Scar-related Ventricular Tachycardia Research Articles

Catheter ablation of ventricular tachycardia in ischemic cardiomyopathy: Impact of concomitant amiodarone therapy on short- and long-term clinical outcomes

Substrate catheter ablation of scar-related ventricular tachycardia (VT) is a widely accepted therapeutic option for patients with ischemic cardiomyopathy (ICM). The purpose of this study was to investigate whether concomitant amiodarone therapy affects procedural outcomes. A total of 134 consecutive patients (89% male; age 66± 10 years) with ICM undergoing catheter ablation of VT were included in the study. Patients were sorted by amiodarone therapy before ablation. In all patients, a substrate-based catheter ablation (endocardial ± epicardial) in sinus rhythm abolishing all "abnormal" electrograms within the scar was performed. The endpoint of the procedure was VT noninducibility. After the ablation procedure, all antiarrhythmic medications were discontinued. All patients had an implantable cardioverter-defibrillator, and recurrences were analyzed through the device. In 84 patients (63%), the ablation was performed on amiodarone; the remaining 50 patients (37%) were off amiodarone. Patients had comparable baseline characteristics. Mean scar size area was 143.6 ± 44.9 cm2 on amiodarone vs 139.2 ± 36.8 cm2 off amiodarone (P = .56). More radiofrequency time was necessary to achieve noninducibility in the off-amiodarone group compared to the on-amiodarone group (68.1 ± 20.1 minutes vs 51.5 ± 19.7 minutes; P <.001). In addition, due to persistent VT inducibility, more patients in the off-amiodarone group required epicardial ablation than in the on-amiodarone group (13/50 [26%] vs 5/84 [6%], respectively; P <.001). During mean follow-up of 23.9 ± 11.6 months, recurrence of any ventricular arrhythmias off antiarrhythmic drugs was 44% (37/84) in the on-amiodarone group vs 22% (11/50) in the off-amiodarone group (P = .013). Albeit, VT noninducibility after substrate catheter ablation for scar related VT was achieved faster, with less radiofrequency time and less need for epicardial ablation in patients taking amiodarone, these patients had significantly higher VT recurrence at long-term follow-up when this medication was discontinued.

Specific electrogram characteristics impact substrate ablation target area in patients with scar-related ventricular tachycardia-insights from automated ultrahigh-density mapping.

Substrate-based catheter ablation approaches to ventricular tachycardia (VT) focus on low-voltage areas and abnormal electrograms. However, specific electrogram characteristics in sinus rhythm are not clearly defined and can be subject to variable interpretation. We analyzed the potential ablation target size using automatic abnormal electrogram detection and studied findings during substrate mapping in the VT isthmus area. Electrogram characteristics in 61 patients undergoing scar-related VT ablation using ultrahigh-density 3D-mapping with a 64-electrode mini-basket catheter were analyzed retrospectively. Forty-four complete substrate maps with a mean number of 10319 ± 889 points were acquired. Fractionated potentials detected by automated annotation and manual review were present in 43 ± 21% of the entire low-voltage area (<1.0 mV), highly fractionated potentials in 7 ± 8%, late potentials in 13 ± 15%, fractionated late potentials in 7 ± 9% and isolated late potentials in 2 ± 4%, respectively. Highly fractionated potentials (>10 ± 1 fractionations) were found in all isthmus areas of identified VT during substrate mapping, while isolated late potentials were distant from the critical isthmus area in 29%. The ablation target area varies enormously in size, depending on the definition of abnormal electrograms. Clear linking of abnormal electrograms with critical VT isthmus areas during substrate mapping remains difficult due to a lack of specificity rather than sensitivity. However, highly fractionated, low-voltage electrograms were found to be present in all critical VT isthmus sites.

Close-coupled pacing to identify the “functional” substrate of ventricular tachycardia: Long-term outcomes of the paced electrogram feature analysis technique

The conduction delay and block that compose the critical isthmus of macroreentrant ventricular tachycardia (VT) is partly "functional" in that they only occur at faster cycle lengths. Close-coupled pacing stresses the myocardium's conduction capacity and may reveal late potentials (LPs) and fractionation. Interest has emerged in targeting this functional substrate. The purpose of this study was to assess the feasibility and efficacy of a functional substrate VT ablation strategy. Patients with scar-related VT undergoing their first ablation were recruited. A closely coupled extrastimulus (ventricular effective refractory period + 30 ms) was delivered at the right ventricular apex while mapping with a high-density catheter. Sites of functional impaired conduction exhibited increased electrogram duration due to LPs/fractionation. The time to last deflection was annotated on an electroanatomic map, readily identifying ablation targets. A total of 40 patients were recruited (34 [85%] ischemic). Median procedure duration was 330 minutes (interquartile range [IQR] 300-369), and ablation time was 49.4 minutes (IQR 33.8-48.3). Median functional substrate area was 41.9 cm2 (IQR 22.1-73.9). It was similarly distributed across bipolar voltage zones. Noninducibility was achieved in 34 of 40 patients (85%). Median follow-up was 711 days (IQR 255.5-972.8), during which 35 of 39 patients (89.7%) did not have VT recurrence, and 3 of 39 (7.5%) died. Antiarrhythmic drugs were continued in 53.8% (21/39). Functional substrate ablation resulted in high rates of noninducibility and freedom from VT. Mapping times were increased considerably. Our findings add to the encouraging trend reported by related techniques. Randomized multicenter trials are warranted to assess this next phase of VT ablation.

Prognostic value of cardiac magnetic resonance septal late gadolinium enhancement patterns for periaortic ventricular tachycardia ablation: Heterogeneity of the anteroseptal substrate in nonischemic cardiomyopathy

Ventricular tachycardia (VT) from the anteroseptal subtype of nonischemic cardiomyopathy has a high probability of recurrence after catheter ablation. The purpose of this study was to determine the predictive value of septal scar patterns by late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) on ablation outcomes in patients with VT arising from an anteroseptal substrate. Patients with periaortic VT arising from an anteroseptal substrate with preprocedural wideband LGE-CMR were divided into 2 groups by the degree of longitudinal septal LGE extension as full-length septal (≥80% anteroposterior length) or partial septal (<80% anteroposterior length). Septal LGE volumes were quantified in those with and without VT recurrence. Among 234 patients referred for scar-related VT ablation between 2017 and 2020, 25 patients (92% male; age 64 ± 8 years) and a total of 108 VTs were analyzed. A greater number of VT morphologies were induced in patients with full-length septal LGE compared to partial septal LGE (median [interquartile range]: 5 [3-9] vs 2 [1-4]; P = .005). Patients with VT recurrence had larger septal LGE volumes compared to those without recurrence (11.4 mL [8.8-13.9] vs 4.2 mL [0-9.5]; P = .012). At median follow-up of 16 months (5-22), overall freedom from VT recurrence was 52% and significantly higher in patients with partial septal LGE than in those with full-length septal LGE (80% vs 20%; P = .005). VT originating from an anteroseptal substrate is associated with heterogeneous patterns and extent of CMR septal scar. Preprocedural imaging may substratify this challenging patient population for the propensity for multiple induced VT morphologies and recurrence after catheter ablation.

Abstract 14725: Image-based Virtual-heart Predictions Co-localize With ECG-based Automated Localization of Scar-related Ventricular Tachycardias

Introduction: We previously developed an LGE-MRI-based virtual-heart arrhythmia ablation targeting (VAAT) methodology to non-invasively determine potential ablation targets for infarct-related VT. However, it is unknown whether VAAT’s predictions correspond with surface ECG predictions. Hypothesis: We hypothesized that the VAAT predicted VT circuits and potential ablation lesions would co-localize with ECG-based VT-exit predictions from a previously validated population-derived automated VT exit localization (PAVEL) system. Methods: We retrospectively enrolled 5 post-infarct patients who underwent LV endocardial VT ablation and had pre-procedural 2D LGE-MRIs. The PAVEL system based on a population-derived statistical method was used to localize VT-exit sites onto one of 238 triangles on the patient-specific virtual-heart LV endocardial surface using 8 independent ECG leads (I, II, V1-V6). The VAAT methodology incorporating patient-specific scar and infarct border zone distributions was used to identify potential VT circuits and find ablation lesions. Results: Eleven induced VTs were analyzed. Ten VT-exit sites were localized onto the patient-specific virtual-heart LV endocardial surface by the PAVEL system, and were used for the comparisons. One VT-exit site was too basal to be localized onto the virtual-heart geometry. The spatial resolution of the 10 predicted VT-exit sites was 13.8 ± 1.8 mm. VAAT-predicted VT circuits and ablation lesions correlated well with all 10 predicted VT-exit sites. Lastly, VAAT ablation lesions fell within the regions ablated clinically. Conclusions: The VAAT-predicted VT circuits and ablation lesions matched VT-exit sites predicted by the surface ECG-based PAVEL system. Combining these two complementary technologies may improve accuracy for non-invasively identifying optimal ablation targets to increase ablation efficacy.

Functional Activation Mapping of Scar-Related Ventricular Tachycardia Substrate

The optimal method to identify the arrhythmogenic substrate of scar-related ventricular tachycardia (VT) is unknown. Sites of activation slowing during sinus rhythm (SR) often co-localize with the VT circuit. This is a report of two scar related VT substrate mapping using a strategy of voltage-independent approach.

Periprocedural Acute Kidney Injury in Patients With Structural Heart Disease Undergoing Catheter Ablation of VT.

This study sought to examine the impact of periprocedural acute kidney injury (AKI) in scar-related ventricular tachycardia (VT) patients undergoing radiofrequency catheter ablation (RFCA) on short- and long-term outcomes. The clinical significance of periprocedural AKI in patients with scar-related VT undergoing RFCA has not been previously investigated. This study included 317 consecutive patients with scar-related VT undergoing RFCA (age: 64 ± 13 years, mean left ventricular ejection fraction: 33 ± 13%, 55% ischemic cardiomyopathy). Periprocedural AKI was defined as an absolute increase in creatinine of≥0.3mg/dl over 48h or an increase of >1.5× the baseline values within 1week post-procedure. Periprocedural AKI occurred in 31 patients (10%). Independent predictors of AKI included chronic kidney disease (odds ratio [OR]: 3.43; 95% confidence interval [CI]: 1.48 to 7.96; p=0.004), atrial fibrillation (OR: 2.42; 95%CI: 1.01 to 5.78; p=0.047), and peri-procedural acute hemodynamic decompensation (OR: 3.98; 95%CI: 1.17 to 13.52; p=0.003). After a median follow-up of 39months (interquartile range: 6 to 65months), 95 patients (30%) died. Periprocedural AKI was associated with increased risk of early mortality (within 30days; hazard ratio [HR]: 9.91; 95%CI: 2.87 to 34.22; p<0.001) and late mortality (within 1 year) (HR: 4.57; 95%CI: 2.08 to 10.05; p<0.001). After multivariable adjustment, AKI remained independently associated with increased risk of early and late mortality (HR: 4.49; 95%CI: 1.1 to 18.36; p=0.04, and HR: 3.28; 95%CI: 1.43 to 7.49; p=0.005, respectively). Periprocedural AKI occurs in 10% of patients undergoing RFCA of scar-related VT and is strongly associated with increased risk of early and late post-procedural mortality.

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.

In-silico pace-mapping using a detailed whole torso model and implanted electronic device electrograms for more efficient ablation planning

BackgroundPace-mapping is a commonly used electrophysiological (EP) procedure which aims to identify exit sites of ventricular tachycardia (VT) by matching ventricular activation patterns (assessed by QRS morphology) at specific pacing locations with activation during VT. However, long procedure durations and the need for VT induction render this technique non-optimal.To demonstrate the potential of in-silico pace-mapping, using stored electrogram (EGM) recordings of clinical VT from implanted devices to guide pre-procedural ablation planning. MethodSix scar-related VT episodes were simulated in a 3D torso model reconstructed from computed tomography (CT) imaging data, including three different infarct anatomies mapped from infarcted porcine imaging data. In-silico pace-mapping was performed to localise VT exit sites and isthmuses by using 12-lead electrocardiogram (ECG) signals and different combinations of EGM sensing vectors from implanted devices, through the creation of conventional correlation maps and reference-less maps. ResultsOur in-silico platform was successful in identifying VT exit sites for a variety of different VT morphologies from both ECG correlation maps and corresponding EGM maps, with the latter dependent upon the number of sensing vectors used. We also showed the added utility of both ECG and EGM reference-less pace-mapping for the identification of slow-conducting isthmuses, uncovering the optimal algorithm parameters. Finally, EGM-based pace-mapping was shown to be more dependent upon the mapped surface (epicardial/endocardial), relative to the VT origin. ConclusionsIn-silico pace-mapping can be used along with EGMs from implanted devices to localise VT ablation targets in pre-procedural planning.

Prognostic significance of extensive versus limited induction protocol during catheter ablation of scar-related ventricular tachycardia.

Testing for inducible ventricular tachycardia (VT) pre- and postablation forms the cornerstone of contemporary scar-related VT ablation procedures. There is significant heterogeneity in reported VT induction protocols. We examined the utility of an extensive induction protocol (up to 4 extra-stimuli [ES] ± burst ventricular pacing) compared to the current guideline-recommended protocol (up to 3ES, defined as limited induction protocol) in patients with scar-related VT. Sixty-two patients (age: 64 ± 14 years; left ventricular ejection fraction: 37 ± 13%, ischemic cardiomyopathy: 31, nonischemic cardiomyopathy: 31) with at least one inducible VT were included. An extensive testing protocol induced 11%-17% more VTs, compared to the limited induction protocol before, and after the final ablation. VT recurred in 48% of patients during a mean follow up of 566 ± 428 days. Patients who were noninducible for any VT using the limited induction protocol had worse ventricular arrhythmia (VA)-free survival (12 months, 43% vs. 82%; p = .03) and worse survival free of VA, transplantation and mortality (12 months 46% vs. 82%; p = .02), compared to patients who were noninducible for any VT using the extensive induction protocol. Between 11% and 17% of inducible VTs may be missed if 4ES and burst pacing are not performed in induction protocols before and after ablation. Noninducibility for any VT after an extensive induction protocol after the final ablation portends more favorable prognostic outcomes when compared with the current guideline-recommended induction protocol of up to 3ES. This data suggests that the adoption of an extensive induction protocol is of prognostic benefit after VT ablation.

Non-invasive stereotactic body radiation therapy for refractory ventricular arrhythmias: an institutional experience.

Initial studies have reported excellent safety and efficacy for stereotactic body radiation therapy (SBRT) in patients with refractory ventricular tachycardia (VT). This is a single-center retrospective analysis of eight consecutive patients who underwent SBRT for refractory, scar-related VT. The anatomic target for radioablation was defined based on surface 12-lead ECG VT morphology, cardiac magnetic resonance imaging, and electroanatomic mapping data when available. The target volume treated and the prescribed radiation dose (15-25Gy) was based on the combined clinical assessment of the cardiac electrophysiologist and radiation oncologist. Ventricular arrhythmias, radiation-related outcomes, and adverse events were monitored at follow-up. Eight patients underwent nine SBRT sessions. All patients were male with an average age of 75 ± 7.3years and mean ejection fraction of 21 ± 7%. SBRT was performed with delivery of an average of 22.2 ± 3.6Gy in a single session with a procedure time of 18.2 ± 6.0min. All but one session was performed on an inpatient basis. No acute complications occurred. During a median follow-up of 7.8months (IQR 4.8, 9.9), ICD therapies decreased from median 69.5 (43.5, 115.8) pre-SBRT to 13.3 (IQR 7.7, 35.8) post-SBRT (p = 0.036). There were three patient deaths in the follow-up period, unrelated to SBRT. Apparent clinical benefit occurred 33% of the time after SBRT. The patients experienced overall reduction in VT burden following SBRT, though not with the immediate effect seen in other patient series. Further studies (basic, translational, and clinical) are essential to determine the benefit of SBRT and if so, the optimal protocols and patient selection.

Tachycardies ventriculaires réfractaires : quelle place pour la radiothérapie et comment ?

Myocardial scar-related ventricular tachycardia is a serious and potentially life-threatening arrhythmia. The prevention of sudden rhythmic death and ventricular tachycardia recurrence relies on implantable cardioverter defibrillator (ICD), anti-arrhythmic drugs and more recently on radiofrequency catheter ablation. Nevertheless, these approaches have their own risk of adverse events and complications, with a recurrence rate up to 50 % at 2 years. Stereotactic body radiotherapy, delivered in a single dose of 25Gy, has emerged as a new therapeutic tool in the management of highly refractory ventricular tachycardia. In 2017, the very first prospective 5-patient cohort suffering from recurrent ventricular tachycardia on structural heart disease (40 % of ischemic cardiomyopathy) who benefited from cardiac stereotactic body radiotherapy was published. After stereotactic body radiotherapy, the authors observed a strong ventricular tachycardia burden reduction at 12 months, with no major side effects. Since then, around 100 cases have been described in the literature, particularly in the prospective ENCORE-VT study, with positive short- and medium-term outcomes in terms of safety and ventricular tachycardia burden reduction. Recently, another American prospective 5-patient series, published in March 2020, mitigated these results since all patients presented a ventricular tachycardia recurrence at 12 months despite an initial reduction in ventricular tachycardia burden. This article describes the use of stereotactic body radiotherapy in refractory VT, the rationale of the technique, its implementation, preliminary results and potential acute and long-term consequences.

Scar nonexcitability using simultaneous pacing for substrate ablation of ventricular tachycardia.

To describe an expedited strategy of simultaneous high-output pacing during radiofrequency ablation to achieve scar homogenization and electrical inexcitability as an approach for substrate ablation for scar-related ventricular tachycardia (VT). Scar homogenization with additional testing for electrical inexcitability is known endpoints for catheter ablation, but achieving both can be time consuming. We describe a strategy of simultaneous pacing during radiofrequency ablation to expedite this approach. Ten patients (age 74 ± 6 years; all men, (LV) ejection fraction of 33% ± 8%, ischemic cardiomyopathy, 9; VT storm, 7) underwent scar homogenization with electrical inexcitability to pacing (10mA, 9ms pulse width), as well as noninducibility of any VT as an acute procedural endpoint. Thirty-four VTs were inducible in 10 patients with a total of 1127 ablation lesions applied. Median ablation lesions per patient were 97 (interquartile range [IQR]25-75 71-151), and the total ablation time was 49 minutes (IQR25-75 45-56 minutes) with average duration per lesion of 32.2 seconds (IQR25-75 25.8-37.8 seconds). Average power was 33 W (IQR25-75 32-38 W), average contact force was 13g (IQR25-75 11.9-14.6g) with a median impedance drop of 9.6 Ω/lesion (IQR25-75 8.1-10.0 Ω). There were no ventricular fibrillation episodes using this strategy. The median procedure time was 246 minutes (IQR25-75 214-293 minutes). Acute procedural success was seen in nine patients with 97% of VTs noninducible. Simultaneous ablation with high output pacing to achieve scar inexcitability, when combined with scar homogenization and noninducibility of any VT may be an expeditious, safe, and effective technique for catheter ablation.

Signature signal strategy: Electrogram-based ventricular tachycardia mapping

Multiple decades of work have recognized complexities of substrates responsible for ventricular tachycardia (VT). There is sufficient evidence that 3 critical components of a re-entrant VT circuit, namely, region of slow conduction, zone of unidirectional block, and exit site, are located in spatial vicinity to each other in the ventricular scar. Each of these components expresses characteristic electrograms in sinus rhythm, at initiation of VT, and during VT, respectively. Despite this, abnormal electrograms are widely targeted without appreciation of these signature electrograms during contemporary VT ablation. Our aim is to stimulate physiology-based VT mapping and a targeted ablation of VT. In this article, we focus on these 3 underappreciated aspects of the physiology of ischemic scar-related VT circuits that have practical applications during a VT ablation procedure. We explore the anatomic and functional elements underlying these distinctive bipolar electrograms, specifically the contribution of tissue branching, conduction restitution, and wave curvature to the substrate, as they pertain to initiation and maintenance of VT. We propose a VT ablation approach based on these 3 electrogram features that can be a potential practical means to recognize critical elements of a VT circuit and target ablation.

Prospective Assessment of an Automated Intraprocedural 12-Lead ECG-Based System for Localization of Early Left Ventricular Activation.

To facilitate ablation of ventricular tachycardia (VT), an automated localization system to identify the site of origin of left ventricular activation in real time using the 12-lead ECG was developed. The objective of this study was to prospectively assess its accuracy. The automated site of origin localization system consists of 3 steps: (1) localization of ventricular segment based on population templates, (2) population-based localization within a segment, and (3) patient-specific site localization. Localization error was assessed by the distance between the known reference site and the estimated site. In 19 patients undergoing 21 catheter ablation procedures of scar-related VT, site of origin localization accuracy was estimated using 552 left ventricular endocardial pacing sites pooled together and 25 VT-exit sites identified by contact mapping. For the 25 VT-exit sites, localization error of the population-based localization steps was within 10 mm. Patient-specific site localization achieved accuracy of within 3.5 mm after including up to 11 pacing (training) sites. Using 3 remotes (67.8±17.0 mm from the reference VT-exit site), and then 5 close pacing sites, resulted in localization error of 7.2±4.1 mm for the 25 identified VT-exit sites. In 2 emulated clinical procedure with 2 induced VTs, the site of origin localization system achieved accuracy within 4 mm. In this prospective validation study, the automated localization system achieved estimated accuracy within 10 mm and could thus provide clinical utility.

P1125 Safety and efficacy of ventricular tachycardia ablation during sinus rhythm in patients with structural heart disease

Abstract Funding Acknowledgements Project “PI-0057-2017”, funded by Junta de Andalucía and co-funded by European Union (ERDF/ESF, “Invesing in your future”) Background The best strategy for scar related ventricular tachycardia (VT) ablation is not yet established. Recently, the use of ventricular assist devices is being proposed to allow ablation during unstable VT. Purpose Analyze the results of a multicenter registry of substrate-guided VT ablation performed primarily during stable rhythm. Methods This prospective multicenter registry included 433 VT ablation procedures performed in 372 consecutive patients with structural heart disease undergoing VT ablation. Substrate ablation (scar dechanneling technique) during sinus rhythm without initial VT induction was the standard protocol. Any episode of sustained VT or appropriate ICD therapy was considered VT recurrence. Results Myocardial infarction was the arrhythmogenic substrate in 64% of patients. 90.5% of patients were male, mean age 64 ± 13 years. Mean LVEF was 38 ± 13%.No ventricular assist device was used in any case. After substrate ablation no VT was inducible in 69% of cases. End-procedure non-inducibility was achieved in 73.1% of cases. Complication rate was 6.7 %. 30-days mortality was 1.9% (7 patients), including one procedure related death. At one year after first procedure 17 patients died (4.5%). Age, chronic obstructive pulmonary disease and renal failure were independent predictors of mortality. One-year freedom from VT recurrence was 84%. Conclusion Substrate-guided VT ablation during stable rhythm as main approach for scar-related VT treatment is associated to low complication and recurrence rates in this prospective multicenter study.

221Evaluating the ability of different substrate mapping techniques to identify scar-related ventricular tachycardia circuits using computational modelling

Abstract Funding Acknowledgements National Institute for Health Research; British Heart Foundation; and The Wellcome Trust and Engineering and Physical Sciences Research Council. Background Accurate identification of targets for catheter ablation therapy of ventricular tachycardias (VTs) in the postinfarction heart remains a significant challenge. Identification of such targets often requires VT-induction to delineate the entry/exit points of the reentrant circuit sustaining the VT. However, inducibility may not be possible due to hemodynamic instability. In this scenario, substrate ablation strategies can still be performed to uncover the arrhythmogenic substrate during sinus or paced rhythm. However, substrate mapping may fail to accurately delineate the reentrant circuit resulting in VT recurrence after the procedure. Purpose To use computer simulations to compare the ability of different electroanatomical maps constructed following typical substrate ablation strategies to identify the VT exit site. Methods An image-based computational model of the porcine post-infarction left ventricle was constructed to simulate VT and paced rhythm. Electroanatomical maps were constructed based on the following features extracted from electrograms computed on the endocardial surface: activation time (AT), bipolar electrogram amplitude, signal fractionation and the reentry vulnerability index (RVI - a metric combining activation and repolarization timings to identify tissue susceptibility to reentry). Potential ablation targets during substrate mapping were compared for: highest 5% AT gradient; lowest 5% bipolar signal amplitudes; areas with fragmented signals (more than one peak); and lowest 5% RVI. The minimum distance, d, between the manually identified VT exit site and the targets was measured. Results The RVI performed better than the other metrics at detecting the VT exit site (see Figure). The minimum distance between sites of lowest RVI and the exit site was 3.2mm compared to 13.1mm and 15.9mm in traditional AT and voltage maps, respectively. As the scar was not transmural, parameters derived from all electrograms (including those located on dense scar regions) were used to construct the electroanatomical maps. This improved the performance of the RVI significantly, making it more specific than the other metrics as can be seen in the Figure. Conclusions Among all metrics investigated here, the RVI identified the vulnerable region closest to VT exit site. This finding suggests that activation-repolarization metrics may improve the detection of pro-arrhythmic regions without having to induce VT. Moreover, the RVI may be particularly well suited for detecting vulnerable regions within non-transmural scars. Abstract Figure. VT and Substrate Mapping

Double-balloon technique for retrograde venous ethanol ablation of ventricular arrhythmias in the absence of suitable intramural veins

Venous ethanol infusion via an occlusive balloon has been used as a bailout approach to treat ablation-refractory ventricular arrhythmias (VAs). Unfavorable venous anatomy (lack of intramural veins at the targeted site or collateral vein-ethanol shunting) limits its efficacy. Blocking collateral flow with a second balloon may optimize myocardial ethanol delivery. The purpose of this study was to validate the "double-balloon" approach to enhance ethanol delivery in cases of unfavorable venous anatomy. Eight patients referred after failed ablations (3 left ventricular [LV] summit, 5 scar-related ventricular tachycardia) underwent endocardial mapping and additional radiofrequency ablation without VA resolution. Coronary veins were mapped using a multipolar catheter or wire, and selective venograms were obtained. The double balloon was used when (1) distal collateral branches shunted flow away from the targeted region; (2) the target vein had optimal signals only proximally; or (3) a large vein was targeted that had multiple branches for a large area of interest. Acute successful ethanol infusion myocardial delivery and resolution of VA was accomplished using the posterolateral LV veins (n = 2 patients, 3 procedures), lateral LV vein (n = 1), apical anterior interventricular vein (AIV; n = 1), middle cardiac vein (n = 1), and septal branches of the AIV (n = 3). At median follow-up of 313.5 days, 2 patients experienced recurrence. The double-balloon technique can enhance ethanol delivery to target isolated vein segments, block collateral flow, or target extensive areas, and can expand the utility of venous ethanol for treatment of VAs.

Left-lateral thoracotomy for catheter ablation of scar-related ventricular tachycardia in patients with inaccessible pericardial access

ObjectivesWe aimed to describe the feasibility of a surgical left thoracotomy for catheter ablation of scar-related ventricular tachycardia (VT) in patients with inaccessible pericardial access.BackgroundPericardial adhesion due to prior cardiac surgery or previous epicardial ablation procedures limits epicardial access in patients with drug-refractory VT originated from the epicardium.MethodsSix patients who underwent a surgical left lateral thoracotomy epicardial access for catheter ablation of VT after failed subxiphoid percutaneous epicardial access were reviewed. Patients’ baseline characteristics and procedural characteristics including epicardial access, mapping, and ablation were described. Epicardial access was successfully obtained in all patients by a surgical left lateral thoracotomy.ResultsThe reasons of pericardial adhesion were prior cardiac surgery (n = 3, 50%) and previous epicardial ablation procedures (n = 3, 50%). Epicardial mapping of the lateral and inferior left ventricle was acquired, and a total of 15 different VTs originated from those regions were abolished. Unless one patient with ST elevation myocardial infarction due to periprocedural occlusion of the posterior descending artery no further complications occurred. All patients were discharged 10.2 ± 4 days after the procedure. VT recurred in 1 patient (17%) and was controlled with oral amiodarone therapy during follow-up (median follow-up: 479 days).ConclusionsA surgical left lateral thoracotomy is feasible and safe for selected patients. This approach provides epicardial ablation in patients with VT located at the infero-lateral left ventricle and pericardial adhesions due to previous cardiac surgery or previous ablation procedures.Graphic abstract

Ablation of Reentry-Vulnerable Zones Determined by Left Ventricular Activation From Multiple Directions: A Novel Approach for Ventricular Tachycardia Ablation: A Multicenter Study (PHYSIO-VT).

The optimal method to identify the arrhythmogenic substrate of scar-related ventricular tachycardia (VT) is unknown. Sites of activation slowing during sinus rhythm (SR) often colocalize with the VT circuit. However, the utility and limitations of such approach for guiding ablation are unknown. We conducted a multicenter study in patients with infarct-related VT. The left ventricular (LV) was mapped during activation from 3 directions: SR (or atrial pacing), right ventricular, and LV pacing at 600 ms. Ablation was applied selectively to the cumulative area of slow activation, defined as the sum of all regions with activation times of ≥40 ms per 10 mm. Hemodynamically tolerated VTs were mapped with activation or entrainment. The primary outcome was a composite of appropriate implanted cardioverter-defibrillator therapies and cardiovascular death. In 85 patients, the LV was mapped during activation from 2.4±0.6 directions. The direction of LV activation influenced the location and magnitude of activation slowing. The spatial overlap of activation slowing between SR and right ventricular pacing was 84.2±7.1%, between SR and LV pacing was 61.4±8.8%, and between right ventricular and LV pacing was 71.3±9.6% (P<0.05 between all comparisons). Mapping during SR identified only 66.2±8.2% of the entire area of activation slowing and 58% critical isthmus sites. Activation from other directions by right ventricular and LV stimulation unmasked an additional 33% of slowly conducting zones and 25% critical isthmus sites. The area of maximal activation slowing often corresponded to the site where the wavefront first interacted with the infarct. During a follow-up period of 3.6 years, the primary end point occurred in 14 out of 85 (16.5%) patients. The spatial distribution of activation slowing is dependent on the direction of LV activation with the area of maximal slowing corresponding to the site where the wavefront first interacts with the infarct. This data may have implications for VT substrate mapping strategies.