Ventricular Tachycardia Substrate Ablation Research Articles

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.

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.

Epicardial catheter ablation of ventricular tachycardia in patients of acm - from a university hospital report in switzerland

Abstract Background Arrhythmogenic left ventricular cardiomyopathy (ALVC) as a subtype of arrhythmogenic cardiomyopathy (ACM) is increasingly being recognized. Cardiac magnetic resonance (CMR) has emerged as the primary imaging modality for the diagnosis of ACM. In patients with right-dominant ACM (ARVC) and recurrent sustained ventricular tachycardia (VT), endocardial +/-epicardial ablation yields good clinical outcomes in the long-term. However, studies on VT ablation in ACM with LV involvement are scarce. Purpose We sought to investigate clinical outcomes of VT ablation in ACM patients with LV involvement. Methods The study included patients from the Zurich ACM Registry who met 2020 "Padua Criteria" for ACM and underwent VT ablation between January 2018 and July 2023. Epicardial ablation was performed in patients with recurrent sustained VT despite endocardial ablation, those lacking and endocardial substrate or if the ECG of the VT / substrate on CMR was suggestive of an epicardial origin. Catheter ablation was guided by activation/entrainment mapping for mappable VT, and pace mapping/voltage mapping during sinus rhythm for unmappable VT. Consecutive follow-up of all patients was performed according to our protocol. Results Twenty-one ACM patients underwent n=24 VT ablation procedures. Of those 20 patients, 6 patients (30%) had LV involvement on CMR. Eight (33%) patients underwent epicardial +/- endocardial ablation. Among patients receiving epicardial ablation, 3 patients (38%) had LV involvement. These three underwent a single ablation procedure, which was epicardial only. Total follow-up was 30 months (range 4-43). Three-month sustained VT/VF recurrence rates were 12% in the ACM group with LV involvement vs 25% in ACM without LV involvement. All patients with sustained VT/VF recurrence underwent repeat ablation via an epicardial approach within 3 months and were free of sustained VT/VF thereafter during a median follow-up of 12 months. One-year recurrence rate did not differ between ACM patients with LV involvement vs. without LV involvement (7.7% vs 8.3%, P＝0.117). Seven out of eight epicardial ablations achieved freedom from VT/VF after one-year follow-up. One ARVC patient with previous endocardial ablation had recurrent VT one month after epicardial ablation, which was free of VT after Flecainide combined with beta-blocker. No significant differences were found in the use of beta-blockers and antiarrhythmic drugs between both groups (ACM with LV involvement vs. without LV involvement) at baseline and during one-year follow-up. Conclusions Single or adjuvant epicardial substrate ablation of VT in arrhythmogenic cardiomyopathy is promising in terms of postprocedural VT free survival, especially in patients with left ventricular involvement demonstrated by CMR.Figure 1Figure 2

Optimal cardiac rhythm during substrate mapping in scar-related ventricular tachycardia: Significance of wavefront direction on identifying critical sites

BackgroundA rotational activation pattern (RAP) around the localized line of a conduction block often correlates with sites specific to the critical zones of ventricular tachycardia (VT). The wavefront direction during substrate mapping affects manifestation of the RAP and line of block. ObjectiveThe purpose of this study was to investigate the most optimal cardiac rhythm for identifying RAP and line of block in substrate mapping. MethodsWe retrospectively evaluated 71 maps (median 3205 points/map) in 46 patients (65 ± 15 years; 33% with ischemic cardiomyopathy) who underwent high-density substrate mapping and ablation of scar-related VT. Appearance of a RAP during sinus, right ventricular (RV)-paced, left ventricular (LV)-paced, and biventricular-paced rhythms was investigated. ResultsRAP was identified in 24 of 71 maps (34%) in the region where wavefronts from a single direction reached but not in the region where wavefronts from multiple directions centripetally collided. The probability of identifying the RAP depended on scar location; that is, anteroseptal and inferoseptal, inferior and apical, and basal lateral RAPs were likely to be identified during sinus/atrial, RV-paced, and LV-paced rhythms, respectively. In 13 patients, the RAP was not evident in the baseline map but became apparent during remapping in the other rhythm, in which the wavefront reached the site earlier within the entire activation time. ConclusionThe optimal rhythm for substrate mapping depends on the spatial distribution of the area of interest. A paced rhythm with pacing sites near the scar may facilitate the identification of critical VT zones.

Ventricular tachycardia substrate ablation in patients with slightly depressed left ventricular ejection fraction. Predictors of VT-free survival in a prospective multicentre registry

Abstract Funding Acknowledgements Type of funding sources: None. Background There is no consensus about the need for ICD implantation in patients with slightly depressed left ventricle ejection fraction (LVEF) after catheter ablation for hemodynamically tolerated ventricular tachycardia (VT). Purpose This study aims to investigate predictors of mortality VT-free survival in this population. Methods We evaluated predictors of VT-free survival in patients with LVEF&amp;gt;40% from a prospective multicenter register of patients undergoing VT substrate ablation for hemodynamically tolerated VT. Decision to protect with ICD implantation at hospital discharge was performed according to the judgment of the treating cardiologist. The patients included in the study were followed every six months. Ventricular arrhythmia-free survival was the primary endpoint. Any episode of sustained VT (&amp;gt; 30 s) or appropriate ICD therapy was considered VT recurrence. Results One-hundred thirty-two patients [67±13 years, 91% male, 50±8% mean LVEF, 85 (65%) with ischemic heart disease] with a LVEF&amp;gt;40% were identified. Twenty-one (16%) of them were non-inducible at the end of the procedure and were discharged without ICD implantation as they were considered to have a low risk of recurrences. After a mean follow-up of 26±23 months, 32 (24%) patients had VT recurrences. A complete arrhythmogenic substrate elimination [HR: 0.34 (0.16-0.7), p&amp;lt;0.01] and the use multiple ventricular extrastimuli for hidden slow conduction (HSC) identification and ablation [HR: 0.51 (0.27-1.1), p=0.09] were related with VT-free survival (Figure 1). 53 (40%) patients fulfilled both criteria, having a 8% recurrence rate during the follow-up. Compared with the clinical decision making of ICD implantation at hospital discharge, the use of these two variables better identify patients at risk for VT recurrences, with a net reclassification improvement of 23% (Figure 2). Conclusions VT recurrence after VT substrate ablation in patients with slightly depressed LVEF remains high. However, complete substrate elimination and HSC analysis and ablation are related with higher VT-free survival and identify a subgroup of patients in whom ICD might be not beneficial.

A method to identify which patients will have VT substrate ablation targets prior to ablation procedure

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): Dr Nanthakumar is a recipient of the Mid-career Investigator Award from the Heart &amp; Stroke Foundation of Ontario Background Recent trials in ventricular tachycardia (VT) ablation suggest that early ablation could reduce VT burden. A method to predict which patients will have substrate ablation targets based on non-invasive testing prior to the procedure does not exist and could be of value in selecting ideal patients for early VT substrate ablation. Decrement-evoked potential (DeEP) mapping is used to identify VT substrate ablation targets.1 A method for predicting which patients would have DeEP targets on a pre-ablation 12-lead ECG has not yet been developed. Objective To develop a metric to predict the presence of physiological substrate VT ablation targets from the 12-lead ECG. Method 22 electrophysiology (EP) lab VT cases that had undergone DeEP mapping were extracted from the CARTO® 3 system and were analysed retrospectively. For each case, DeEP was calculated by subtracting last component of the nearfield evoked response in the pacing train (S1) from the latest component of the nearfield evoked decremented response of the extra stimulus (S2). By inference, 12-lead ECG prediction was calculated by subtracting the width of the 12-lead surface ECG envelope of S1 from the width of the 12-lead ECG envelope of S2. Cases were divided into three categories: - Cases displaying intracardiac DeEP between 0-10ms – no ablation targets - Cases displaying intracardiac DeEP between 10-50ms – DeEP positive - Cases displaying intracardiac DeEP &amp;gt;50ms – prominent DeEP present Results Out of the 22 cases, 8 were characterised as no ablation targets, 12 as DeEP positive, and 2 as prominent DeEP present. The 12-lead surface ECG measurement means were 3.5±4.6ms for the no ablation target group, 23.2±9.1ms for positive DeEP group, and 80.9±8.1ms for prominent DeEP group. The surface ECG decrement was significantly different P&amp;lt;0.0001 between the three groups. Consequently, we propose that ECG QRS widening of envelope width of 20ms or more may indicate the presence of DeEP targets during invasive mapping. Conclusion It may be possible to detect which patients will have substrate ablation targets based on 12-lead ECG, prior to the VT ablation procedure. Additionally, this prediction rule, based on its association with arrhythmogenic potentials, may be able to predict which ambulatory patients who have not had manifest VT, may be prone to develop VT thus help identify early VT ablation candidates. This concept should be validated in larger data sets and is ideal for training and testing using surface ECG envelopes with artificial intelligence algorithms.

Outcomes of ventricular tachycardia substrate ablation facilitated by preprocedural imaging scar characterization. A prospective multicenter registry

Abstract Funding Acknowledgements Type of funding sources: None. Background Catheter ablation is a recommended therapy for patients with ventricular tachycardia (VT). However, recurrences rate in non-ischemic cardiomyopathy (NICM) patients remains high. Objectives To analyze outcomes of VT substrate ablation facilitated by the integration into the navigator system of the preprocedural image scar characterization in both, patients with ischemic cardiomyopathy (ICM) cand NICM. Methods One hundred and sixty-five consecutive patients with structural heart disease undergoing scar related left-side VT ablation were included in a prospective European multicenter (5 centers) registry. Pixel signal intensity (PSI) maps from the late gadolinium enhancement-CMR (LGE-CMR) and/or the multi-detector cardiac tomography (MDCT) were imported into the navigator system. Ablation approach (e.g. endo vs epicardial; left vs right side) was based in the scar distribution aiming to eliminate the entire arrhythmogenic substrate. Mapping and ablation were focused in the scar areas. In all patients Scar dechanneling was the substrate ablation technique used. Results 165 [153 (93%) men, 66+12 y.o, 117 (71%) with ischemic heart disease] patients were included. Pre-procedure CMR was performed in 65 (39%), MDCT in 12 (7%) and both in 88 (53%) patients. VT induction protocol was negative after substrate ablation in 121 (73%) patients, completing the procedure in stable sinus rhythm. Procedure related complication rate was 5.5%. Arter a mean follow-up of 18+19 months, overall survival was 91% and 44 (27%) patients had VT recurrences. There was no difference in VT-free survival in ischemic vs non-ischemic patients (Log rank:0.9), as Figure 1 shows. Conclusions A strategy of VT substrate ablation facilitated by the integration into the navigator system of the preprocedural image scar characterization with the aim of eliminate the entire arrhythmogenic substrate results in a low recurrence rate. This approach minimizes the gap in VT-free survival after ablation in patients with ICM and NICM.

Cardiac magnetic resonance-aided ventricular tachycardia substrate ablation in corrected tetralogy of Fallot.

Cardiac magnetic resonance-aided ventricular tachycardia substrate ablation in corrected tetralogy of Fallot.

High-density Approaches to Ventricular Tachycardia Substrate Ablation

Ventricular tachycardia (VT) ablation is a challenging procedure with significant clinical benefit for patients. The classic VT ablation approach centers on arrhythmia induction and entrainment of tachycardia to identify the critical components of a VT circuit. In the post-coronary reperfusion era, smaller infarct size and subsequently faster VT cycle lengths have led to an increased occurrence of unstable, unmappable VT cases, making the classic approach untenable. While approaches of signal-based substrate modification have shown clinical efficacy in the past, these approaches are sometimes imprecise and require extensive ablation. With the advancement of high-density (HD) mapping technology and recognition of functional tissue properties requisite for VT initiation and propagation, a more finely targeted VT ablation approach may be pursued. Benefits of HD mapping include better tissue and signal characterization, avoidance of ‘perpendicular blinding’ and better identification of VT putative channels. Functional characterization of tissue, such as isochronal late activation mapping or decremental evoked potential mapping, allow for the identification of functional slowing required for VT reentry. Pre-ablative imaging continues to play an increasing role in substrate characterization and pre-operative planning. Using a comprehensive, tailored, substrate-based functional HD VT ablation strategy can allow for safe and effective ablation of even unstable and unmappable VT.

Preventive substrate ablation in chronic post-myocardial infarction patients with high-risk scar characteristics for ventricular arrhythmias: rationale and design of PREVENT-VT study.

Recent studies showed that an early strategy for ventricular tachycardia (VT) ablation resulted in reduction of VT episodes or mortality. Cardiac magnetic resonance (CMR)-derived border zone channel (BZC) mass has proved to be a strong non-invasive predictor of VT in post-myocardial infarction (MI). CMR-guided VT substrate ablation proved to be safe and effective for reducing sudden cardiac death (SCD) and VA occurrence. PREVENT-VT is a prospective, randomized, multicenter, and controlled trial designed to evaluate the safety and efficacy of prophylactic CMR-guided VT substrate ablation in chronic post-MI patients with CMR-derived arrhythmogenic scar characteristics. Chronic post-MI patients with late gadolinium enhancement (LGE) CMR will be evaluated. CMR images will be post-processed and the BZC mass measured: patients with a BZC mass > 5.15g will be eligible. Consecutive patients will be enrolled at 3 centers and randomized on a 1:1 basis to undergo a VT substrate ablation (ABLATE arm) or optimal medical treatment (OMT arm). Primary prevention ICD will be implanted following guideline recommendations, while non-ICD candidates will be implanted with an implantable cardiac monitor (ICM). The primary endpoint is a composite outcome of sudden cardiac death (SCD) or sustained monomorphic VT, either treated by an ICD or documented with ICM. Secondary endpoints are procedural safety and efficiency outcomes of CMR-guided ablation. In some patients, the first VA episode causes SCD or severe neurological damage. The aim of the PREVENT-VT is to evaluate whether primary preventive substrate ablation may be a safe and effective prophylactic therapy for reducing SCD and VA occurrence in patients with previous MI and high-risk scar characteristics based on CMR. ClinicalTrials.gov, NCT04675073, registered on January 1, 2021.

Automated quantification and identification of decremental response after extrastimulus: validation of a novel software

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Junta de Andalucia Background Automatic identification of myocardial electrograms (EGMs) with decremental conduction (DC) is a promising field in catheter ablation procedures, allowing the identification of the critical isthmus of tachycardias with re-entry mechanisms. In this work, a novel artificial intelligence (AI)-based software was developed for the automatic analysis of delays between evoked responses in the coronary sinus (CS), allowing signal quantification. Methods Atrioventricular (AV) and ventriculoatrial (VA) conduction was analysed in coronary sinus signals obtained from patients undergoing electrophysiological study. A simple pacing (S=400-600ms) and extra-stimulus protocol (S2=ERP + 20-60ms) were used in all cases. An AI-based algorithm was developed for EGM delineation with the objective of localising the onsets and offsets of each independent local and far field activations. The algorithm consisted in several steps. Firstly, an AI-based QRS detector was employed (Figure 1A). Secondly, the located QRS’ were used alongside another AI model to delineate the EGMs corresponding to all bipolar electrodes in the CS (Figure 1B). Thirdly, majority voting is performed on the delineations to obtain an overall prediction for all CS electrodes (Figure 1C). Fourthly, the predictions are cleaned and a rule-based algorithm is employed to automatically exclude faulty registries (e.g. loss of capture or AV/VA block after S2). Finally, the determination of decremental response is performed by computing the time difference between the last paced beat and the S2 extrastimulus. This was measured using the onsets of morphologically similar activations in the trace, correcting for misalignments. A decremental response was defined as a difference &amp;gt;10 ms between the AV/VA interval during the S1 drive and the same interval immediately after the S2. Four experts validated results of the automated analysis. Results 321 tracings from 50 patients were analysed. 81 tracings were automatically excluded due to loss of capture or AV/VA block after S2. The AV/VA interval was automatically annotated in 236 EGMs. 192 tracings exhibited decremental conduction properties, whereas 48 tracings showed non-decremental AV or VA conduction due to accessory pathways. Automatic analysis accurately classified 191 tracings as decremental (93.75% sensitivity, 91.47% specificity) and 45 tracings as non-decremental (85.42% sensitivity, 98.53% specificity). Conclusions AI-based algorithms are able to produce objective quantifications over real-world data, discriminating between local and far field signals and accurately identifying EGMs with decremental evoked response. Automated data analysis can accelerate research and reduce clinical workload. Moreover, a quantification-based approach can be employed in many other applications. Validation of this software on ventricular signals could facilitate ventricular tachycardia substrate ablation procedures.

Cardiovascular magnetic resonance determinants of ventricular arrhythmic events after myocardial infarction.

To non-invasively characterize, by means of late gadolinium enhancement cardiac magnetic resonance (LGE-CMR), scar differences, and potential variables associated with ventricular tachycardia (VT) occurrence in chronic post-myocardial infarction (MI) patients. A case-control study was designed through retrospective LGE-CMR data analysis of chronic post-MI patients (i) consecutively referred for VT substrate ablation after a first VT episode (n = 66) and (ii) from a control group (n = 84) with no arrhythmia evidence. The myocardium was characterized differentiating core, border zone (BZ), and BZ channels (BZCs) using the ADAS 3D post-processing imaging platform. Clinical and scar characteristics, including a novel parameter, the BZC mass, were compared between both groups. One hundred and fifty post-MI patients were included. Four multivariable Cox proportional hazards regression models were created for total scar mass, BZ mass, core mass, and BZC mass, adjusting them by age, sex, and left ventricular ejection fraction (LVEF). A cut-off of 5.15 g of BZC mass identified the cases with 92.4% sensitivity and 86.9% specificity [area under the ROC curve (AUC) 0.93 (0.89-0.97); P < 0.001], with a significant increase in the AUC compared to other scar parameters (P < 0.001 for all pairwise comparisons). Adding BZC mass to LVEF allowed to reclassify 33.3% of the cases and 39.3% of the controls [net reclassification improvement = 0.73 (0.71-0.74)]. The mass of BZC is the strongest independent variable associated with the occurrence of sustained monomorphic ventricular tachycardia in post-MI patients after adjustment for age, sex, and LVEF. Border zone channel mass measurement could permit a more accurate VT risk stratification than LVEF in chronic post-MI patients.

Long-term outcome of ventricular tachycardia ablation in patients who did not undergo programmed electrical stimulation after ablation.

Ventricular arrhythmia inducibility is one of the ideal endpoints of ventricular tachycardia (VT) ablation. However, it may be challenging to implement programmed electrical stimulation (PES) at the end of the procedure under several circumstances. The long-term outcome of patients who did not undergo PES after VT ablation remains largely unknown. To investigate the details and long-term outcome of VT ablation in patients who did not undergo PES at the end of the ablation procedure. Among 183 VT ablation procedures in patients with structural heart disease who underwent VT ablation using an irrigated catheter, we enrolled those who did not undergo PES after VT ablation. VT ablation strategy involved targeting clinical VT plus pacemap-guided substrate ablation if inducible. When VT was not inducible, substrate-based ablation was performed. The primary endpoint was VT recurrence. In 58 procedures, post-ablation VT inducibility was not assessed. The causes were non-inducibility of sustained VT before ablation (27/58, 46.6%), long procedure time (27.6%, mean 392min), complications (10.3%), intolerant hemodynamic state (10.3%), and inaccessible or unsafe target (6.9%). With regard to the primary endpoint, 23 recurrences (39.7%) were observed during a mean follow-up period of 2.5years. Patients with non-inducibility before ablation showed less VT recurrences (4/27, 14.8%) during follow-up than patients with other causes of untested PES after ablation (19/31, 61.2%) (Log-rank < 0.001). VT recurrence was not observed in approximately 60% of the patients who did not undergo PES at the end of the ablation procedure. PES after VT ablation may be not needed among patients with pre-ablation non-inducibility.

Metabolic Scar Assessment with18F-FDG PET: Correlation to Ischemic Ventricular Tachycardia Substrate and Successful Ablation Sites.

The functional and molecular imaging characteristics of ischemic ventricular tachycardia (VT) substrate are incompletely understood. Our objective was to compare regional 18F-FDG PET tracer uptake with detailed electroanatomic maps (EAMs) in a more extensive series of postinfarction VT patients to define the metabolic properties of VT substrate and successful ablation sites. Methods: Three-dimensional (3D) metabolic left ventricular reconstructions were created from perfusion-normalized 18F-FDG PET images in consecutive patients undergoing VT ablation. PET defects were classified as severe (defined as <50% uptake) or moderate (defined as 50%-70% uptake), as referenced to the maximal 17-segment uptake. Color-coded PET scar reconstructions were coregistered with corresponding high-resolution 3D EAMs, which were classified as indicating dense scarring (defined as voltage < 0.5 mV), normal myocardium (defined as voltage > 1.5 mV), or border zones (defined as voltage of 0.5-1.5 mV). Results: All 56 patients had ischemic cardiomyopathy (ejection fraction, 29% ± 12%). Severe PET defects were larger than dense scarring, at 63.0 ± 48.4 cm2 versus 13.8 ± 33.1 cm2 (P < 0.001). Similarly, moderate/severe PET defects (≤70%) were larger than areas with abnormal voltage (≤1.5 mV) measuring 105.1 ± 67.2 cm2 versus 56.2 ± 62.6 cm2 (P < 0.001). Analysis of bipolar voltage (23,389 mapping points) showed decreased voltage among severe PET defects (n = 10,364; 0.5 ± 0.3 mV) and moderate PET defects (n = 5,243; 1.5 ± 0.9 mV, P < 0.01), with normal voltage among normal PET areas (>70% uptake) (n = 7,782, 3.2 ± 1.3 mV, P < 0.001). Eighty-eight percent of VT channel or exit sites (n = 44) were metabolically abnormal (severe PET defect, 78%; moderate PET defect, 10%), whereas 12% (n = 6) were in PET-normal areas. Metabolic channels (n = 26) existed in 45% (n = 25) of patients, with an average length and width of 17.6 ± 12.5 mm and 10.3 ± 4.2 mm, respectively. Metabolic channels were oriented predominantly in the apex or base (86%), harboring VT channel or exit sites in 31%. Metabolic rapid-transition areas (>50% change in 18F-FDG tracer uptake/15 mm) were detected in 59% of cases (n = 33), colocalizing to VT channels or exit sites (15%) or near these sites (85%, 12.8 ± 8.5 mm). Metabolism-voltage mismatches in which there was a severe PET defect but voltage indicating normal myocardium were seen in 21% of patients (n = 12), 41% of whom were harboring VT channel or exit sites. Conclusion: Abnormal 18F-FDG uptake categories could be detected using incremental 3D step-up reconstructions. They predicted decreasing bipolar voltages and VT channel or exit sites in about 90% of cases. Additionally, functional imaging allowed detection of novel molecular tissue characteristics within the ischemic VT substrate such as metabolic channels, rapid-transition areas, and metabolism-voltage mismatches demonstrating intrasubstrate heterogeneity and providing possible targets for imaging-guided ablation.

Arrhythmogenic substrate detection in chronic ischaemic patients undergoing ventricular tachycardia ablation using multidetector cardiac computed tomography: compared evaluation with cardiac magnetic resonance

Late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) permits characterizing ischaemic scars, detecting heterogeneous tissue channels (HTCs) which constitute the arrhythmogenic substrate (AS). Late gadolinium enhancement cardiac magnetic resonance also improves the arrhythmia-free survival when used to guide ventricular tachycardia (VT) substrate ablation. However, its availability may be limited. We sought to evaluate the performance of multidetector cardiac computed tomography (MDCT) imaging in identifying HTCs detected by LGE-CMR in ischaemic patients undergoing VT substrate ablation. Thirty ischaemic patients undergoing both LGE-CMR and MDCT before VT substrate ablation were included. Using a dedicated post-processing software, two blinded operators, assigned either to LGE-CMR or MDCT analysis, characterized the presence of CMR and computed tomography (CT) channels, respectively. Cardiac magnetic resonance channels were classified as endocardial (layers < 50%), epicardial (layers ≥ 50%), or transmural. Cardiac magnetic resonance- vs. CT-channel concordance was considered when showing the same orientation and American Heart Association (AHA) segment. Mean age was 69 ± 10 years; 90% were male. Mean left ventricular ejection fraction was 35 ± 10%. All patients had CMR channels (n = 76), whereas only 26/30 (86.7%) had CT channels (n = 91). Global sensitivity (Se) and positive predictive values for detecting CMR channels were 61.8% and 51.6%, respectively. MDCT performance improved in patients with epicardial CMR channels (Se 80.5%) and transmural scars (Se 72.2%). In 4/11 (36%) patients with subendocardial myocardial infarction (MI), MDCT was unable to identify the AS. Compared to LGE-CMR, myocardial wall thickness assessment using MDCT fails to detect the presence of AS in 36% of patients with subendocardial MI, showing modest sensitivity identifying HTCs but a better performance in patients with transmural scars.

Safety and Outcomes of Ventricular Tachycardia Substrate Ablation During Sinus Rhythm: A Prospective Multicenter Registry.

This study sought to analyze safety and outcomes of ventricular tachycardia (VT) substrate ablation during sinus rhythm (SR), without baseline VT induction. Safety and outcomes after scar-related VT ablation during SR are not well known. Hemodynamic instability and need for electrical cardioversion can compromise safety of VT ablation procedures. Four hundred twelve consecutive patients with structural heart disease undergoing VT ablation were included in a prospective multicenter registry. Substrate ablation during SR, without baseline VT induction, was the first step of the ablation procedure and the standard protocol. Scar dechanneling was the substrate ablation technique used. VT inducibility was tested after substrate ablation. VT induction protocol was negative after substrate ablation in 289 patients (70.1%), completing the procedure in SR. Procedure-related complication rate was 6.5%, including 1 death (0.2%). Thirty-day mortality after first VT ablation procedure was 1.7%. Overall survival was 95.8% and 88.6% at 1 and 3 years of follow-up, respectively. In a multivariable proportional hazards regression model, age≥70 years (hazard ratio [HR]: 4.95 [2.59 to 9.47]; p<0.001), chronic obstructive pulmonary disease (HR: 2.37 [1.24 to 4.52]; p=0.008), left ventricular ejection fraction<30% (HR: 2.43 [1.37 to 4.33]; p=0.002), and incomplete substrate ablation (HR: 2.37 [1.24 to 4.52]; p=0.026) were independent predictors of overall mortality. At 12months' follow-up, VT-free survival was 82.5% after 1 procedure and 87.8% after n procedures CONCLUSIONS: Substrate ablation during SR avoiding multiple VT induction has low procedure-related complications and low early mortality. Age, chronic obstructive pulmonary disease, and reduced left ventricular ejection fraction, but also incomplete substrate elimination, are predictors of mortality.

P1111Arrhythmogenic substrate detection in ischemic patients undergoing ventricular tachycardia ablation using multi-detector computed tomography: compared evaluation with cardiac magnetic resonance

Abstract Background Cardiac magnetic resonance (CMR) is capable of accurately identifying arrhythmogenic substrate (AS), leading to longer arrhythmia-free survival when used to guide ventricular tachycardia (VT) substrate ablation procedures. However, the use of CMR may be limited in certain centers or patient subsets. Purpose To evaluate the performance of multidetector cardiac computed tomography (MDCT) imaging in identifying heterogeneous tissue channels (HTCs) detected by CMR in ischemic patients undergoing VT substrate ablation. Methods Thirty ischemic patients undergoing both CMR and MDCT before VT substrate ablation were included. Using a dedicated post-processing software, two blinded operators, assigned either to CMR or MDCT analysis, characterized the presence of CMR- and CT-channels, respectively. CMR-channels were classified as endocardial (layers &amp;lt;50%), epicardial (layers ≥50%) or transmural. CMR- vs. CT-channel concordance was considered when the orientation was the same and they were located in the same AHA segment. Results Mean age was 69 ± 10 years; 90% were male. Mean left ventricular ejection fraction (LVEF) was 35 ± 10%. All patients had CMR-channels (n = 76), whereas only 26/30 (86.7%) had CT-channels (n = 91). Global sensitivity (Se) and positive predictive values (PPV) for detecting CMR-channels were 61.8% and 51.6%, respectively. MDCT performance improved in patients with epicardial CMR-channels (Se 80.5%), and transmural scars (Se 72.2%). In 4/11 (36%) patients with subendocardial MI, MDCT was unable to identify the AS. Conclusion MDCT fails to detect the presence of AS in 36% of patients with subendocardial MI and shows a modest sensitivity identifying the presence of HTCs, although its performance improves in patients with transmural scar. Abstract Figure. Multimodality imaging AS detection

Long-term outcomes of ventricular tachycardia substrate ablation incorporating hidden slow conduction analysis

Ventricular tachycardia substrate ablation (VTSA) incorporating hidden slow conduction (HSC) analysis allows further arrhythmic substrate identification. The purpose of this study was to analyze whether the elimination of HSC electrograms (HSC-EGMs) during VTSA results in better short- and long-term outcomes. Consecutive patients (N = 70; 63% ischemic; mean age 64 ± 14.6 years) undergoing VTSA were prospectively included. Bipolar EGMs with >3 deflections and duration <133 ms were considered as potential HSC-EGMs. Whenever a potential HSC-EGM was identified, double or triple ventricular extrastimuli were delivered. If a local potential showed up as a delayed component, it was annotated as HSC-EGM. Ablation was delivered at conducting channel entrances and HSC-EGMs. Radiofrequency time, ventricular tachycardia (VT) inducibility after VTSA, and VT/ventricular fibrillation recurrence at 24 months after the procedure were compared with data from a historical control group. A total of 5076 EGMs were analyzed; 1029 (20.2%) qualified as potential HSC-EGMs, and 475 of them were tagged as HSC-EGMs. Scars in patients with HSC-EGMs (n = 43 [61.4%]) were smaller (32.2 [17-58] cm2 vs 85 [41-92.4] cm2; P = .006) and more heterogeneous (core/scar area ratio 0.15 [0.05-0.44] vs 0.44 [0.33-0.57]; P = .017); 32.4% of HSC-EGMs were located in normal voltage tissue. Patients undergoing VTSA incorporating HSC analysis required less radiofrequency time (15.6 [8-23.1] vs 23.9 [14.9-30.8]; P < .001) and had a lower rate of VT inducibility after VTSA (28.6% vs 52.9%; P = .003) than did the historical controls. Patients undergoing VTSA incorporating HSC analysis showed a higher 2-year VT/ventricular fibrillation-free survival (75.7% vs 58.8%; log-rank, P = .046) after VTSA. VTSA incorporating HSC analysis allowed further arrhythmic substrate identification (especially in the border zone and normal voltage areas) and was associated with increased VTSA efficiency and better short- and long-term outcomes.

Cardiac Magnetic Resonance-Guided Ventricular Tachycardia Substrate Ablation

This study assessed the feasibility and potential benefit of performing ventricular tachycardia (VT) substrate ablation procedures guided by cardiac magnetic resonance (CMR)-derived pixel signal intensity (PSI) maps. CMR-aided VT ablation using PSI maps from late gadolinium enhancement-CMR (LGE-CMR), together with electroanatomical map (EAM) information, has been shown to improve outcomes of VT substrate ablation. Eighty-four patients with scar-dependent monomorphic VT who underwent substrate ablation were included in the study. In the last 28 (33%) consecutive patients, the procedure was guided by CMR. Procedural data, as well as acute and follow-up outcomes, were compared between patients who underwent guided CMR and 2 control groups: 1) patients who had PSI maps were available but the EAM was acquired and used to select the ablation targets (CMR aided); and 2) patients with no CMR-derived PSI maps available (no CMR). Mean procedure duration was lower in CMR-guided substrate ablation compared with CMR-aided and no CMR (107 ± 59min vs. 203 ± 68min and 227 ± 52min; p<0.001 for both comparisons). CMR-guided ablation required less fluoroscopy time than CMR-aided ablation and no CMR (10 ± 4min vs. 23 ± 11min and 20 ± 9min, respectively; p<0.001 for both comparisons) and less radiofrequency time (15 ± 8min vs. 20 ± 15min and 26 ± 10min; p=0.16 and p<0.001, respectively). After substrate ablation, VT inducibility was lower in CMR-guided ablation compared with CMR-aided ablation and no CMR (18% vs. 32% and 46%; p=0.35 and p=0.04, respectively), without significant differences in complications. After 12months, VT recurrence was lower in those who underwent CMR-guided ablation compared with no CMR (log-rank: 0.019), with no differences with CMR-aided ablation. CMR-guided VT ablation is feasible and safe, significantly reduces the procedural, fluoroscopy, and radiofrequency times, and is associated with a higher noninducibility rate and lower VT recurrence after substrate ablation.

Hybrid Ventricular Tachycardia Ablation after Failed Percutaneous Endocardial and Epicardial Ablation

Introduction: Recurrent ventricular tachycardia (VT) after percutaneous ablation is associated with a high morbidity and mortality. We assessed the feasibility of open chest extracorporeal circulation (ECC)-supported 3D multielectrode mapping and targeted VT substrate ablation in patients with previously failed percutaneous endocardial and epicardial VT ablations. Methods: In patients with previously failed percutaneous endocardial and epicardial VT ablations and a high risk of hemodynamic collapse during the procedure, open chest ECC-supported mapping and ablation were performed in a hybrid EP lab setting. Electro-anatomic maps (3D) were acquired during sinus rhythm and VT using a multielectrode mapping catheter (HD grid; Abbott or Pentaray, Biosense Webster). Irrigated radiofrequency ablations of all inducible VT were performed with a contact force ablation catheter. Results: Hybrid VT ablation was performed in 5 patients with structural heart disease (i.e., 3 with previous old myocardial infarction and 2 with nonischemic cardiomy­opathy) and recurrent VT. Acute procedural success was achieved in all patients. Four patients were successfully weaned off the ECC. In 1 patient with a severely reduced LVEF (16%), damage to the venous graft occurred after sternotomy and that patient died after 1 month. Four patients (80%) remained VT free after a median follow-up of 6 (IQR 4–10) months. Conclusion: In high-risk patients with previously failed percutaneous endocardial and epicardial VT ablations, open chest ECC-supported multielectrode epicardial mapping revealed a VT substrate in all of the patients, and targeted epicardial ablation abolished VT substrate in these patients.