Bipolar ablation of refractory ventricular arrhythmias using a novel dedicated adapter. A multicenter study

Background

Bipolar ablation (BA) recently emerged as an alternative for treatment of ventricular tachycardia (VT) and premature ventricular contractions (PVC) refractory to a classic unipolar ablation (UA). Data on the use of available BA systems is lacking.

Purpose

To determine feasibility, safety and efficacy of a novel BA adapter in consecutive patients with refractory VT/PVC undergoing repeat ablations.

Methods

The study group consisted of consecutive patients with VT/PVC after failure of at least one standard UA who underwent redo procedures performed with a support of BA at six European centers. A second ablation catheter was connected in the position of a return electrode using a novel BA adapter.

Results

Between March 2021 and March 2022 a total number of 19 patients after failed ablation attempts underwent redo procedure using a novel BA adapter (17 males, age 61±11, number of prior ablation attempts 2,5±1,6; range 1–7). The main indication for redo ablation was recurrence of frequent PVC (n=10), VT (n=8) or electrical storm (n=1). Fifteen patients underwent combined UA+BA procedure during redo ablation, whereas 4 remaining patients underwent BA only. Two patients required epicardial access. Mean procedural time was 157±77 minutes. The mean BA time was 367±245s (power 32±9W) and mean UA time was 349±290s (power 43±6W). Apart from 1 anticipated AV block there were no major complications. Minor complications included char formation at 8mm tip electrode and steam pop without sequalae in one VT patient. BA+UA led to acute elimination of clinical PVC/VT in 18 patients. In the remaining 1 patient no effect on clinical VT during UA+BA was observed. The follow up lasted 4±3 months. Six (75%) VT patients remained arrhythmia-free and significant PVC burden reduction was achieved in nine (90%) PVC patients during follow-up. One patient treated for electrical storm experienced a single VT episode after 11 months. One patient after initially failed UA+BA underwent successful bipolar reablation after 2 months.

Conclusions

Bipolar ablation of refractory ventricular arrhythmias using a novel dedicated adapter is feasible, seems safe and effective. These encouraging preliminary results need to be confirmed in properly designed prospective trials.

Funding Acknowledgement

Type of funding sources: None.

Reversed U-curve mapping and ablation of the left pulmonic cusp for treatment of the left ventricular summit arrhythmias

Funding Acknowledgements

Type of funding sources: None.

Introduction

Catheter ablation (CA) of the left ventricular summit (LVS) arrhythmias can be challenging. Close proximity of the left pulmonic cusp (LPC) offers a unique opportunity for targeting the LVS region. Whether LPC can serve as a vantage point for mapping and CA of LVS premature ventricular contractions (PVC) and ventricular tachycardia (VT) has not yet been systematically evaluated.

Methods

This is a retrospective analysis of consecutive patients who underwent CA of LVS PVC/VT and concomitant mapping and/or ablation within the LPC using reversed U-curve technique. PVC/VT activation precocity was determined and CA (unipolar, sequential unipolar and/or bipolar ablation) was performed involving LPC when necessary.

Results

A total number of 18 patients (age 59±15 years, 10 females) were included in this study. LPC mapping using reversed U-curve was successful in 17 (94%) patients. An earliest PVC/VT activation was recorded in LPC in 7 (39%). No early activation in the LPC was found in 5 (28%) patients. Selective LPC ablation (24W, 206s) led to acute suppression with late VT recurrence in one patient, whereas LPC served as an additional ablation target for sequential CA (37±4W, 416±252s) in 11 (61%) patients. 6 (33%) patients required combined sequential unipolar and bipolar CA (37±8W, 690±248s) between LPC and adjacent LVOT and this approach led to PVC/VT elimination in 5 patients. There were no procedure-related complications. During follow up 4 (22%) patients required redo ablation. Ultimately clinical success was achieved in 14 (78%) patients.

Conclusions

LPC mapping of LVS PVC/VT using reversed U-curve is safe and can be helpful for determination of LVS arrhythmia site of origin. While LPC ablation alone is rarely successful in eliminating LVS arrhythmias, it can serve as an anatomical vantage point for additional ablation of LVS PVC/VT as a part of sequential unipolar or bipolar CA.

Right anterior ganglionated plexus ablation for the treatment of vagally-mediated atrial fibrillation

Funding Acknowledgements

Type of funding sources: None.

Background

Pulmonary vein isolation (PVI) is a cornerstone for catheter ablation of atrial fibrillation (AF), however, exact mechanisms of PVI efficacy remain debatable. PVI is an invasive left-atrial procedure which may be associated with complications. It has been postulated that in patients with increased vagal tone AF can be treated by attenuation of parasympathetic drive to the heart using cardioneuroablation (CNA) by means of radiofrequency (RF) ablation of the ganglionated plexi, however, data in literature are lacking.

Objectives

To examine the mid-term efficacy of RF-CNA targeting the right anterior ganglionated plexus (RAGP) in the management of AF using right-atrial (RA) approach only.

Methods

We included consecutive 12 male patients (age 55±11) with vagally-mediated AF (decelaration capacity (DC) >7 ms, mean 11,2±3,7ms) who underwent RF-CNA of RAGP. RAGP was targeted anatomically at the septal area below superior vena cava (SVC) from RA only. The aim was to achieve ≥30% heart rate acceleration (HRA). The follow up consisted of regular visits combined with ECG conducted every 3 months and 24h or 7-day Holter ECG.

Results

The RF time was 126±61 sec, power - 34±7W and procedure time - 44±18 min. The ≥30% HRA was achieved in 7 (58%) patients (pre-RF vs post-RF: 58±7 bpm vs 80±9 bpm, p=0,0000013). There were no complications during procedures. The follow up lasted 11±6 months. All patients reported significant symptom improvement post-CNA. AF-free survival was significantly higher in patients with ≥30% HRA during RF-CNA (≥30% HRA vs <30% HRA, 60% vs 14%, log rank p=0,0203) Conclusions: Right atrial RF-CNA of RAGP can be effective in patients with vagally-mediated AF. Larger prospective studies are needed to confirm these preliminary findings.

Catheter ablation of atrial fibrillation without pulmonary vein isolation

Funding Acknowledgements

Type of funding sources: None.

Background

Pulmonary vein isolation (PVI) is a cornerstone for catheter ablation (CA) of atrial fibrillation (AF), however, long-term efficacy of PVI is frequently below expectations. PVI is invasive, expensive and may be associated with devastating complications. It has been postulated that vagally-mediated AF can be treated by attenuation of parasympathetic drive to the heart using cardioneuroablation by means of radiofrequency CA (RFCA) of the right anterior ganglionated plexus (RAGP), however, data in literature and guidelines are lacking.

Purpose

To examine the efficacy of RFCA targeting RAGP without PVI in management of vagal AF.

Methods

We included consecutive 9 male patients with vagal AF who underwent RFCA of RAGP without PVI. RAGP was targeted anatomically from the right atrium (RA) at the postero-septal area below superior vena cava (SVC) and from the left atrium (LA) if needed. The aim was to achieve >30% increase in heart rate (HR) . The follow up consisted of regular visits and Holter ECG conducted every 3 months.

Results

A total number of 9 patients (age 52 ± 13) with vagally-mediated AF underwent RFCA of RAGP (mean RAGP RF time 147 ± 85, max power 34 ± 8W). The mean procedure time was 60 ± 29min. HR increase >30% was achieved in 8 (89%) patients (pre-RF vs post-RF: 58 ± 8bpm vs 87 ± 12bpm, p = 0.00002) . Transseptal  to reach RAGP also from the LA was needed in 2 (22%) patients. There were no major complications during the procedures. The follow up lasted 6 ± 2 months. Antiarrhythmic drugs were discontinued in 8 (89%) patients. There was 1 (11%) AF recurrence in the patient in whom targeted HR acceleration during RFCA was not achieved. B-blockers were administered in  6 (67%) patients due to increased HR and such treatment was well tolerated by all.

Conclusions

Catheter ablation of RAGP without performing PVI is feasible and can be effective in majority of patients with vagally-mediated AF. Increased HR after such cardioneuroablation can be well controlled using b-blockers and is usually associated with mild symptoms. The role of cardioneuroablation for treatment of vagally-mediated AF needs to be determined in prospective trials. Abstract Figure. Cardioneuroablation in vagal AF

Epitope Specific Antibodies and T Cell Receptors in the Immune Epitope Database

The Immune Epitope Database (IEDB) is a free public resource which catalogs experiments characterizing immune epitopes. To accommodate data from next generation repertoire sequencing experiments, we recently updated how we capture and query epitope specific antibodies and T cell receptors. Specifically, we are now storing partial receptor sequences sufficient to determine CDRs and VDJ gene usage which are commonly identified by repertoire sequencing. For previously captured full length receptor sequencing data, we have calculated the corresponding CDR sequences and gene usage information using IMGT numbering and VDJ gene nomenclature format. To integrate information from receptors defined at different levels of resolution, we grouped receptors based on their host species, receptor type and CDR3 sequence. As of August 2018, we have cataloged sequence information for more than 22,510 receptors in 18,292 receptor groups, shown to bind to more than 2,241 distinct epitopes. These data are accessible as full exports and through a new dedicated query interface. The later combines the new ability to search by receptor characteristics with previously existing capability to search by epitope characteristics such as the infectious agent the epitope is derived from, or the kind of immune response involved in its recognition. We expect that this comprehensive capture of epitope specific immune receptor information will provide new insights into receptor-epitope interactions, and facilitate the development of novel tools that help in the analysis of receptor repertoire data.

The immune epitope database 2.0

The Immune Epitope Database (IEDB, www.iedb.org) provides a catalog of experimentally characterized B and T cell epitopes, as well as data on Major Histocompatibility Complex (MHC) binding and MHC ligand elution experiments. The database represents the molecular structures recognized by adaptive immune receptors and the experimental contexts in which these molecules were determined to be immune epitopes. Epitopes recognized in humans, nonhuman primates, rodents, pigs, cats and all other tested species are included. Both positive and negative experimental results are captured. Over the course of 4 years, the data from 180 978 experiments were curated manually from the literature, which covers ∼99% of all publicly available information on peptide epitopes mapped in infectious agents (excluding HIV) and 93% of those mapped in allergens. In addition, data that would otherwise be unavailable to the public from 129 186 experiments were submitted directly by investigators. The curation of epitopes related to autoimmunity is expected to be completed by the end of 2010. The database can be queried by epitope structure, source organism, MHC restriction, assay type or host organism, among other criteria. The database structure, as well as its querying, browsing and reporting interfaces, was completely redesigned for the IEDB 2.0 release, which became publicly available in early 2009.

Relevance of the diversity among members of the Trypanosoma cruzi trans-sialidase family analyzed with camelids single-domain antibodies

The sialic acid present in the protective surface mucin coat of Trypanosoma cruzi is added by a membrane anchored trans-sialidase (TcTS), a modified sialidase that is expressed from a large gene family. In this work, we analyzed single domain camelid antibodies produced against trans-sialidase. Llamas were immunized with a recombinant trans-sialidase and inhibitory single-domain antibody fragments were obtained by phage display selection, taking advantage of a screening strategy using an inhibition test instead of the classic binding assay. Four single domain antibodies displaying strong trans-sialidase inhibition activity against the recombinant enzyme were identified. They share the same complementarity-determining region 3 length (17 residues) and have very similar sequences. This result indicates that they likely derived from a unique clone. Probably there is only one structural solution for tight binding inhibitory antibodies against the TcTS used for immunization. To our surprise, this single domain antibody that inhibits the recombinant TcTS, failed to inhibit the enzymatic activity present in parasite extracts. Analysis of individual recombinant trans-sialidases showed that enzymes expressed from different genes were inhibited to different extents (from 8 to 98%) by the llama antibodies. Amino acid changes at key positions are likely to be responsible for the differences in inhibition found among the recombinant enzymes. These results suggest that the presence of a large and diverse trans-sialidase family might be required to prevent the inhibitory response against this essential enzyme and might thus constitute a novel strategy of T. cruzi to evade the host immune system.

Curation of complex, context-dependent immunological data

Background

The Immune Epitope Database and Analysis Resource (IEDB) is dedicated to capturing, housing and analyzing complex immune epitope related data .

Description

To identify and extract relevant data from the scientific literature in an efficient and accurate manner, novel processes were developed for manual and semi-automated annotation.

Conclusion

Formalized curation strategies enable the processing of a large volume of context-dependent data, which are now available to the scientific community in an accessible and transparent format. The experiences described herein are applicable to other databases housing complex biological data and requiring a high level of curation expertise.