Ventricular Tachycardia Substrate Research Articles

Stereotactic Arrhythmia Radioablation (STAR) for refractory ventricular tachycardia- the initial Australian experience.

Stereotactic arrhythmia radioablation (STAR) is a novel, noninvasive technique for the management of refractory ventricular tachycardia (VT). This retrospective study aimed to assess the feasibility, efficacy, and safety of STAR in an Australian cohort. From February 2020 to August 2023, 12 patients with drug-refractory VT who had either failed catheter ablation or were unsuitable, were treated with stereotactic ablative radiotherapy (STAR) in two Australian centres. A combination of electrocardiograms, multi-modality imaging and non-invasive/invasive mapping data was used to target the presumed ventricular tachycardia substrate. All treatments (25 Gy in one fraction) were delivered without anaesthesia. Efficacy endpoints were defined as the number of VT episodes, anti-tachycardia pacing (ATP), VT storms and shocks six months before and after treatment (6-week blanking period). Mortality and adverse event data were collected over 12-month follow-up (FU). In the nine patients who survived the blanking period, a significant reduction (64.5%, P = 0.011) in VT burden and VT storm (71.7%, P = 0.027) was observed over a 6-month FU. However, 66.7% (6/9) of these patients experienced VT recurrence. 3/6 patients with recurrence with ECGs available for review had the same VT morphology as pre-STAR. Over a 12-month FU, five patients died, and three adverse events were recorded (undersensing of defibrillator lead, increased rate of reflux and radiation pneumonitis). This paper summarises the initial Australian experience treating refractory VT with STAR. It demonstrates that STAR can significantly decrease the VT and VT storm burden over a 6-month FU with an acceptable acute side-effects profile, albeit with a high VT recurrence rate.

Lamotrigine promotes reentrant ventricular tachycardia in murine hearts.

In 2021, the US Food and Drug Administration issued a safety warning concerning lamotrigine use in patients with underlying cardiac disorders. This warning was based on invitro data that predicted class Ib antiarrhythmic activity for lamotrigine. Therefore, we investigated the proarrhythmic potential of lamotrigine in the murine heart and compared its effect with flecainide. Murine hearts were perfused with clinically relevant concentrations of lamotrigine 3.8 μg/mL (15 μmol·L-1) or flecainide .4 μg/mL (1 μmol·L-1). Ex vivo electrocardiography revealed a high prevalence of ventricular tachycardia (VT) in lamotrigine-perfused hearts (7/9 hearts), whereas only two hearts exposed to flecainide evidenced VT. Optical voltage mapping showed that lamotrigine preferentially decreased ventricular conduction velocity (CV) in the longitudinal direction at all pacing frequencies tested (-22% ± 8.6%, -30% ± 15.4%, and -33% ± 13.3% for pacing frequency of 200-ms, 180-ms, and 150-ms cycle length, respectively, p ≤ .05) compared to the transverse direction, which only slowed CV at the fastest pacing frequency (-15% ± 16% for pacing frequency of 150-ms cycle length, p ≤ .01). Notably, the preferential CV slowing in the longitudinal direction altered the anisotropic ratio, giving rise to a functional substrate for reentrant VT. In contrast, flecainide slowed CV uniformly in both longitudinal and transverse directions (-30% ± 8.5% vs. -27% ± 5.3%, -32% ± 9.4% vs. -29% ± 6.9%, and - 29% ± 8.3% vs. -27% ± 10% for pacing frequency of 200-ms, 180-ms, and 150-ms cycle length, respectively, p ≤ .05). Our findings provide mechanistic insight into the proarrhythmic impact of lamotrigine.

Age-Related Ventricular Tachycardia Substrate Characteristics for Repaired Tetralogy of Fallot Before Transcatheter Pulmonary Valve Placement.

Ventricular tachycardia (VT) substrate characteristics before transcatheter pulmonary valve replacement (TPVR) in repaired tetralogy of Fallot (rTOF) are unknown. In this study, the authors sought to evaluate substrates for sustained monomorphic VT before TPVR in rTOF. Retrospective (2017 to 2021) and prospective (commencing 2021) rTOF patients with native right ventricular outflow tract referred for electrophysiology study (EPS) before TPVR were included. Electrophysiologic findings and outcomes of VT ablation were determined. One-hundred eighty patients (mean age 39 ± 14 years, 54% male, 71 retrospective, 109 prospective) were identified. At EPS, monomorphic VT was induced in 45 (25%), and a slowly conducting anatomic isthmus alone was observed in 40 (22%). VT isthmus conduction velocity decreased (-0.08m/s per decade; P=0.008) and VT inducibility (P< 0.001 for trend) and cycle length (CL) (+15ms per decade, P=0.005) increased with age. Multivariable factors associated with shorter VT CL included preserved isthmus conduction velocity (-50ms per m/s; P=0.02), absence of atrial flutter (-18ms; P=0.007), and improved RV ejection fraction (-16ms per 10% increase; P=0.007). Catheter ablation was acutely successful in 80/83 (96%). At repeated EPS after a median of 5months, previously ablated substrates were evident in 3/24 (13%) and new VT substrates in 3/33 (9%). Pre-TPVR VT substrates in rTOF demonstrate age-related degeneration that was associated with VT inducibility and VT CL. Both recovery of VT isthmus conduction and new VT substrates were observed after TPVR despite successful catheter ablation.

Stereotactic arrhythmia radioablation for ventricular tachycardia: a review of clinical trials and emerging roles of imaging.

Ventricular tachycardia (VT) is a severe arrhythmia commonly treated with implantable cardioverter defibrillators, antiarrhythmic drugs and catheter ablation (CA). Although CA is effective in reducing recurrent VT, its impact on survival remains uncertain, especially in patients with extensive scarring. Stereotactic arrhythmia radioablation (STAR) has emerged as a novel treatment for VT in patients unresponsive to CA, leveraging techniques from stereotactic body radiation therapy used in cancer treatments. Recent clinical trials and case series have demonstrated the short-term efficacy and safety of STAR, although long-term outcomes remain unclear. Imaging techniques, such as electroanatomical mapping, contrast-enhanced magnetic resonance imaging and nuclear imaging, play a crucial role in treatment planning by identifying VT substrates and guiding target delineation. However, challenges persist owing to the complex anatomy and variability in target volume definitions. Advances in imaging and artificial intelligence are expected to improve the precision and efficacy of STAR. The exact mechanisms underlying the antiarrhythmic effects of STAR, including potential fibrosis and improvement in cardiac conduction, are still being explored. Despite its potential, STAR should be cautiously applied in prospective clinical trials, with a focus on optimizing dose delivery and understanding long-term outcomes. Collaborative efforts are necessary to standardize treatment strategies and enhance the quality of life for patients with refractory VT.

Ventricular septal defect characteristics influence presence of septal anatomical isthmuses in patients with repaired tetralogy of Fallot.

In repaired tetralogy of Fallot (rTOF), the septal anatomical isthmuses (AI), AI 3, between the ventricular septal defect (VSD) and pulmonary annulus, and AI 4, between the VSD and tricuspid annulus, are important ventricular tachycardia (VT) substrates when slow conducting. Our aim was to assess the influence of VSD characteristics, specifically the presence of muscular or fibrous tissue at its border, on the presence or absence of septal AIs, potentially related to VT. All consecutive rTOF patients who underwent electroanatomical mapping between January 2005 and March 2023 with an available surgical report providing VSD details (n = 91) were included. The majority of patients had an outlet perimembranous VSD (n = 76, 84%), 6 (7%) an outlet muscular VSD, and 7 (8%) a doubly committed juxta-arterial VSD. In patients with an outlet perimembranous VSD, AI 3 was present in almost all (97%), whereas no AI 4 was observed. In patients with an outlet muscular VSD, AI 3 and AI 4 were present in 83% and 33%, respectively. In all patients with a doubly committed VSD, where the outlet septum is hypoplastic/fibrous, AI 3 was absent. Among patients with a doubly committed VSD with a muscular postero-inferior rim, 50% had AI 4, whereas none of those with a fibrous postero-inferior rim had AI 4. Ventricular septal defect characteristics aid in determining the presence of septal AIs potentially related to VT. In patients with doubly committed VSDs, septal VT substrates are unlikely. Detailed knowledge of anatomical VSD characteristics is desirable for understanding VT in rTOF.

Ventricular Tachycardia Substrate in Cardiomyopathy With Excessive Trabeculation Evaluated by Magnetic Resonance and Functional Mapping.

Ventricular Tachycardia Substrate in Cardiomyopathy With Excessive Trabeculation Evaluated by Magnetic Resonance and Functional Mapping.

Termination Without Global Propagation in Re-Entrant Ventricular Tachycardia: Electrophysiologic Characteristics and 3D-Electroanatomical Mapping Analysis.

Termination of ventricular tachycardia (VT) by a pacing stimulus that does not generate a QRS complex (termination without global propagation [TWGP]) can be a marker for a critical re-entry circuit isthmus. However, the electrophysiologic and anatomic features of these sites and their relation to VT substrate defined by 3-dimensional electroanatomical maps (3D-EAM) remain unknown. This retrospective study aimed to characterize TWGP sites and their relation to VT substrate identified by 3D-EAM. A total of 632 consecutive cases of catheter ablation for scar-related VT at 2 University medical centers were reviewed to identify TWGP. TWGP was observed 12 times at 11 different sites in 10 patients (5 ischemic cardiomyopathy). The TWGP stimulus fell immediately before or synchronous with the QRS in all cases, and evidence of local capture despite absence of a QRS complex was observed 6 times. In 5 sites, pacing after VT termination produced a QRS different than the VT. Four sites were in dense scar areas (<0.1mV), and 6 in abnormal low voltage zone (0.1-1.5mV). Additional mapping or ablation that abolished VT were consistent with the TWGP site being in a VT isthmus. A substrate marker for VT of late potentials, evoked delayed potentials, or slow conduction was present at 6 of 11 TWGP sites. TWGP may be a marker for detecting a re-entry circuit isthmus that has escaped detection based on electrogram or pace mapping-based substrate mapping.

Stereotactic arrhythmia radioablation - A systematic review and meta-analysis of the prospective clinical studies

Abstract Background Stereotactic arrhythmia radioablation (STAR) is increasingly being evaluated in prospective studies as a new promising treatment option for patients with therapy-refractory ventricular tachycardia (VT). In STAR, the VT substrate is noninvasively treated with a high dose of radiotherapy. Recently, several single-arm prospective studies evaluating the clinical outcomes of STAR were published. Considering that the evidence base consists mainly of retrospective case series, we conducted a systematic review and meta-analysis to synthesize the prospective data on outcomes of STAR. Purpose To perform a systematic review and meta-analysis of prospective studies evaluating clinical outcomes of STAR for VT. Methods This study was registered in PROSPERO and adhered to the PRISMA reporting guidelines. Full-text studies describing prospective studies evaluating the safety and efficacy of STAR for VT were included in this study. Records published until August 2023 were retrieved from OVID MEDLINE, OVID Embase, Web of Science Core Collection, the Cochrane Central Register of Controlled Trials, and Google Scholar search engine (top 200 hits), deduplicated, and screened for eligibility. Abstract screening, full-text screening, data extraction and quality assessment were performed by two reviewers independently. Endpoints were defined as treatment related CTCAE grade ≥3 adverse events within 90 days after treatment, overall survival (OS), time to VT recurrence, and recurrence-free survival. Rates of patients achieving pre-defined 50%, 75% and 95% VT burden reduction thresholds were summarised. Random-effects generalized linear mixed-effects models and inverse variance models were used for the meta-analysis. Results 1861 records were identified, 987 were screened, and 10 full-text manuscripts published between 2019 and 2023 describing the results of STAR in 82 patients were included in this study. The majority were male (n=72; 88%), between 45 and 85 years old, and suffered from ischaemic cardiomyopathy (n=51; 62%). Median left ventricular ejection fraction ranged from 21 to 38% between studies. 20 patients did not undergo a prior catheter ablation for VT. All patients were treated with a single dose of 25 Gy and median planned target volume ranged from 45 to 198 cc between studies. Pooled 12-month OS rate was 0.73, and the proportion of patients experiencing grade ≥3 adverse events within 90 days after STAR was 0.11 (Figure 1). Reduction in VT burden is shown in Table 1. Although these were not pooled because of large heterogeneity in VT reduction time frame definitions, it can be appreciated that most of the patients experienced a reduction in VT burden. Conclusion The increasing evidence from prospective studies on STAR shows acceptable 12-month OS in a population of patients with advanced heart failure and refractory VT. Moreover, there is a modest rate of high-grade adverse events and most patients experience a reduction in VT burden.

Targeting ventricular tachycardia originating from the anterolateral papillary muscle with stereotactic body radioablation therapy

Abstract Background Ventricular Tachycardia (VT) is prevalent in the setting of non-ischaemic cardiomyopathy (NICM), a heterogeneous group of conditions characterized by myocardial dysfunction in the absence of coronary artery disease. Challenges of catheter ablation to treat VT in NICM patients are well known, and recurrence rates can be as high as 58%. Stereotactic body radioablation therapy (SBRT) involves precise delivery of radiation to arrhythmogenic substrates, and represents a novel treatment to reduce recurrent implantable cardioverter defibrillator (ICD) therapies in patients with refractory VT. Though SBRT has shown preliminary effectiveness in reducing VT episodes, its effectiveness in NICM patients has not been widely evaluated. Purpose To evaluate SBRT effectiveness in NICM patients with scars at the basal anterolateral papillary muscle at a tertiary care center between November-December 2022. Methods Eligible patients had their VT substrate mapped using a single-use ECGI vest and a 4D-CT simulation scan. In addition, MRI scans were used to aid anatomical identification of the anterolateral papillary muscle which could not be seen on the non-contrast diagnostic CTs. SBRT was delivered in a single fraction of 25 Gy under image guidance. Effectiveness of the treatment was evaluated as changes in frequencies of total antitachycardia pacing (ATP) and ICD shock episodes from 6 months pre-, and within to 3, 6, and 12 months follow up post SBRT. Results Participants were 3 males with NICM, aged 56, 60, and 73 with previous dual chamber ICD implantation, 2 of whom had a history of VT ablation/ VT storm and paroxysmal atrial fibrillation. All participants had basal lateral scar, and were receiving beta blockers, mexiletine, and amiodarone with refractory VT before SBRT treatment. Prior to SBRT, ICD device interrogation showed a total of 119 (77, 7, and 35 in patients 1-3 respectively) ATPs, and 27 (10, 1, and 16 in patients 1-3 respectively) ICD shocks delivered. At 12 month follow-up, none of the participants experienced any episodes of ATP or ICD shock. Ejection fraction remained consistent pre-post SBRT. Conclusion SBRT showed remarkable success in reducing ATP and ICD shock episodes, facilitating uncomplicated 1 year follow-up in 3 male patients with NICM and VT from the anterolateral papillary muscle.

Dynamic Voltage Mapping of the Post-infarct Ventricular Tachycardia Substrate: A Practical Technique to Help Differentiate Scar from Borderzone Tissue.

During catheter ablation of post-infarct ventricular tachycardia (VT), substrate mapping is used when VT is non-inducible or poorly tolerated. Substrate mapping aims to identify regions of slowly conducting myocardium (borderzone) within and surrounding myocardial scar for ablation. Historically, these tissue types have been identified using bipolar voltage mapping, with areas of low bipolar voltage (<0.50 mV) defined as scar, and areas with voltages between 0.50 mV and 1.50 mV as borderzone. In the era of high-density mapping, studies have demonstrated slow conduction within areas of bipolar voltage <0.50 mV, suggesting that this historical cut-off is outdated. While electrophysiologists often adapt voltage cut-offs to account for this, the optimal scar-borderzone threshold is not known. In this review, we discuss dynamic voltage mapping, a novel substrate mapping technique we have developed, which superimposes data from both activation and voltage maps, to help delineate the post-infarct VT circuit through identification of the optimal scar-borderzone voltage threshold.

Magnetic Resonance-Guided StereotacticRadioablation for SeptalVentricular Tachycardias.

Stereotactic arrhythmia radioablation (STAR) was introduced to treat ventricular tachycardia (VT) refractory to catheter ablation. No data are now available in the septal VT substrate setting, representing a challenge when using conventional techniques. This study sought to evaluate the arrhythmic burden in patients with septal VT treated with magnetic resonance-guided STAR (MRgSTAR). We enrolled consecutive patients with septal VT substrate. The therapy target was achieved by combining anatomic/functional and electrophysiologic information. Patients were treated with a single fraction of 25Gy adopting MRgSTAR. All patients were clinically followed up, and all implantable cardiac devices were remotely monitored. The efficacy outcome included recurrences of any sustained VT beyond the 6-week blanking period after MRgSTAR. The safety outcome was the incidence of adverse events and atrioventricular block. We included 11 patients with septal substrate VT (median age: 68 years; Q1-Q3: 64.5-78 years; 100% male). Clinical presentation was an electrical storm in 81.8% of patients. No complications occurred after MRgSTAR, and 6(54.5%) patients were discharged on the same day of treatment. During a mean follow-up of 12 ± 6months, the efficacy outcome occurred in 3 (27.3%) cases. A significative reduction of implantable cardioverter-defibrillator (ICD) therapy (23.6 before MRgSTAR vs 1.7 after MRgSTAR; P< 0.001) was observed. Left ventricular ejection fraction increased significantly after treatment (38% [Q1-Q3: 33.5%-42.0%] before MRgSTAR vs 43.8% [Q1-Q3: 35%-47%] after MRgSTAR; P=0.04). No adverse effects were observed in the implantable cardioverter-defibrillator and lead system; in the 7 patients with preserved atrioventricular conduction, no atrioventricular block was reported. MRgSTAR represents a safe and effective strategy for treating septal VT.

Detailed analysis of electrogram peak frequency to guide ventricular tachycardia substrate mapping.

Differentiating near-field (NF) and far-field (FF) electrograms (EGMs) is crucial in identifying critical arrhythmogenic substrate during ventricular tachycardia (VT) ablation. A novel algorithm annotates NF-fractionated signals enabling EGM peak frequency (PF) determination using wavelet transformation. This study evaluated the algorithms' effectiveness in identifying critical components of the VT circuit during substrate mapping. A multicentre, international cohort undergoing VT ablation was investigated. VT activation maps were used to demarcate the isthmus zone (IZ). Offline analysis was performed to evaluate the diagnostic performance of low-voltage area (LVA) PF substrate mapping. A total of 30 patients encompassing 198 935 EGMs were included. The IZ PF was significantly higher in sinus rhythm (SR) compared to right ventricular paced (RVp) substrate maps (234 Hz (195-294) vs. 197 Hz (166-220); P = 0.010). Compared to LVA PF, the IZ PF was significantly higher in both SR and RVp substrate maps (area under curve, AUC: 0.74 and 0.70, respectively). The LVA PF threshold of ≥200 Hz was optimal in SR maps (sensitivity 69%; specificity 64%) and RVp maps (sensitivity 60%; specificity 64%) in identifying the VT isthmus. In amiodarone-treated patients (n = 20), the SR substrate map IZ PF was significantly lower (222 Hz (186-257) vs. 303 Hz (244-375), P = 0.009) compared to amiodarone-naïve patients (n = 10). The ≥200 Hz LVA PF threshold resulted in an 80% freedom from VT with a trend towards reduced ablation lesions and radiofrequency times. LVA PF substrate mapping identifies critical components of the VT circuit with an optimal threshold of ≥200 Hz. Isthmus PF is influenced by chronic amiodarone therapy with lower values observed during RV pacing.

MRI Accurately Visualizes RF Ablation Delivery Targeted to MRI-Defined Arrhythmia Substrates in the Left Ventricle.

Investigate the capacity of MRI to evaluate efficacy of radiofrequency (RF) ablations delivered to MRI-defined arrhythmogenic substrates. Baseline MRI was performed at 3 T including 3D LGE in a swine model of chronic myocardial infarct (N = 8). MRI-derived maps of scar and heterogeneous tissue channels (HTCs) were generated using ADAS 3D. Animals underwent electroanatomic mapping and ablation of the left ventricle in CARTO3, guided by MRI-derived scar maps. Post-ablation MRI (in vivo at 3 T in 5/8 animals; ex vivo at 1.5 T in 3/8) included 3D native T1-weighted IR-SPGR (TI = 700-800 ms) to visualize RF lesions. T1-derived RF lesions were compared against excised tissue. The locations of T1-derived RF lesions were compared against CARTO ablation tags, and segment-wise sensitivity and specificity of lesion detection were calculated within the AHA 17-segment model. RF lesions were clearly visualized in HTCs, scar, and myocardium. Ablation patterns delivered in CARTO matched T1-derived RF lesion patterns with high sensitivity (88.9%) and specificity (94.7%), and were closely matched in registered MR-EP data sets, with a displacement of 5.4 ±3.8 mm (N = 152 ablation tags). Integrating MRI into ablative procedures for RF lesion assessment is feasible. Patterns of RF lesions created using a standard 3D EAM system are accurately reflected by MRI visualization in healthy myocardium, scar, and HTCs comprising the MRI-defined arrhythmia substrate. MRI visualization of RF lesions can provide near-immediate ( 24 h) assessment of ablation, potentially indicating whether critical MRI-defined ventricular tachycardia substrates have been adequately ablated.

Whole-Heart Histological and Electroanatomic Assessment of Postinfarction Cardiac Magnetic Resonance Imaging Scar and Conducting Channels.

Cardiac magnetic resonance imaging (CMR)-defined ventricular scar and anatomic conduction channels (CMR-CCs) offer promise in delineating ventricular tachycardia substrate. No studies have validated channels with coregistered histology, nor have they ascertained the histological characteristics of deceleration zones (DZs) within these channels. We aimed to validate CMR scar and CMR-CCs with whole-heart histology and electroanatomic mapping in a postinfarction model. Five sheep underwent anteroseptal infarction. CMR (116±20 days post infarct) was postprocessed using ADAS-3D, varying pixel intensity thresholds (5545, 6040, 6535, and 7030). DZs were identified by electroanatomic mapping (129±12 days post infarct). Explanted hearts were sectioned and stained with Picrosirius red, and whole-heart histopathologic shells were generated. Scar topography as well as percentage fibrosis, adiposity, and remaining viable myocardium within 3 mm histological biopsies and within CMR-CCs were determined. Using the standard 6040 thresholding, CMR had 83.8% accuracy for identifying histological scar in the endocardium (κ, 0.666) and 61.4% in the epicardium (κ, 0.276). Thirty-seven CMR-CCs were identified by varying thresholding; 23 (62%) were unique. DZs colocalized to 19 of 23 (83%) CMR-CCs. Twenty (87%) CMR-CCs were histologically confirmed. Within-channel histological fibrosis did not differ by the presence of DZs (P=0.242). Within-channel histological adiposity was significantly higher at sites with versus without DZs (24.1% versus 8.3%; P<0.001). Postprocessed CMR-derived scars and channels were validated by histology and electroanatomic mapping. Regions of CMR-CCs at sites of DZs had higher adiposity but similar fibrosis than regions without DZs, suggesting that lipomatous metaplasia may contribute to arrhythmogenicity of postinfarction scar.

Multi-Faceted Approach to Ventricular Tachycardia: A Review of Management Strategies

Ventricular tachycardia poses a significant therapeutic challenge. It can manifest over a spectrum from minimal palpitation symptoms to sudden cardiac death. This makes large-scale trials on the treatment of ventricular tachycardia difficult to perform. The mechanism of ventricular tachycardia must also be understood before embarking on treatment. Patients with or without structural heart disease will have different mechanisms for the onset and propagation of these arrhythmias. Catheter ablation is an established management option for ventricular tachycardia; however, it is not always successful and anti-arrhythmic medications are often necessary to control these life-threatening arrhythmias. Although anti-arrhythmics can suppress ventricular tachycardias they also carry side effects. In certain substrates, some of these medications can exacerbate arrhythmias or heart failure. For these reasons, a multifaceted approach to treating ventricular tachycardia is necessary. This paper is a comprehensive review of the comprehensive management strategies for ventricular tachycardia. Anti-arrhythmic medications have an important role and their use in various cardiomyopathies and channelopathies is reviewed in detail. We also review the promising effects of gene therapy and artificial intelligence on different substrates for ventricular tachycardia.

Spatial analysis and characteristics of persistent late potentials after ablation of scar-related VT substrate: Implications for late potential elimination as a procedural endpoint with high-resolution mapping

BackgroundLate potential (LP) elimination has been proposed as a surrogate endpoint for scar-related ventricular tachycardia (VT) ablation procedures. The characteristics, distribution, and predictors of persistent late potentials (pLPs) after ablation have not been studied. ObjectiveThe purpose of this study was to characterize the spatial distribution and features of pLP after catheter ablation of VT substrate with high-resolution mapping. MethodsCases of scar-related VT ablation with adequate pre- and postablation electroanatomic maps (EAMs) acquired exclusively using a high-density grid catheter were reviewed from 2021 to 2023. ResultsA total of 62 EAMs (pre- and postablation) from 31 cases using a high-density grid catheter were reviewed. pLPs were observed in 19 cases (61%) after ablation. New LP, spatially distinct from preablation LP, at the periphery of the ablation area comprised the majority of pLPs (16/19 [84%]). Isolated pLPs were more prevalent than fractionated pLPs, with a median amplitude of 0.26 mV (0.09–0.59 mV). The presence of pLP was associated with a significantly lower left ventricular ejection fraction (LVEF) and septal ablation but not low voltage, LP, or ablation area compared to absence of pLP (22.8% ± 7.8% vs 31.5% ± 8.0%, P = .008 for LVEF; 83% vs 44%, P = .033 for septal ablation). ConclusionFormation of spatially distinct new LP after targeted VT ablation is common, especially in patients with lower LVEF and septal substrate independent of ablation burden. This finding highlights the limitations of complete LP elimination as an endpoint to VT ablation procedures.

RIPPLE-VT study: Multicenter prospective evaluation of ventricular tachycardia substrate ablation by targeting scar channels to eliminate latest scar potentials without direct ablation

BackgroundRecurrent ventricular tachycardia (VT) can be treated by substrate modification of the myocardial scar by catheter ablation during sinus rhythm without VT induction. Better defining this arrhythmic substrate could help improve outcome and reduce ablation burden. ObjectiveThe study aimed to limit ablation within postinfarction scar to conduction channels within the scar to reduce VT recurrence. MethodsPatients undergoing catheter ablation for recurrent implantable cardioverter-defibrillator therapy for postinfarction VT were recruited at 5 centers. Left ventricular maps were collected on CARTO using a Pentaray catheter. Ripple mapping was used to categorize infarct scar potentials (SPs) by timing. Earliest SPs were ablated sequentially until there was loss of the terminal SPs without their direct ablation. The primary outcome measure was sustained VT episodes as documented by device interrogations at 1 year, which was compared with VT episodes in the year before ablation. ResultsThe study recruited 50 patients (mean left ventricular ejection fraction, 33% ± 9%), and 37 patients (74%) met the channel ablation end point with successful loss of latest SPs without direct ablation. There were 16 recurrences during 1-year follow-up. There was a 90% reduction in VT burden from 30.2 ± 53.9 to 3.1 ± 7.5 (P < .01) per patient, with a concomitant 88% reduction in appropriate shocks from 2.1 ± 2.7 to 0.2 ± 0.9 (P < .01). There were 8 deaths during follow-up. Those who met the channel ablation end point had no significant difference in mortality, recurrence, or VT burden but had a significantly lower ablation burden of 25.7 ± 4.2 minutes vs 39.9 ± 6.1 minutes (P = .001). ConclusionScar channel ablation is feasible by ripple mapping and can be an alternative to more extensive substrate modification techniques.

Near-field detection and peak frequency metric for substrate and activation mapping of ventricular tachycardias in two- and three-dimensional circuits.

Successful ventricular arrhythmia (VA) ablation requires identification of functionally critical sites during contact mapping. Estimation of the peak frequency (PF) component of the electrogram (EGM) may improve correct near-field (NF) annotation to identify circuit segments on the mapped surface. In turn, assessment of NF and far-field (FF) EGMs may delineate the three-dimensional path of a ventricular tachycardia (VT) circuit. A proprietary NF detection algorithm was applied retrospectively to scar-related re-entry VT maps and compared with manually reviewed maps employing first deflection (FDcorr) for VT activation maps and last deflection (LD) for substrate maps. Ventricular tachycardia isthmus location and characteristics mapped with FDcorr vs. NF were compared. Omnipolar low-voltage areas, late activating areas, and deceleration zones (DZ) in LD vs. NF substrate maps were compared. On substrate maps, PF estimation was compared between isthmus and bystander sites. Activation mapping with entrainment and/or VT termination with radiofrequency (RF) ablation confirmed critical sites. Eighteen patients with high-density VT activation and substrate maps (55.6% ischaemic) were included. Near-field detection correctly located critical parts of the circuit in 77.7% of the cases compared with manually reviewed VT maps as reference. In substrate maps, NF detection identified deceleration zones in 88.8% of cases, which overlapped with FDcorr VT isthmus in 72.2% compared with 83.3% overlap of DZ assessed by LD. Applied to substrate maps, PF as a stand-alone feature did not differentiate VT isthmus sites from low-voltage bystander sites. Omnipolar voltage was significantly higher at isthmus sites with longer EGM durations compared with low-voltage bystander sites. The NF algorithm may enable rapid high-density activation mapping of VT circuits in the NF of the mapped surface. Integrated assessment and combined analysis of NF and FF EGM-components could support characterization of three-dimensional VT circuits with intramural segments. For scar-related substrate mapping, PF as a stand-alone EGM feature did not enable the differentiation of functionally critical sites of the dominant VT from low-voltage bystander sites in this cohort.

Predictors of decremental conduction after extrastimulus in post-infarction ventricular tachycardia substrate maps

Abstract Introduction Ventricular tachycardia (VT) substrate ablation techniques attempt to identify areas of decremental conduction (DC) within the scar, given their close relationship with VT isthmuses. DC identification requires the systematic use of extrastimuli during substrate mapping. This can be time consuming and induce ventricular arrhythmias during mapping. Objective This study aims to identify predictors of decremental response after extastimulus that allow recognizing areas with higher probability of DC conduction in order to focus functional mapping of the substrate on them. Methods Sixteen consecutive ischemic patients (93.8% male, 66.3±12.4 years) undergoing VT substrate ablation were included. A detailed substrate map during right ventricular (RV) pacing was obtained in all of them. Systematic analysis of electrograms (EGMs) recorded from the infarct area was performed during RV pacing at 600-500 ms, and during a short-coupled RV extrastimulus. Electrograms during RV pacing exhibiting decremental evoked conduction delay after an extrastimulus (DECD-AE) were compared to those not showing DECD-AE. Results Mean low voltage (&amp;lt;1.5 mV) area was 45±18.6 cm2. A total of 1744 EGMs were analyzed. Of them, 453 (26%) showed DECD-AE. Bipolar EGMs showing DECD-AE exhibited a higher number of deflections [4(interquartile range 3-5) vs 2(1-3); p&amp;lt;0.0001], a higher amplitude [0.52(0.27-1) vs 0.3(0.14-0.7) mV; p=0.003] and similar duration [114(102-135) vs 117(100-133 ms); p=0.492] compared to EGMs without DECD-AE. The area under curve was 0.64 for bipolar voltage and 0.8 for number of bipolar deflections. The presence of &amp;lt;3 bipolar deflections excluded DECD-AE with a negative predictive value of 98.5%. Conclusions In areas of myocardial scar, bipolar EGMs with &amp;lt;3 deflections are unlikely to present DECD-AE. Focusing functional mapping on signals with ≥3 deflections could simplify procedures and save time.

Stereotactic arrhythmia radioablation for refractory ventricular tachycardia. A retrospective analysis and optimisation of the planning phase

Abstract Introduction Stereotactic arrhythmia radioablation (STAR) is used as a rescue treatment for refractory ventricular tachycardia (VT). However, the planning phase to accurately delineate the clinical target volume (CTV) still suffers from limitations due to the incompatibility of data formats between 3D electro-anatomical mapping systems (EAM) used for VT ablation and STAR planning software. The concordance between the CTVs as defined by the planning software (CTVSTAR) and the CTV based on EAM data (CTVEAM) remains unknown. Purpose Within the STOPSTORM European consortium, we compared the concordance between CTVSTAR and CTVEAM in our series of 13 patients (pts) treated by STAR for refractory VT. We also evaluated need for redo ablation of VT after STAR. Method Using the software Slicer3D, two protocols were retrospectively compared: Protocol 1 comprised the manual contouring of the CTVSTAR based on 4D-CT SCAN drawn side-by-side using EAM (Carto3, Biosense Webster) screenshots and diagnostic reports. Protocol 2 comprised semiautomatic segmentation of CTVEAM based on 4D-CT SCAN using imported EAMs annotated with landmarks for VT substrate delimitation. The delineation of CTVEAM included 3 steps: (1) semiautomatic segmentation of ventricular myocardium (VM), the blood-pool of the concerned ventricle and at least 2 additional cardiac cavities; (2) 3D-alignment of EAM with the segmented cavities; and (3), 3D-delineation of CTVSTAR identified as the transmural section of VM segment surrounding the EAM’s VT substrate delimited by STAR tags (Figure 1). Volume overlap (Dice coefficient, 100% meaning complete overlap) and volume absolute difference (VAD, 0% meaning similar volumes) between CTVs were compared. The following cumulative averages were computed over time: redo ablation (RedoA) and CTV. Results Figure 1 illustrates the last treated patient (#13) in whom the delineated volumes, CTVSTAR (red) and CTVEAM (blue), displayed good matching (Dice 72% and VAD 4. Figure 2 shows the comparison between CTVSTAR and CTVEAM for the 13 pts (65±7 yo) treated with STAR, resulting in a mean Dice of 47±17% and mean VAD of 40±51%. Figure 3 shows the cumulative RedoA and the cumulative averaged CTVSTAR and CTVEAM over time. Interestingly, the need for redo ablation decreased with increasing CTVs. Conclusion Our study demonstrates the efficacy of STAR treatment for refractory VT. Our confidence in STAR led to higher CTVs and lower RedoA over time. The high variability of CTV delineation using two different protocols suggests that STAR planning phase can be optimised by appointing intraprocedural anatomical landmarks to the VT substrate.