VT Ablation Research Articles

PO-05-001 TARGETING WAVEFRONT DISCONTINUITY LINES FOR SCAR-RELATED VENTRICULAR TACHYCARDIA ABLATION

Late activation mapping can identify wavefront discontinuities during functional substrate mapping. Automated visualization of wavefront discontinuity lines (WaDLs) representing conduction block or delay may be a suitable target for a focused VT ablation. To describe WaDLs in multiple types of cardiomyopathy undergoing VT ablation, with correlation to critical VT circuit sites and bipolar low voltage scar. Patients who underwent high density substrate ablation with late activation mapping in sinus or paced wavefront were retrospectively analyzed. An automated mapping algorithm was used to visually demarcate WaDLs by identifying adjacent points where mapped activation times were greater than a certain timing threshold (CARTO®,Biosense Webster) Extended Early Meets Late module). Timing threshold was set to 25-35% of the mapped activation time. The number, total length, and distance to critical VT site of WaDLs was compared at each threshold 34 patients (20 post-infarct, 10 dilated, 1 Chagas, 1 sarcoid, 1 ARVC, 1 lamin) with 46 endocardial or epicardial surface substrate maps (10 epicardial, 36 endocardial; mean 1898 points) were included. WaDLs were present in each cardiomyopathy and surface, and represented average timing discontinuities of 50-61 ms (25%-35% WaDL threshold) with no difference in number or length of WaDLs by the mapped chamber, cardiomyopathy type, or wavefront. Parallel WaDLs forming putative channels were present in 37.2% of mapped chambers. In 15 patients with a critical VT site identified, the median distance from critical site to nearest WaDL was 7.4 mm (IQR 2.2-18.6 mm), with shorter distances on the epicardial surfaces compared to endocardial (1.4 vs 13.9 mm at 30% WaDL, P = 0.015). Functional substrate ablation in this cohort covered a mean 26% of the bipolar low voltage scar area (< 1.5 mV). Automated WaDLs represent easily visualized significant discontinuities that correlate with clinical VT circuits, are present in a wide variety of cardiomyopathy types and both epicardial and endocardial surfaces. Targeting WaDLs requires a smaller ablation area than low voltage homogenization.

PO-05-158 DESCRIBING THE PHENOTYPE OF THE FLMC GENE TO INCLUDE SEPTAL SCARRING

Filamin C (FLNC) gene variants have been reported to be associated with arrhythmogenic cardiomyopathy (ACM), dilated cardiomyopathy (DCM), and sudden cardiac death. Currently left ejection fraction and sudden cardiac death risks do not appear to be clearly associated. FLNC and DSP + cardiomyopathy tend to show ring-shaped sub-epicardial scars. Although there is evidence to suggest FLNC variants can cause arrhythmia or sudden cardiac arrest, it continues to be reported as a variant of uncertain significance. The primary objective was to further describe the phenotype of FLNC gene variants to include the presence of cardiac septal scarring. A retrospective review was completed of patients with known FLNC gene variants using the Phoenix Cardiac Genetic Registry (PCGR) database. The PCGR includes patients that have undergone cardiomyopathy and arrhythmia genetic testing due to clinical abnormalities including reduced left ventricular ejection fraction, cardiac scarring on baseline imaging, and/or arrhythmia. Left ventricular ejection fraction, cardiac arrhythmia, and cardiac scarring locations were compared to further describe the FLNC phenotype. The PCGR database included 115 patients with cardiomyopathy and arrhythmia genetic testing completed between 2015 and 2022 ranging from 25 to 77 years of age. Of these patients, 10 patients came back with an FLNC variant. The mean LVEF was 31% (+/- SD 14.0). Ventricular arrhythmia history was reported in 9 patients, 6 of which had PVC or VT ablations. Atrial arrhythmia history was reported in 8 patients, 7 of which required ablations. Cardiac magnetic resonance imaging (CMRI) was completed in 6 out of the 10 patients revealing septal scarring in 4 patients. Variants of unknown significance in the FLNC gene are associated with septal substrate abnormalities, suggesting that the majority of patients with VT may be pathogenic.

PO-05-038 CONDUCTION SYSTEM CONCERNS DURING PVC ABLATION AT THE POSTERIOR SUPERIOR PROCESS OF THE LEFT VENTRICLE: A SAFE APPROACH FROM ALL ANGLES

Ventricular arrhythmias (VA) originating from the posterior superior process (PSP) are infrequent and challenging to treat with catheter ablation due to their location in the highest portion of the inferior left ventricular (LV) septum , proximity to the conduction system and origin between LV and right atrium. The incidence of conduction system abnormality from ablation in this area is ill-defined. To describe procedural approach and outcome of PSP ablation including conduction system effect. We reviewed our institutional VA ablation database between 1/2019-11/2022 to identify patients (pts) who underwent PSP ablation. Incidence, procedural technique, and outcomes (including conduction abnormalities and procedural success) are evaluated. Among 556 pts who underwent VA ablation during this period, nine patients (1.6%) underwent PSP ablation. Sustained VT was present in 1 and the remainder had ablation for PVCs. Three patients (33%) were female, 3 pts had prior VA ablation. Mean LVEF was 50.6% +/-7 %, and two patients had structural heart disease with scar on cardiac MRI. The VA morphology had some variance but shared common characteristics including leftward axis, rs in II, negative (QS or rS) in III, and predominantly positive concordance in precordial leads, similar to previously reported series (Figure 1). During ablation, five pts (55.5%) had fast junctional rhythm, and one (11.1%) had transient complete heart block. No one had HV or QRS prolongation post procedure. Two (22.2%) patients had >30 msec AH prolongation, and four (44.4%) patients had >30 msec PR prolongation. Ablation from the right atrium (RA) in 2, coronary sinus (CS) in 3, and from the left ventricular (LV) septum in 8 patients. The patient who had transient complete heart block had full recovery and did not require pacemaker (PPM) implant, and one patient with post procedure AH and PR prolongation required PPM ten months after the procedure. During mean follow-up of 13.8 +/- 10.5 months, 83.3% patients had <3% PVC burden, and there were 92% absolute reduction in PVC burden (P<0.05). Ablation for VA originating from the PSP is associated with a risk of damage to the upper AV conduction, predominantly manifesting as AH prolongation. Care should be taken to monitor conduction during ablation to avoid permanent damage to the conduction system. Despite this, successful ablation can be achieved from the RA, CS or the LV septum.Tabled 1Table 1VA ablation at PSPN=9Age66.4 +/- 16.4Female3 (33%)LVEF (%)50.6 +/-7 %Prior VA ablation0.78 +/- 1.5Abnormal imaging with scar2 (22%)Conduction system disturbance during procedureFast junctional rhythm during ablation5 (55.5%)Transient heart block during ablation1 (11.1%)AH prolongation > 30msec post procedure2 (22.2%)HV prolongation > 30msec post procedure0PR prolongation > 30msec post procedure4 (44.4%)QRS prolongation > 10msec post procedure0Procedure detailAblation form the RA2 (22.2%)Ablation from the CS3 (33.3%)Ablation from the LV8 (88.8%)Ablation with RF energy9 (100%)Ablation with cryo energy0Procedure outcomeMean follow up (months)13.8 +/- 10.5Pre procedure PVC burden (%) *14.8+/- 11.5Post procedure PVC burden (%) **1.32 +/- 1.9VT recurrence ***0Required pacemaker implant1 (11.1%)* Seven patients had information on pre-procedure PVC burden. ** Six patients had information on post-procedure PVC burden. *** One patient had VT ablation. VA: Ventricular arrhythmia, PSP: posterior superior process, LVEF: left ventricular ejection fraction, RA: right atrium, CS: coronary sinus, LV: left ventricle, RF: radiofrequency. Open table in a new tab

PO-01-051 EARLY PHYSICIAN ARRIVAL TO ELECTROPHYSIOLOGY LABORATORY INCREASES LAB EFFICIENCY BY DECREASING PREPARATION TIME

Many cardiac arrhythmia patients benefit from interventions performed in the electrophysiology (EP) lab. EP labs are a valuable resource that if not used efficiently may lead to delay in patient care, increased cost to the medical system, and challenges with recruiting and retaining staff. Prep time is defined as the time from when a patient (pt) enters a procedural room until the procedure start. Prep time is affected by many factors, including but not limited to: pt factors, staffing ratios, sedation plan, need for invasive hemodynamic monitoring, and complexity of procedure (proc). Physician arrival to the EP lab is an important component of prep time. To determine if earlier physician arrival to the EP lab shortens prep time. Pt and physician in-room times, proc start times, and proc characteristics were recorded over a 5 month period from 5/22 through 8/22. Quantitative data was divided into subgroups based on proc type – ablation (abl) or device. Means and standard deviation of physician arrival time and proc start time were calculated. A scatter plot of proc start time compared to physician arrival was created and a best-fit polynomial regression was performed (Fig 1). Point of maximum correlation (PMC) was calculated using Pearson’s method and linear regression was applied from that point onward. Cases that were understaffed and VT ablation were highlighted. Of 539 cases, 235 (44%) were device implants and 304 (56%) were abl. The difference between the earliest average physician arrival time compared to the latest average physician arrival time was 17min for device and 16 min for abl. Prep time was 15 minutes shorter for the earliest arriving physician for device, and 28 min shorter for abl. The PMC for abl and device implants were 25mins and 30mins respectively. Every minute of delay after the PMC was directly related to the MD not being present in the lab. For the interval prior to the PMC, there are many factors causing delays in the lab, leading to questionable direct correlation between MD arrival and prep time. The minimum prep time for both abl and implants appears to be 20 mins in this lab with the current staffing and culture. Earlier MD in room times increase lab efficiency by reducing procedure start times.Tabled 1Mean in Room Times to Access (min) +/-SDAblationDevice ImplantMean Pt Room to EP RoomMean Pt Room to AccessMean Pt Room to EP RoomMean Pt Rm to AccessEP115+/-1347+/-1111+/-1246+/-10EP211+/-942+/-1011+/-942+/-10EP318+/-850+/-1213+/-1647+/-16EP425+/-1449+/-1126+/-2149+/-16EP524+/-1660+/-2021+/-1652+/-14EP68+/-1032+/-84+/-837+/-9EP78+/-831+/-107+/-637+/-7 Open table in a new tab

PO-03-094 IMAGE INTEGRATION IN VENTRICULAR TACHYCARDIA (VT) ABLATION USING SENSE2 PROTOCOL MAPPING

We have previously developed the sense protocol functional substrate mapping technique for VT ablation. This involves targeting areas of decremental signal delay during single extra pacing at short coupling interval. However, functional substrate characterization can involve protracted mapping time. We incorporated the MRI and CT data using ADAS-3D software into the mapping workflow to integrate structural mapping information into the functional mapping substrate characterization to improve procedural efficiency. Cardiac MRI/CTs were performed on 33 patients with ischemia-related VT (group A). These were processed with the ADAS-3D software to characterize the extent of ventricular scars. Focused substrate maps were then performed in patients, guided by the extent of ADAS scar and corridors, looking at the scar substrate in intrinsic rhythm and then functional channels using single extra pacing from the RV apex. Following the delineation of functional channels pace mapping and entrainment mapping were used to confirm targets for ablation. Group A was then compared to a matched cohort who underwent sense protocol mapping without MRI (group B) and an institutional cohort who underwent conventional mapping and ablation using entrainment or pace mapping (group C). 33 patients (mean age 68 years; 31 male subjects, mean EF 32%) underwent ablation. Median procedure time was 175 minutes compared with 305 and 246 minutes in groups B and C(p=<0.001) Mean substrate mapping time was 17 mins vs 80 and 63 mins in groups B and C (p=<0.001). 85% of patients were free from symptomatic VT/ anti-tachycardia pacing or implantable cardioverter defibrillator shocks at a median follow-up of 171 days. The mean VT burden was reduced from 22 events per patient in the six months pre-ablation to 1 event per patient in the median follow-up period of 171 days post-ablation (p=0.02). Sense2 protocol showed a reduced probability of device therapy compared with institutional and sense protocol (Log-rank p=0024 in the figure). The Sense2 protocol integrated structural MRI findings into functional signal ablation of VT. It shortened procedure times by enabling focused substrate maps to be performed without requiring complete geometry. Outcomes compare favourably with our previous data from sense protocol but with significantly shorter procedure times. There were improved outcomes compared to our institutional standard ablation cohort.

PO-01-021 VASCULAR ACCESS COMPLICATIONS DURING CATHETER ABLATION OF VENTRICULAR ARRHYTHMIAS: IMPACT OF VASCULAR CLOSURE DEVICE

In patients (pts) with ventricular arrhythmias (VAs) undergoing catheter ablation (CA), the need for multiple vascular access points with large bore sheaths predisposes to vascular complications. Whether arterial/venous vascular closure devices prevent vascular complications is unknown. We investigated the benefit of vascular closure devices in pts undergoing CA of VAs. Consecutive pts undergoing CA of VAs between 2018-2020 were included. Vascular accesses were obtained with ultrasound guidance. At the discretion of the operator, arterial (Perclose or AngioSeal) and/or venous (Vascade or figure-of-eight suture) were used. Pts were divided into 3 groups: no use of vascular closure devices for any of the arterial/venous accesses (No-Closure), use of vascular closure devices for some but not the all of the arterial/venous accesses (Partial-Closure), use of vascular closure devices for all of the arterial/venous accesses (Complete-Closure). Vascular complications were defined minor if they didn’t require intervention or major if they required intervention (transfusion, percutaneous/surgical repair). 522 pts (62±13 years, BMI 30±6 kg/m2, 26% female) underwent ablation of VT (41%) or PVCs (59%) during the study period. 134 (34%) were on oral anticoagulation before the procedure (interrupted in 129, uninterrupted in 5). 477 arterial accesses were obtained in 471 (90%) pts (single access in 465 pts – 7.5±1.4 Fr size, two accesses in 6 – 7±1.5 Fr and 7±4 Fr). 1258 venous accesses were obtained in 520 (99.6%) pts (unilateral in 24%, bilateral in 75.6%, N. of accesses 2.4±0.7/pt, size 8.4±1.33 Fr). 142 (27%) pts received No-Closure, 201 (39%) Partial-Closure and 179 (34%) Complete-Closure. A vascular access-related complication occurred in 31 (5.9%) pts, including a minor hematoma in 4.6% and a major complication in 1.3%. The rate of vascular complications was 7% (5.6% minor and 1.4% major) in the No-Closure group, 6.9% (5% minor and 1.9% major) in the Partial-Closure group, and 3.9% (3.4% minor and 0.5% major, P=0.15 for comparison) in the Complete-Closure group. In pts undergoing CA of VAs, Complete-Closure using dedicated arterial/venous closure devices/sutures appeared associated with lower absolute rates of minor and major vascular-related complications compared to No-Closure or Partial-Closure. Although the differences did not reach statistical significance, they suggest a potential benefit of Complete-Closure and require further investigation in larger cohorts.

PO-03-090 NOVEL HIGH RESOLUTION MR IMAGING IMPROVES PRE-PROCEDURE IDENTIFICATION OF ABLATION TARGETS IN POST-INFARCT VENTRICULAR TACHYCARDIA

MRI-based personalized virtual heart models (VHM) are a useful tool for reconstructing scar distribution and identifying VT circuits for planning catheter ablation procedure, an effective therapy for preventing sudden cardiac death from VT in patients with myocardial infarction. However, the MRI resolution used to reconstruct VHMs may not be sufficient to accurately detect all VT circuits, possibly leading to erroneous predictions. To predict catheter ablation targets in the arrhythmogenic substrate using VHMs reconstructed from both clinical and high-resolution 2D MRI datasets and compare the predictions. High-resolution (1.352 x 3mm) short-axis cardiac MRI were acquired by combining two subsequent clinical resolution (1.352 x 6mm) short-axis MRI from nine post-infarct patients undergoing VT ablation. The high-resolution and two clinical MRI were used to reconstruct a total of three personalized VHMs for each patient that represented the patient-specific infarct remodeling. Rapid pacing was used to assess the VT circuits and identify ablation targets in each VHM. Differences in VT inducibility and location were assessed between the high and clinical resolution VHM reconstructions, as well as between the two clinical resolution VHM reconstructions. Virtual ablations were performed to identify emergent VTs and were also compared between the VHMs for each patient. The amount of fibrotic remodeling changed by 12.6 ± 3.3% between the high-resolution and two clinical MRI VHMs for each patient, while the distribution was only moderately affected (Fig 1). The heterogeneity of the myocardium and the fractal dimension (complexity) of the scar tissue was not statistically different between the VHMs for each patient (Fig 1). VT inducibility was observed in all VHMs with an average of 2.7 [1-4] unique VT morphologies induced in each VHM. In two patients, only one clinical VHM was able to identify all the unique VT morphologies observed in the high-resolution VHM. VT exit sites in the clinical MRI VHMs were within 5mm of the exit sites observed in the high-resolution VHMs in 72.2% of cases. Virtual ablations uncovered emergent VT circuits in two of the high-resolution VHMs, compared to only one of the corresponding clinical MRI VHMs. The distribution of ablation targets required to terminate VT was statistically different in 44.4% of cases (Fig 1). VHMs reconstructed from high-resolution MRI more accurately identify VT circuits and may improve catheter ablation outcomes.

PO-04-062 CRYOABLATION OF INTRAMURAL SUBSTRATE IN AN IDIOPATHIC CRUX VT MAPPED BY NAVIGATING OTHERWISE INACCESSIBLE CS ANATOMY USING 2FR MAPPING CATHETER

Idiopathic cardiac crux VTs are are difficult to map and ablate due to their inaccessible location often requiring epicardial ablation. We report a unique case of a recurrent idiopathic crux VT originating near a trifurcated confluence of CS branches that required extensive mapping only accessible with the 2Fr EP catheter that was successfully ablated with cryoablation (due to proximity to coronary artery) from within the CS and the site-opposite (epicardially). Case Report A 40 year old man with idiopathic VT (normal Echo and cardiac MRI without LGE), prior endocardial VT ablation (RV septum and mid MCV), asthma, OSA, and the Arnold-Chiari malformation, was noted to have continued symptomatic PVCs and monomorphic wide-complex tachycardia at 164 bpm. A monomorphic VT (Figure) with CL 320-380 ms was only inducible with isoproterenol infusion at 20mcg/kg/min. We attempted to better define the CS anatomy and assess if there is a route via the CS to reach the Crux. The main body CS was noted to have a trifurcation into the MCV, a posterolateral branch and an anterior branch (extension of the CS main body) all meeting at an area of confluence (Figure 1). Detailed mapping was made possible using the CS-L telescoping catheter to carry the smaller 2French EP Star catheter deep into the multiple CS branches. We noted that the proximal MCV was 28ms early in VT (but not the best pace match) and the proximal lateral CS branch across from the MCV early site within the confluence had the best pace match. This suggests the origin was likely deep in between the two sites with the exit closer to the lateral branch site. Given that we noted that the PDA is in borderline proximity (5-6mm) to the site of ablation on coronary angiography, we chose to use to cryoablation (8 minute lesions) at the confluence of these branches at the marked sites to mitigate coronary injury. VT terminated with ablations at this site. Epicardial mapping was performed and no scar was noted. An additional single lesion was performed at the site opposite from the confluence with the best pace-map and VT was no longer inducible on repeat testing with isoproterenol. CSL telescoping catheter harboring the EP star catheter can be used to overcome challenging CS anatomy to bracket the Crux VT origin. Cryoablation (not without risk completely) can be potentially effective for Crux VTs approached from CS, especially if within borderline proximity to a coronary artery.

PO-04-095 ACCURATE EAM-BASED TARGET DELINEATION IN STEREOTACTIC ARRHYTHMIA RADIOABLATION OF VT

Stereotactic Arrhythmia Radiotherapy (STAR) aided by precise image-guided delivery and respiratory motion management has been used successfully for experimental treatment of refractory VT. However, accurate target selection remains challenging. Current methods often rely on manual delineation and/or visual estimation of predefined cardiac segments. Develop a systematic process for registering VT targets from electroanatomic maps (EAM) to reference imaging coordinates of the planning CT (pCT) used for radiation treatment. The goal is to minimize potential variations in target site selection as well as treated volumes. In patients on antiarrhythmic treatment and undergoing a 2nd unsuccessful VT ablation, EA maps of the LV (and LA/RV when possible) and more focal maps of VT target sites were acquired (CARTO®3, Biosense-Webster, CA, USA) and exported. In-house software was used to register these to a planning image set and convert them to DICOM structure files (Fig 1). Dice similarity coefficients were calculated between ventricular mesh data and corresponding reference contours. Initial targets (GTV) were expanded to include internal target volumes (ITV) and planning target volumes (PTV) to account for respiratory and cardiac motion and residual uncertainties, with minor manual adjustments guided by consensus among electrophysiologists, radiation oncologists and medical physicists. STAR was delivered as a single fraction of 25 Gy using volumetric-modulated arc therapy or dynamic conformal arc therapy depending on the target shape. 7 patients with refractory VT were treated by defining targets based on registering individualized EAM maps on the planning images. Dice similarity indices between transferred reference map and reference contours were 0.83 ± 0.04 and 0.72 ± 0.04 for LV and LA/RV, respectively (table 1). The median clinical target was 22cc, with PTVs ranging from 62.4 to 199.6 cc. All patients demonstrated a significant reduction in VT events by 6 weeks post STAR. We have developed an effective methodology for direct registration of VT targets selected for STAR, based on direct anatomic registration of individualized EA maps acquired during ablation procedures. This process offers a way to efficiently delineate variable target boundaries in a semi-automated way, which is advantageous when unusual contours make standard segmentation inaccurate and visual estimation difficult. However, rigorous comparison with other approaches remains to be done.Tabled 1Patient-specific metrics1234567Dice, LV0.8680.8450.7910.8060.7210.8720.794Dice, LA/RV0.7520.6670.734N/A0.382N/A0.338GTV (cc)22.313.526.520.759.863.927.2ITV (cc)45.529.142.230.959.8127.829.6PTV (cc)98.662.488.275.5166.8199.672.8 Open table in a new tab

PO-05-089 COMPARISON OF VIRTUAL HEART ARRHYTHMIA ABLATION TARGETING PREDICTIONS WITH AREAS OF ISOCHRONAL CROWDING IN SCAR-DEPENDENT VENTRICULAR TACHYCARDIA

Isochronal late activation mapping (ILAM) is a functional substrate mapping technique which detects deceleration zones (DZ) in those with scar-dependent VT. DZ have been shown to correlate with the critical isthmus during re-entrant VT. Personalised virtual heart arrhythmia ablation targeting (VAAT) is a technique which aims to non-invasively identify the optimum ablation targets through computational modelling. The association of the VAAT predictions with DZ is unknown, nor is the effect of extrastimulus pacing on identification of DZ. To assess to relationship between VAAT predicted targets with areas of slow conduction on ILAM in those with scar-dependent VT. Gadolinium-enhanced MRI scans were used to reconstruct virtual heart models. Simulated ventricular pacing was performed to demonstrate VT inducibility and predict optimum lesion sets to terminate all likely VTs in the models. ILAMs were generated by annotating the latest activation of ventricular electrograms during right ventricular and extrastimulus pacing at 20ms above VERP. DZ were defined as > 3 isochrones in a 1cm radius. VAAT predictions were superimposed on the invasive ILAM. The spatial relationship was assessed. DZ identified during RV and extrastimulus pacing were compared. 11 patients (100% male) with scar-dependent VT underwent invasive ILAM mapping and VAAT protocol. 3195 ± 935 EAM points per patient were analysed. Mean VAAT-predicted area was 11.2 ± 4.3 cm2 representing 22.3% of the total MRI infarct area. RV pacing identified 13 DZ (mean 1.2 DZ per patient, range 0-3). 10/13 (76.9%) were located within 5mm of a VAAT predicted site, whereas 3/13 (23.1%) were remote (>5mm from a predicted site). Extrastimulus pacing identified 25 DZ (mean 2.3 DZ per patient, range 1-4). 21/25 (84%) were within 5mm of a VAAT predicted site, 4/25 (16%) were remote. More DZ were identified during extrastimulus compared to RV pacing (25 vs 13, p = 0.04). The mean distance of RV pacing-identified DZ and extrastimulus-identified DZ from VAAT predictions was not significantly different (3.3 ± 6.7 mm vs 2.9 ± 5.4 mm respectively, p = 0.84). 11/13 (84.6%) of RV pacing-identified DZ were also identified by extrastimulus pacing. 14/25 (56%) of extrastimulus-identified DZ were novel, having not been detected by RV pacing. Deceleration zones visualised on ILAM are closely spatially associated with VAAT-predicted optimum targets for VT ablation. Extrastimulus pacing identifies significantly more DZ compared to RV pacing.

CE-452773-3 ASSESSMENT OF OPTIMAL VOLTAGE THRESHOLDS FOR VENTRICULAR SCAR SUBSTRATE CHARACTERIZATION

Despite the advancement in technology, historic cut-offs of <0.5mV for dense scar and 0.5-1.5mV for scar borderzone continue to be used in contemporary electrophysiology. Modern multipolar mapping catheters employ smaller electrodes and interelectrode spacing that theoretically allows for mapping with increased resolution and reduced far-field electrogram (EGM) component. We aimed to assess the optimal voltage cut-offs for ventricular scar substrate characterization using HD Grid multipolar mapping catheter against cardiac MRI-derived scar. We compared optimal voltage cut-offs using conventional bipolar sampling,Best Duplicate Algorithm and HD wave solution plus best duplicate algorithm on. A multicenter study of 33 patients with ischaemic heart disease undergoing VT ablation. Substrate mapping was performed using the high-density HD-grid multipolar mapping catheter. Bipolar voltage maps were co-registered with cardiac MRI/CT obtained before the procedure to assess the voltage characteristics of the scar defined by the image. Pre-procedure contrast-enhanced MRI data were analysed using ADAS software (Galgo medical). Data points were collected in regions of scar during (1) HD wave mapping with best duplicate algorithm on(Waveon), (2) Mapping with HD wave off and best duplicate on (Waveoff) and (3) with conventional bipolar mapping (Alloff). 29,633 voltage points were analyzed and compared to their location with the fused MRI voltage map. The median bipolar voltage for regions of dense MRI/CT scar using (Waveon) HD wave solution and best duplicate algorithm was 0.24mV (IQR 0.12 – 0.43). The median voltage with (Waveoff) HD wave off was 0.29mV (0.15 – 0.45). The median voltage with (Alloff) HD wave off and best duplicate off was 0.32mV (0.19 – 0.5). ROC analysis using AUC suggested the optimal cut-off for endocardial dense scar using (Waveon) HD wave mapping and best duplicate algorithm was 0.31mV (sensitivity: 69.6%, specificity: 60.74%) (Figure), (Waveoff) cut-off with the best duplicate and without the HD wave mapping was 0.34mV (sensitivity: 88.0%, specificity: 42.96%) and (Alloff) without wave mapping or best duplication was 0.36mV (sensitivity: 84%, specificity: 52%). Ventricular substrate characterization with newer mapping technology using narrow electrode spacing and smaller electrode sizes suggests that traditional voltage cut-offs may need revision. The optimal cut-off for dense scar delineation with the HD Grid and wave technology is 0.31mV.

PO-04-200 ANALYSIS OF RELATIONSHIP BETWEEN PACING SITE AND EXIT SITE IN REGIONS WITH STIMULUS-QRS DELAY AND IMAGING DEFINED MYOCARDIAL FIBROSIS

Delay between ventricular pacing stimulus and QRS onset (S-QRS delay), often seen in regions of myocardial fibrosis, suggests conduction along a protected channel which often represents substrate for re-entrant arrhythmias. 1. To analyze the relationship between pacing stimulus site and myocardial exit site in regions with stimulus-QRS delay and imaging-defined myocardial fibrosis undergoing VT ablation and 2. To consider conduction time between these two locations. Six patients with structural heart disease who underwent VT catheter ablation with pre-procedural cardiac CT image processing (InHeart Models (Pessac, France)) and evidence of late-iodine enhancement were included. CT images were registered with electroanatomic mapping. At pacing sites with S-QRS delay >40 msec, catheter location was compared to the exit site, predicted using a previously validated algorithm (RAPID-VT). Imputed conduction velocity (CV) between stimulus site and exit site was calculated (stim-QRS time/Euclidian distance). Stimulus to QRS delay in regions of imaging derived fibrosis ranged 40 to 291.4 ms; At 9 pacing sites, multiple QRS morphologies were generated. Imputed CV was reduced in dense scar and borderzone compared to values seen in healthy myocardium and varied between 0.16 and 0.65 m/s. These results may under-estimate true tissue CV given complex routes between pacing and exit sites. In the same region, following delivery of RF, mean imputed CV was reduced, raising the possibility that conduction was altered, potentially diverted along a different path (0.21m/s vs 0.14m/s, p=0.024). Myocardial fibrosis defined on CT may be associated with slowed conduction through protected channels. Delivery of RF increases conduction time and results in different exit sites following pacing, indicating multiple and likely complex routes of conduction in regions of imaging-defined fibrosis. Visualization of predicted exit sites in real time could help focus RF to interrupt these conduction paths.Tabled 1Patient #Stim to QRS onset (ms)Imputed conduction velocity (m/s)166.8±15.20.18±0.09241.0±1.50.65±0.08351.0±9.10.30±0.10460.6±11.50.20±0.105103.7±0.160.16±0.10674.3±13.60.19±0.02 Open table in a new tab

PO-04-029 TRIANGULATING THE LV SUMMIT: A NOVEL BIPOLAR RADIOFREQUENCY CATHETER ABLATION STRATEGY

Bipolar radiofrequency catheter ablation (RFCA) is an off-label strategy used to target ventricular arrhythmias (VA) from difficult substrates such as the LV summit. To achieve greater transmural RFCA lesions in challenging anatomy with a novel bipolar RFCA strategy. N/A A 51-year-old male with familial HCM and prior catheter ablation for persistent AF presented with pallor and palpitations in the setting of wide complex tachycardia of 210 BPM (Figure A). The patient was given a bolus of IV amiodarone and externally cardioverted. Amiodarone was discontinued given his history of amiodarone-induced hyperthyroidism. During the hospitalization, he had recurrences of sustained VAs that were suppressed with lidocaine. Cardiac MRI was obtained, which showed LVEF 42% and an extensive LGE in the LV (Figure B). The patient was brought to the EP lab for VT ablation. Extensive mapping in the RVOT, distal CS, and peri-aortic area was performed. The best pacemap was achieved with the 2F EPstar catheter (Baylis Medical) in the AIV. The ablation catheter was not able to be advanced into the distal branch in the coronary sinus. A total of 17 unipolar RFCA lesions were delivered from endocardial LV but the clinical VA remained easily inducible. A second ablation catheter was advanced to the posteroseptal RVOT on the opposite side of the septum for bipolar RFCA. The 2F EPstar catheter was positioned in the AIV near the region of best pacemap for tripolar effect (Figure C). A significant difference in the ablation impedance decline was noted between unipolar and bipolar ablations utilizing this novel strategy (Figure D top - unipolar, D bottom - bipolar). Following five bipolar RCFA lesions, the clinical VA was no longer inducible. The patient tolerated the procedure well with no further recurrence of VAs. Bipolar RFCA with a mapping catheter triangulating the target may help achieve deeper lesions.

Nightmare in EP Lab: A case of Septal VT Mapping & Ablation

Nightmare in EP Lab: A case of Septal VT Mapping & Ablation

Electrical Storm Has Worse Prognosis Compared to Sustained Ventricular Tachycardia after VT Ablation

Electrical storm (ES) represents a serious heart rhythm disorder. This study investigates the impact of ES on acute ablation success and long-term outcomes after VT ablation compared to non-ES patients. In this large single-centre study, patients presenting with ES and undergoing VT ablation from June 2018 to April 2021 were compared to patients undergoing VT ablation due to ventricular tachyarrhythmias but without ES. The primary prognostic outcome was VT recurrence, and secondary endpoints were rehospitalization rates and cardiovascular mortality, all after a median follow-up of 22 months. A total of 311 patients underwent a first VT ablation due to ventricular tachyarrhythmias and were included (63 ± 14 years; 86% male). Of these, 108 presented with ES. In the ES cohort, dilated cardiomyopathy as underlying heart disease was significantly higher (p = 0.008). Major complications were equal across both groups (all p > 0.05). Ablation of the clinical VT was achieved in 94% of all patients (p > 0.05). Noninducibility of any VT was achieved in 91% without ES and in 76% with ES (p = 0.001). Patients with ES revealed increased VT recurrence rates during follow-up (65% vs. 40%; log rank p = 0.001; HR 1.841, 95% CI 1.289-2.628; p = 0.001). Furthermore, ES patients suffered from increased rehospitalization rates (73% vs. 48%; log rank p = 0.001; HR 1.948, 95% CI 1.415-2.682; p = 0.001) and cardiovascular mortality (18% vs. 9%; log rank p = 0.045; HR 1.948, 95% CI 1.004-3.780; p = 0.049). After multivariable adjustment, ES was a strong independent predictor of VT recurrence and rehospitalization rates, but not for mortality. In a propensity score-matched cohort, patients with ES still had a higher risk of VT recurrences and rehospitalizations compared to non-ES patients. VT ablation in patients with ES is challenging and these patients reveal the highest risk for recurrent VTs, rehospitalization and cardiovascular mortality. These patients need close follow-ups and optimal guideline-directed therapy.

The year in cardiovascular medicine 2022: the top 10 papers in arrhythmias.

(A) Comprehensive clinical, electrocardiographic, and genetic overview of the various diseases associated with VA or SCD as reported in the 2022 ESC Guidelines for VA and SCD.1 The VA/SCD Guidelines provide many updated recommendations for the management of patients with congenital heart disease, idiopathic VF, acquired Long QT, Brugada and early repolarization syndrome, as well as catecholaminergic polymorphic VT, and short QT syndrome. (B) From the same Guidelines, an algorithm for the management of sustained monomorphic ventricular tachycardia in patients with chronic coronary artery disease.1 The algorithm also holdsin partfor non-ischaemic pathologies. Note, the new VA/SCD Guidelines promote VT ablation significantly. It may e.g. be performed to ameliorate or avoid ICD therapy, or to enhance resynchronization therapy by ablation of frequent monomorphic PVCs (extrasystolopathy). The trials PARTITA, PAUSE-SCD, and SURVIVE-VT, discussed in the present paper, all strengthen the recommendations for application of catheter ablation.57 (C) Exercise causes downregulation of genes coding intercalated disk proteins, as well as scaffolding and ion channel proteins, both in normal mice and PKP2 conditional knockouts. Consistent with PKP2-dependent muscle mass deficit, cardiac dimensions in human athletes carrying PKP2 mutations were reduced (data not shown), compared with matched controls. Exercise challenges a cardiomyocyte desmosomal reserve which, if impaired genetically (e.g. Plakophilin2 loss), can cause accelerated progression of the cardiomyopathy.3 Reprinted with permission.

Sex differences in one-year recurrence and all-cause mortality following catheter ablation of ventricular tachycardia in structural heart disease.

We aimed to establish sex-specific predictors for 1-year VT recurrence and 1-year all-cause mortality in patients with structural heart disease undergoing catheter ablation. We analyzed data of 299 patients recorded in our structured registry. These included medical history, echocardiography parameters, laboratory results, VT properties, procedural data. Out of the 299 patients, 34 (11%) were female. No significant difference was found between women and men in terms of VT recurrence (p = 0.74) or mortality (p = 0.07). In females, severe mitral regurgitation (MR), tricuspid regurgitation (TR), presentation with incessant VT, and preprocedural electrical storm (ES) were associated with increased risk of VT recurrence. Diabetes, implanted CRT, VT with hemodynamic instability, ES and advanced MR were the risk factors of mortality in women. ACEi/ARB use predicted a favorable outcome in both endpoints among females. In men, independent predictors of VT recurrence were the composite parameter of ES and multiple ICD therapies, presentation with incessant VT, severe MR, while independent predictors of mortality were age, LVEF, creatinine and previously implanted CRT. According to our investigation, there are pronounced sex differences in predictors of recurrence and mortality following VT ablation.

Catheter Ablation of Ventricular Tachycardia in Arrhythmogenic Right Ventricular Cardiomyopathy.

Arrhythmogenic right ventricular cardiomyopathy is an inherited desmosomal myopathy characterized by progressive fibrofatty replacement of the myocardium, right ventricular enlargement, and malignant ventricular arrhythmias. Ventricular tachycardias is one of the most common initial presentation of ARVC. This manuscript addresses invasive VT ablation options for the managmenet of VT in patients with ARVC.

Abstract 14115: Multivariate Predictors of Long-Term Outcome From Ventricular Tachycardia Ablation in a Large Registry

Introduction: It remains difficult to identify clinical risk predictors of long-term outcomes from VT ablation. Hypothesis: We hypothesized that analysis of detailed clinical and laboratory features in a large registry may enable prediction of long-term outcomes from VT ablation. Methods: 623 consecutive patients enrolled in our VT ablation registry with 50 prespecified features included in this study. Ablation strategy was left to the discretion of each operator based on each clinical scenario, and included entrainment, activation mapping, substrate modification or a combination of these strategies. Patients were followed up for 3 years. Recurrent VT (&gt;30 seconds, appropriate device therapy or repeat ablation) or death were determined by clinical follow-up plus natural language processing of device interrogation. Results: Follow-up was available in N=596 (age 58.7±14.8y, 32.3% female). The overall VT-free survival was 65.3% at 1Y and 50.4% at 3Y, and was lower in patients with cardiomyopathy, particularly if ischemic (Figure). There was substantial inter-patient variability. Multivariate predictors of 3-Y VT-free survival (Table) were heart failure and systolic dysfunction (Hazard Ratio [HR]: 2.01, P &lt;0.0001), chronic kidney disease (HR: 1.70, P =0.0004), obstructive sleep apnea (HR: 1.36, P=0.0307), and serum sodium (HR: 0.89, P=0.0506) and calcium (HR: 0.85, P =0.0045). 1-Y predictors were similar. Conclusion: We identify novel clinical features of 1- and 3-year VT ablation outcomes in a large well characterized registry. These combinations of clinical and laboratory factors may guide procedural planning, and should be validated in other registries.

Abstract 10034: Novel Late-Gadolinium Enhanced Cardiac Magnetic Resonance (LGE-CMR)-Based Computational Heart Paradigm Predicts Optimal Ventricular Tachycardia (VT) Ablation Targets in Arrhythmogenic Right Ventricular (RV) Cardiomyopathy (ARVC)

Introduction: ARVC is an inherited cardiac disease that increases risk of life-threatening VTs in young adults. Catheter ablation, a mainstay of VT treatment in ARVC, remains challenging due to difficulties in identifying optimal VT ablation targets. Hypothesis: Right Ventricular Cardiomyopathy Ablation Targeting (RVCAT) is a novel digital-heart paradigm that accurately predicts the optimal VT ablation targets of ARVC patients. Methods: We retrospectively enrolled 11 ARVC patients; 8 presented with clinical VTs and underwent VT ablation. In all patients, RV hyperenhancement on LGE-CMR was identified. For this study, we developed RVCAT, the first computational heart model integrating RV personalized diffuse and dense fibrosis as VT substrates. Each region was assigned ARVC-specific electrophysiologic properties. VT inducibility was assessed via rapid pacing in each model. If inducible, optimal ablation targets, which rendered the RV substrate non-inducible for each VT, were determined. Targets were compared to electroanatomic voltage maps (EAM), locations of clinical ablations, and clinical records. Results: Personalized model predictions correlated well with clinical observations. All 8 models of the patients with a history of clinical VT had inducible VTs (Fig A). Furthermore, model VT circuit locations matched the clinical description. Substrate distribution in models matched low-voltage zones in EAM. The predicted ablation targets coincided with clinical ablations (Fig B). Results showed that the volume of model ablation lesions was significantly smaller than that of clinical ablations (1.02±0.68 versus 1.45±0.91, p&lt;0.05, Fig C). For the 3 patients who did not have VTs, their corresponding heart models correctly predicted that no VTs would be induced. Conclusions: RVCAT is a novel digital-heart technology for optimal ARVC VT ablation guidance that can be potentially integrated into clinical workflows for augmenting therapeutic precision.