site in 73%, and most of these sites did not have a QS unipolar EGM (Figure). Conclusions: Bipolar EGM activation timing guided successful ablation of OT PVCs better than unipolar EGM analysis. A QS unipolar EGM did not reliably predict best ablation sites, especially for intramural PVCs.