Outcomes of very high-power short-duration ablation using 90w for pulmonary vein isolation in patients with atrial fibrillation: a real world observation study

Introduction

Pulmonary vein isolation (PVI) ablation is the established gold standard therapy for patients with symptomatic drug refractory atrial fibrillation (AF). Advancements in radiofrequency (RF) ablation, have led to the development of the novel contact force-sensing temperature-controlled very high-power short-duration (vHPSD) RF ablation. This setting delivers 90W for up to 4 seconds with a constant irrigation flow rate of 8ml/min. The aim of this study was to compare procedural outcomes and safety with conventional radiofrequency ablation.

Methods

An observational study was conducted with patients who underwent first time PVI ablation from 2019 to 2021. The cohort was divided in to: 1) vHPSD ablation – QMODE+ via QDOT MICRO catheter, 2) QMODE via QDOT MICRO catheter and 3) Conventional power-controlled RF (PCRF) ablation via THERMOCOOOL SMARRTOUCH SF (STSF) catheter. The QMODE+ vHPSD ablation group was prospectively recruited while the QMODE and PCRF group were retrospectively collected. Primary outcomes were procedural success, PVI duration, ablation duration and incidence of perioperative adverse events. Secondary outcomes were intraprocedural morphine and midazolam requirement.

Results

A total of 155 patients were included in the study with 80, 30 and 45 patients in the QMODE+ (vHPSD), QMODE and PCRF, respectively. PVI was successfully attained in all patients. QMODE+ (vHPSD) demonstrated significantly reduced time required for PVI and total energy application in comparison to the QMODE and PCRF groups (68.3±3.30 vs. 92.9±4.86 vs. 93.6±4.34 min, P<0.0001; 9.7±0.452 vs. 33.9±0.452 vs. 36.0±1.56 min, P<0.0001, respectively) (Figure 1). Intravenous morphine and midazolam requirement was lower in the QMODE+ (vHPSD) group compared to the QMODE and PCRF groups (10.3±0.45 vs. 16.1±0.935 vs. 15.3±0.686 mg, P<0.0001; 4.05±0.402 vs. 8.63±1.07 vs. 8.58±0.821 mg, P<0.0001) (Figure 2). QMODE+ (vHPSD) observed a non-significant reduction in fluoroscopy time compared to QMODE and PCRF. One cardiac tamponade were observed in both the QMODE+ (vHPSD) and QMODE group while the PCRF group exhibited an embolic stoke and two pericardial effusions that did not require drainage.

Conclusion

In this study, QMODE+ (vHPSD) demonstrated a comparable safety profile to the other treatment arms. Procedural duration and energy application time was substantially reduced while a non-significant reduction was observed for fluoroscopy time for QMODE+. Furthermore, sedation requirement was reduced and thus potentially conveyed greater patient tolerability of the procedure when conducted with QMODE+.

Notwithstanding the limitations of observational study design, these preliminary findings are promising with respect to periprocedural outcomes and safety of QMODE+. Longer term outcomes with respect to maintenance of sinus rhythm and symptomatic burden will be essential to assessing the overall efficacy of this novel technology.

Funding Acknowledgement

Type of funding sources: None.

Atrial fibrillation virtual ward: reshaping the future of AF care

Background

Atrial fibrillation (AF) hospital admissions represent significant AF related treatment costs nationally. In the year 2019–2020 our hospital reported 1,333 admissions with a primary diagnosis of AF, with a 10% annual increase. A virtual ambulatory AF ward providing multidisciplinary care with remote hospital-level monitoring could reshape the future model of AF management.

Methods

An AF virtual ward was implemented at our UK tertiary centre, as a proof-of-concept model of care. Patients admitted with a primary diagnosis of AF satisfying the AF virtual ward (AFVW) entry criteria (i.e., haemodynamically stable, HR <140 bpm with other acute conditions excluded) were given access to a single lead ECG recording device, a Bluetooth integrated blood pressure machine and pulse oximeter with instruction to record daily ECGs, blood pressure readings, oxygen saturations and fill an online AF symptom questionnaire via a smart phone or electronic tablet. Data were uploaded to an integrated digital platform for review by the clinical team who undertook twice daily virtual ward rounds. Medication adjustment was arranged through the hospital pharmacy. Data was collected prospectively for patients admitted to the AF virtual ward between 31 January and 11 March 2022. Outcomes included length of hospital stay, admission avoidance and re-admissions. Re-admission avoidance was assessed using the index admission criteria as a parameter for re-admission likelihood. Patients' satisfaction was assessed using the NHS family and friends' test (FFT).

Results

Over the 6-week period a total of 14 patients were enrolled. One patient was unable to be onboarded because of technology related anxiety with 13 patients onboarded to the virtual ward, 30.7% (n=4) did not have smart phones and were provided with electronic tablets. The age on admission was 64±10 years (mean±SD) with the oldest at 78 years of age. All patients were in AF with a mean heart rate of 122±24 bpm, and 38.5% (n=5) were discharged from the virtual ward in sinus rhythm. One patient was onboarded directly from pacemaker clinic and hence hospital admission was completely avoided, and 5 re-admissions were avoided for 3 patients. One patient required brief readmission due to persistent tachycardia requiring acute cardioversion. The FFT yielded 100% positive responses among patients.

Conclusion

This proof-of-concept is a first real world experience of a virtual ward for hospital patients with fast AF. It demonstrates a promising new telemedicine-based care model and with clear appetite among both patients and health professionals. This model of care has the potential to reduce the financial and backlog pressures caused by AF admissions without compromising patients' care or safety. Work is ongoing to further confirm the safety and cost-effectiveness upon further progress in a larger patient cohort.

Funding Acknowledgement

Type of funding sources: None.

Short term outcomes of distal (ventricular) His bundle pacing: A single centre retrospective study

Funding Acknowledgements

Type of funding sources: None.

Introduction

Chronic right ventricular apical pacing can lead to pacing induced cardiomyopathy in a significant proportion of patients. Conduction system pacing may restore more physiological activation of the heart, and has recently been shown to have favourable outcomes in clinical trials. However there remains concern regarding the long-term outcomes due to lead displacement and high pacing thresholds. The most widely used technique in current practice is to pace the His bundle proximal to the tricuspid valve. Distal His bundle pacing has a number of advantages over proximal His pacing, including, lower capture thresholds, a more stable lead position, less far field atrial sensing and better spacing from the AV node in case ablation of this is required for AF rate control. Despite these, outcomes of distal His bundle pacing from the ventricular aspect are less well defined.

Methods

We performed a retrospective review of patients who underwent conduction system pacing between January 2020 and October 2021 at our centre. During this period all procedures were performed employing a distal His bundle pacing approach with the lead placed on the ventricular aspect of the tricuspid annulus. Data was collected at implant, follow-up at 1 month and then every 6 months.

Results

Out of 35 patients, 33 underwent successful His bundle pacing (acute success rate of 94%), 1 patient had left bundle branch pacing and another patient had an unsuccessful procedure. Mean age was 74 years, median LVEF 45% and median pre-implant QRS was 108ms. 80% of the cohort had a history of AF. The indications for pacing were as follows: AF - for pace & ablate (60%); high grade AV block with narrow QRS and mild LVSD (17%); failed LV lead (14%); and other 9%. Mean procedure duration and fluoroscopy time were 78 minutes and 12.05 minutes, respectively. Median threshold at implant was 1.00V (IQR 0.719V). Selective His bundle pacing was achieved in 60% and non-selective in 34%. Mean follow-up duration was 150 days with median threshold at last f/up of 0.75V (IQR 0.750V). There were no acute procedural complications. 1 patient had a significant rise in threshold at follow-up and therefore required upgrade to CRT-P.

Discussion

Our data shows that distal His bundle pacing is a safe and effective technique for conduction system pacing. Thresholds appear stable at follow-up and failure rate was found to be comparable to biventricular pacing. We noted an initial learning curve for both implanter and physiologists with relatively poorer outcomes for the earlier cases. Longer term follow-up is ongoing, including functional assessment and follow-up to assess for remodelling with echocardiography. Prospective randomised trials are needed to compare conduction system pacing vs RV pacing in AF patients with HFpEF or mild LVSD undergoing AVN ablation, and vs biventricular pacing in the severe LVSD population.

Short term outcome of distal (ventricular) His bundle pacing and atrioventricular node ablation in patients with symptomatic atrial fibrillation - Refining the concept

Funding Acknowledgements

Type of funding sources: None.

Introduction

Many patients with atrial fibrillation (AF) do not benefit from rhythm control due to failed catheter ablation, advanced left atrial disease and comorbidities. "Pace and AV node (AVN) ablation" strategy is often adopted for rate control but with a substantial risk of pacing-induced cardiomyopathy. His bundle pacing (HBP) enables physiological biventricular activation through the His Purkinje conduction system. However, the proximity of the HBP lead to the site of AV node ablation may potentially compromise lead integrity in patients who undergo conventional HBP and AVN ablation. Therefore, we have modified HBP by placing the HBP lead distally at the ventricular side of the His bundle (D-HBP) before AVN ablation in patients with symptomatic AF. All patients had a backup RV lead.

Method

Patients who had D-HBP as part of a "Pace and AVN ablation" strategy were retrospectively analysed. Implant and device clinic follow-up data were collected and analysed.

Result

Twenty-one patients who had "pace and AVN ablation strategy" with D-HBP between 26th February 2020 and 3rd November 2021 were included. They had a mean age of 75 ± 1.4 years (mean ± SEM), NYHA class of 2.1 ± 0.2, QRS duration of 106 ± 5.3ms and 50% had at least moderately impaired LV systolic function. Seventeen patients (81%) had narrow QRS duration. D-HBP was successful in twenty of twenty-one patients (95%). At D-HBP implant, the mean acute threshold of the HBP lead was 0.96 ± 0.12V at 0.5 ± 0.05ms and the mean HBP lead impedance was 548.1 ± 29.5Ω. Selective HBP pacing was observed in thirteen of twenty patients. The mean QRS duration of HBP paced beats was 104.5 ± 4.7ms. Failure to capture the His bundle was observed in one patient. AVN ablation was performed on the same day after D-HBP in eleven patients and as a subsequent procedure in nine patients. The mean duration of procedure and fluoroscopy for D-HBP were 77.4 ± 4.6 minutes and 11.9 ± 1.4 minutes respectively. There were no acute procedural complications with no lead damage, displacement or lead perforation observed. The median follow-up period was 207 days. The mean D-HBP lead threshold following AVN ablation was 1.1 ± 0.2 V at 0.6 ± 0.07 ms and the mean lead impedance was 433.8 ± 20.7Ω, which were similar to before AVN ablation. One patient was reprogrammed with RV pacing only for elevated HBP lead threshold after AVN ablation to 4.2 V at 1ms. The mean D-HBP percentage was 92.3 ± 6.6% and the mean estimated battery longevity of the pacemaker was 7.9 ± 0.6 years at the last follow up. There was improvement in heart failure symptoms in eight patients from previously symptomatic to NYHA class I following D-HBP and AVN ablation.

Conclusion

D-HBP appear to be safe with potentially more favourable lead parameters than conventional proximal HBP in patients with symptomatic AF offered "Pace and AVN ablation" strategy.

128Non-invasive 3D mapping of earliest activation of premature ventricular complexes originating from intracardiac structures to guide catheter ablation

Funding Acknowledgements

Research funding from Catheter Precision, Inc.

Introduction

Catheter ablation for ventricular arrhythmias such as premature ventricular complexes and ventricular tachycardia is an established management approach.  Non-invasive mapping to localise the earliest activation (site of origin) on the myocardium may help guide ablation.  Established ECGi methods using the inverse solution to reconstruct epicardial electrograms are unable to accurately locate arrhythmias from the endocardium or from intracardiac structures.  VIVO™ (Catheter Precision) is a novel vectorcardiography based 3D mapping system that may be able to localise arrhythmias from any part of the ventricle.

Methods

We reviewed our initial experience utilising this mapping system to guide catheter ablation of ventricular ectopics from the inter-ventricular septum, coronary cusp or papillary muscle.  A patient-specific 3D heart and torso model was created using semi-automated segmentation of MRI or CT scan images.  A 3D topographic image of the patient’s torso was taken to accurately position surface ECG electrode locations onto the 3D heart-torso model.  An ECG of the PVC was imported from LabSystemPro (Bard) into VIVO™ for analysis prior to ablation.  The result was then compared with the site of earliest activation identified using invasive electro-anatomical (EA) mapping.

Results

VIVO™ was used in 12 cases where the PVC was localised to an intracardiac structure – six papillary muscle, four to the septum and two from the coronary cusp.  VIVO™ was able to accurately localise the earliest activation site when compared to the invasive map in 5/6 papillary muscle cases, 3/4 septal cases and 2/2 coronary cusp cases.  Ablation was acutely successful in all cases.  One additional patient had a PVC localised non-invasively to the postero-medial papillary muscle, however an invasive 3D electro-anatomical map or ablation was not performed.

In three cases we were able to merge the 3D geometry of the non-invasive map from VIVO™ into the Carto™ system to guide mapping and ablation in real time (see figure).

Conclusion

Our experience shows promising results for accurate non-invasive localisation of ventricular arrhythmias originating from intracardiac structures.  Non-invasive localisation is of particular value in cases where the arrhythmia is infrequent, difficult to induce or poorly tolerated haemodynamically.  The two cases where PVC localisation was inaccurate were performed using an older version of the software. With recent refinements, localisation is anticipated to be improved further.

We also present the first experience of combining the VIVO™ geometry with the real-time invasive EA map.  This has potential to significantly speed up mapping time and reduce the need for expensive multi-polar catheters by allowing the operator to see their target in real time 3D.  Further work is ongoing to validate the accuracy of VIVO™ prospectively and quantitatively.

Abstract Figure. VIVO map merged with Carto LV geometry

P439Could regional electrogram desynchronization identified using mean phase coherence be potential ablation targets in persistent atrial fibrillation?

Funding Acknowledgements

This work was supported by the NIHR Leicester Biomedical Research Centre. XL was funded by MRC(MR/S037306/1) and BHF (PG/18/33/33780)

Background

It remains controversial as to whether rotors detected using phase mapping during persistent atrial fibrillation (persAF) represent main drivers of the underlying mechanism as others found rotors to be located near line of conduction block. Regional electrogram desynchronization (RED) has been suggested as successful targets for persAF ablation, but automatic tools and quantitative measures are lacking.

Purpose

We aim to use mean phase coherence (MPC) to automatically identify RED regions during persAF. This method was compared with phase singularity density (PSD) maps.

Methods

Patients undergoing left atrial (LA) persAF ablation were enrolled (n = 10). 2048-channel virtual electrograms (VEGMs) were collected from each patient using non-contact mapping (St Jude Velocity System, Ensite Array) for 10 seconds.  To remove far field ventricular activities, QRS onset and T wave end locations were detected from ECG lead I (Figure 1A) and only the VEGM segments from T end to QRS onset were included in the analysis. VEGMs were reconstructed using sinusoidal wavelets fitting and the phase of VEGMs determined using Hilbert transform. Phase singularities (PS) were detected using the topological charge method and repetitive PSD maps were generated. RED was defined as the average of MPC of each node against direct neighbouring nodes on the 3D mesh (Figure 1A-B). Linear regression analysis was used to compare the average MPC vs. PSD and vs. the standard deviation of MPC (MPC_SD).

Results

A total of 221,184 VEGM segments were analysed with mean duration of 364.2 milliseconds.  MPC has shown the ability to quantify the level of synchronisation between VEGMs (Figure 1B). Inverse correlation was found between PSD and average MPC values for all 10 patients (p < 0.0001, Figure 1C). Average MPC and MPC_SD were found to be inversely correlated (p < 0.0001, Figure 1C). Spatially, similar graphic patterns can be found from LA MPC maps and PSD maps for all patients (Figure 1D).

Conclusion

We have proposed a method to quantify the level of synchronisation between VEGMs. Phase density mapping showed a considerable agreement with RED regions reflecting regional conducting delays, which supports the previous finding where rotors found at conduction block. Inverse correlation between local average MPC and MPC_SD suggests that conduction delays of the identified regions are not heterogenous, posing directional preferences. Rather than solely looking for rotational activities, this method could identify comprehensive RED regions, which may also explain the conflicting results from different studies targeting rotational activities, where incomplete subsets of RED regions could have been targeted. Atrial RED regions can easily be identified with simultaneously collected electrograms from multi-polar catheters and should be targeted in future persAF studies.

Abstract Figure 1

P1113Patchy localisation of late gadolinium enhancement associated with ventricular arrhythmia in dilated cardiomyopathy

Funding Acknowledgements

None

Introduction

Myocardial fibrosis detected using late gadolinium enhancement(LGE) on cardiac magnetic resonance(CMR) imaging holds prognostic value in dilated cardiomyopathy(DCM). Recent reports have demonstrated the localisation of LGE to be promising predictors of ventricular arrhythmic (VA).Aim: To determine the localisation of LGE associated with high risk of VA in DCM patients. Methods: Retrospective review of consecutive DCM patients(n = 85) implanted with an implantable cardioverter defibrillator(ICD) at a single tertiary centre between 2011-2018. All patients with insufficient follow-up data, cardiac channelopathies, primary valvular pathology and congenital heart disease were excluded from analysis(n = 11). Details of VA occurrence were obtained from medical and pacing notes. VA was defined as VA causing haemodynamic compromise or appropriate device therapy (anti-tachycardia pacing/shock). Localisation of LGE was defined as midwall, patchy, subepicardial or transmural. Left ventricular ejection fraction(LVEF) <35% was defined as severely impaired function. Results:74 DCM patients implanted with an ICD were identified for analysis; LGE was observed in 18(60%) VA and 29(66%) non-VA patients(p = 0.6). There was no observed difference in mean age for patients with and without LGE (68 ± 10 vs. 65 ± 10 years,p = 0.07). A significant difference was seen between localisation and VA (p = 0.04), with patchy LGE demonstrating a higher arrhythmic risk(p = 0.005). There was no association between LVEF and LGE(p = 0.2) however, a significant difference was seen in LVEF and arrhythmic risk, with a more severely impaired LV function seen in patients without VA(p = 0.01). Conclusion:This study has demonstrated a patchy LGE localisation to be strongly associated with ventricular arrhythmia in DCM. Whilst this is a valuable tool in risk stratification, a prospective study with a larger population is required to confirm the validity of this finding. Moreover, an additional method will need to be considered to identify high risk patients without LGE.

Ventricular Arrhythmia (n = 30) No Ventricular Arrhythmia (n = 44) P Value Male(%) 20(67%) 24(55%) p = 0.29 Age(Mean ± SD) 65 ± 12 65 ± 10 p = 0.36 LGE Midwall 10(56%) 24(83%) p = 0.04 Subepicardial 1(5.5%) 2(7%) p = 0.85 Transmural 1(5.5%) 2(7%) p = 0.85 Patchy 6(33%) 1(3%) p = 0.005 LVEF <35% 23(77%) 42(95%) p = 0.01

Localization of the binding site on fibrin for the secondary binding site of thrombin

Affinity chromatography of active site inhibited thrombin on immobilized fragments derived from the central (desAB-NDSK) and terminal (D1) globular domains of fibrinogen revealed that the site responsible for the binding of thrombin at its secondary fibrin binding site is located in the central domain. Chromatography of various domains of the central nodule (desAB-NDSK, fibrinogen E, and fibrin E) having nonidentical amino acid sequences showed that all of these fragments are capable of binding to PMSF-thrombin-Sepharose, suggesting that the thrombin binding site resides within the peptide regions common to all of these fragments: alpha(Gly17-Met51), beta(Val55-Met118), and gamma(Tyr1-Lys53). Competitive affinity chromatography of the same binding domains revealed that there is no detectable difference in their binding constants to PMSF-thrombin-Sepharose, indicating that the alpha(Lys52-Lys78), beta(Gly15-Lys54)/(Tyr119-Lys122), and gamma(Thr54-Met78) peptide segments do not contribute significantly to the binding of thrombin. Chromatography of the isolated chains of fibrinogen E showed that the alpha(Gly17-Lys78) peptide region itself contains a strong binding site for PMSF-thrombin-Sepharose. The location of the binding site suggests that the secondary site interaction may play an important role in determining the cleavage specificity of thrombin on fibrinogen and can affect the rate of release of the fibrinopeptides. Affinity chromatography of fragments prepared from polymerized fibrin showed that cross-linked DD (D x D) itself does not bind to thrombin, whereas the D x DE complex remained attached to the column, suggesting that the binding site on fragment E for thrombin is distinct from its binding site for D x D.(ABSTRACT TRUNCATED AT 250 WORDS)