Targeting the Hidden Substrate Unmasked by Right Ventricular Extrastimulation Improves Ventricular Tachycardia Ablation Outcome After Myocardial Infarction

Evolution of Substrate for Ventricular Arrhythmias Early Postinfarction: Insights From a Porcine Ischemia-Reperfusion Model

BACKGROUND

The evolution of myocardial scar and its arrhythmogenic potential postinfarct is incompletely understood.

OBJECTIVES

This study sought to investigate scar and border zone (BZ) channels evolution in an animal ischemia-reperfusion injury model using late gadolinium enhancement cardiac magnetic resonance (LGE-CMR).

METHODS

Five swine underwent 90-minute balloon occlusion of the mid-left anterior descending artery, followed by LGE-CMR at day (d) 3, d30, and d58 postinfarct. Invasive electroanatomic mapping (EAM) was performed at 2 months. Topographical reconstructions of LGE-CMR were analyzed for left ventricular core and BZ scar, BZ channel geometry, and complexity, including transmurality, orientation, and number of entrances/exits.

RESULTS

LVEF reduced from 48.0% ± 1.8% to 41.3% ± 2.3% postinfarct. Total scar mass reduced over time (P = 0.008), including BZ (P = 0.002) and core scar (P = 0.05). A total of 72 BZ channels were analyzed across all animals and timepoints. Channel length (P = 0.05) and complexity (P = 0.02) reduced progressively from d3 to d58. However, at d58, 64% of channels were newly formed and 36% were midmyocardial. Conserved channels were initially longer and more complex. All LGE-CMR channels colocalized to regions of maximal decrement on EAM, with significantly greater decrement (115 ± 31 ms vs 83 ± 29 ms; P < 0.001) and uncovering of split potentials (24.8% vs 2.6%; P < 0.001) within channels. In total, 3 of 5 animals had inducible VT and tended to have more channels with greater midmyocardial involvement and functional decrement than those without VT.

CONCLUSIONS

BZ channels form early postinfarct and demonstrate evolutionary complexity and functional conduction slowing on EAM, highlighting their arrhythmogenic potential. Some channels regress in complexity and length, but new channels form at 2 months' postinfarct, which may be midmyocardial, reflecting an evolving, 3-dimensional substrate for VT. LGE-CMR may help identify BZ channels that may support VT early postinfarct and lead to sudden death.

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

BACKGROUND

Late 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.

OBJECTIVE

The purpose of this study was to characterize the spatial distribution and features of pLP after catheter ablation of VT substrate with high-resolution mapping.

METHODS

Cases 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.

RESULTS

A 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).

CONCLUSION

Formation 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.

Excellent Outcomes After First-Line Ablation in Post-MI Patients With Tolerated VT and LVEF >35

BACKGROUND

Post-myocardial infarction (MI) patients with ventricular tachycardia (VT) are considered at risk for VT recurrence and sudden cardiac death (SCD). Recent guidelines indicate that in selected patients catheter ablation should be considered instead of an implantable cardioverter-defibrillator (ICD).

OBJECTIVES

This study aimed to analyze outcomes of patients referred for VT ablation according to left ventricular ejection fraction (LVEF), tolerance of VT, and acute ablation outcome.

METHODS

Post-MI patients without prior ICD undergoing VT ablation at a single center between 2009 and 2022 were included. Patients who presented with tolerated VT and who had an LVEF >35% were offered catheter ablation as first-line therapy. ICD implantation was offered to all patients but was subject to shared decision according to clinical presentation, LVEF, and ablation outcome.

RESULTS

Eighty-six patients (mean age 69 ± 9 years, 84% male, mean LVEF 41 ± 9%) underwent VT ablation. In 66 patients, LVEF was >35%, of whom 51 had tolerated VT. Of these 51 patients, 37 (73%) were rendered noninducible. In 5 of 37 noninducible and in 11 of 14 inducible patients, an ICD was implanted. During a median follow-up of 40 months (Q1-Q3: 24-70 months), 10 of 86 patients had VT recurrence. The overall mortality was 27%, and 1 patient with ICD died suddenly. Among the 37 patients (none on antiarrhythmic drugs) with LVEF >35%, tolerated VT, and noninducibility, no SCD or VT recurrence occurred. Among the 14 patients with LVEF >35%, tolerated VT, and inducibility after ablation, no SCD occurred, but VT recurred in 29%.

CONCLUSIONS

Post-MI patients with LVEF >35%, tolerated VT, and noninducibility after ablation have an excellent prognosis. Deferring ICD implantation seems to be safe in these patients.

Catheter Ablation of Ventricular Tachycardia in Ischemic Heart Disease: What Is Known and New Perspectives

PURPOSE OF THE REVIEW

This review aims to evaluate current evidence regarding ventricular tachycardia ablation in patients with ischemic heart disease and explore novel approaches currently developing to improve procedural and long-term outcomes.

RECENT FINDINGS

Recently published trials (PARTITA, PAUSE-SCD, and SURVIVE-VT) have demonstrated the prognostic benefit of prophylactic ventricular tachycardia ablation compared to current clinical practice. Advanced cardiac imaging provides a valuable pre-procedural evaluation of the arrhythmogenic substrate, identifying ablation targets non-invasively. Advanced cardiac mapping techniques allow to better characterize arrhythmogenic substrate during ablation procedure. Emerging technologies like pulsed field ablation and ultra-low temperature cryoablation show promise in ventricular tachycardia ablation. Advancements in mapping techniques, ablation technologies, and pre-procedural cardiac imaging offer promise for improving ventricular tachycardia ablation outcomes in ischemic heart disease.

Non-invasive detection of slow conduction with cardiac magnetic resonance imaging for ventricular tachycardia ablation

AIMS

Non-invasive myocardial scar characterization with cardiac magnetic resonance (CMR) has been shown to accurately identify conduction channels and can be an important aid for ventricular tachycardia (VT) ablation. A new mapping method based on targeting deceleration zones (DZs) has become one of the most commonly used strategies for VT ablation procedures. The aim of the study was to analyse the capability of CMR to identify DZs and to find predictors of arrhythmogenicity in CMR channels.

METHODS AND RESULTS

Forty-four consecutive patients with structural heart disease and VT undergoing ablation after CMR at a single centre (October 2018 to July 2021) were included (mean age, 64.8 ± 11.6 years; 95.5% male; 70.5% with ischaemic heart disease; a mean ejection fraction of 32.3 ± 7.8%). The characteristics of CMR channels were analysed, and correlations with DZs detected during isochronal late activation mapping in both baseline maps and remaps were determined. Overall, 109 automatically detected CMR channels were analysed (2.48 ± 1.15 per patient; length, 57.91 ± 63.07 mm; conducting channel mass, 2.06 ± 2.67 g; protectedness, 21.44 ± 25.39 mm). Overall, 76.1% of CMR channels were associated with a DZ. A univariate analysis showed that channels associated with DZs were longer [67.81 ± 68.45 vs. 26.31 ± 21.25 mm, odds ratio (OR) 1.03, P = 0.010], with a higher border zone (BZ) mass (2.41 ± 2.91 vs. 0.87 ± 0.86 g, OR 2.46, P = 0.011) and greater protectedness (24.97 ± 27.72 vs. 10.19 ± 9.52 mm, OR 1.08, P = 0.021).

CONCLUSION

Non-invasive detection of targets for VT ablation is possible with CMR. Deceleration zones found during electroanatomical mapping accurately correlate with CMR channels, especially those with increased length, BZ mass, and protectedness.

Area-weighted unipolar voltage to predict heart failure outcomes in patients with ischaemic cardiomyopathy and ventricular tachycardia

AIMS

Patients with ischaemic cardiomyopathy (ICM) referred for catheter ablation of ventricular tachycardia (VT) are at risk for end-stage heart failure (HF) due to adverse remodelling. Local unipolar voltages (UV) decrease with loss of viable myocardium. A UV parameter reflecting global viable myocardium may predict prognosis. We evaluate if a newly proposed parameter, area-weighted unipolar voltage (awUV), can predict HF-related outcomes [HFO; HF death/left ventricular (LV) assist device/heart transplant] in ICM.

METHODS AND RESULTS

From endocardial voltage maps of consecutive patients with ICM referred for VT ablation, awUV was calculated by weighted interpolation of local UV. Associations between clinical and mapping parameters and HFO were evaluated and validated in a second cohort. The derivation cohort consisted of 90 patients [age 68 ±8 years; LV ejection fraction (LVEF) 35% interquartile range (IQR) (24-40)] and validation cohort of 60 patients [age 67 ± 9, LVEF 39% IQR (29-45)]. In the derivation cohort, during a median follow-up of 45 months [IQR (34-83)], 36 (43%) patients died and 23 (26%) had HFO. Patients with HFO had lower awUV [4.51 IQR (3.69-5.31) vs. 7.03 IQR (6.08-9.2), P < 0.001]. A reduction in awUV [optimal awUV (5.58) cut-off determined by receiver operating characteristics analysis] was a strong predictor of HFO (3-year HFO survival 97% vs. 57%). The cut-off value was confirmed in the validation cohort (2-year HFO-free survival 96% vs. 60%).

CONCLUSION

The newly proposed parameter awUV, easily available from routine voltage mapping, may be useful at identifying ICM patients at high risk for HFO.

Identification of Human Ventricular Tachycardia Demarcated by Fixed Lines of Conduction Block in a 3-Dimensional Hyperboloid Circuit

BACKGROUND

The circuit boundaries for reentrant ventricular tachycardia (VT) have been historically conceptualized within a 2-dimensional (2D) construct, with their fixed or functional nature unresolved. This study aimed to examine the correlation between localized lines of conduction block (LOB) evident during baseline rhythm with lateral isthmus boundaries that 3-dimensionally constrain the VT isthmus as a hyperboloid structure.

METHODS

A total of 175 VT activation maps were correlated with isochronal late activation maps during baseline rhythm in 106 patients who underwent catheter ablation for scar-related VT from 3 centers (42% nonischemic cardiomyopathy). An overt LOB was defined by a deceleration zone with split potentials (≥20 ms isoelectric segment) during baseline rhythm. A novel application of pacing within deceleration zone (≥600 ms) was implemented to unmask a concealed LOB not evident during baseline rhythm. LOB identified during baseline rhythm or pacing were correlated with isthmus boundaries during VT.

RESULTS

Among 202 deceleration zones analyzed during baseline rhythm, an overt LOB was evident in 47%. When differential pacing was performed in 38 deceleration zones without overt LOB, an underlying concealed LOB was exposed in 84%. In 152 VT activation maps (2D=53, 3-dimensional [3D]=99), 69% of lateral boundaries colocalized with an LOB in 2D activation patterns, and the depth boundary during 3D VT colocalized with an LOB in 79%. In VT circuits with isthmus regions that colocalized with a U-shaped LOB (n=28), the boundary invariably served as both lateral boundaries in 2D and 3D. Overall, 74% of isthmus boundaries were identifiable as fixed LOB during baseline rhythm or differential pacing.

CONCLUSIONS

The majority of VT circuit boundaries can be identified as fixed LOB from intrinsic or paced activation during sinus rhythm. Analysis of activation while pacing within the scar substrate is a novel technique that may unmask concealed LOB, previously interpreted to be functional in nature. An LOB from the perspective of a myocardial surface is frequently associated with intramural conduction, supporting the existence of a 3D hyperboloid VT circuit structure. Catheter ablation may be simplified to targeting both sides around an identified LOB during sinus rhythm.

Ablation targets of scar-related ventricular tachycardia identified by dynamic functional substrate mapping

BACKGROUND

Dynamic functional substrate mapping of scar-related ventricular tachycardia offers better identification of ablation targets with limited ablation lesions. Several functional substrate mapping approaches have been proposed, including decrement-evoked potential (DEEP) mapping. The aim of our study was to compare the short- and long-term efficacy of a DEEP-guided versus a fixed-substrate-guided strategy for the ablation of scar-related ventricular tachycardia (VT).

RESULTS

Forty consecutive patients presenting for ablation of scar-related VT were randomized to either DEEP-guided or substrate-guided ablation. Late potentials were tagged and ablated in the non-DEEP group, while those in the DEEP group were subjected to RV extrastimulation after a drive train. Only potentials showing significant delay were ablated. Patients were followed for a median duration of 12 months. Twenty patients were allocated to the DEEP group, while the other 20 were allocated to the non-DEEP group. Twelve patients (60%) in the DEEP group had ischemic cardiomyopathy versus 10 patients (50%) in the non-DEEP group (P-value 0.525). Intraoperatively, the median percentage of points with LPs was 19% in the DEEP group and 20.6% in the non-DEEP group. The procedural time was longer in the DEEP group, approaching but missing statistical significance (P-value 0.059). VT non-inducibility was successfully accomplished in 16 patients (80%) in the DEEP group versus 17 patients (85%) in the non-DEEP group (P value 0.597). After a median follow-up duration of 12 months, the VT recurrence rate was 65% in both groups (P value 0.311), with a dropout rate of 10% in the DEEP group. As for the secondary endpoints, all-cause mortality rates were 20% and 25% in the DEEP and non-DEEP groups, respectively (P-value 0.342).

CONCLUSIONS

DEEP-assisted ablation of scar-related ventricular tachycardia is a feasible strategy with comparable short- and long-term outcomes to a fixed-substrate-based strategy with more specific ablation targets, albeit relatively longer but non-significant procedural times and higher procedural deaths. The imbalance between the study groups in terms of epicardial versus endocardial mapping, although non-significant, warrants the prudent interpretation of our results. Further large-scale randomized trials are recommended.

TRIAL REGISTRATION

clinicaltrials.gov, registration number: NCT05086510, registered on 28th September 2021, record https://classic.

CLINICALTRIALS

gov/ct2/show/NCT05086510.

Comparison and predictors of implantable cardioverter-defibrillator therapy for primary and secondary prevention

BACKGROUND

Implantable cardioverter-defibrillators (ICDs) are effective in detecting and treating ventricular arrhythmias. Studies on ICD therapy for different indications (primary and secondary prevention) and possible predictors of ICD therapy are limited. In this study, the incidence and type of ICD therapy were related to the indication and the underlying cardiac pathology.

METHODS

A single-centre, retrospective and observational study was performed of 482 patients who underwent ICD implantation for primary (53.3%) or secondary prevention (46.7%) between 2015 and 2020 at the Radboud University Medical Centre.

RESULTS

During a median follow-up of 2.4 years (interquartile range 0.2-3.9), the occurrence of appropriate ICD therapy for primary versus secondary prevention was 9.7% and 27.6%, respectively (p < 0.001). Time to appropriate ICD therapy was significantly shorter in the secondary prevention group (p < 0.001). No difference in ICD therapy was seen for different underlying aetiologies. In the majority of cases (70%) ICD therapy was given for ventricular tachycardia (VT). The occurrence of adverse events (16.3% vs 17.3%, p = 0.772), hospitalisation for cardiovascular reasons (29.2% vs 35.1%, p = 0.559) and all-cause mortality (12.5% vs 11.6%, p = 0.763) were similar in both groups. Male gender (3.53, 95% confidence interval (CI) (1.003, 12.403), p = 0.049) and secondary prevention indication (4.90, 95% CI (1.495, 16.066), p = 0.009) were predictors of appropriate ICD therapy.

CONCLUSION

The risk associated with appropriate ICD therapy is higher in secondary prevention patients, who have their first therapy within a shorter time frame after device implantation. Rates of complications, hospitalisation and all-cause mortality are comparable. Future treatment options should target the prevention of ICD therapy, mainly by preventing the recurrence of VT.

Electroanatomic mapping in athletes: Why and when. An expert opinion paper from the Italian society of sports cardiology

Three-dimensional electroanatomical mapping (EAM) has the potential to identify the pathological substrate underlying ventricular arrhythmias (VAs) in different clinical settings by detecting myocardial areas with abnormally low voltages, which reflect the presence of different cardiomyopathic substrates. In athletes, the added value of EAM may be to enhance the efficacy of third-level diagnostic tests and cardiac magnetic resonance (CMR) in detecting concealed arrhythmogenic cardiomyopathies. Additional benefits of EAM in the athlete include the potential impact on disease risk stratification and the consequent implications for eligibility to competitive sports. This opinion paper of the Italian Society of Sports Cardiology aims to guide general sports medicine physicians and cardiologists on the clinical decision when to eventually perform an EAM study in the athlete, highlighting strengths and weaknesses for each cardiovascular disease at risk of sudden cardiac death during sport. The importance of early (preclinical) diagnosis to prevent the negative effects of exercise on phenotypic expression, disease progression, and worsening of the arrhythmogenic substrate is also addressed.

Wavefront directionality and decremental stimuli synergistically improve identification of ventricular tachycardia substrate: insights from personalized computational heart models

AIMS

Multiple wavefront pacing (MWP) and decremental pacing (DP) are two electroanatomic mapping (EAM) strategies that have emerged to better characterize the ventricular tachycardia (VT) substrate. The aim of this study was to assess how well MWP, DP, and their combination improve identification of electrophysiological abnormalities on EAM that reflect infarct remodelling and critical VT sites.

METHODS AND RESULTS

Forty-eight personalized computational heart models were reconstructed using images from post-infarct patients undergoing VT ablation. Paced rhythms were simulated by delivering an initial (S1) and an extra-stimulus (S2) from one of 100 locations throughout each heart model. For each pacing, unipolar signals were computed along the myocardial surface to simulate substrate EAM. Six EAM features were extracted and compared with the infarct remodelling and critical VT sites. Concordance of S1 EAM features between different maps was lower in hearts with smaller amounts of remodelling. Incorporating S1 EAM features from multiple maps greatly improved the detection of remodelling, especially in hearts with less remodelling. Adding S2 EAM features from multiple maps decreased the number of maps required to achieve the same detection accuracy. S1 EAM features from multiple maps poorly identified critical VT sites. However, combining S1 and S2 EAM features from multiple maps paced near VT circuits greatly improved identification of critical VT sites.

CONCLUSION

Electroanatomic mapping with MWP is more advantageous for characterization of substrate in hearts with less remodelling. During substrate EAM, MWP and DP should be combined and delivered from locations proximal to a suspected VT circuit to optimize identification of the critical VT site.

Substrate Mapping Alters Ventricular Tachycardia Inducibility

BACKGROUND

Initiation of ventricular tachycardia (VT) by programmed electrical stimulation (PES) has an important role to allow mapping and assess ablation end points. We hypothesized that substrate mapping may alter VT inducibility by mechanical bumping of critical sites.

METHODS

Subjects with left ventricular scar-related VT that was inducible by PES who were undergoing ablation were included. PES was repeated after substrate mapping (Group I) or after time under sedation/anesthesia during which additional imaging and transeptal puncture were performed without substrate mapping (Group II). The response to the second PES was categorized as type I if the same VT was induced, type II if a different VT was induced, and type III if VT was not inducible.

RESULTS

Twenty-eight patients (median age 66 years, 61% ischemic cardiomyopathy), 14 in Group I and 14 in Group II, were included. Age, time between initial and second PES, type of cardiomyopathy, ejection fraction, and anesthesia methods were not different between the 2 groups. Initial VT cycle length, however, was shorter in Group I (305 millisecond [range, 235-600] versus 350 millisecond [range, 235-600], P=0.016). Also, Group I required more extrastimuli to induce VT in PES 1 (2 [1-4] versus 2 [1-3], P=0.022). In Group I, following substrate mapping, the second PES induced the same VT in 3 patients (21%), a different VT in 9 (64%), and no VT in 2 (14%) patients. In contrast, in Group II the same VT was induced in 10 (71%) patients, a different VT in 3 (21%) and no VT in 1 (7%) patient (P=0.017).

CONCLUSIONS

Mechanical effects of substrate mapping commonly alter inducibility of VT. This has important implications for catheter ablation procedure planning and acute assessment of outcome and can potentially account for some recurrent VTs that are not recognized at the time of the procedure.

High-resolution structural-functional substrate-trigger characterization: Future roadmap for catheter ablation of ventricular tachycardia

Introduction

Patients with ventricular tachyarrhythmias (VT) are at high risk of sudden cardiac death. When appropriate, catheter ablation is modestly effective, with relatively high VT recurrence and complication rates. Personalized models that incorporate imaging and computational approaches have advanced VT management. However, 3D patient-specific functional electrical information is typically not considered. We hypothesize that incorporating non-invasive 3D electrical and structural characterization in a patient-specific model improves VT-substrate recognition and ablation targeting.

Materials and methods

In a 53-year-old male with ischemic cardiomyopathy and recurrent monomorphic VT, we built a structural-functional model based on high-resolution 3D late-gadolinium enhancement (LGE) cardiac magnetic resonance imaging (3D-LGE CMR), multi-detector computed tomography (CT), and electrocardiographic imaging (ECGI). Invasive data from high-density contact and pace mapping obtained during endocardial VT-substrate modification were also incorporated. The integrated 3D electro-anatomic model was analyzed off-line.

Results

Merging the invasive voltage maps and 3D-LGE CMR endocardial geometry led to a mean Euclidean node-to-node distance of 5 ± 2 mm. Inferolateral and apical areas of low bipolar voltage (<1.5 mV) were associated with high 3D-LGE CMR signal intensity (>0.4) and with higher transmurality of fibrosis. Areas of functional conduction delay or block (evoked delayed potentials, EDPs) were in close proximity to 3D-LGE CMR-derived heterogeneous tissue corridors. ECGI pinpointed the epicardial VT exit at ∼10 mm from the endocardial site of origin, both juxtaposed to the distal ends of two heterogeneous tissue corridors in the inferobasal left ventricle. Radiofrequency ablation at the entrances of these corridors, eliminating all EDPs, and at the VT site of origin rendered the patient non-inducible and arrhythmia-free until the present day (20 months follow-up). Off-line analysis in our model uncovered dynamic electrical instability of the LV inferolateral heterogeneous scar region which set the stage for an evolving VT circuit.

Discussion and conclusion

We developed a personalized 3D model that integrates high-resolution structural and electrical information and allows the investigation of their dynamic interaction during arrhythmia formation. This model enhances our mechanistic understanding of scar-related VT and provides an advanced, non-invasive roadmap for catheter ablation.

Intracardiac Electrogram Targets for Ventricular Tachycardia Ablation

The pathogenesis of ventricular tachycardia (VT) in most patients with a prior myocardial scarring is reentry involving compartmentalized muscle fibers protected within the scar. Often the 12-lead ECG morphology of the VT itself is not available when treated with a defibrillator. Consequently, VT ablation takes on an interesting challenge of finding critical targets in sinus rhythm. High-density recordings are essential to evaluate a substrate based on whole electrogram voltage and activation delay, supplemented with substrate perturbation through alternate site pacing or introducing an extra stimulation. In this article, we discuss contemporary intracardiac electrogram targets for VT ablation, with explanation on each of their specific fundamental physiology.

Distribution of evoked delayed potential and delayed potential in a patient with subendocardial inferior infarction and transmural postero-lateral infarction: A case report

A 47-year-old man with transmural posterolateral myocardial infarction (MI) and subendocardial inferior MI underwent catheter ablation for monomorphic ventricular tachycardia (VT). Right ventricular extra stimulation could unmask evoked delayed potentials in the subendocardial infarction area without delayed potentials in the sinus rhythm. Extra stimulation mapping for VT is useful for hidden VT substrates, particularly in the subendocardial infarction area.

Ventricular Tachycardia Ablation Guided by Functional Substrate Mapping: Practices and Outcomes

Catheter ablation of ventricular tachycardia has demonstrated its important role in the treatment of ventricular tachycardia in patients with structural cardiomyopathy. Conventional mapping techniques used to define the critical isthmus, such as activation mapping and entrainment, are limited by the non-inducibility of the clinical tachycardia or its poor hemodynamic tolerance. To overcome these limitations, a voltage mapping strategy based on bipolar electrograms peak to peak analysis was developed, but a low specificity (30%) for VT isthmus has been described with this approach. Functional mapping strategy relies on the analysis of the characteristics of the electrograms but also their propagation patterns and their response to extra-stimulus or alternative pacing wavefronts to define the targets for ablation. With this review, we aim to summarize the different functional mapping strategies described to date to identify ventricular arrhythmic substrate in patients with structural heart disease.

Substrate-based approaches in ventricular tachycardia ablation

Catheter ablation for ventricular tachycardia (VT) in patients with structural heart disease is now part of standard care. Mapping and ablation of the clinical VT is often limited when the VT is noninducible, nonsustained or not haemodynamically tolerated. Substrate-based ablation strategies have been developed in an aim to treat VT in this setting and, subsequently, have been shown to improve outcomes in VT ablation when compared to focused ablation of mapped VTs. Since the initial description of linear ablation lines targeting ventricular scar, many different approaches to substrate-based VT ablation have been developed. Strategies can broadly be divided into three categories: 1) targeting abnormal electrograms, 2) anatomical targeting of conduction channels between areas of myocardial scar, and 3) targeting areas of slow and/or decremental conduction, identified with “functional” substrate mapping techniques. This review summarises contemporary substrate-based ablation strategies, along with their strengths and weaknesses.

High Density Pace-Mapping for Scar-related Ventricular Tachycardia Ablation

Despite advances in medical and interventional therapies, ventricular tachycardia (VT) due to reentrant activity within complex regions of myocardial scar remains a common late complication of myocardial infarction This article is protected by copyright. All rights reserved.

Purkinje network and myocardial substrate at the onset of human ventricular fibrillation: implications for catheter ablation

AIMS

Mapping data of human ventricular fibrillation (VF) are limited. We performed detailed mapping of the activities underlying the onset of VF and targeted ablation in patients with structural cardiac abnormalities.

METHODS AND RESULTS

We evaluated 54 patients (50 ± 16 years) with VF in the setting of ischaemic (n = 15), hypertrophic (n = 8) or dilated cardiomyopathy (n = 12), or Brugada syndrome (n = 19). Ventricular fibrillation was mapped using body-surface mapping to identify driver (reentrant and focal) areas and invasive Purkinje mapping. Purkinje drivers were defined as Purkinje activities faster than the local ventricular rate. Structural substrate was delineated by electrogram criteria and by imaging. Catheter ablation was performed in 41 patients with recurrent VF. Sixty-one episodes of spontaneous (n = 10) or induced (n = 51) VF were mapped. Ventricular fibrillation was organized for the initial 5.0 ± 3.4 s, exhibiting large wavefronts with similar cycle lengths (CLs) across both ventricles (197 ± 23 vs. 196 ± 22 ms, P = 0.9). Most drivers (81%) originated from areas associated with the structural substrate. The Purkinje system was implicated as a trigger or driver in 43% of patients with cardiomyopathy. The transition to disorganized VF was associated with the acceleration of initial reentrant activities (CL shortening from 187 ± 17 to 175 ± 20 ms, P < 0.001), then spatial dissemination of drivers. Purkinje and substrate ablation resulted in the reduction of VF recurrences from a pre-procedural median of seven episodes [interquartile range (IQR) 4-16] to 0 episode (IQR 0-2) (P < 0.001) at 56 ± 30 months.

CONCLUSIONS

The onset of human VF is sustained by activities originating from Purkinje and structural substrate, before spreading throughout the ventricles to establish disorganized VF. Targeted ablation results in effective reduction of VF burden.

KEY QUESTION

The initial phase of human ventricular fibrillation (VF) is critical as it involves the primary activities leading to sustained VF and arrhythmic sudden death. The origin of such activities is unknown.

KEY FINDING

Body-surface mapping shows that most drivers (≈80%) during the initial VF phase originate from electrophysiologically defined structural substrates. Repetitive Purkinje activities can be elicited by programmed stimulation and are implicated as drivers in 37% of cardiomyopathy patients.

TAKE-HOME MESSAGE

The onset of human VF is mostly associated with activities from the Purkinje network and structural substrate, before spreading throughout the ventricles to establish sustained VF. Targeted ablation reduces or eliminates VF recurrence.

Structure and function of the ventricular tachycardia isthmus

Catheter ablation of postinfarction reentrant ventricular tachycardia (VT) has received renewed interest owing to the increased availability of high-resolution electroanatomic mapping systems that can describe the VT circuits in greater detail, and the emergence and need to target noninvasive external beam radioablation. These recent advancements provide optimism for improving the clinical outcome of VT ablation in patients with postinfarction and potentially other scar-related VTs. The combination of analyses gleaned from studies in swine and canine models of postinfarction reentrant VT, and in human studies, suggests the existence of common electroanatomic properties for reentrant VT circuits. Characterizing these properties may be useful for increasing the specificity of substrate mapping techniques and for noninvasive identification to guide ablation. Herein, we describe properties of reentrant VT circuits that may assist in elucidating the mechanisms of onset and maintenance, as well as a means to localize and delineate optimal catheter ablation targets.

Multisite conduction block in the epicardial substrate of Brugada syndrome

BACKGROUND

The Brugada pattern manifests as a spontaneous variability of the electrocardiographic marker, suggesting a variability of the underlying electrical substrate.

OBJECTIVE

The purpose of this study was to investigate the response of the epicardial substrate of Brugada syndrome (BrS) to programmed ventricular stimulation and to Na blocker infusion.

METHODS

We investigated 6 patients (all male; mean age 54 ± 14 years) with BrS and recurrent ventricular fibrillation. Five had no type 1 BrS electrocardiogram pattern at admission. They underwent combined epicardial-endocardial mapping using multielectrode catheters. Changes in epicardial electrograms were evaluated during single endocardial extrastimulation and after low-dose ajmaline infusion (0.5 mg/kg in 5 minutes).

RESULTS

All patients had a region in the anterior epicardial right ventricle with prolonged multicomponent electrograms. Single extrastimulation prolonged late epicardial components by 59 ± 31 ms and in 4 patients abolished epicardial components at some sites, without reactivation by surrounding activated sites. These localized blocks occurred at an initial coupling interval of 335 ± 58 ms and then expanded to other sites, being observed in up to 40% of epicardial sites. Ajmaline infusion prolonged electrogram duration in all and produced localized blocks in 62% of sites in the same patients as during extrastimulation. Epicardial conduction recovery after ajmaline occurred intermittently and at discontinuous sites and produced beat-to-beat changes in local repolarization, resulting in an area of marked electrical disparity. These changes were consistent with models based on microstructural alterations under critical propagation conditions.

CONCLUSION

In BrS, localized functional conduction blocks occur at multiple epicardial sites and with variable patterns, without being reactivated from the surrounding sites.

Maximizing detection and optimal characterization of local abnormal ventricular activity in nonischemic cardiomyopathy: LAVAMAX & LAVAFLOW

Background

Sites of local abnormal ventricular activation (LAVA) are ventricular tachycardia (VT) ablation targets. In nonischemic cardiomyopathy (NICM), minute and sparse LAVA potentials are mapped with difficulty with direction-sensitive bipolar electrograms (EGM). A method for its optimal characterization independent of electrode orientation has not been explored.

Objective

Maximize voltages and calculate overall activation direction at LAVA sites, independent of catheter and wave direction, using omnipolar technology (OT) in NICM.

Methods

Four diseased isolated human hearts from NICM patients were mapped epicardially using a high-density grid. Bipolar EGMs with at least 2 activation segments separated by at least 25 ms were identified. We used OT to maximize voltages (LAVA_MAX) and measured overall wave direction (LAVA_FLOW) for both segments. Clinically relevant voltage proportion (CRVP) was used to estimate the proportion of directionally corrected bipoles. Concordance and changes in direction vectors were measured via mean vector length and angular change.

Results

OT provides maximal LAVA voltages (OT: 0.83 ± 0.09 mV vs Bi: 0.61 ± 0.06 mV, P < .05) compared to bipolar EGMs. OT optimizes LAVA voltages, with 32% (CRVP) of LAVA bipoles directionally corrected by OT. OT direction vectors at LAVA sites demonstrate general concordance, with an average of 62% ± 5%. A total of 72% of direction vectors change by more than 35° at LAVA sites.

Conclusion

The omnipolar mapping approach allows maximizing voltage and determining the overall direction of wavefront activity at LAVA sites in NICM.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias: executive summary

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

Dynamic spatial dispersion of repolarization is present in regions critical for ischemic ventricular tachycardia ablation

BACKGROUND

The presence of dynamic substrate changes may facilitate functional block and reentry in ventricular tachycardia (VT).

OBJECTIVE

We aimed to study dynamic ventricular repolarization changes in critical regions of the VT circuit during sensed single extrastimulus pacing known as the Sense Protocol (SP).

METHODS

Twenty patients (aged 67 ± 9 years, 17 male) underwent VT ablation. A bipolar voltage map was obtained during sinus rhythm (SR) and right ventricular SP pacing at 20 ms above ventricular effective refractory period. Ventricular repolarization maps were constructed. Ventricular repolarization time (RT) was calculated from unipolar electrogram T waves, using the Wyatt method, as the dV/dtmax of the unipolar T wave. Entrainment or pace mapping confirmed critical sites for ablation.

RESULTS

The median global repolarization range (max-min RT per patient) was 166 ms (interquartile range [IQR] 143-181 ms) during SR mapping vs 208 ms (IQR 182-234) during SP mapping (P = .0003 vs intrinsic rhythm). Regions of late potentials (LP) had a longer RT during SP mapping compared to regions without LP (mean 394 ± 40 ms vs 342 ± 25 ms, P < .001). In paired regions of normal myocardium there was no significant spatial dispersion of repolarization (SDR)/10 mm2 during SP mapping vs SR mapping (SDR 11 ± 6 ms vs 10 ± 6 ms, P = .54). SDR/10 mm2 was greater in critical areas of the VT circuit during SP mapping 63 ± 29 ms vs SR mapping 16 ± 9 ms (P < .001).

CONCLUSION

Ventricular repolarization is prolonged in regions of LP and increases dynamically, resulting in dynamic SDR in critical areas of the VT circuit. These dynamic substrate changes may be an important factor that facilitates VT circuits.

Dynamic High-density Functional Substrate Mapping Improves Outcomes in Ischaemic Ventricular Tachycardia Ablation: Sense Protocol Functional Substrate Mapping and Other Functional Mapping Techniques

Post-infarct-related ventricular tachycardia (VT) occurs due to reentry over surviving fibres within ventricular scar tissue. The mapping and ablation of patients in VT remains a challenge when VT is poorly tolerated and in cases in which VT is non-sustained or not inducible. Conventional substrate mapping techniques are limited by the ambiguity of substrate characterisation methods and the variety of mapping tools, which may record signals differently based on their bipolar spacing and electrode size. Real world data suggest that outcomes from VT ablation remain poor in terms of freedom from recurrent therapy using conventional techniques. Functional substrate mapping techniques, such as single extrastimulus protocol mapping, identify regions of unmasked delayed potentials, which, by nature of their dynamic and functional components, may play a critical role in sustaining VT. These methods may improve substrate mapping of VT, potentially making ablation safer and more reproducible, and thereby improving the outcomes. Further large-scale studies are needed.

The prognostic value of J-wave pattern for recurrence of ventricular tachycardia after catheter ablation in patients with myocardial infarction

BACKGROUND

J-waves and fragmented QRS (fQRS) on surface ECGs have been associated with the occurrence of ventricular tachyarrhythmias. Whether these non-invasive parameters can also predict ventricular tachycardia (VT) recurrence after radiofrequency catheter ablation (RFCA) is unknown. Of interest, patients with a wide QRS-complex have been excluded from clinical studies on J-waves, although a J-wave like pattern has been described for wide QRS.

METHODS

We retrospectively included 168 patients (67 ± 10 years; 146 men) who underwent RFCA of post-infarct VT. J-wave pattern were defined as J-point elevation ≥ 0.1 mV in at least two leads irrespective of QRS width. fQRS was defined as various RSR` pattern in patients with narrow QRS and more than two R wave in those with wide QRS. The primary endpoint was VT recurrence after RFCA up to 24 months.

RESULTS

J-wave pattern and fQRS were present in 27 and 28 patients, respectively. Overlap of J-wave pattern and fQRS was observed in nine. During a median follow-up of 20 (interquartile range 9-24) months, 46 (27%) patients had VT recurrence. Kaplan-Meier curves revealed that both J-wave pattern and fQRS were associated with VT recurrence. Multivariate Cox regression analysis demonstrated that the presence of J-wave pattern (hazard ratio [HR] 2.84; 95% confidence interval [CI] 1.45-5.58; P = .002) and greater number of induced VT (HR 1.29; 95% CI 1.15-1.45; P < .001) were the independent predictors of VT recurrence.

CONCLUSIONS

A J-wave pattern-but not fQRS-is independently associated with an increased risk of post-infarct VT recurrence after RFCA irrespective of QRS width. This simple non-invasive parameter may identify patients who require additional treatment.

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

BACKGROUND

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.

OBJECTIVE

The purpose of this study was to assess the feasibility and efficacy of a functional substrate VT ablation strategy.

METHODS

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.

RESULTS

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).

CONCLUSION

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.

Decrement Evoked Potential Mapping to Guide Ventricular Tachycardia Ablation: Elucidating the Functional Substrate

Empirical approaches to targeting the ventricular tachycardia (VT) substrate include mapping of late potentials, local abnormal electrogram, pace-mapping and homogenisation of the abnormal signals. These approaches do not try to differentiate between the passive or active role of local signals as the critical components of the VT circuit. By not considering the functional components, these approaches often view the substrate as a fixed anatomical barrier. Strategies to improve the success of VT ablation need to include the identification of critical functional substrate. Decrement-evoked potential (DeEP) mapping has been developed to elucidate this using an extra-stimulus added to a pacing drive train. With knowledge translation in mind, the authors detail the evolution of the DeEP concept by way of a study of simultaneous panoramic endocardial mapping in VT ablation; an in silico modelling study to demonstrate the factors influencing DeEPs; a multicentre VT ablation validation study; a practical approach to DeEP mapping; the potential utility of DeEPs to identify arrhythmogenic atrial substrate; and, finally, other functional mapping strategies.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

Impact of Micro-, Mini- and Multi-Electrode Mapping on Ventricular Substrate Characterisation

Accurate substrate characterisation may improve the evolving understanding and treatment of cardiac arrhythmias. During substrate-based ablation techniques, wide practice variations exist with mapping via dedicated multi-electrode catheter or conventional ablation catheters. Recently, newer ablation catheter technology with embedded mapping electrodes have been introduced. This article focuses on the general misconceptions of voltage mapping and more specific differences in unipolar and bipolar signal morphology, field of view, signal-to-noise ratio, mapping capabilities (density and resolution), catheter-specific voltage thresholds and impact of micro-, mini- and multi-electrodes for substrate mapping. Efficiency and cost-effectiveness of different catheter types are discussed. Increasing sampling density with smaller electrodes allows for higher resolution with a greater likelihood to record near-field electrical information. These advances may help to further improve our mechanistic understanding of the correlation between substrate and ventricular tachycardia, as well as macro-reentry arrhythmia in humans.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias: Executive summary

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

Multicenter Study of Dynamic High-Density Functional Substrate Mapping Improves Identification of Substrate Targets for Ischemic Ventricular Tachycardia Ablation

OBJECTIVES

The goal of this study was to evaluate the role of dynamic substrate changes in facilitating conduction delay and re-entry in ventricular tachycardia (VT) circuits.

BACKGROUND

The presence of dynamic substrate changes facilitate functional block and re-entry in VT but are rarely studied as part of clinical VT mapping.

METHODS

Thirty patients (age 67 ± 9 years; 27 male subjects) underwent ablation. Mapping was performed with the Advisor HD Grid multipolar catheter. A bipolar voltage map was obtained during sinus rhythm (SR) and right ventricular sense protocol (SP) single extra pacing. SR and SP maps of late potentials (LP) and local abnormal ventricular activity (LAVA) were made and compared with critical sites for ablation, defined as sites of best entrainment or pace mapping. Ablation was then performed to critical sites, and LP/LAVA identified by the SP.

RESULTS

At a median follow-up of 12 months, 90% of patients were free from antitachycardia pacing (ATP) or implantable cardioverter-defibrillator shocks. SP pacing resulted in a larger area of LP identified for ablation (19.3 mm² vs. 6.4 mm²) during SR mapping (p = 0.001), with a sensitivity of 87% and a specificity of 96%, compared with 78% and 65%, respectively, in SR.

CONCLUSIONS

LP and LAVA observed during the SP were able to identify regions critical for ablation in VT with a greater accuracy than SR mapping. This may improve substrate characterization in VT ablation. The combination of ablation to critical sites and SP-derived LP/LAVA requires further assessment in a randomized comparator study.

Local impedance guides catheter ablation in patients with ventricular tachycardia

AIMS

Catheter contact and local tissue characteristics are relevant information for successful radiofrequency current (RFC)-ablation. Local impedance (LI) has been shown to reflect tissue characteristics and lesion formation during RFC-ablation. Using a novel ablation catheter incorporating three mini-electrodes, we investigated LI in relation to generator impedance (GI) in patients with ventricular tachycardia (VT) and its applicability as an indicator of effective RFC-ablation.

METHODS AND RESULTS

Baseline impedance, Δimpedance during ablation and drop rate (Δimpedance/time) were analyzed for 625 RFC-applications in 28 patients with recurrent VT undergoing RFC-ablation. LI was lower in scarred (87.0 Ω [79.0-95.0]) compared to healthy myocardium (97.5 Ω ([82.75-111.50]; P = .03) while GI did not differ between scarred and healthy myocardium. ΔLI was higher (18 Ω [9.4-26.0]) for VT-terminating as compared to non-terminating RFC-ablation (ΔLI 13 Ω [8.85-18.0]; P = .03), but did not differ for ΔGI between terminating vs nonterminating RFC-ablation. Correspondingly, LI drop rate was higher for RFC-ablation terminating the VT compared with RFC-ablation not terminating the VT (0.63 Ω/s [0.52-0.76] vs 0.32 Ω [0.20-0.58]; P = .008) while there was no difference for GI drop rate. ΔLI was higher in patients with nonischemic cardiomyopathy vs patients with ischemic cardiomyopathy (16 Ω [11.0-20.0] vs 11.0 Ω [7.85-17.00]; P = .003).

CONCLUSION

Our findings suggest that LI is a sensitive parameter to guide RFC-ablation in patients with VT. LI indicates differences in tissue characteristics and generally is higher in patients with nonischemic cardiomyopathy. Hence, the etiology of the underlying cardiomyopathy needs to be considered when adopting LI for monitoring catheter ablation of VT.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias: Executive summary

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

2019 HRS/EHRA/APHRS/LAHRS expert consensus statement on catheter ablation of ventricular arrhythmias

Ventricular arrhythmias are an important cause of morbidity and mortality and come in a variety of forms, from single premature ventricular complexes to sustained ventricular tachycardia and fibrillation. Rapid developments have taken place over the past decade in our understanding of these arrhythmias and in our ability to diagnose and treat them. The field of catheter ablation has progressed with the development of new methods and tools, and with the publication of large clinical trials. Therefore, global cardiac electrophysiology professional societies undertook to outline recommendations and best practices for these procedures in a document that will update and replace the 2009 EHRA/HRS Expert Consensus on Catheter Ablation of Ventricular Arrhythmias. An expert writing group, after reviewing and discussing the literature, including a systematic review and meta-analysis published in conjunction with this document, and drawing on their own experience, drafted and voted on recommendations and summarized current knowledge and practice in the field. Each recommendation is presented in knowledge byte format and is accompanied by supportive text and references. Further sections provide a practical synopsis of the various techniques and of the specific ventricular arrhythmia sites and substrates encountered in the electrophysiology lab. The purpose of this document is to help electrophysiologists around the world to appropriately select patients for catheter ablation, to perform procedures in a safe and efficacious manner, and to provide follow-up and adjunctive care in order to obtain the best possible outcomes for patients with ventricular arrhythmias.

Substrate Mapping and Ablation for Ventricular Tachycardia in Patients with Structural Heart Disease: How to Identify Ventricular Tachycardia Substrate

Catheter ablation for ventricular tachycardia (VT) has been increasingly used over the past two decades in patients with structural heart disease (SHD). In these individuals, a substrate mapping strategy is being more commonly applied to identify targets for VT ablation, which has been shown to be more effective versus targeting mappable VTs alone. There are a number of substrate mapping methods in existence that aim to explore potential VT isthmuses, although their success rates vary. Most of the reported electrogram-based mapping studies have been performed with ablation catheters; meanwhile, the use of multipolar mapping catheters with smaller electrodes and closer interelectrode spacing has emerged, which allows for an assessment of detailed near-field abnormal electrograms at a higher resolution. Another recent advancement has occurred in the use of imaging techniques in VT ablation, particularly in refining the substrate. The goal of this paper is to review the key developments and limitations of current mapping strategies of substrate-based VT ablation and their outcomes. In addition, we briefly summarize the role of cardiac imaging in delineating VT substrate.

Ventricular Tachycardia Isthmus Characteristics: Insights from High-density Mapping

In the context of structural heart disease, ventricular tachycardia (VT) is related to surviving fibres in incomplete scar. New technologies which allow electroanatomic mapping at higher density and with smaller, more closely spaced electrodes have allowed new insights into the characteristics of VT circuits. VT isthmuses are complex structures, with multiple entrances, exits and dead ends of activation. The isthmus is frequently defined by regions of functional block and several VT circuits can be possible in a VT "critical zone". In this review, we discuss these new insights and how they may improve VT ablation strategies, as well as discussing emerging technologies which may further develop our understanding.

Is it feasible to offer 'targeted ablation' of ventricular tachycardia circuits with better understanding of isthmus anatomy and conduction characteristics?

Successful mapping and ablation of ventricular tachycardias remains a challenging clinical task. Whereas conventional entrainment and activation mapping was for many years the gold standard to identify reentrant circuits in ischaemic ventricular tachycardia ablation procedures, substrate mapping has become the cornerstone of ventricular tachycardia ablation. In the last decade, technology has dramatically improved. In parallel to high-density automated mapping, cardiac imaging and image integration tools are increasingly used to assess the structural ventricular tachycardia substrate. The aim of this review is to describe the technologies underlying these new mapping systems and to discuss their possible role in providing new insights into identification and visualization of reentrant tachycardia mechanisms.