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Competing Interests: Funding Support and Author Disclosures Dr Reza is supported by the National Heart, Lung, and Blood Institute of the National Institutes of Health under award number K23HL166961; has received consulting fees/speaking honoraria from Zoll Inc, Roche Diagnostics, American Regent, and Bristol Myers Squibb; and has received research grants to the institution from Bristol Myers Squibb. Ms Marzolf has received consulting fees from Bristol-Myers Squibb and Cytokinetics. Dr Margulies has received research grant support from Bristol Myers Squibb and Amgen. Dr Owens is supported by the Winkelman Family Fund for Innovation and has received consulting fees/research support from Cytokinetics, MyoKardia/Bristol-Myers Squibb, Pfizer, Lexicon Pharmaceuticals, Tenaya Therapeutics, Stealth BioTherapeutics, Renovacor, Edgewise Therapeutics, and BioMarin Pharmaceuticals. Dr Frankel is supported by the EP Research and Education Fund. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.

Background: The importance of nonpulmonary vein (PV) triggers for the initiation/recurrence of atrial fibrillation (AF) is well established., Objectives: This study sought to assess the incremental benefit of provocative maneuvers for identifying non-PV triggers., Methods: We included consecutive patients undergoing first-time AF ablation between 2020 and 2022. The provocation protocol included step 1, identification of spontaneous non-PV triggers after cardioversion of AF and/or during sinus rhythm; step 2, isoproterenol infusion (3, 6, 12, and 20-30 μg/min); and step 3, atrial burst pacing to induce AF followed by cardioversion during residual or low-dose isoproterenol infusion or induce focal atrial tachycardia. Non-PV triggers were defined as non-PV ectopic beats triggering AF or sustained focal atrial tachycardia., Results: Of 1,372 patients included, 883 (64.4%) underwent the complete stepwise provocation protocol with isoproterenol infusion and burst pacing, 334 (24.3%) isoproterenol infusion only, 77 (5.6%) burst pacing only, and 78 (5.7%) no provocative maneuvers (only step 1). Overall, 161 non-PV triggers were found in 135 (9.8%) patients. Of these, 51 (31.7%) non-PV triggers occurred spontaneously, and the remaining 110 (68.3%) required provocative maneuvers for induction. Among those receiving the complete stepwise provocation protocol, there was a 2.2-fold increase in the number of patients with non-PV triggers after isoproterenol infusion, and the addition of burst pacing after isoproterenol infusion led to a total increase of 3.6-fold with the complete stepwise provocation protocol., Conclusions: The majority of non-PV triggers require provocative maneuvers for induction. A stepwise provocation protocol consisting of isoproterenol infusion followed by burst pacing identifies a 3.6-fold higher number of patients with non-PV triggers., Competing Interests: Funding Support and Author Disclosures This work was supported by the Leducq Foundation FANTASY Network and the Richard T and Angela Clark Innovation Fund in Cardiovascular Medicine. Dr Marchlinski serves as a consultant for Abbott Medical, Biosense Webster, and Medtronic Inc. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: Epicardial (Epi) access is commonly required during ventricular tachycardia ablation. Conventional Epi (ConvEpi) access targets a "dry" pericardial space presenting technical challenges and risk of complications. Recently, intentional puncture of coronary venous branches with Epi carbon dioxide insufflation (EpiCO 2 ) has been described as a technique to improve Epi access. The safety of this technique relative to conventional methods remains unproven., Objectives: The authors sought to compare the feasibility and safety of EpiCO 2 to ConvEpi access., Methods: All patients at a high-volume center undergoing Epi access between January 2021 and December 2023 were included and grouped according to ConvEpi or EpiCO 2 approach. Access technique was according to the discretion of the operator., Results: Epi access was attempted in 153 cases by 17 different operators (80 ConvEpi vs 73 EpiCO 2 ). There was no difference in success rate whether the ConvEpi or EpiCO 2 approach was used (76 [95%] cases vs 67 [91.8%] cases; P = 0.4). Total Epi access time was shorter in the ConvEpi group compared with the EpiCO 2 group (16.3 ± 11.6 minutes vs 26.9 ± 12.7 minutes; P < 0.001), though the total procedure duration was similar. Major Epi access-related complications occurred in only the ConvEpi group (6 [7.5%] ConvEpi vs 0 [0%] EpiCo 2 ; P = 0.02). Bleeding ≥80 mL was more frequently observed following ConvEpi access (14 [17.5%] cases vs 4 [5.5%] cases; P = 0.02). After adjusting for age, repeat Epi access, and antithrombotic therapy, EpiCO 2 was associated with a reduction in bleeding ≥80 mL (OR: 0.27; 95% CI: 0.08-0.89; P = 0.03)., Conclusions: EpiCO 2 access is associated with lower rates of major complication and bleeding when compared with ConvEpi access., Competing Interests: Funding Support and Author Disclosures Drs Oraii, Marchlinski, and Hyman are supported by the Leducq Foundation (TNE FANTASY 19CV03). Dr Chaumont also acknowledges the “Fédération Française de Cardiologie,” the “Fondation Charles Nicolle-Normandie,” the “GSC G4,” the “Working Group of Pacing and Electrophysiology of the French Society of Cardiology,” and the “Philippe Foundation.” Dr Hyman has been a consultant for Asahi Intecc, Inc. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 American College of Cardiology Foundation. All rights reserved.)

Background: Although the epicardial predominance of substrate abnormalities has been well demonstrated in early stages of arrhythmogenic right ventricular cardiomyopathy (ARVC), endocardial (ENDO) ablation may suffice to eliminate ventricular tachycardia (VT) in some patients., Objectives: This study aimed to report the long-term outcomes of ENDO-only ablation in ARVC patients and factors that predict VT-free survival., Methods: We included consecutive patients with Task Force Criteria diagnosis of ARVC undergoing a first ENDO-only VT ablation between 1998 and 2020. Ablation was predominantly guided by activation/entrainment mapping for mappable VTs and pace mapping/targeting abnormal electrograms for unmappable VTs. The primary endpoint was freedom from any recurrent sustained VT after the last ENDO-only ablation., Results: Seventy-four ARVC patients underwent ENDO-only VT ablation. VT noninducibility was achieved in 49 (66%) patients. During median follow-up of 6.6 years (Q1-Q3: 3.4-11.2 years), 40 (54.1%) patients remained free from any VT recurrence with rare VT ≤2 episodes in additional 12.2%. Among patients with noninducibility, VT-free survival was 75.5% during long-term follow-up. In multivariable analysis, >45 y of age at diagnosis (HR: 0.41; 95% CI: 0.17-0.98) and VT noninducibility (HR: 0.36; 95% CI: 0.16-0.80) were predictors of VT-free survival., Conclusions: Long-term VT-free survival can be achieved in over half of ARVC patients following ENDO-only VT ablation, increasing to over 75% if VT noninducibility is achieved. Our results support consideration of a stepwise ENDO-only approach before proceeding to epicardial ablation if VT noninducibility can be achieved particularly in older patients., Competing Interests: Funding Support and Author Disclosures This work was supported by the Winkelman Family Fund in Cardiovascular Innovation, Katherine J. Miller EP Research Fund, Bogle Family Fund in Cardiac Electrophysiology, and F. Harlan Batrus EP Research Fund. Dr Chaumont acknowledges the Fédération Française de Cardiologie, Fondation Charles Nicolle-Normandie, GSC G4, Working Group of Pacing and Electrophysiology of the French Society of Cardiology, and Philippe Foundation. Dr Nazarian has served as a consultant for and received research funding from Biosense Webster Inc. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Electrophysiologic testing with programmed ventricular stimulation (PVS) has been utilized to induce ventricular tachycardia (VT), thereby improving risk stratification for patients with ischemic and nonischemic cardiomyopathies and determining the effectiveness of antiarrhythmic therapies, especially catheter ablation. A variety of procedural aspects can be modified during PVS in order to alter the sensitivity and specificity of the test including the addition of multiple baseline pacing cycle lengths, extrastimuli, and pacing locations. The definition of a positive result is also critically important, which has varied from exclusively sustained monomorphic VT (>30 seconds) to any ventricular arrhythmia regardless of morphology. In this review, we discuss the history of PVS and evaluate its role in sudden cardiac death risk stratification in a variety of patient populations. We propose an approach to future investigations that will capitalize on the unique ability to vary the sensitivity and specificity of this test. We then discuss the application of PVS during and following catheter ablation. The strategies that have been utilized to improve the efficacy of intraprocedural PVS are highlighted during a discussion of the limitations of this probabilistic strategy. The role of noninvasive programmed stimulation is also reviewed in predicting recurrent VT and informing management decisions including repeat ablations, modifications in antiarrhythmic drugs, and implantable cardioverter-defibrillator programming. Based on the available evidence and guidelines, we propose an approach to future investigations that will allow clinicians to optimize the use of PVS for risk stratification and assessment of therapeutic efficacy., Competing Interests: Funding Support and Author Disclosures This research was supported by the F. Harlan Batrus EP Research Fund and the Mark Marchlinski EP Research and Education Fund. Dr Markman has reported that he has no relationships relevant to the contents of this paper to disclose. Dr Marchlinski has received research funding from Biosense Webster; and lecture honoraria from Abbott, Boston Scientific, and Medtronic. Dr Callans has received consulting fees and lecture honoraria from Abbott, Biosense Webster, Biotronik, and Boston Scientific. Dr Frankel has received research support from Biosense Webster; and lecture honoraria from Abbott., (Copyright © 2024 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: Premature ventricular complexes (PVCs) are common and associated with worse outcomes in patients with heart failure. Class 1C antiarrhythmic drugs (AADs) effectively suppress PVCs, but guidelines currently restrict their use in structural heart disease., Objectives: This study aimed to assess the safety and efficacy of class 1C AADs in patients with nonischemic cardiomyopathy (NICM) and implantable cardioverter-defibrillators (ICDs)., Methods: All patients with NICM and an ICD treated with flecainide or propafenone at the Hospital of the University of Pennsylvania between 2014 and 2022 were identified. PVC burden, left ventricular ejection fraction (LVEF), and biventricular pacing percentage were compared before and during class 1C AAD treatment. Safety outcomes included sustained atrial and ventricular arrhythmias, heart failure admissions, and death., Results: We identified 34 patients, 23 receiving flecainide and 11 propafenone. Most patients (62%) had failed other AADs or catheter ablation (68%) prior to class 1C AAD initiation. PVC burden decreased from 20% ± 13% to 6% ± 7% (P < 0.001), LVEF increased from 33% ± 9% to 37% ± 10% (P = 0.01), and biventricular pacing percentage increased from 85% ± 9% to 93% ± 7% (P = 0.01). Sustained ventricular tachycardia (2 vs 9 patients) and admissions for decompensated heart failure (2 vs 3 patients) decreased compared with the 12 months prior to class 1C AAD initiation., Conclusions: Class 1C AADs effectively suppressed PVCs in patients with NICM and ICDs, leading to increases in LVEF and biventricular pacing percentage. In this limited sample, their use was safe. Larger studies are needed to confirm the safety of this approach., Competing Interests: Funding Support and Author Disclosures Funding was provided by the EP Research and Education Fund. The authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2024 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: Entrainment and pace mapping are used to identify critical components (CCs) of ventricular tachycardia (VT) circuits. In patients with dense myocardial scarring, VT circuits may elude capture at standard high pacing outputs (up to 10 mA at a 2-millisecond pulse width)., Objectives: The purpose of this study was to assess the utility of very high-output pacing (V-HOP, 50 mA at 2 milliseconds) for identifying CCs of VT circuits after standard high pacing output failed to elicit capture in densely scarred myocardial tissue., Methods: Our standard VT ablation approach included electroanatomic mapping for substrate characterization and entrainment and/or pace mapping to identify CCs of VT circuits. Patients that required V-HOP to capture sites of interest comprised the study cohort. Ablation endpoints were VT termination and noninducibility., Results: Twenty-five patients (71 ± 10 years of age, all males) undergoing 26 VT ablations met the inclusion criteria. The mean left ventricular ejection fraction was 30% ± 14%, and 85% had ischemic cardiomyopathy. V-HOP was used to successfully entrain VT in 17 patients, yielding central isthmus sites in 10 and entrance/exit sites in 4. VT terminated with radiofrequency ablation at these sites in 15 patients. In 9 patients, V-HOP identified scar locations with a delayed exit. Acute procedural success was achieved in 24 patients without any adverse events. Over a follow-up period of 16 ± 21 months, 2 patients experienced VT recurrence requiring repeat ablation during which the same location was targeted successfully in 1 patient., Conclusions: In VT patients with a dense scar that is traditionally inexcitable, V-HOP can identify CCs of the re-entrant circuit and guide successful ablation., Competing Interests: Funding Support and Author Disclosures This study was supported by the Bogle Family Fund in Cardiac Electrophysiology and the Katherine J. Miller EP Research Fund. The authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2023 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: Targeting nonpulmonary vein triggers (NPVTs) of atrial fibrillation (AF) after pulmonary vein isolation can be challenging. NPVTs are often single ectopic beats with a surface P-wave obscured by a QRS or T-wave., Objectives: The goal of this study was to construct an algorithm to regionalize the site of origin of NPVTs using only intracardiac bipolar electrograms from 2 linear decapolar catheters positioned in the posterolateral right atrium (along the crista terminalis with the distal bipole pair in the superior vena cava) and in the proximal coronary sinus (CS)., Methods: After pulmonary vein isolation in 42 patients with AF, pacing from 15 typical anatomic NPVT sites was conducted. For each pacing site, the electrogram activation sequence was analyzed from the CS catheter (simultaneous/chevron/inverse chevron/distal-proximal/proximal-distal) and activation time (ie, CSCTAT) between the earliest electrograms from the 2 decapolar catheters was measured referencing the earliest CS electrogram; a negative CSCTAT value indicates the crista terminalis catheter electrogram was earlier, and a positive CSCTAT value indicates the CS catheter electrogram was earlier. A regionalization algorithm with high predictive value was defined and tested in a validation cohort with AF NPVTs localized with electroanatomic mapping., Results: In the study patient cohort (71% male; 43% with persistent AF, 52% with left atrial dilation), the algorithm grouped with high precision (positive predictive value 81%-99%, specificity 94%-100%, and sensitivity 30%-94%) the 15 distinct pacing sites into 9 clinically useful regions. Algorithm testing in a 98 patient validation cohort showed predictive accuracy of 91%., Conclusions: An algorithm defined by the activation sequence and timing of electrograms from 2 linear multipolar catheters provided accurate regionalization of AF NPVTs to guide focused detailed mapping., Competing Interests: Funding Support and Author Disclosures This work was supported by the Richard T. and Angela Clark Innovation Fund in Cardiovascular Medicine, the Mark S. Marchlinski EP Research and Education Fund, the Winkelman Family Fund in Cardiovascular Innovation, and the Leducq Foundation Fantasy Network. Dr Marchlinski has served as consultant for Abbott Medical, Biosense Webster, Biotronik, Boston Scientific, and Medtronic Inc. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2023 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: Intraprocedural identification of intramural septal substrate for ventricular tachycardia (ISS-VT) in nonischemic cardiomyopathy (NICM) is challenging. Delayed (>40 ms) transmural conduction time (DCT) with right ventricular basal septal pacing has been previously shown to identify ISS-VT., Objectives: This study sought to determine whether substrate catheter ablation incorporating areas of DCT may improve acute and long-term outcomes., Methods: We included patients with NICM and ISS-VT referred for catheter ablation between 2016 and 2020. ISS-VT was defined by the following: 1) confluent septal areas of low unipolar voltage (<8.3 mV) in the presence of normal or minimal bipolar abnormalities; and 2) presence of abnormal electrograms in the septum. Substrate ablation was guided by the following: 1) activation and/or entrainment mapping for tolerated VT and pace mapping with ablation of abnormal septal electrograms for unmappable VTs (n = 57, Group 1); and 2) empirically extended to target areas of DCT during right ventricular basal septal pacing regardless of their participation in inducible VT(s) but sparing the conduction system when possible (n = 24, Group 2)., Results: There were no significant baseline differences between Groups 1 and 2. Noninducibility of any VT programmed stimulation at the end of ablation was higher in Group 2 compared with Group 1 (80% vs 53%; P = 0.03). At 12-month follow-up, single-procedure VT-free survival was significantly higher (79% vs 46%; P = 0.006) and the time to VT recurrence was longer (mean 10 ± 3 months vs 7 ± 4 months; P = 0.02) in Group 2 compared with Group 1., Conclusions: In patients with NICM and ISS-VT, a substrate ablation strategy that incorporates areas of DCT appears to improve freedom from recurrent VT., Competing Interests: Funding Support and Author Disclosures This work was supported by the Richard T and Angela Clark Innovation Fund in Cardiovascular Medicine, the Mark S. Marchlinski EP Research and Education Fund, and the Winkelman Family Fund in Cardiovascular Innovation. Dr Santangeli has served as consultant for Abbott Medical, Biosense Webster, Biotronik, and Medtronic Inc. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2023 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: Neuromodulation is increasingly recognized as a therapeutic strategy for patients with refractory ventricular arrhythmias (VAs). Percutaneous stellate ganglion blockade (SGB), transcutaneous magnetic stimulation (TcMS), and surgical cardiac sympathetic denervation (CSD) have all been utilized in this setting., Objectives: This study sought to characterize contemporary use and outcomes of these neuromodulation techniques for patients with refractory VA., Methods: This retrospective cohort study included all patients at the Hospital of the University of Pennsylvania with antiarrhythmic drug (AAD)-refractory VA from 2019 to 2021 who were treated with SGB, TcMS, or CSD., Results: A total of 34 patients (age 61 ± 14 years, 15 polymorphic VAs [44%], refractory to 1.8 ± 0.8 AADs) met inclusion criteria. SGB was performed on 11 patients (32%), TcMS on 19 (56%), and CSD on 7 (21%). Neuromodulation was associated with a reduction in the number of episodes of sustained VAs from 7 [IQR: 4-12] episodes in the 24 hours before the initial neuromodulation strategy to 0 [IQR: 0-1] episodes in the subsequent 24 hours (P < 0.001). During 1.2 ± 1.1 years of follow-up, 21 (62%) experienced recurrent VAs, and among those patients, the median time to recurrence was 3 [IQR: 1-25] days. Outcomes were similar among patients with monomorphic and polymorphic VAs. Among patients who had an acute myocardial infarction within 30 days before neuromodulation, the burden of VAs decreased from 11 [IQR: 7-12] episodes to 0 episodes in the 24 hours after treatment., Conclusions: Autonomic neuromodulation with SGB, TcMS, or CSD in patients with AAD-refractory VAs is safe and results in substantial acute reduction of VA although recurrent arrhythmias are common, and not all patients experience a reduction in arrhythmia burden., Competing Interests: Funding Support and Author Disclosures Dr Frankel is a consultant for Biosense Webster, Boston Scientific, Medtronic, and Stryker. Dr Epstein serves on the advisory board or events committees for Abbott, Boston Scientific, Medtronic, and Zoll. Dr Callans has served as a consultant for Abbott Medical, Boston Scientific, and Medtronic. Dr Marchlinski has served as a consultant for Abbott Medical, Biosense Webster, Biotronik, Boston Scientific, and Medtronic; and receives research funding from Biosense Webster and the Leducq Foundation. Dr Nazarian is a consultant for CardioSolv and Circle CVI; and principal investigator for research funding from Biosense Webster, ImriCor, Siemens, ADAS software, and the US National Institutes of Health. The University of Pennsylvania Conflict of Interest Committee manages all commercial arrangements. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2023 American College of Cardiology Foundation. All rights reserved.)

Background: Although efficacious, catheter ablation (CA) of ventricular arrhythmias (VAs) originating from left ventricular (LV) papillary muscles (PAPs) has the potential to affect mitral valve (MV) function., Objectives: The aim of this study was to determine whether lesions delivered during CA of VAs from LV PAPs affected MV function., Methods: Consecutive patients undergoing CA of LV PAP VAs from January 2015 to December 2020 in whom both preprocedural and postprocedural transthoracic echocardiography was performed were included. Radiofrequency ablation was performed with an irrigated-tip catheter with or without contact force sensing and intracardiac echocardiographic guidance. The PAPs were delineated into segments: tip, body, and base. Pre- and post-CA transthoracic echocardiograms were reviewed to assess MV regurgitation, which was graded 0 (none), 1 (mild), 2 (moderate), or 3 (severe). A change of ≥2 grades from baseline was considered significant., Results: A total of 103 patients (mean age 63 ± 15 years, 78% men) were included. VAs were ablated from the anterolateral PAP in 35% (n = 36), posteromedial PAP in 55% (n = 57), and both PAPs in 10% (n = 10). Lesion distribution was as follows: PAP tip in 52 (50%), PAP base in 34 (33%), PAP body in 13 (13%), and entire PAP in 4 (4%). The mean number of lesions delivered was 16 ± 13 (median 14). Of 103 patients, 102 (99%) showed no change in MV function., Conclusions: Using intracardiac echocardiographic guidance, lesions can be safely delivered on various aspects of this structure without adverse impact on MV function., Competing Interests: Funding Support and Author Disclosures This work was supported by the Richard T and Angela Clark Innovation Fund in Cardiovascular Medicine. Dr Lin has received a speaker honorarium from Abbott. Dr Frankel is a scientific advisory board member for Biosense Webster. Dr Santangeli has received a research grant from Biosense Webster; and is an advisory board member for Biosense Webster and Abbott. Dr Nazarian has received a research grant from Biosense Webster. Dr Hyman has given educational lectures for Biosense Webster. Dr Epstein is an advisory board and events committee member for Abbott; and is an events committee member for Boston Scientific and Medtronic. Dr Callans is an advisory board member for Abbott and Biosense Webster; and has received honoraria for lectures from Biosense Webster. Dr Marchlinski has received a lecture honorarium from and is a scientific advisory board member for Abbott; and is a scientific advisory board member for and has received a lecture honorarium and research support from Biosense Wesbet. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2022 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Background: Guidelines recommend that initial trial of a "pill-in-the-pocket" (PIP) Class 1C antiarrhythmic drug (AAD) for cardioversion of atrial fibrillation (AF) be performed in a monitored setting because of the potential for adverse reactions., Objectives: This study sought to characterize real-world, contemporary use of the PIP approach, including the setting of initiation and incidence of adverse events., Methods: This retrospective cohort study included all patients at the Hospital of the University of Pennsylvania treated with a PIP approach for AF between 2007 and 2020., Results: A total of 273 patients (age 56 ± 13 years; 182 [67%] male; CHA 2 DS 2 VASc score 1.1 ± 1.2) took a first dose of PIP AAD. Flecainide was used in 151 (55%) and propafenone in 122 (45%). The first dose of PIP AAD was taken in a monitored setting in 167 (62%). Significant adverse events occurred in 7 patients (3%), 2 of whom had taken the dose in a monitored setting. Significant adverse events included unexplained syncope (1 of 7), symptomatic bradycardia/hypotension (4 of 7), and 1:1 atrial flutter (2 of 7). All occurred in patients taking 300 mg of flecainide (n = 4) or 600 mg of propafenone (n = 3). Electrical cardioversion was performed in 29 (11%) patients because of failure of the AAD to terminate AF. One patient required intravenous fluids and vasopressors for 2 hours because of persistent hypotension and bradycardia. Two patients required permanent pacemakers for bradycardia. The remaining patients required no intervention., Conclusions: Our data support the current recommendation to initiate PIP AAD in a monitored setting because of rare significant adverse reactions that can require urgent intervention., Competing Interests: Funding Support and Author Disclosures The authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2022 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study sought to explore whether prolonged duration (PD) radiofrequency ablation (RFA) from adjacent endocardial locations can improve catheter ablation (CA) outcomes of left ventricular summit (LVS) ventricular arrhythmias (Vas)., Background: CA of VAs originating from the LVS region can be challenging., Methods: Patients undergoing CA of LVS VAs from January 1, 2015, to December 31, 2019, were included. Standard RFA approach involved incremental power titration (20-45 W) over 60-120 seconds with irrigated tip catheter to achieve 10%-12% impedance drop. Prolonged duration RFA involved similar power titration; however, lesion application was extended beyond 120 seconds (maximum 5 minutes). Lesions were confined to lowest aspect of aortic cusps and/or subvalvular LV outflow tract region (≤0.5 cm from the valve). Procedural success was defined as suppression of VA ≥30 minutes postablation and clinical success as no arrhythmia symptoms on follow-up and >80% reduction of VA burden on postprocedure monitor., Results: This study included 102 patients (60±14 years old, 62% male): standard RFA in 80 and PD RFA in 38. Procedural success was achieved in 54 patients with standard and 32 patients with PD RFA (68% vs 84%; P = 0.05). Short-term clinical success was achieved in 48 patients (60%) with standard and 30 patients (79%) with PD RFA (P = 0.04). Two pericardial effusions occurred (1 in each group) and no steam pops were noted. Patients in whom standard RFA was successful were more likely to have R/S ratio >1 or absence of qS in lead I (odds ratio: 3.35; 95% CI: 1.20-9.35; P = 0.03)., Conclusions: Prolonged duration RFA from adjacent endocardial locations is a safe and effective technique for successfully targeting challenging LVS VAs that fail standard RFA., Competing Interests: Funding Support and Author Disclosures Supported by the Richard T. and Angela Clark Innovation Fund in Cardiovascular Medicine. The authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2022 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: The goal of this study was to characterize the relationship between DF, the electroanatomic mapping (EAM) substrate, and outcomes of catheter ablation of VT in NICM., Background: A substantial proportion of patients with nonischemic dilated cardiomyopathy (NICM) and ventricular tachycardia (VT) do not have scar detectable by cardiac magnetic resonance late gadolinium enhancement (LGE) imaging. In these patients, the significance of diffuse fibrosis (DF) detected with T 1 mapping has not been previously investigated., Methods: This study included 51 patients with NICM and VT undergoing catheter ablation (median age 55 years; 77% male subjects) who had no evidence of LGE on pre-procedural cardiac magnetic resonance. Post-contrast T 1 relaxation time determined on the septum was assessed as a surrogate of DF burden. The extent of endocardial low-voltage areas (LVAs) at EAM was correlated with T 1 mapping data., Results: Bipolar LVAs were present in 22 (43%) patients (median extent 15 cm 2 [8 to 29 cm 2 ]) and unipolar LVA in all patients (median extent 48 cm 2 [26 to 120 cm 2 ]). A significant inverse correlation was found between T 1 values and both unipolar-LVA (R 2  = 0.64; β = -0.85; p < 0.01) and bipolar-LVA (R 2  = 0.16; β = -1.63; p < 0.01). After a median follow-up of 45 months (22 to 57 months), 2 (4%) patients died, 3 (6%) underwent heart transplantation, and 8 (16%) experienced VT recurrence. Shorter post-contrast T 1 time was associated with an increased risk of VT recurrence (hazard ratio: 1.16; 95% confidence interval: 1.03 to 1.33 per 10 ms decrease; p = 0.02)., Conclusions: In patients with NICM and no evidence of LGE undergoing catheter ablation of VT, DF estimated by using post-contrast T 1 mapping correlates with the voltage abnormality at EAM and seems to affect post-ablation outcomes., Competing Interests: Funding Support And Author Disclosures This study was partially supported by the Winkelman Family Fund in Cardiovascular Innovation. The authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2021 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study sought to examine the impact of periprocedural acute kidney injury (AKI) in scar-related ventricular tachycardia (VT) patients undergoing radiofrequency catheter ablation (RFCA) on short- and long-term outcomes., Background: The clinical significance of periprocedural AKI in patients with scar-related VT undergoing RFCA has not been previously investigated., Methods: This study included 317 consecutive patients with scar-related VT undergoing RFCA (age: 64 ± 13 years, mean left ventricular ejection fraction: 33 ± 13%, 55% ischemic cardiomyopathy). Periprocedural AKI was defined as an absolute increase in creatinine of ≥0.3 mg/dl over 48 h or an increase of >1.5× the baseline values within 1 week post-procedure., Results: Periprocedural AKI occurred in 31 patients (10%). Independent predictors of AKI included chronic kidney disease (odds ratio [OR]: 3.43; 95% confidence interval [CI]: 1.48 to 7.96; p = 0.004), atrial fibrillation (OR: 2.42; 95% CI: 1.01 to 5.78; p = 0.047), and peri-procedural acute hemodynamic decompensation (OR: 3.98; 95% CI: 1.17 to 13.52; p = 0.003). After a median follow-up of 39 months (interquartile range: 6 to 65 months), 95 patients (30%) died. Periprocedural AKI was associated with increased risk of early mortality (within 30 days; hazard ratio [HR]: 9.91; 95% CI: 2.87 to 34.22; p < 0.001) and late mortality (within 1 year) (HR: 4.57; 95% CI: 2.08 to 10.05; p < 0.001). After multivariable adjustment, AKI remained independently associated with increased risk of early and late mortality (HR: 4.49; 95% CI: 1.1 to 18.36; p = 0.04, and HR: 3.28; 95% CI: 1.43 to 7.49; p = 0.005, respectively)., Conclusions: Periprocedural AKI occurs in 10% of patients undergoing RFCA of scar-related VT and is strongly associated with increased risk of early and late post-procedural mortality., Competing Interests: Funding Support and Author Disclosures Dr. Kuo has received support from Taipei Veterans General Hospital-National Yang-Ming University Excellent Physician Scientists Cultivation Program No. 106-V-A-009. Dr. Nazarian has served as a consultant for Biosense Webster, CardioSolv, Siemens, and ImriCor; and has served as a principal investigator for St. Jude Medical (Abbott) MRI Ready Study. Dr. Marchlinski has received support from the Winkelman Family Fund in Cardiovascular Innovation. Dr. Santangeli has received support from the Winkelman Family Fund in Cardiovascular Innovation; has served as a consultant for Biosense Webster, Abbott, Baylis Medical, and InHeart. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose. The University of Pennsylvania Conflict of Interest Committee manages all commercial arrangements., (Copyright © 2021 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study sought to address whether technological innovations such as contact force sensing (CFS) can improve acute and long-term ablation outcomes of left ventricular papillary muscle (LV PAP) ventricular arrhythmias (VAs)., Background: Catheter ablation of LV PAP VAs has been less efficacious than another focal VAs. It remains unclear whether technological innovations such as CFS can improve acute and long-term ablation outcomes of LV PAP VA., Methods: From January 2015 to December 2019, a total of 137 patients underwent LV PAP VA ablation. VA site of origin (SOO) was identified using activation and pace-mapping guided by intracardiac echocardiography. Radiofrequency energy (20 to 50 W for 60 to 90 s) was delivered by irrigated catheter with or without CFS. We defined acute success as complete suppression of targeted VA ≥30 min post ablation and clinical success as ≥80% VA burden reduction at outpatient follow-up., Results: VA manifested as premature ventricular complexes in 98 (71%), nonsustained ventricular tachycardia in 18 (13%), sustained ventricular tachycardia in 12 (9%) and premature ventricular complexes induced ventricular fibrillation in 9 (7%). VA SOO was anterolateral PAP in 51 (37%), posteromedial PAP in 73 (53%), and both PAPs in 13 (10%). VAs were targeted using CFS in 97 (71%) and non-CFS in 40 (29%). After a single procedure, acute success was achieved in 130 (95%) and clinical success was achieved in 112 (82%); neither was impacted by VA SOO and/or CFS. Complications occurred in 5 patients (3.6%)., Conclusion: Independent of CFS technology, intracardiac echocardiography-guided catheter ablation is highly efficacious and may be considered as first-line therapy in the management of LV PAP VA., (Copyright © 2020 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study aimed to characterize the incidence, clinical characteristics, and electrocardiographic and electrophysiologic features of LVA VA in the absence of CAD and to describe the experience with catheter ablation (CA) in this group., Background: The left ventricular apex (LVA) is a well-described source of ventricular arrhythmias (VAs) in patients with coronary artery disease (CAD) and history of apical infarction but is a rare source of VA in the absence of CAD., Methods: Patients referred for CA of VA at our institution were retrospectively reviewed, and those with LVA VA in the absence of CAD were identified., Results: Of 3,710 consecutive patients undergoing VA ablation, CA of LVA VA was performed in 24 patients (20 with monomorphic ventricular tachycardia, 4 with premature ventricular contractions or nonsustained ventricular tachycardia; 18 men; mean age: 54 ± 15 years). These cases comprised 10 of 35 (29%) hypertrophic cardiomyopathy, 9 of 789 (1.2%) nonischemic cardiomyopathy, and 5 of 1,432 (0.4%) idiopathic VA ablation procedures. VA QRS morphology was predominantly right bundle with slurred upstroke and right superior frontal plane axis with precordial transition ≤V3. Epicardial ablation was performed in 14 of 24 (58%). After a median of 1 procedure (range 1 to 4) at this institution and median follow-up of 47 months (range 0-176), VA recurred in 1 patient (4%)., Conclusions: LVA VA in the absence of CAD is unusual and may occur in patients with hypertrophic cardiomyopathy or nonischemic cardiomyopathy or, rarely, in the absence of structural heart disease. It can be recognized by characteristic ECG features. CA of LVA VA is challenging; multiple procedures, including epicardial approaches, may be required to achieve VA control over long-term follow-up., (Copyright © 2020 American College of Cardiology Foundation. All rights reserved.)

Objectives: This study investigated the prevalence and prognostic significance of concealed myocardial abnormalities identified by cardiac magnetic resonance (CMR) imaging in patients with apparently idiopathic premature ventricular contractions (PVCs)., Background: The role of CMR imaging in patients with frequent PVCs and otherwise negative diagnostic workup is uncertain., Methods: This was a multicenter, international study that included 518 patients (age 44 ± 15 years; 57% men) with frequent (>1,000/24 h) PVCs and negative routine diagnostic workup. Patients underwent a comprehensive CMR protocol including late gadolinium enhancement imaging for detection of necrosis and/or fibrosis. The study endpoint was a composite of sudden cardiac death, resuscitated cardiac arrest, and nonfatal episodes of ventricular fibrillation or sustained ventricular tachycardia that required appropriate implantable cardioverter-defibrillator therapy., Results: Myocardial abnormalities were found in 85 (16%) patients. Male gender (odds ratio [OR]: 4.28; 95% confidence interval [CI]: 2.06 to 8.93; p = 0.01), family history of sudden cardiac death and/or cardiomyopathy (OR: 3.61; 95% CI: 1.33 to 9.82; p = 0.01), multifocal PVCs (OR: 11.12; 95% CI: 4.35 to 28.46; p < 0.01), and non-left bundle branch block inferior axis morphology (OR: 14.11; 95% CI: 7.35 to 27.07; p < 0.01) were all significantly related to the presence of myocardial abnormalities. After a median follow-up of 67 months, the composite endpoint occurred in 26 (5%) patients. Subjects with myocardial abnormalities on CMR had a higher incidence of the composite outcome (n = 25; 29%) compared with those without abnormalities (n = 1; 0.2%; p < 0.01)., Conclusions: CMR can identify concealed myocardial abnormalities in 16% of patients with apparently idiopathic frequent PVCs. Presence of myocardial abnormalities on CMR predict worse clinical outcomes., (Copyright © 2019 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study investigated the impact of the type of catheter irrigant used during delivery of radiofrequency ablation., Background: The use of half-normal saline (HNS) as an irrigant has been suggested as a method for increasing ablation lesion size but has not been rigorously studied in the beating heart or the use of a low-flow irrigation catheter., Methods: Sixteen swine underwent left ventricular mapping and ablation using either normal saline (NS) (group 1: n = 9) or half-normal saline (HNS) (group 2: n = 7). All lesions were delivered using identical parameters (40 W with 10-second ramp, 30-second duration, 15 ml/min flow, and 8- to14-g target contact force). An occurrence of steam pop, catheter char, or thrombus was assessed using intracardiac echocardiography and catheter inspection following each application. Lesion depth, width, and area were measured using electronic calibers., Results: A total of 109 lesions were delivered in group 1 and 77 in group 2. There were significantly more steam pops in group 2 (32 of 77 [42%] vs. 24 of 109 [22%], respectively). The frequencies of catheter tip char were similar (group 1: 9 of 109 [8%] vs. group 2: 10 of 77 [13%]; p = 0.29). Lesion depths, widths, and areas also were similar in both groups., Conclusions: The use of an HNS irrigant using a low-flow open irrigated ablation catheter platform results in more tissue heating due to higher radiofrequency current delivery directed to tissue, but this can lead to higher rate of steam pops. In this in vivo porcine beating-heart model, the use of HNS does not appear to significantly increase lesion size in normal myocardium despite evidence of increased radiofrequency heating., (Copyright © 2020 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study sought to examine clinical characteristics of procedural and long-term outcomes in patients undergoing catheter ablation (CA) of outflow tract ventricular arrhythmias (OT-VAs) over 16 years., Background: CA is an effective treatment strategy for OT-VAs., Methods: Patients undergoing CA for OT-VAs from 1999 to 2015 were divided into 3 periods: 1999 to 2004 (early), 2005 to 2010 (middle), and 2011 to 2015 (recent). Successful ablation site (right ventricular OT, aortic cusps/left ventricular OT, or coronary venous system/epicardium), VA morphology (right bundle branch block or left bundle branch block), and acute and clinical success rates were assessed., Results: Six hundred eighty-two patients (336 female) were included (early: n = 97; middle: n = 204; recent: n = 381). Over time there was increase in use of irrigated ablation catheters and electroanatomic mapping, and more VAs were ablated from the aortic cusp/left ventricular OT or coronary venous system/epicardium (14% vs. 45% vs. 56%; p < 0.0001). Acute procedural success was achieved in 585 patients (86%) and was similar between groups (82% vs. 84% vs. 88%; p = 0.27). Clinical success was also similar between groups (86% vs. 87% vs. 88%; p = 0.94), but more patients in earlier periods required repeat ablation (18% vs. 17% vs. 9%; p = 0.02). Overall complication rate was 2% (similar between groups)., Conclusions: Over a 16-year period there was an increase in patients undergoing CA for OT-VTs, with more ablations performed at non-right ventricular outflow tract locations using electroanatomic mapping and irrigated-tip catheters. Over time, single procedure success has improved and complications have remained limited., (Copyright © 2020 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study sought to evaluate the prevalence, mapping features, and ablation outcomes of non-scar-related ventricular tachycardia (NonScar-VT) and Purkinje-related VT (Purkinje-VT) in patients with structural heart disease., Background: VT in structural heart disease is typically associated with scar-related myocardial re-entry. NonScar-VTs arising from areas of normal myocardium or Purkinje-VTs originating from the conduction system are less common., Methods: We retrospectively analyzed 690 patients with structural heart disease who underwent VT ablation between 2013 and 2017., Results: A total of 37 (5.4%) patients (16 [43%] with ischemic cardiomyopathy, 16 [43%] with nonischemic dilated cardiomyopathy, and 5 [14%] others) demonstrated NonScar/Purkinje-VTs, which represented the clinical VT in 76% of cases. Among the 37 VTs, 31 (84%) were Purkinje-VTs (28 bundle branch re-entrant VT). The remaining 6 (16%) VTs were NonScar-VTs and included 4 idiopathic outflow tract VTs. A total of 16 patients had prior history of VT ablations: empirical scar substrate modification was performed in 6 (38%) patients and residual inducibility of VT had not been assessed in 7 (44%). In all 37 patients, the NonScar/Purkinje-VT was successfully ablated. After a median follow-up of 18 months, the targeted NonScar/Purkinje-VT did not recur in any patients, and 28 (76%) of patients were free from any recurrent VT episodes., Conclusions: NonScar/Purkinje-VTs can be identified in 5.4% of patients undergoing VT ablation in the setting of structural heart disease. Careful effort to induce, characterize, and map these VTs is important because substrate-based ablation strategies would fail to eliminate these types of VT., (Copyright © 2020 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objective: This study sought to investigate incidence of left atrial appendage (LAA) triggers of atrial fibrillation (AF) and/or organized atrial tachycardias (OAT) in patients undergoing AF ablation and to evaluate outcomes after ablation., Background: Although LAA isolation is being increasingly performed during AF ablation, the true incidence of LAA triggers for AF remains unclear., Methods: All patients with LAA triggers of AF and/or OAT during AF ablation from 2001 to 2017 were included. LAA triggers were defined as atrial premature depolarizations from the LAA, which initiated sustained AF and/or OAT., Results: Out of 7,129 patients undergoing AF ablation over 16 years, LAA triggers were observed in 21 (0.3%) subjects (age 60 ± 9 years; 57% males; 52% persistent AF). Twenty (95%) patients were undergoing repeat ablation. The LAA was the only nonpulmonary vein trigger in 3 patients; the remaining 18 patients had both LAA and other nonpulmonary vein triggers. LAA triggers were eliminated in all patients (focal ablation in 19 patients; LAA isolation in 2 patients). Twelve months after ablation, 47.6% remained free from recurrent arrhythmia. After overall follow-up of 5.0 ± 3.6 years (median: 3.7 years; interquartile range: 1.4 to 8.9 years), 38.1% were arrhythmia-free. All 3 patients with triggers limited to the LAA remained free of AF recurrence. One patient undergoing LAA isolation developed LAA thrombus during follow-up., Conclusions: The incidence of true LAA triggers is very low (0.3%). Most patients with LAA triggers have additional nonpulmonary vein triggers, and despite elimination of LAA triggers, long-term arrhythmia recurrence rates remain high. Potential risks of empiric LAA isolation during AF ablation (especially first-time AF ablation) may outweigh benefits., (Copyright © 2020 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study sought to compare efficacy and safety of the septal mitral isthmus line (SMIL) with that of the lateral mitral isthmus line (LMIL) for treatment of mitral annular flutter (MAF)., Background: MAF is the most common left atrial macro-re-entrant organized atrial tachycardia (OAT) occurring after catheter ablation of atrial fibrillation. The 2 most common lesion sets for treating MAF include linear ablation from the anteroseptal mitral annulus to the right superior pulmonary vein (SMIL) and from the lateral mitral annulus to left inferior pulmonary vein (LMIL)., Methods: The study included all mitral isthmus ablations performed at the Hospital of the University of Pennsylvania in 2016 and 2017. Acute procedural results and long-term arrhythmia-free survival were compared between groups., Results: Of 114 total MILs, conduction block was achieved across 73 (93.6%) SMILs compared with 29 (80.6%) LMILs (p = 0.05). Although the length of the SMIL was longer (48.9 ± 12.8 cm vs. 38.7 ± 12.8 cm; p = 0.001), time required to achieve block was shorter (25.2 ± 15.9 min vs. 36.6 ± 21.3 min; p = 0.03). Coronary sinus ablation was required in 58.3% of LMILs due to inability to achieve conduction block with left atrial ablation alone. In multivariate analysis, only failure to achieve acute MIL block remained significantly associated with subsequent OAT recurrence (hazard ratio: 6.39; 95% confidence interval: 1.37 to 29.9; p = 0.02)., Conclusions: The SMIL requires less time to complete and more frequently results in acute MIL block than the LMIL. Additionally, ablation is rarely required outside the left atrium. Failure to achieve acute MIL block is strongly associated with subsequent OAT recurrence., (Copyright © 2019 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study sought to characterize ventricular arrhythmia (VA) ablated from the basal inferoseptal left ventricular endocardium (BIS-LVe) and identify electrocardiographic characteristics to differentiate from inferobasal crux (IBC) VA., Background: The inferior basal septum is an uncommon source of idiopathic VAs, which can arise from its endocardial or epicardial (crux) aspect. Because the latter are often targeted from the coronary venous system or epicardium, distinguishing between the 2 is important for successful ablation., Methods: Consecutive patients undergoing ablation of idiopathic VA from the BIS-LVe or IBC from 2009 to 2018 were identified and clinical characteristics and electrocardiographs of VA were compared., Results: Of 931 patients undergoing idiopathic VA ablation, Virginia was eliminated from the BIS-LVe in 19 patients (2%) (17 male, age 63.7 ± 9.2 years, LV ejection fraction: 45.0 ± 9.3%). QRS complexes typically manifested right bundle branch block morphology with "reverse V 2 pattern break" and left superior axis (more negative in lead III than II). VA elimination was achieved after median of 2 lesions (interquartile range [IQR]: 1-6; range 1 to 20) (radiofrequency ablation time: 123 s [IQR: 75-311]). Compared with 7 patients with IBC VA (3 male, age 51.9 ± 20.1 years, LV ejection fraction: 51.4 ± 17.7%), BIS-LVe VA less frequently had initial negative forces (QS pattern) in leads II, III, and/or aVF (p < 0.001), R-S ratio <1 in lead V 1 (p = 0.005), and notching in lead II (p = 0.006) were narrower (QRS duration: 178.2 ± 22.4 vs. 221.1 ± 41.9 ms; p = 0.04) and more frequently had maximum deflection index of <0.55 (p < 0.001)., Conclusions: The BIS-LVe region is an uncommon source of idiopathic VA. Distinguishing these from IBC VA is important for procedural planning and ablation success., (Copyright © 2019 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study describes the use of septal coronary venous mapping to facilitate substrate characterization and ablation of intramural septal ventricular arrhythmia (VA)., Background: Intramural septal VA represents a challenge for substrate definition and catheter ablation., Methods: Between 2015 and 2018, 12 patients with structural heart disease, recurrent VA, and suspected intramural septal substrate underwent a septal coronary venous procedure in which mapping was performed by advancement of a wire into the septal perforator branches of the anterior interventricular vein. A total of 5 patients with idiopathic VA were also included as control subjects to compare substrate characteristics., Results: Patients were 63 ± 14 years of age, and 11 (92%) were men. Most patients with structural heart disease had nonischemic cardiomyopathy (83%). Six patients underwent ablation for premature ventricular contractions (PVC) and 6 for ventricular tachycardia. All patients had larger septal unipolar voltage abnormalities than bipolar voltage abnormalities (mean area 35.3 ± 16.8 cm 2 vs. 10.7 ± 8.4 cm 2 , respectively; p = 0.01), Patients with idiopathic VA had normal voltage. Septal coronary venous mapping revealed low-voltage, fractionated, and multicomponent electrograms in sinus rhythm in all patients with substrate compared to that in patients with idiopathic VA (amplitude 0.9 ± 0.9 mV vs. 4.4 ± 3.7 mV, respectively; p = 0.007; and duration 147 ± 48 ms vs. 92 ± 10 ms, respectively; p = 0.03). Ablation targeted early activation, pace map match, and/or good entrainment sites from intraseptal recording. Over a mean follow-up of 339 ± 240 days, the PVC and insertable cardioverter-defibrillator therapies burden were significantly reduced (from a mean of 22 ± 11% to 4 ± 8%; p = 0.005; and a mean 5 ± 2 to 1 ± 1; p = 0.001, respectively). Most patients (80%) with idiopathic VA remained arrhythmia free., Conclusions: In patients with suspected intramural septal VA, mapping of the septal coronary veins may be helpful to characterize the arrhythmia substrate, identify ablation targets, and guide endocardial ablation., (Copyright © 2019. Published by Elsevier Inc.)

Objectives: This study sought to assess the performance of established risk models in predicting outcomes after catheter ablation (CA) in patients with nonischemic dilated cardiomyopathy (NIDCM) and ventricular tachycardia (VT)., Background: A correct pre-procedural risk stratification of patients with NIDCM and VT undergoing CA is crucial. The performance of different pre-procedural risk stratification approaches to predict outcomes of CA of VT in patients with NIDCM is unknown., Methods: The study compared the performance of 8 prognostic scores (SHFM [Seattle Heart Failure Model], MAGGIC [Meta-analysis Global Group in Chronic Heart Failure], ADHERE [Acute Decompensated Heart Failure National Registry], EFFECT [Enhanced Feedback for Effective Cardiac Treatment-Heart Failure], OPTIMIZE-HF [Organized Program to Initiate Lifesaving Treatment in Hospitalized Patients with Heart Failure], CHARM [Candesartan in Heart Failure-Assessment of Reduction in Mortality], EuroSCORE [European System for Cardiac Operative Risk Evaluation], and PAINESD [Chronic Obstructive Pulmonary Disease, Age > 60 Years, Ischemic Cardiomyopathy, New York Heart Association Functional Class III or IV, Ejection Fraction <25%, Presentation With VT Storm, Diabetes Mellitus]) for the endpoints of death/cardiac transplantation and VT recurrence in 282 consecutive patients (age 59 ± 15 years, left ventricular ejection fraction: 36 ± 13%) with NIDCM undergoing CA of VT. Discrimination and calibration of each model were evaluated through area under the curve (AUC) of receiver-operating characteristic curve and goodness-of-fit test., Results: After a median follow-up of 48 (interquartile range: 19-67) months, 43 patients (15%) died, 24 (9%) underwent heart transplantation, and 58 (21%) experienced VT recurrence. The prognostic accuracy of SHFM (AUC = 0.89; goodness-of-fit p = 0.68 for death/transplant and AUC = 0.77; goodness-of-fit p = 0.16 for VT recurrence) and PAINESD (AUC = 0.83; goodness-of-fit p = 0.24 for death/transplant and AUC = 0.68; goodness-of-fit p = 0.58 for VT recurrence) were significantly superior to that of other scores., Conclusions: In patients with NIDCM and VT undergoing CA, the SHFM and PAINESD risk scores are powerful predictors of recurrent VT and death/transplant during follow-up, with similar performance and significantly superior to other scores. A pre-procedural calculation of the SHFM and PAINESD can be useful to predict outcomes., (Copyright © 2019 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study sought to determine the impact of repeat catheter ablation (CA) prior to hospital discharge based on inducibility of clinical ventricular tachycardia (VT) during noninvasive programmed ventricular stimulation (NIPS)., Background: Inducibility of clinical VT during NIPS performed several days after CA identifies patients at high risk of recurrence. The impact of NIPS-guided repeat CA has not been reported., Methods: Consecutive patients with structural heart disease undergoing CA of VT followed by NIPS were studied. Clinical VT was defined by comparison with 12-lead electrocardiograms and stored implantable cardioverter-defibrillator electrograms from spontaneous VT episodes. Among those with inducible clinical VT at NIPS, VT-free survival was compared between those in whom ablation was repeated (group 1) versus those in whom ablation was not repeated (group 2) prior to hospital discharge., Results: Among 469 patients (64 ± 12 years of age; 85% males; 60% ischemic), 216 patients (46%) underwent NIPS 3 days (interquartile range: 2 to 4 days) after CA. Clinical VT was induced in 45 patients (21%). Among those 45, CA was repeated in 11 patients (24%). There were no significant differences in baseline clinical or index CA characteristics between groups 1 and 2. Over a median 36-month follow-up, only 1 patient (9%) in group 1 experienced VT recurrence compared to 24 patients (71%) in group 2 (p < 0.01). In univariate Cox regression, repeat CA guided by NIPS (hazard ratio: 0.07; 95% confidence interval: 0.01 to 0.58; p = 0.01) was the only predictor of VT-free survival., Conclusions: In patients with inducible clinical VT during post-ablation NIPS, repeat CA was associated with significantly lower risk of subsequent recurrence., (Copyright © 2019 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study sought to investigate the substrate, procedural strategies, safety, and outcomes of catheter ablation (CA) for ventricular tachycardia (VT) in patients with aortic valve replacement (AVR)., Background: VT ablation in patients with AVR is challenging, particularly when mapping and ablation in the periaortic region are necessary., Methods: We identified consecutive patients with mechanical, bioprosthetic, and transcatheter AVR who underwent CA for VT refractory to antiarrhythmic drugs and analyzed VT substrate, approach to LV access, complications, and long-term outcomes., Results: Overall, 29 patients (87% men, mean age 67.9 ± 9.8 years, left ventricular ejection fraction 39 ± 10%) with prior AVR (13 mechanical, 15 bioprosthetic, 1 transcatheter AVR) underwent 40 ablations from 2004 to 2016. Left-sided mapping/CA was performed in 27 patients (36 procedures). Access was retrograde aortic in 11 procedures (all bioprosthetic), transseptal in 24 (13 mechanical; 10 bioprosthetic; 1 transcatheter AVR), or transventricular septal in 1. Periaortic bipolar or unipolar scar was detected in all 24 patients in whom detailed periaortic mapping was performed. Clinical VT circuit(s) involved the periaortic region in 10 patients (34%), 2 (7%) had bundle branch re-entry VT, and 17 (59%) had substrate unrelated to AVR. There were 2 major complications (both related to vascular access). Only 2 patients (9.1%) had VT recurrence. Over median follow-up of 12.8 months, 11 patients died (none as a result of recurrent VT)., Conclusions: Whereas most patients undergoing CA for VT after AVR had VT from substrate unrelated to AVR, periaortic scar is universally present and bundle branch re-entry can be the VT mechanism. CA can be safely performed with excellent long-term VT elimination., (Copyright © 2019 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: The purpose of this study was to determine the ventricular arrhythmia (VA) substrates in patients with unoperated and post-surgical Ebstein's Anomaly (EA)., Background: EA is associated with variable atrialization of the right ventricle and a propensity for VA and sudden death. There are scant data on catheter ablation for VA in this population., Methods: This was a retrospective study involving 11 congenital heart disease centers., Results: A total of 24 patients (median age 17 [interquartile range (IQR): 11 to 37] years; age range 1 to 68 years; 42% men) with EA undergoing catheter ablation were identified. Prior tricuspid valve (TV) surgery had been performed in 12 (50%). Presenting symptoms were palpitations in 15, syncope in 4, aborted cardiac arrest in 4, and none in 1. At procedure, 28 VA substrates were encountered and 25 were completely characterized (median 1 per patient; cycle length 305 [IQR: 268 to 400] ms). In 3 cases, premature ventricular contraction (PVC) foci were targeted (1 with a history of PVC-induced ventricular fibrillation). VA mechanisms were focal in 15 and macro-re-entrant in 10, and did not differ significantly between those with and those without prior TV surgery (p = 0.7). Focal VAs predominantly localized to the atrialized right ventricle ARV in unoperated patients and to diseased myocardium or Purkinje tissue after TV surgery. Macro-re-entry was related to isolated scar or split potentials in the ARV in unoperated patients, and larger, more diffuse scar after TV surgery. Complete success was achieved in 22 (92%). There were 2 of 13 complications in patients <18 years of age and none in patients >18 years of age. There was a single recurrence over a median follow-up of 3.4 years., Conclusions: VA in EA may be either focal or macro-re-entrant. In the absence of surgery, substrates chiefly involve the ARV. After surgery, focal VA involves injured myocardium or Purkinje tissue and re-entrant ventricular tachycardia is related to post-surgical scar. Catheter ablation is a reasonable therapeutic approach for these patients., (Copyright © 2018 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study sought to characterize septal substrate in patients with nonischemic left ventricular cardiomyopathy (NILVCM) undergoing ventricular tachycardia (VT) ablation., Background: The interventricular septum is an important site of VT substrate in NILVCM., Methods: The authors studied 95 patients with NILVCM and VT. Electroanatomic mapping using standard bipolar (<1.5 mV) and unipolar (<8.3 mV) low-voltage criteria identified septal scar location and size. Analysis of unipolar voltage was performed and scars quantified using graded unipolar cutoffs from 4 to 8.3 mV were correlated with delayed gadolinium-enhanced cardiac magnetic resonance (DE-CMR), performed in 57 patients., Results: Detailed LV endocardial mapping (mean 262 ± 138 points) showed septal bipolar and unipolar voltage abnormalities (VAs) in 44 (46%) and 79 (83%) patients, most commonly with basal anteroseptal involvement. Of the 59 patients in whom the septum was targeted, bipolar and unipolar septal VAs were seen in 36 (61%) and 54 (92%). Of the 35 with CMR-defined septal scar, bipolar and unipolar septal VAs were seen in 18 (51%) and 31 (89%). In 12 patients without CMR septal scar, 6 (50%) had isolated unipolar septal VAs on electroanatomic mapping, a subset of whom the septum was targeted for ablation (44%). In the graded unipolar analysis, the optimal cutoff associated with magnetic resonance imaging septal scar was 4.8 mV (sensitivity 75%, specificity 70%; area under the curve: 0.75; 95% confidence interval: 0.60 to 0.90)., Conclusions: Septal substrate by unipolar or bipolar voltage mapping in patients with NILVCM and VT is common. A unipolar voltage cutoff of 4.8 mV provides the best correlation with DE-CMR. A subset of patients with septal VT had normal DE-CMR or endocardial bipolar voltage with abnormal unipolar voltage., (Copyright © 2018 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study sought to characterize ventricular tachycardia (VT) ablation outcomes across nonischemic cardiomyopathy (NICM) etiologies and adjust these outcomes by patient-related comorbidities that could explain differences in arrhythmia recurrence rates., Background: Outcomes of catheter ablation of VT in patients with NICM could be related to etiology of NICM., Methods: Data from 2,075 patients with structural heart disease referred for catheter ablation of VT from 12 international centers was retrospectively analyzed. Patient characteristics and outcomes were noted for the 6 most common NICM etiologies. Multivariable Cox proportional hazards modeling was used to adjust for potential confounders., Results: Of 780 NICM patients (57 ± 14 years of age, 18% women, left ventricular ejection fraction 37 ± 13%), underlying prevalence was 66% for dilated idiopathic cardiomyopathy (DICM), 13% for arrhythmogenic right ventricular cardiomyopathy (ARVC), 6% for valvular cardiomyopathy, 6% for myocarditis, 4% for hypertrophic cardiomyopathy, and 3% for sarcoidosis. One-year freedom from VT was 69%, and freedom from VT, heart transplantation, and death was 62%. On unadjusted competing risk analysis, VT ablation in ARVC demonstrated superior VT-free survival (82%) versus DICM (p ≤ 0.01). Valvular cardiomyopathy had the poorest unadjusted VT-free survival, at 47% (p < 0.01). After adjusting for comorbidities, including age, heart failure severity, ejection fraction, prior ablation, and antiarrhythmic medication use, myocarditis, ARVC, and DICM demonstrated similar outcomes, whereas hypertrophic cardiomyopathy, valvular cardiomyopathy, and sarcoidosis had the highest risk of VT recurrence., Conclusions: Catheter ablation of VT in NICM is effective. Etiology of NICM is a significant predictor of outcomes, with ARVC, myocarditis, and DICM having similar but superior outcomes to hypertrophic cardiomyopathy, valvular cardiomyopathy, and sarcoidosis, after adjusting for potential covariates., (Copyright © 2018 American College of Cardiology Foundation. All rights reserved.)

Objectives: This study reports outcomes of bailout atrial balloon septoplasty (ABS) to overcome challenging left atrial (LA) access in patients undergoing atrial fibrillation (AF) ablation., Background: Transseptal puncture (TSP) and LA access for AF ablation can be challenging in patients with prior atrial septal surgery, percutaneous closure, or scarred septum due to multiple prior TSPs., Methods: The study identified patients who underwent AF ablation at 2 ablation centers from 2011 to 2017 with challenging TSP in whom bailout percutaneous ABS was performed to allow LA access. Following TSP, the transseptal sheath could not be advanced to the LA despite multiple attempts or approaches including use of a stiff wire sequentially in the left and right pulmonary veins, use of a stiff pigtail exchange wire advanced in the LA or left ventricle, or sequential dilation with progressively larger diameter long dilators. ABS was performed using a noncompliant balloon (diameter 4 to 10 mm) advanced over a stiff wire deployed in the left superior pulmonary vein, allowing passage of the transseptal sheaths for completion of the AF ablation procedure., Results: Fifteen patients (mean age 54.4 ± 15.5 years, 9 women) with challenging TSP (7 patients with prior surgical ASD repair, 2 with percutaneous ASD closure devices, and 13 with ≥1 previous TSP) underwent bailout ABS for AF ablation. After TSP (radiofrequency assisted in 10 cases), ABS was successful and permitted access to the LA for ablation in all patients. Mean time required to perform ABS was 21.3 ± 19.4 min, and mean total procedure time was 241.1 ± 114.6 min (fluoroscopy time 62.0 ± 29.9 min). There were no procedural complications., Conclusions: In patients undergoing AF ablation with difficult transseptal access due to scarred, surgically, or percutaneously repaired atrial septum, ABS is a safe and effective bailout strategy to obtain transseptal access., (Copyright © 2018 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study determined whether obesity increased the risk of failed shocks and complications among subcutaneous implantable cardioverter-defibrillator (S-ICD) recipients., Background: The S-ICD is an established treatment for patients at high risk for ventricular arrhythmias. Obesity may increase the transvenous defibrillation threshold and the rate of complications., Methods: We analyzed data from the 321 patients enrolled in the S-ICD Investigational Device Exemption (IDE) study. They were categorized into 3 body mass index (BMI) groups: <25 kg/m 2 (underweight and normal), 25 to 30 kg/m 2 (overweight), and >30 kg/m 2 (obese). Patients underwent implantation followed by defibrillation testing at 65 J. Chronic defibrillation testing was repeated >150 days post implantation in a subset of patients., Results: Seventy-nine patients had BMI <25 kg/m 2 , 105 had BMI 25 to 30 kg/m 2 , and 137 had BMI >30 kg/m 2 . A failed first shock of any kind occurred in 52 patients, including 41 patients during implant defibrillation testing, 11 patients during chronic defibrillation testing, and 5 patients during spontaneous ventricular arrhythmias. The rate of failed first shocks during implant defibrillation testing increased across BMI categories (5.1% among underweight and normal patients, 13.3% among overweight patients, and 16.9% among obese patients; p = 0.04). Among obese patients, shock impedance was higher during failed first shocks than successful first shocks (103.5 ohms vs. 84.6 ohms; p = 0.001). The rate of failed first shocks during chronic defibrillation testing and spontaneous ventricular arrhythmias did not significantly differ among BMI groups, nor did the rate of complications. Of the 8 underweight patients, there were no failed shocks or complications., Conclusions: Obese patients are at increased risk of failed first S-ICD shocks during defibrillation testing. Whether this can be overcome by optimal implantation techniques remains unknown. Rates of complications were not increased among obese patients., (Copyright © 2018 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study sought to characterize the electroanatomic (EAM) substrate in patients with cardiac sarcoidosis (CS) and ventricular tachycardia and its relationship to imaging findings of inflammation and fibrosis., Background: CS is characterized by coexistence of active inflammation and replacement fibrosis., Methods: A total of 42 patients with CS based on established criteria and ventricular tachycardia underwent high-density EAM mapping. Abnormal electrograms (EGM) were collected and independently classified as multicomponent fractionated, isolated, late, and split according to standard criteria and regardless of the peak-to-peak bipolar/unipolar voltage. A total of 29 patients (69%) underwent pre-procedural cardiac magnetic resonance (CMR) and positron emission tomography (PET)/computed tomography (CT). The distribution of EAM substrate was correlated with regions of late gadolinium enhancement (LGE) on CMR and increased 18F-fluorodeoxyglucose uptake on PET/CT., Results: Of 21,451 bipolar and unipolar EGM, 4,073 (19%) were classified as abnormal with a predominant distribution in the basal perivalvular segments and interventricular septum. Using the standard bipolar (<1.5 mV) and unipolar (<8.3 mV for left ventricle <5.5 mV for the right) voltage cutoff values, 40% and 22% of the abnormal EGM were located outside the EAM low-voltage areas, respectively. LGE was present in 26 of 29 patients (90%), whereas abnormal 18F-fluorodeoxyglucose uptake in 14 of 29 patients (48%) with imaging. Segments with abnormal EGM had more LGE-evident scar transmurality [median: 24% (interquartile range [IQR]: 4% to 40%) vs. median: 5% (IQR: 0% to 15%); p < 0.001] and lower metabolic activity (median: 20 g glucose [IQR: 14 g to 30 g] vs. median: 29 g glucose [IQR: 18 g to 39 g]; p < 0.001). Overall, the agreement between the presence of abnormal EGM was higher with the presence of LGE (κ = 0.51; p < 0.001) than with the presence of active inflammation (κ = -0.12; p = 0.003)., Conclusions: In patients with CS and ventricular tachycardia, pre-procedural imaging with CMR and PET/CT can be useful in detecting EAM abnormalities that are potential targets for substrate ablation. Abnormal EGM were more likely located in segments with more scar transmurality (LGE) at CMR and a lower degree of inflammation on PET., (Copyright © 2018 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study reports the long-term outcome of patients with bundle branch re-entrant tachycardia (BBRT) who underwent catheter ablation for ventricular tachycardia (VT)., Background: BBRT is an uncommon mechanism of VT. Data on long-term outcomes of patients with BBRT treated with catheter ablation are insufficient., Methods: Between 2005 and 2016, 32 patients had a sustained VT due to a bundle branch re-entrant mechanism. Diagnosis of BBRT was established per standard published criteria., Results: The mode of presentation was syncope in 17 patients (53%) and palpitations in 15 (47%). BBRT was inducible in all subjects, and successful ablation of the right bundle branch in 19 patients (59%) or the left bundle branch in 13 patients (41%) was performed. During follow-up of 95 ± 36 months, 6 patients (19%) died, 3 of progressive heart failure and 3 of noncardiac causes. Recurrent VT due to BBRT did not occur in any patient. At baseline, 25 patients (78%) had a prolonged HV interval (>55 ms) and 7 (22%) had a normal HV interval (≤55 ms). In patients with a normal HV interval, there was only 1 death (due to malignancy), and no one developed heart block during 90 ± 36 months of follow-up. Ten patients (31%) had normal left ventricular (LV) function (LV ejection fraction ≥50%), and 22 (69%) had depressed LV function (LV ejection fraction <50%). No deaths were recorded in patients with normal LV function (5 with no implantable cardioverter-defibrillator) compared with 6 deaths among patients with depressed LV function (n = 22; p = 0.07)., Conclusions: Radiofrequency ablation of the bundle branch is an effective therapy for treatment of BBRT. Sustained BBRT can be seen in patients with normal LV systolic function and HV interval with excellent long-term outcomes after ablation., (Copyright © 2018 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study sought to determine the extent, time course, and predictors of improvement following cardiac resynchronization therapy (CRT) upgrade among pacing-induced cardiomyopathy (PICM) patients., Background: PICM is an important cause of heart failure in patients exposed to frequent right ventricular (RV) pacing. CRT may reverse PICM., Methods: We retrospectively studied 1,279 consecutive patients undergoing CRT procedures between 2003 and 2016. Patients undergoing CRT upgrade from a dual-chamber or single-chamber ventricular pacemaker for PICM were included. PICM was defined as decrease of ≥10% in left ventricular ejection fraction (LVEF), resulting in LVEF <50% among patients experiencing ≥20% RV pacing without an alternative cause of cardiomyopathy. Severe PICM was defined as pre-upgrade LVEF ≤35%. Clinical, electrocardiographic, and echocardiographic characteristics associated with both the extent of LVEF recovery and with post-upgrade LVEF of >35% among those with severe PICM were identified., Results: Of 69 PICM patients, LVEF improved from 29.3% to 45.3% over a median 7.0 months. Of 54 patients with severe PICM, 39 (72.2%) improved to LVEF >35% over a median 7.0 months. Most improvement occurred within the first 3 months, although improvement continued over the remainder of the first year. In linear regression, narrower native QRS was associated with greater LVEF improvement following CRT upgrade (+2.00% per 10-ms decrease; p = 0.05)., Conclusions: CRT is highly efficacious in reversing PICM, with 72% of severe PICM patients achieving LVEF >35% and most of the improvement occurring within 1 year. These data support initial upgrade to a CRT pacemaker with consideration of further upgrade to CRT defibrillator after 1 year if LVEF remains ≤35%., (Copyright © 2018 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study sought to evaluate the clinical outcomes of patients receiving hemodynamic support (HS) during ventricular tacchycardia (VT) ablation., Background: There are limited real-world data evaluating its effect of HS in ablation outcomes., Methods: An analysis of 1,655 patients from the International VT Ablation Center Collaborative group was performed. A total of 105 patients received HS with percutaneous ventricular assist device., Results: Patients in the HS group had lower left ventricular ejection fraction (LVEF), higher New York Heart Association (NYHA) functional class, and more implantable cardioverter-defibrillator (ICD) shocks, VT storm, and antiarrhythmic drug use (all p < 0.05). The HS group also required significantly longer fluoroscopy, procedure, and total lesion time. Acute procedural success (71.8% vs. 73.7%; p = 0.04) was significantly lower and complications (12.5% vs. 6.5%; p = 0.03) and 1-year mortality (34.7% vs. 9.3%; p < 0.001) were significantly higher in the HS group. Multivariate Cox regression analysis demonstrated HS as an independent predictor of mortality (hazard ratio: 5.01; 95% confidence interval: 3.44 to 7.20; p < 0.001). There was no significant difference in VT recurrence between groups. In a subgroup analysis including LVEF ≤20% and NYHA functional class III to IV patients, acute procedural success (74.0% vs. 70.5%; p = 0.8), complications (15.6% vs. 7.8%; p = 0.2), VT recurrence (30.2% vs. 38.1%; p = 0.44), and 1-year mortality (40.0% vs. 28.8%; p = 0.2) were no different between the HS and no-HS groups., Conclusions: Patients requiring HS were sicker with multiple comorbidities and, as expected, had a significantly higher 1-year mortality than did those patients in the no-HS group. In patients with LVEF ≤20% and NYHA functional class III to IV, there was also no significant difference in clinical outcomes when compared with no HS. Further studies are needed to systematically evaluate patients undergoing VT ablation receiving HS., (Copyright © 2017 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: The goal of this study was to determine the long-term outcomes of catheter ablation (CA) of electrical storm in patients with nonischemic dilated cardiomyopathy (NIDCM) compared with patients with ischemic cardiomyopathy (ICM)., Background: CA of ventricular tachycardia (VT) electrical storm has been shown to improve VT-free survival in patients with ICM. Data on the outcomes of CA of electrical storm in patients with NIDCM are insufficient., Methods: The study included 267 consecutive patients with NIDCM (n = 71; ejection fraction 32 ± 14%) and ICM (n = 196; ejection fraction 28 ± 12%). Endo-epicardial CA was performed in 59 (22%) patients. CA was guided by activation and entrainment mapping for tolerated VT and pacemapping/targeting of abnormal substrate for unmappable VT., Results: After a median follow-up of 45 (25th to 75th percentile: 9 to 71) months and 1 (25th to 75th percentile: 1 to 8) procedures, 76 (29%) patients died, 25 (9%) underwent heart transplantation, 87 (33%) experienced VT recurrence, and 13 (5%) had recurrence of electrical storm. Overall VT-free survival was 54% at 60 months (48% in NIDCM and 54% in ICM; p = 0.128). Patients with VT recurrence experienced a median of 2 (1 to 10) VT episodes in the 5 (1 to 14) months after the procedure. Death/transplantation-free survival was 62% at 60 months (53% in NIDCM and 64% in ICM; p = 0.067). Persistent inducibility of any VT with cycle length ≥250 ms at programmed stimulation at the end of the procedure was the only independent predictor of VT recurrence. Low ejection fraction, New York Heart Association functional class, and VT recurrence over follow-up independently predicted death/transplantation., Conclusions: CA of electrical storm was similarly effective in patients with NIDCM compared with patients with ICM, with elimination of electrical storm in 95% of cases and achievement of complete VT control at long-term follow-up in most patients., (Copyright © 2017 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study sought to examine long-term outcomes in patients with structural heart disease in whom amiodarone was reduced/discontinued after ventricular tachycardia (VT) ablation., Background: VT in patients with structural heart disease increases morbidity and mortality. Amiodarone can decrease VT burden, but long-term use may result in organ toxicities and possibly increased mortality. Catheter ablation can also decrease VT burden. Whether amiodarone can be safely reduced/discontinued following ablation remains unknown., Methods: We studied consecutive patients undergoing VT ablation from 2008 to 2011, typically followed by noninvasive programmed stimulation several days later. Patients were divided into 3 groups by amiodarone use: group A-amiodarone reduced/discontinued following ablation; group B-amiodarone not reduced; group C-not on amiodarone at time of ablation. Baseline characteristics and outcomes were compared between groups., Results: Overall, 231 patients (90% male; mean age: 63.4 ± 12.9 years; 53.7% ischemic cardiomyopathy) were included (group A: 99 patients; group B: 29 patients; group C: 103 patients). Group B patients were older with more advanced heart failure. Group A patients less frequently had inducible VT at the end of ablation or noninvasive programmed stimulation. In follow-up, 1-year VT-free survival was similar between groups (p = 0.10). Mortality was highest in group B (p < 0.001). Higher amiodarone dose after ablation (hazard ratio: 1.23; 95% confidence interval: 1.03 to 1.47; p = 0.02) was independently associated with shorter time to death., Conclusions: After successful VT ablation, as confirmed by noninducibility at the end of ablation and noninvasive programmed stimulation, amiodarone may be safely reduced/discontinued without an unacceptable increase in VT recurrence. Reduction/discontinuation of amiodarone should be considered an important goal of VT ablation., (Copyright © 2017 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study sought to identify predictors of transplantation/left ventricular assist device (LVAD)-free survival among patients with left ventricular nonischemic cardiomyopathy (NICM) and ventricular tachycardia (VT)., Background: Outcomes vary widely among these patients., Methods: The derivation cohort consisted of patients with NICM undergoing VT ablation from 2007 to 2011. Scar percentage was defined as the area of low voltage divided by total surface area. Cox proportional hazard modeling was performed to identify predictors of shorter time to the primary endpoint of death, transplantation, or LVAD. A risk score was created using β regression coefficients. The risk score was then validated in a separate cohort of patients undergoing ablation from 2004 to 2007., Results: Of 100 patients with NICM undergoing VT ablation, 41 experienced an endpoint during 1.2 years mean follow-up. In multivariate modeling, VT storm, wider native QRS duration, greater endocardial/epicardial bipolar scar percentage, and lower left ventricular ejection fraction (LVEF) identified worse transplantation/LVAD-free survival. The risk score = (VT storm × 83) + (greater of endocardial/epicardial bipolar scar percentage × 4) + (QRS duration) - (LVEF × 3). A score >180 identified patients at high risk for the endpoint, whereas a score <100 identified low risk. Among the 50-patient validation cohort, the high-risk group again had worse transplantation/LVAD-free survival during a mean 3.0 years of follow-up (<10% vs. 50% for intermediate and >80% for low, p < 0.001)., Conclusions: Wider native QRS duration, greater bipolar scar percentage, VT storm, and lower LVEF are potent predictors of time to death, transplantation, or LVAD. By combining these variables into an "electrophysiological risk score," patient risk can be refined., (Copyright © 2015 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Objectives: This study sought to determine the safety and efficacy of ventricular tachycardia (VT) ablation in elderly patients with structural heart disease., Background: As patients with cardiomyopathy live longer, the number of elderly patients with VT is increasing. Catheter ablation is an effective treatment for VT; however, outcomes may differ among elderly patients., Methods: We studied 238 consecutive patients with ischemic or nonischemic cardiomyopathies who underwent catheter ablation for VT refractory to antiarrhythmic medications. Patients were divided into 3 age groups (Group A, <65 years; Group B, 65 to 75 years; and Group C, >75 years)., Results: Compared with Groups A and B, patients in Group C were more likely to have ischemic cardiomyopathy, lower left ventricular ejection fraction, longer mean VT cycle length, and less likely to undergo epicardial ablation. Acute procedural success, complications, 28-day survival, and 1-year VT-free survival rates were similar across groups (p = 0.9, 0.3, 0.3, and 0.9, respectively). As expected, Group C patients had worse survival in long-term follow-up (p < 0.001)., Conclusions: VT ablation can be performed in elderly patients with structural heart disease with similar efficacy and complication rates as in younger patients. VT ablation should not be withheld for older age alone., (Copyright © 2015 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)