Substrate-based Ventricular Tachycardia Ablation Research Articles

Ventricular tachycardia ablation after myocardial infarction guided by cardiac magnetic resonance/multidetector computed tomography image integration

Abstract INTRODUCTION The persistent challenge of ventricular tachycardia (VT) ablation lies in the elevated morbidity and mortality due to the underlying disease progression and the complexity of the arrhythmogenic substrate. As imaging methods are evolving, substrate-based VT ablation is moving closer to the realm of precision medicine. CASE PRESENTATION A 52-year-old patient with a history of hypertension, type II diabetes mellitus, hyperlipidemia, and stage IIIB chronic kidney disease was referred to our hospital for sustained monomorphic VT. Upon admission, the patient was hemodynamically stable. Laboratory results indicated mild anemia, moderate renal dysfunction, and normal myocardial enzymes. ECG during sinus rhythm showed widespread repolarization abnormalities in the apical and postero-lateral leads. Echocardiography revealed mild left ventricular dysfunction and coronary angiography confirmed significant lesions in multiple coronary arteries that were treated with drug-eluting stents (DES). Cardiac MRI showed relatively limited areas of old myocardial infarctions in the left circumflex artery and left anterior descending artery territories, therefore we decided to perform VT ablation. We used a Carto 3 Biosense Webster electro-anatomical mapping system (EAM) guided by fusion imaging (cardiac MRI and multidetector computed tomography - MDCT) with the aid of ADAS 3D software. The voltage map created during sinus rhythm, was concordant with the lesions identified on LGE-CMR. Radiofrequency (RF) catheter ablation targeted abnormal signals from the EAM, which were identified based on conduction channels (CCs) from the fusion imaging. There was complete VT non-inducibility at programmed ventricular stimulation (PVS). At the 3-month follow-up, echocardiography showed a slight improvement in LVEF and repeated PVS proved persistent ventricular arrhythmia non-inducibility. CONCLUSION Substrate-based VT ablation in structural heart disease has greatly improved by high-resolution substrate imaging with detailed anatomy, allowing successful personalized treatment. There is room for further improvement in the near future with the contribution of artificial intelligence, possibly with a more targeted and automated VT ablation.

Periprocedural acute hemodynamic decompensation associated with substrate-based ablation of ventricular tachycardia in patients with structural heart disease - rare and nonpredictable event

Abstract Funding Acknowledgements Type of funding sources: None. Background Radiofrequency (RF) catheter ablation is an established treatment method in patients with structural heart disease (SHD) and recurrent ventricular tachycardia (VT). Due to underlying SHD, concomitant heart failure and a high burden of comorbidities, these patients are at considerable risk of periprocedural complications including acute hemodynamic decompensation (AHD) with a reported rate of up to 11%. The PAINESD score [sum of 5, 3, 6, 6, 3, 5, and 3 points for chronic obstructive pulmonary disease (COPD), age >60 years, ischemic cardiomyopathy (ICM), NYHA Class >2, LV ejection fraction (LVEF) <25%, electrical storm (ES), and diabetes mellitus (DM), respectively] was proposed to predict the risk of AHD, and identify the patients who may benefit from pre-emptive use of percutaneous left ventricular assist device (pVAD). Purpose The single-centre, retrospective study investigated the incidence of AHD in large-volume, tertiary referral EP centre and the predictive power of the PAINESD score. Methods We included patients who had their first ablation for SHD-related VT between August 2006 and December 2020. The procedure was performed under conscious sedation except for patients who were on mechanical ventilation because of hemodynamical or electrical instability before the ablation. Substrate mapping/ablation was performed primarily during spontaneous rhythm or right-ventricular pacing. Induced VTs were terminated by overdrive pacing or cardioverted. Activation and entrainment mapping were used rarely – only in well-tolerated VTs. The goal of ablation was to abolish all inducible VTs. A purposely established institutional registry for complications of invasive procedures was used to collect all periprocedural complications that were subsequently adjudicated using the source medical records. AHD triggered by ablation procedure was defined as intraprocedural or early post-procedural (<12 h) development of acute pulmonary oedema or refractory hypotension, requiring urgent intervention including (but not limited to) inotropic agents and/or artificial ventilation and/or pVAD implant. Results The study cohort consisted of 1143 patients (age: 63±13 years, males: 87%, ICM: 67%, ES: 25%, NYHA Class: 2.1±1.0, LVEF: 34±13%, DM: 32%, COPD: 12%). Their PAINESD score was 11.4±6.6 (median: 12, interquartile range: 6–17). The ablation procedure (total duration 187±78 min, RF time: 23±15 min) was complicated by AHD in 13/1143 = 1.1% patients and these adverse events were not predicted by PAINESD score (Figure). Conclusions We observed a substantially lower rate (1.1%) of AHD than previously reported (up to 11%). These events did not accumulate in patients with upper-tertile PAINESD score in whom the highest AHD risk was reported (up to 24%). This observation may be explained by careful substrate-based ablation under conscious sedation that prevents prolonged low-output state related to repeated VT induction and mapping in general anaesthesia.

Abstract 12471: Ventricular Tachycardia Ablation vs Antiarrhythmic Drug Efficacy and Safety: A Meta-Analysis and Systematic Review of Randomized Studies

Introduction: Ventricular tachycardia (VT) poses a significant risk in patients with ischemic cardiomyopathy. Antiarrhythmic drugs (AAD) and catheter ablation are the 2 strategies employed to reduce the risk of future VT episodes. It is not established if one strategy is superior to the other. Hypothesis: Recently, randomized trials have been published comparing the efficacy and safety of both strategies for VT management. Unfortunately, most of these trials included a relatively small number of patients and had different outcomes or composite of outcomes limiting their utility. Methods: We performed a meta-analysis of randomized clinical trials comparing these treatment modalities for VT management. Criteria for appropriate studies were the inclusion of outcome data for both ablation and AAD arms, history of documented VT or ICD therapy before enrollments, and use of ICD to reliably monitor the incidence. Due to recent advances in substrate-based VT ablation and changes in ICD algorithms we limited our search for studies published in last 10 years. We identified four studies that met our inclusion and exclusion criteria. Results: Our included studies randomized 609 patients, 303 in ablation, and 310 in AAD groups. All-cause mortality data were available for all included studies. The cumulative odds ratio (OR) for all-cause mortality for VT ablation compared to AADs was 0.88, 95% confidence interval [0.56-1.39], p-value 0.58. Cumulative OR for cardiac death was 0.81 [95% CI 0.47-1.38], p-value 0.44, OR for ICD shocks was 0.82[0.57-1.18], p-value 0.29 and the OR for heart failure or cardiac rehospitalization was 0.82 [95% CI 0.53-1.25] p-value 0.35. Treatment-related complications were reported in only two studies with cumulative OR 0.31 [95% CI 0.19-0.51] p <0.00001. Studies used different definitions of treatment related complications. Conclusions: VT ablation and antiarrhythmic drugs appear to be equally effective treatment strategies to prevent all-cause death, cardiac death, heart failure rehospitalization, and ICD shocks but there is a trend towards better results for all stated outcomes with ablation. There was statistically significantly lower incidence of the reported treatment-related complications with ablation compared to AADs.

A novel algorithm for 3-D visualization of electrogram duration for substrate-mapping in patients with ischemic heart disease and ventricular tachycardia.

BackgroundMyocardial slow conduction is a cornerstone of ventricular tachycardia (VT). Prolonged electrogram (EGM) duration is a useful surrogate parameter and manual annotation of EGM characteristics are widely used during catheter-based ablation of the arrhythmogenic substrate. However, this remains time-consuming and prone to inter-operator variability. We aimed to develop an algorithm for 3-D visualization of EGM duration relative to the 17-segment American Heart Association model.MethodsTo calculate and visualize EGM duration, in sinus rhythm acquired high-density maps of patients with ischemic cardiomyopathy undergoing substrate-based VT ablation using a 64-mini polar basket-catheter with low noise of 0.01 mV were analyzed. Using a custom developed algorithm based on standard deviation and threshold, the relationship between EGM duration, endocardial voltage and ablation areas was studied by creating 17-segment 3-D models and 2-D polar plots.Results140,508 EGMs from 272 segments (n = 16 patients, 94% male, age: 66±2.4, ejection fraction: 31±2%) were studied and 3-D visualization of EGM duration was performed. Analysis of signal processing parameters revealed that a 40 ms sliding SD-window, 15% SD-threshold and >70 ms EGM duration cutoff was chosen based on diagnostic odds ratio of 12.77 to visualize rapidly prolonged EGM durations. EGMs > 70 ms matched to 99% of areas within dense scar (<0.2 mV), in 95% of zones within scar border zone (0.2–1.0 mV) and detected ablated areas having resulted in non-inducibility at the end of the procedure. Ablation targets were identified with a sensitivity of 65.6% and a specificity of 94.6% avoiding false positive labeling of prolonged EGMs in segments with healthy myocardium.ConclusionThe novel algorithm allows rapid visualization of prolonged EGM durations. This may facilitate more objective characterization of arrhythmogenic substrate in patients with ischemic cardiomyopathy.

Ventricular tachycardia burden reduction after substrate ablation: Predictors of recurrence

Substrate-based ventricular tachycardia (VT) ablation is a first-line treatment in patients with structural cardiac disease and sustained VT refractory to medical therapy. Despite technological improvements and increased knowledge of VT substrate, recurrence still is frequent. Published data are lacking on the possible reduction in VT burden after ablation despite recurrence. The purpose of this study was to assess VT burden reduction during long-term follow-up after substrate ablation and identify predictors of VT recurrence. We analyzed 234 consecutive VT ablation procedures in 207 patients (age 63 ± 14.9 years; 92% male; ischemic heart disease in 65%) who underwent substrate ablation in a single center from 2013 to2018. After follow-up of 3.14 ± 1.8 years, the VT recurrence rate was 41.4%. Overall, a 99.6% reduction in VT burden (median VT episodes per year: preprocedural 3.546 [1.347-13.951] vs postprocedural 0.001 [0-0.689]; P = .001) and a 96.3% decrease in implantable cardioverter-defibrillator (ICD) shocks (preprocedural 1.145 [0.118-4.467] vs postprocedural 0.042 [0-0.111] per year; P = .017) were observed. In the subgroup of patients who experienced VT recurrences, VT burden decreased by 69.2% (median VT episodes per year: preprocedural 2.876 [1.105-8.801] vs postprocedural 0.882 [0.505-2.283]; P <.001). Multivariable analysis showed persistence of late potentials (67% vs 19%; hazard ratio 3.18 [2.18-6.65]; P <.001) and lower left ventricular ejection fraction (EF) (30 [25-40] vs 39 [30-50]; P = .022) as predictors of VT recurrence. Despite a high recurrence rate during long-term follow-up, substrate-based VT ablation is related to a large reduction in VT burden and a decrease in ICD therapies. Lower EF and persistence of late potentials are predictors of recurrence.

Abstract 14246: Automated Detection of Arrhythmogenic VT Substrate: Performance of a 2019 HRS VT Consensus Document Recommended Strategy

Background: During ventricular tachycardia (VT) ablation, clinical VT is often non-inducible or hemodynamically unstable. Hence, a substrate-based approach is often necessary. Although many strategies have been proposed, none have been automated nor incorporated into current day electro-anatomical mapping (EAM) systems. One strategy, recommended in 2019 HRS guideline, is Decrement Evoked Potential (DeEP) mapping for identification of critical VT substrate. We have developed an automated method to identify critical DeEP VT substrate in an EAM system (CARTO ® 3). Objective: The performance of this novel automated algorithm was retrospectively evaluated in patients who underwent substrate-based VT ablation. Methods: Entire VT ablation using DeEP mapping was performed and recorded in 12 consecutive patients. CARTO ® 3 case data was downloaded and analyzed by a novel automated algorithm for DeEP detection. A blinded electrophysiologist verified the automated electrogram DeEP annotations and assessed its performance in a dichotomous fashion. The effect of bipolar voltage threshold (0.01, 0.02, 0.05, 0.075, 0.1, 0.20, 0.25 and 0.30 mV) on algorithm performance was evaluated. Sensitivity, specificity and ROC curve of the algorithms were calculated. Finally, results from the analysis were merged with voltage map to produce DeEP maps. Results: Results from the ROC curve shows that a bipolar threshold of 0.075mV optimizes specificity and sensitivity. At that threshold the algorithm found 848 true positive and 626 true negatives out of a total of 1975 EGMS being analyzed. Sensitivity and specificity were found to be 65.8% and 82.3% respectively. Conclusions: We have developed an automatic detection algorithm that identifies and locates critical VT substrates. The performance characteristics have been evaluated for a multimodal VT substrate map to provide clinicians mechanistic substrate map in CARTO 3 ® for VT ablation.

Does Ventricular Tachycardia Ablation Targeting Local Abnormal Ventricular Activity Elimination Reduce Ventricular Fibrillation Incidence?

Various strategies for ablation of ventricular tachycardia (VT) have been described, but their impact on ventricular fibrillation (VF) is largely unknown. The aim of our study was to assess the effect of substrate-based VT ablation targeting local abnormal ventricular activity (LAVA) on recurrent VF events in patients with structural heart disease. A retrospective 2-center study was performed on patients with structural heart disease and both VT and VF, with incident VT ablation procedures targeting LAVAs. Generalized estimating equations with a Poisson loglinear model were used to assess the impact of catheter ablation on VF episodes. The change in VF events before and after catheter ablation was compared with matched controls without ablation. From a total of 686 patients with an incident VT ablation procedure targeting LAVAs, 21 patients (age, 57±14 years; left ventricular ejection fraction, 30±10%) had both VT and VF and met inclusion criteria. A total of 80 VF events were recorded in the implantable cardioverter-defibrillator logs the 6 months preceding ablation. Complete and partial LAVA elimination was achieved in 11 (52%) and 10 (48%) patients, respectively. Catheter ablation was associated with a highly significant reduction in VF recurrences (P<0.0001), which were limited to 3 (14%) patients at 6 months. The total number of VF events thereby decreased from 80 to 3, from a median of 1.0 (range, 1-29) to 0.0 (range, 0-1) in the 6 months before and after ablation, respectively. The reduction in VF events was significantly greater in patients with catheter ablation compared with 21 matched controls during 6-month periods following and preceding a baseline assessment (Poisson β-coefficient, 1.39; P=0.0003). Substrate-guided VT ablation targeting LAVAs may be associated with a significant reduction in recurrent VF, suggesting that VT and VF share overlapping arrhythmogenic substrates in patients with structural heart disease.

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.

MAGNETIC VT study: a prospective, multicenter, post-market randomized controlled trial comparing VT ablation outcomes using remote magnetic navigation-guided substrate mapping and ablation versus manual approach in a low LVEF population.

Patients with ischemic cardiomyopathy (ICM) are prone to scar-related ventricular tachycardia (VT). The success of VT ablation depends on accurate arrhythmogenic substrate localization, followed by optimal delivery of energy provided by constant electrode-tissue contact. Current manual and remote magnetic navigation (RMN)-guided ablation strategies aim to identify a reentry circuit and to target a critical isthmus through activation and entrainment mapping during ongoing tachycardia. The MAGNETIC VT trial will assess if VT ablation using the Niobe™ ES magnetic navigation system results in superior outcomes compared to a manual approach in subjects with ischemic scar VT and low ejection fraction. This is a randomized, single-blind, prospective, multicenter post-market study. A total of 386 subjects (193 per group) will be enrolled and randomized 1:1 between treatment with the Niobe ES system and treatment via a manual procedure at up to 20 sites. The study population will consist of patients with ischemic cardiomyopathy with left ventricular ejection fraction (LVEF) of ≤35% and implantable cardioverter defibrillator (ICD) who have sustained monomorphic VT. The primary study endpoint is freedom from any recurrence of VT through 12months. The secondary endpoints are acute success; freedom from any VT at 1year in a large-scar subpopulation; procedure-related major adverse events; and mortality rate through 12-month follow-up. Follow-up will consist of visits at 3, 6, 9, and 12months, all of which will include ICD interrogation. The MAGNETIC VT trial will help determine whether substrate-based ablation of VT with RMN has clinical advantages over manual catheter manipulation. Clinicaltrials.gov identifier: NCT02637947.

Use of a novel fragmentation map to identify the substrate for ventricular tachycardia in postinfarction cardiomyopathy.

Substrate ablation is commonly performed in patients with postinfarction cardiomyopathy and ventricular tachycardia (VT). Recognition of fragmented and late potentials during sinus rhythm is a tedious process subject to operator fatigue. The purpose of this study was to assess the value of automated analysis to quantify electrogram fragmentation and to determine the relationship of fragmented regions to the VT isthmus. Detailed left ventricular (LV) mapping was performed in 2 groups: (1) 14 patients with previous myocardial infarction and tolerated VT and (2) 14 controls with structurally normal hearts. In patients with VT, mid-isthmus sites were identified using entrainment mapping. Sinus rhythm endocardial LV electrograms underwent time- and frequency-domain analysis and were displayed as fragmentation or frequency maps. The region of fractionated electrograms and their relation to the VT isthmus sites were determined. Cutoffs for abnormal electrogram fragmentation were ventricular fractionation index ≥ 7 and fast Fourier transform ratio ≥ 14%, respectively. In the time domain, LV surface area with fractionated electrograms was significantly smaller than the total scar surface area (27.3% ± 7.1% vs 42.1% ± 12.3%, P <.001), yet contained 100% of VT isthmus sites. In the frequency domain, areas of abnormal fractionation occupied 9.7% ± 6.9% of total LV surface area and included only 60% of the VT isthmus sites. Automated electrogram fractionation analysis represents an objective tool to rapidly quantify electrogram fragmentation and guide substrate-based ablation of VT. Empiric ablation of these regions may be a new strategy for substrate-guided VT ablation.

Elimination of Local Abnormal Ventricular Activities

Background— Catheter ablation of ventricular tachycardia (VT) is effective and particularly useful in patients with frequent defibrillator interventions. Various substrate modification techniques have been described for unmappable or hemodynamically intolerable VT. Noninducibility is the most frequently used end point but is associated with significant limitations, so the optimal end point remains unclear. We hypothesized that elimination of local abnormal ventricular activities (LAVAs) during sinus rhythm or ventricular pacing would be a useful and effective end point for substrate-based VT ablation. As an adjunct to this strategy, we used a new high-density mapping catheter and frequently used epicardial mapping. Methods and Results— Seventy patients (age, 67±11 years; 7 female) with VT and structurally abnormal ventricle(s) were prospectively enrolled. Conventional mapping was performed in sinus rhythm in all, and a high-density Pentaray mapping catheter was used in the endocardium (n=35) and epicardially. LAVAs were recorded in 67 patients (95.7%; 95% confidence interval, 89.2–98.9). Catheter ablation was performed targeting LAVA with an irrigated-tip catheter placed endocardially via a transseptal or retrograde aortic approach or epicardially via the subxiphoid approach. LAVAs were successfully abolished or dissociated in 47 of 67 patients (70.1%; 95% confidence interval, 58.7–80.1). In multivariate analysis, LAVA elimination was independently associated with a reduction in recurrent VT or death (hazard ratio, 0.49; 95% confidence interval, 0.26–0.95; P =0.035) during long-term follow-up (median, 22 months). Conclusions— LAVAs can be identified in most patients with scar-related VT. Elimination of LAVAs is feasible and safe and is associated with superior survival free from recurrent VT.

Efficacy and safety of ventricular tachycardia ablation with mechanical circulatory support compared with substrate-based ablation techniques

Catheter ablation of ventricular tachycardia (VT) can be limited by haemodynamic instability. In these cases, substrate-based ablation is typically performed. An alternative is to perform activation and entrainment mapping during VT supported by a percutaneous left ventricular assist device (pVAD). We sought to compare the complication and success rates of pVAD-assisted VT ablation with scar-based techniques. Thirteen consecutive patients with haemodynamically unstable VT underwent pVAD-assisted ablation (pVAD group) and were retrospectively compared with 18-matched patients undergoing a substrate-based VT ablation (non-pVAD group). There was no significant difference in age or ejection fraction between the groups although pVAD patients tended to have more shocks in the preceding months. Procedure times were longer for the pVAD group. The number of monomorphic VTs induced was greater in the pVAD group (3.2 vs. 1.6, P= 0.04); however, after ablation, there was no difference in inducibility between the pVAD and non-pVAD group (10 of 13 vs. 12 of 18; 77 vs. 67%, P = 0.69). There was no difference in acute complications including stroke or death. At 9 ± 3 months, 1-year freedom from implantable cardioverter-defibrillator (ICD) shocks/therapies for sustained VT were similar (P= 0.96). In multivariable analysis, the absence of atrial fibrillation (hazard ratio=0.15, P= 0.04) was associated with a lower incidence of ICD shocks. In high-risk patients, pVAD-assisted VT ablation guided by activation and entrainment mapping is a feasible alternative to substrate mapping and allows outcomes comparable to substrate mapping.

Head-to-head comparison of contrast-enhanced magnetic resonance imaging and electroanatomical voltage mapping to assess post-infarct scar characteristics in patients with ventricular tachycardias: real-time image integration and reversed registration

Substrate-based ablation of ventricular tachycardia (VT) relies on electroanatomical voltage mapping (EAVM). Integration of scar information from contrast-enhanced magnetic resonance imaging (CE-MRI) with EAVM may provide supplementary information. This study assessed the relation between electrogram voltages and CE-MRI scar characteristics using real-time integration and reversed registration. Fifteen patients without implantable cardiac defibrillator (14 males, 64 ± 9 years) referred for VT ablation after myocardial infarction underwent CE-MRI. Contours of the CE-MRI were used to create three-dimensional surface meshes of the left ventricle (LV), aortic root, and left main stem (LM). Real-time integration of CE-MRI-derived scar meshes with EAVM of the LV and aortic root was performed using the LM and the CARTO surface registration algorithm. Merging of CE-MRI meshes with EAVM was successful with a registration error of 3.8 ± 0.6 mm. After the procedure, voltage amplitudes of each mapping point were superimposed on the corresponding CE-MRI location using the reversed registration matrix. Infarcts on CE-MRI were categorized by transmurality and signal intensity. Local bipolar and unipolar voltages decreased with increasing scar transmurality and were influenced by scar heterogeneity. Ventricular tachycardia reentry circuit isthmus sites were correlated to CE-MRI scar location. In three patients, VT isthmus sites were located in scar areas not identified by EAVM. Integration of MRI-derived scar maps with EAVM during VT ablation is feasible and accurate. Contrast-enhanced magnetic resonance imaging identifies non-transmural scars and infarct grey zones not detected by EAVM according to the currently used voltage criteria and may provide important supplementary substrate information in selected patients.

Anatomic characterization of endocardial substrate for hemodynamically stable reentrant ventricular tachycardia: Identification of endocardial conducting channels

Detailed anatomic characterization of endocardial substrate of ventricular tachycardia (VT) is limited. The purpose of this study was to determine the endocardial dimensions and local electrogram voltage characteristics of the reentrant circuit. VT-related conducting channels corresponding to zones of slow conduction may be identified. Electroanatomic mapping was performed in 26 patients with uniform VT. Entrainment mapping was performed in 53 VTs, of which 19 entrance, 37 isthmus, 48 exit, and 32 outer loop sites were identified. The color display of voltage maps was adjusted to identify conducting channels associated with VT circuits. A conducting channel was defined as a path of multiple orthodromically activated sites within the VT circuit that demonstrated an electrogram amplitude higher than that of surrounding areas as evidenced by voltage color differences. Forty-seven (84%) of 56 entrance or isthmus sites were located within dense scar (<0.5 mV). Nearly all exits (92%) were located in abnormal endocardium (<1.5 mV), with more than half (54%) located in the border zone (0.5-1.5 mV). VT-related conducting channels was identified in 18 of 32 VTs with detailed mapping (average length 32 +/- 22 mm). The voltage threshold in the conducting channels ranges from 0.1 to 0.7 mV (mean 0.33 +/- 0.15 mV). (1) Most entrance and isthmus sites of hemodynamically stable VT are located in dense scar, whereas exits are located in the border zone. (2) VT-related conducting channels may be identified by careful voltage threshold adjustment. These findings have important implications regarding strategies for substrate-based VT ablation.

Short- and Long-Term Success of Substrate-Based Mapping and Ablation of Ventricular Tachycardia in Arrhythmogenic Right Ventricular Dysplasia

Multiple morphologies, hemodynamic instability, or noninducibility may limit ventricular tachycardia (VT) ablation in patients with arrhythmogenic right ventricular dysplasia (ARVD). Substrate-based mapping and ablation may overcome these limitations. We report the results and success of substrate-based VT ablation in ARVD. Twenty-two patients with ARVD were studied. Traditional mapping for VT was limited because of multiple/changing VT morphologies (n=14), nonsustained VT (n=10), or hemodynamic intolerance (n=5). Sinus rhythm CARTO mapping was performed to define areas of "scar" (<0.5 mV) and "abnormal" myocardium (0.5 to 1.5 mV). Ablation was performed in "abnormal" regions, targeting sites with good pace maps compared with the induced VT(s). Linear lesions were created in these areas to (1) connect the scar/abnormal region to a valve continuity or other scar or (2) encircle the scar/abnormal region. Eighteen patients had implanted cardioverter defibrillators, 15 had implanted cardioverter defibrillator therapies, and 7 had sustained VT (6 with syncope). VTs (3+/-2 per patient) were induced (cycle length, 339+/-94 ms), and scar was identified in all patients. Scar areas were related to the tricuspid annulus, proximal right ventricular outflow tract, and anterior/inferior-apical walls. Lesions connected abnormal regions to the annulus (n=12) or other scars (n=4) and/or encircled abnormal regions (n=13). Per patient, a mean of 38+/-22 radiofrequency lesions was applied. Short-term success was achieved in 18 patients (82%). VT recurred in 23%, 27%, and 47% of patients after 1, 2, and 3 years' follow-up, respectively. Substrate-based ablation of VT in ARVD can achieve a good short-term success rate. However, recurrences become increasingly common during long-term follow-up.