Appropriate Selection of Substrate Ablation for Persistent Atrial Fibrillation Using Intraprocedural Assessment.

BACKGROUND: It has not been fully elucidated which patients with persistent atrial fibrillation (PerAF) should undergo substrate ablation plus pulmonary vein isolation (PVI). This study aimed to identify PerAF patients who required substrate ablation using intraprocedural assessment of the baseline rhythm and the origin of atrial fibrillation (AF) triggers. METHODS AND RESULTS: This was a post hoc subanalysis using extended data of the EARNEST-PVI trial, a prospective multicenter randomized trial comparing PVI-alone and PVI-plus (i.e., PVI with added catheter ablation) arms. We divided 492 patients into 4 groups according to baseline rhythm and the location of AF triggers before PVI: Group A (n=22), sinus rhythm with pulmonary vein (PV)-specific AF triggers (defined as reproducible AF initiation from PVs only); Group B (n=211), AF with PV-specific AF triggers; Group C (n=94), sinus rhythm with no PV-specific AF trigger; Group D (n=165), AF with no PV-specific AF trigger. Among the 4 groups, only in Group D (AF at baseline and no PV-specific AF triggers) was arrhythmia-free survival significantly lower in the PVI-alone than PVI-plus arm (P=0.032; hazard ratio 1.68; 95% confidence interval 1.04-2.70). CONCLUSIONS: Patients with sinus rhythm or PV-specific AF triggers did not receive any benefit from substrate ablation, whereas patients with AF and no PV-specific AF trigger benefited from substrate ablation.

A simplified approach to radiofrequency catheter ablation of idiopathic ventricular outflow tract premature ventricular contractions.

INTRODUCTION: Frequently, low voltage areas (LVAs) and diastolic potentials (DPs) are present at ablation sites in sinus rhythm in patients with idiopathic premature ventricular contractions (PVCs). OBJECTIVE: Validate these findings as substrates for PVCs and evaluate the feasibility of a simplified substrate approach based on LVAs and DPs for ablation of idiopathic outflow tract PVCs, in patients with a low PVC burden during the procedure. METHODS: Prospective single-arm clinical trial at two centers with comparison with a historical group, matched to age and gender. The study group consisted of consecutive patients referred for ablation of frequent idiopathic PVCs with inferior axis, that presented with less than two PVCs/min in first 5 min of the procedure. The ablation was based on fast mapping of the right ventricular outflow tract in sinus rhythm looking for LVAs and DPs, defined as isolated small amplitude potentials occurring after the T wave of the surface echocardiogram. The area with LVAs and DPs was tagged, and a simplified activation mapping of the PVCs was done in that area. The procedure time, success rate, and recurrence rate were compared with the historical group in whom ablation was performed based on activation and pace mapping only. A validation group without PVCs was also studied to assess the prevalence of LVAs and DPs in the general population. RESULTS: The study (n = 38), historical (n = 38), and validation (n = 38) groups did not differ in relation to age or gender. Prevalence of LVAs and DPs was significantly higher in the study group in comparison with the validation group, respectively, 71% versus 11%, p < 0.0001 and 87% versus 8%, p < 0.0001. Procedure time was significantly lower in the study group when comparing to the historical group, 130 (100-164) versus 183 (160-203) min, p < 0.0001 and the success rate was significantly higher, 90% versus 64%, p = 0.013. The recurrence rate in patients with a successful ablation was not significantly different between both groups, Log-rank = 0.125. CONCLUSION: The prevalence of LVAs and DPs was significantly higher in the study group than in the validation group. The proposed approach proved to be feasible, faster, and more efficient than the historical approach.

Ventricular tachycardia ablation guided or aided by scar characterization with cardiac magnetic resonance: rationale and design of VOYAGE study.

BACKGROUND: Radiofrequency ablation has been shown to be a safe and effective treatment for scar-related ventricular arrhythmias (VA). Recent preliminary studies have shown that real time integration of late gadolinium enhancement cardiac magnetic resonance (LGE-CMR) images with electroanatomical map (EAM) data may lead to increased procedure efficacy, efficiency, and safety. METHODS: VOYAGE is a prospective, randomized, multicenter controlled open label study designed to compare in terms of efficacy, efficiency, and safety a CMR aided/guided workflow to standard EAM-guided ventricular tachycardia (VT) ablation. Patients with an ICD or with ICD implantation expected within 1 month, with scar related VT, suitable for CMR and multidetector computed tomography (MDCT) will be randomized to a CMR-guided or CMR-aided approach, whereas subjects unsuitable for imaging or with image quality deemed not sufficient for postprocessing will be allocated to standard of care ablation. Primary endpoint is defined as VT recurrences (sustained or requiring appropriate ICD intervention) during 12 months follow-up, excluding the first month of blanking period. Secondary endpoints will include procedural efficiency, safety, impact on quality of life and comparison between CMR-guided and CMR-aided approaches. Patients will be evaluated at 1, 6 and 12 months. DISCUSSION: The clinical impact of real time CMR-guided/aided ablation approaches has not been thoroughly assessed yet. This study aims at defining whether such workflow results in more effective, efficient, and safer procedures. If proven to be of benefit, results from this study could be applied in large scale interventional practice. Trial registrationClinicalTrials.gov, NCT04694079, registered on January 1, 2021.

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

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

Open chest epicardial and transapical endocardial substrate ablation for ventricular tachycardia with left ventricular aneurysm in a porcine model.

BACKGROUND: Endo-epicardial radiofrequency catheter ablation (RFCA) of ventricular tachycardia (VT) as a first-line strategy has been shown to improve outcomes. This study sought to evaluate the feasibility and validity of open-chest epicardial and transapical endocardial substrate ablation for VT with left ventricular aneurysm (LVA) applying to routine cardiac surgery. METHODS: Porcine models of LVA with VT were developed and were divided into a study group (RFCA from the epicardium via direct-view and endocardium via transapical access) and a control group (endocardial RFCA via retrograde transaortic access). Substrate-based mapping and ablation targeting abnormal potentials were performed under thoracotomy. Outcomes, including procedural success and acute freedom from VT, were analysed. RESULTS: Twenty-four of 35 (68.57%) acute myocardial infarction (AMI) pigs developed LVA with VT in a 6-week survival period and were randomly divided into a study group (n=12) and a control group (n=12). All animals in the study group successfully underwent endocardial mapping and ablation by transapical access. The scar size of the endocardium and the left ventricular chamber volume were similar in the two groups. Acute freedom from VT in the study group was remarkably superior to that in the control group (88.33% vs. 58.33%, p=0.04). CONCLUSIONS: Combined, direct epicardial and transapical endocardial substrate mapping and ablation appeared to be feasible and effective for treating VT with LVA under thoracotomy.

Elucidation of hidden slow conduction by double ventricular extrastimuli: a method for further arrhythmic substrate identification in ventricular tachycardia ablation procedures.

Aims: Identification of local abnormal electrograms (EGMs) during ventricular tachycardia substrate ablation (VTSA) is challenging when they are hidden within the far-field signal. This study analyses whether the response to a double ventricular extrastimulus during substrate mapping could identify slow conducting areas that are hidden during sinus rhythm. Methods and results: Consecutive patients (n = 37) undergoing VTSA were prospectively included. Bipolar EGMs with >3 deflections and duration <133 ms were considered as potential hidden slow conduction EGMs (HSC-EGM) if located within/surrounding the scar area. Whenever a potential HSC-EGM was identified, a double ventricular extrastimulus was delivered. If the local potential delayed, it was annotated as HSC-EGM. The incidence of HSC-EGM in core, border-zone, and normal-voltage regions was determined. Ablation was delivered at conducting channel entrances and HSC-EGMs. VT inducibility after VTSA obtained was compared with data from a historic control group. 2417 EGMs were analyzed. 575 (23.7%) qualified as potential HSC-EGM, and 198 of them were tagged as HSC-EGMs. Scars in patients with HSC-EGMs (n = 21, 56.7%) were smaller (35.424.7 vs 67.639.1 cm2; P = 0.006) and more heterogeneous (core/scar area ratio 0.250.2 vs 0.450.19; P = 0.02). 28.8% of HSC-EGMs were located in normal-voltage tissue; 81.3% were targeted for ablation. Patients undergoing VTSA incorporating HSC analysis needed less radiofrequency time (17.411 vs 2310.7 minutes; P = 0.016) and had a lower rate of VT inducibility after VTSA than the historic controls (24.3% vs 50%; P = 0.018). Conclusion: Ventricular tachycardia substrate ablation incorporating HSC analysis allowed further arrhythmic substrate identification (especially in normal-voltage areas) and reduced RF time and VT inducibility after VTSA.

Mini-electrodes help identifying hidden slow conduction during ventricular tachycardia substrate ablation.

A 69-year-old male with dilated non-ischemic cardiomyopathy and history of sustained monomorphic VT (SMVT) underwent an unsuccessful VT substrate ablation due to the proximity of the earliest activation site to the conduction system. A second attempt was performed using an ablation catheter with mini-electrodes (ME) and multiple extrastimuli to unveil hidden slow conduction (HSC) sites, allowing the performance of a successful ablation. No SMVT was induced thereafter. ME-obtained electrograms permit to accurately localize areas of HSC sites within ventricular tachycardia (VT) substrates. In our case, this allowed safe ablation during sinus rhythm to eliminate the VT substrate.

Ventricular Tachycardia Ablation Endpoints: Moving Beyond Noninducibility.

In patients with structural heart disease and ventricular tachycardia (VT) undergoing catheter ablation, the response to programmed electrical stimulation (PES) at the end of the procedure has been traditionally used to evaluate the acute success and predict long-term outcomes. Although noninducibility at PES has been extensively investigated and validated in clinical trials and large multicenter registries, its performance in predicting long-term freedom from VT is suboptimal. In addition, PES has inherent limitations related to the influence of background antiarrhythmic drug therapy, periprocedural use of anesthesia, and the heterogeneity in PES protocols. The increased utilization of substrate-based ablation approaches that focus on ablation of abnormal electrograms identified with mapping in sinus or paced rhythm has been paralleled by a need for additional procedural endpoints beyond VT noninducibility at PES. This article critically appraises the relative merits and limitations of different procedural endpoints according to different ablation techniques for catheter ablation of scar-related VT.

Targeting Wavefront Discontinuity Lines for Scar-Related Ventricular Tachycardia Ablation: A Novel Functional Substrate Ablation Approach.

BACKGROUND: The boundaries of critical isthmuses for re-entrant ventricular tachycardia (VT) are formed by wavefront discontinuities (fixed lines of block, slow propagation, and rotational propagation) seen during baseline rhythm. It is unknown whether wavefront discontinuities can be automatically identified and targeted for ablation using electroanatomic mapping systems. OBJECTIVES: The purpose of this study was to assess the electrophysiologic characteristics of automatically projected wavefront discontinuity lines (WADLs) and outcomes of an ablation strategy targeting WADLs in a mixed cohort of VT patients. METHODS: Late activation substrate maps were analyzed from 1 or more baseline rhythm wavefronts. WADLs were identified using the Carto Extended Early Meets Late module. Number, total length, and distance to critical VT sites were measured. VT recurrence and VT-free survival were followed. RESULTS: In total, 49 patients underwent 52 ablations with 71 unique substrate maps analyzed (18.8% epicardial; 62.0% right ventricular paced, 28.2% sinus rhythm, 9.9% left ventricular paced). A total of 28 VT critical sites were identified in 24 patients. WADLs were present in 49 of 71 (69.0%) maps. WADLs were present regardless of cardiomyopathy etiology, mapping wavefront, or surface. At a WADL threshold of 30%, 73.9% of critical VT sites were in close proximity (≤15 mm) to a WADL. VT-free survival was 62% at 1 year, with a competing risk model estimating a 1-year risk of VT recurrence of 23%. CONCLUSIONS: WADLs can be automatically projected in a majority of patients in a mixed cohort of cardiomyopathy etiology, mapped wavefronts, and myocardial surfaces mapped. Targeting WADLs results in low rate of VT recurrence at 1 year.

Correlation Between Functional Substrate Mapping and Cardiac Computed Tomography-Derived Wall Thinning for Ventricular Tachycardia Ablation.

BACKGROUND: Functional substrate mapping during baseline rhythm can identify arrhythmogenic tissue during ventricular tachycardia (VT) ablation. Wall thinning and wall thickness channels (WTCs) derived from computed tomography angiography have been shown to correlate with low voltage and VT isthmuses. The correlation between functional substrate mapping, wall thinning, and WTCs in patients with infarct- or non-infarct-related cardiomyopathies (ICM and NICM, respectively) has not been previously described. OBJECTIVES: The purpose of this study was to correlate cardiac CTA-derived myocardial wall thinning with functional VT substrate mapping using isochronal late activation mapping. METHODS: In 34 patients with ICM or NICM undergoing VT ablation who had a preprocedure computed tomography angiography, myocardial wall thinning was segmented in layers of 1 to 5 mm. Areas of wall thinning and WTCs were then spatially correlated with deceleration zones (DZs) from registered left ventricular endocardial isochronal late activation maps. RESULTS: In 21 ICM patients and 13 NICM patients, ICM patients had greater surfaces areas of wall thinning (P < 0.001). In ICM patients, 94.1% of primary DZs were located on areas of wall thinning, compared to 20% of DZs in NICM patients overall but 50% if there was any wall thinning present. Fifty-nine percent of DZs in ICM patients and 56% of DZs in NICM patients were located near WTCs. The positive predictive value for WTC in localizing DZs was 22.5% and 37.8% in ICM and NICM patients, respectively. CONCLUSIONS: Wall thinning is highly sensitive for functional substrate in ICM patients. WTCs had modest sensitivity for functional substrate but low positive predictive value for identifying DZs in ICM and NICM patients. These findings suggest that wall thinning may facilitate more efficient mapping in ICM patients, but WTCs are insufficient to localize wavefront discontinuities.

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

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

Real-time cardiovascular magnetic resonance-guided radiofrequency ablation: A comprehensive review.

Cardiac magnetic resonance (CMR) imaging could enable major advantages when guiding in real-time cardiac electrophysiology procedures offering high-resolution anatomy, arrhythmia substrate, and ablation lesion visualization in the absence of ionizing radiation. Over the last decade, technologies and platforms for performing electrophysiology procedures in a CMR environment have been developed. However, performing procedures outside the conventional fluoroscopic laboratory posed technical, practical and safety concerns. The development of magnetic resonance imaging compatible ablation systems, the recording of high-quality electrograms despite significant electromagnetic interference and reliable methods for catheter visualization and lesion assessment are the main limiting factors. The first human reports, in order to establish a procedural workflow, have rationally focused on the relatively simple typical atrial flutter ablation and have shown that CMR-guided cavotricuspid isthmus ablation represents a valid alternative to conventional ablation. Potential expansion to other more complex arrhythmias, especially ventricular tachycardia and atrial fibrillation, would be of essential impact, taking into consideration the widespread use of substrate-based strategies. Importantly, all limitations need to be solved before application of CMR-guided ablation in a broad clinical setting.

Multielectrode Unipolar Voltage Mapping and Electrogram Morphology to Identify Post-Infarct Scar Geometry: Validation by Histology.

OBJECTIVES: This study sought to evaluate the ability of uni- and bipolar electrograms collected with a multielectrode catheter with smaller electrodes to: 1) delineate scar; and 2) determine local scar complexity. BACKGROUND: Early reperfusion results in variable endocardial scar, often overlaid with surviving viable myocardium. Although bipolar voltage (BV) mapping is considered the pillar of substrate-based ablation, the role of unipolar voltage (UV) mapping has not been sufficiently explored. It has been suggested that bipolar electrograms collected with small electrode catheters can better identify complex scar geometries. METHODS: Twelve swine with early reperfusion infarctions were mapped with the 48-electrode OctaRay catheter and a conventional catheter during sinus rhythm. BV electrograms with double components were identified. Transmural (n = 933) biopsy specimens corresponding to mapping points were obtained, histologically assessed, and classified by scar geometry. RESULTS: OctaRay UV (UVOcta) and BV (BVOcta) amplitude were associated with the amount of viable myocardium at a given location, with a stronger association for UVOcta (R2 = 0.767 vs 0.473). Cutoff values of 3.7 mV and 1.0 mV could delineate scar (area under the curve: 0.803 and 0.728 for UVOcta and BVOcta, respectively). The morphology of bipolar electrograms collected with the OctaRay catheter more frequently identified areas with 2 layers of surviving myocardium than electrograms collected with the conventional catheter (84% vs 71%). CONCLUSIONS: UV mapping can generate a map to delineate the area of interest when using a multielectrode catheter. Within this area of interest, the morphology of bipolar electrograms can identify areas in which a surviving epicardial layer may overlay a poorly coupled, potentially arrhythmogenic, endocardium.

Substrate Ablation vs Antiarrhythmic Drug Therapy for Symptomatic Ventricular Tachycardia.

BACKGROUND: In patients with ischemic cardiomyopathy and an implantable cardioverter-defibrillator (ICD), catheter ablation and antiarrhythmic drugs (AADs) reduce ICD shocks, but the most effective approach remains uncertain. OBJECTIVES: This trial compares the efficacy and safety of catheter ablation vs AAD as first-line therapy in ICD patients with symptomatic ventricular tachycardias (VTs). METHODS: The SURVIVE-VT (Substrate Ablation vs Antiarrhythmic Drug Therapy for Symptomatic Ventricular Tachycardia) is a prospective, multicenter, randomized trial including patients with ischemic cardiomyopathy and appropriated ICD shock. Patients were 1:1 randomized to complete endocardial substrate-based catheter ablation or antiarrhythmic therapy (amiodarone + beta-blockers, amiodarone alone, or sotalol ± beta-blockers). The primary outcome was a composite of cardiovascular death, appropriate ICD shock, unplanned hospitalization for worsening heart failure, or severe treatment-related complications. RESULTS: In this trial, 144 patients (median age, 70 years; 96% male) were randomized to catheter ablation (71 patients) or AAD (73 patients). After 24 months, the primary outcome occurred in 28.2% of patients in the ablation group and 46.6% of those in the AAD group (hazard ratio [HR]: 0.52; 95% CI: 0.30-0.90; P = 0.021). This difference was driven by a significant reduction in severe treatment-related complications (9.9% vs 28.8%, HR: 0.30; 95% CI: 0.13-0.71; P = 0.006). Eight patients were hospitalized for heart failure in the ablation group and 13 in the AAD group (HR: 0.56; 95% CI: 0.23-1.35; P = 0.198). There was no difference in cardiac mortality (HR: 0.93; 95% CI: 0.19-4.61; P = 0.929). CONCLUSIONS: In ICD patients with ischemic cardiomyopathy and symptomatic VT, catheter ablation reduced the composite endpoint of cardiovascular death, appropriate ICD shock, hospitalization due to heart failure, or severe treatment-related complications compared to AAD. (Substrate Ablation vs Antiarrhythmic Drug Therapy for Symptomatic Ventricular Tachycardia [SURVIVE-VT]: NCT03734562).

Best Practices for the Catheter Ablation of Ventricular Arrhythmias.

Techniques for catheter ablation have evolved to effectively treat a range of ventricular arrhythmias. Pre-operative electrocardiographic and cardiac imaging data are very useful in understanding the arrhythmogenic substrate and can guide mapping and ablation. In this review, we focus on best practices for catheter ablation, with emphasis on tailoring ablation strategies, based on the presence or absence of structural heart disease, underlying clinical status, and hemodynamic stability of the ventricular arrhythmia. We discuss steps to make ablation safe and prevent complications, and techniques to improve the efficacy of ablation, including optimal use of electroanatomical mapping algorithms, energy delivery, intracardiac echocardiography, and selective use of mechanical circulatory support.

Ablation therapy of postural orthostatic tachycardia syndrome, inappropriate sinus tachycardia and primary electrical diseases: new insights in invasive treatment options in severely symptomatic patients.

Achieving the goal management of some arrhythmic syndromes can be challenging; medical treatment for inappropriate sinus tachycardia (IST) and postural orthostatic tachycardia syndrome (POTS) may be ineffective, necessitating multidisciplinary team treatment. Implantable defibrillator devices (ICDs), along with anti-arrhythmic drugs (AADs), remain the first-line treatment for primary electrical diseases that pose a risk of sudden cardiac death (SCD). Ablation of the arrhythmogenic substrate is not always suggested in patients with these pathologies, but it may be a valuable support for reducing arrhythmic burden, improving quality of life, and treating pathologies that are resistant to pharmacological treatment; however, this option is not often considered due to the potential risks associated with an invasive approach. Minimally invasive hybrid ablation in these syndromes, such as a hybrid thoracoscopic approach and the use of non-invasive mapping systems, reduces post-surgery complications and ensures the best possible outcome for the patient.

Clinical Evidence behind Stereotactic Radiotherapy for the Treatment of Ventricular Tachycardia (STAR)-A Comprehensive Review.

The electrophysiology-guided noninvasive cardiac radioablation, also known as STAR (stereotactic arrhythmia radioablation) is an emerging treatment method for persistent ventricular tachycardia. Since its first application in 2012 in Stanford Cancer Institute, and a year later in University Hospital Ostrava, Czech Republic, the authors from all around the world have published case reports and case series, and several prospective trials were established. In this article, we would like to discuss the available clinical evidence, analyze the potentially clinically relevant differences in methodology, and address some of the unique challenges that come with this treatment method.

Catheter Ablation in Persistent AF, the Evolution towards a More Pragmatic Strategy.

Atrial fibrillation (AF) is the most common cardiac arrhythmia worldwide and represents a heterogeneous disorder with a complex pathological basis. While significant technological advances have taken place over the last decade in the field of catheter ablation of AF, response to ablation varies and long-term success rates in those with persistent AF remain modest. Mechanistic studies have highlighted potentially different sustaining factors for AF in the persistent AF population with substrate-driven focal and re-entrant sources in the body of the atria identified on invasive and non-invasive mapping studies. Translation to clinical practice, however, remains challenging and the application of such mapping techniques to clinical ablation has yet to demonstrate a significant benefit beyond pulmonary vein isolation (PVI) alone in the persistent AF cohort. Recent advances in catheter and ablation technology have centered on improving the durability of ablation lesions at index procedure and although encouraging results have been demonstrated with early studies, large-scale trials are awaited. Further meaningful improvement in clinical outcomes in the persistent AF population requires ongoing advancement in the understanding of AF mechanisms, coupled with continuing progress in catheter technology capable of delivering durable transmural lesions.

Ventricular tachycardia burden reduction after substrate ablation: Predictors of recurrence.

BACKGROUND: 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. OBJECTIVE: 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. METHODS: 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 to 2018. RESULTS: 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. CONCLUSION: 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.

Successful Substrate Ablation for Ventricular Fibrillation in a Patient With Nonischemic Cardiomyopathy.

A 58-year-old woman with nonischemic cardiomyopathy underwent an ablation for refractory ventricular fibrillation (VF). In addition to elimination of the premature ventricular contraction triggering VF, substrate ablation entailed elimination of dormant Purkinje potentials, which were unmasked in regions where local pacing revealed a narrow QRS with stimulus QRS latency. VF trigger and abnormal Purkinje ablation completely eliminated the refractory VF. (Level of Difficulty: Intermediate.).