The Safety and Efficacy of Epicardial Carbon Dioxide Insufflation Compared With Conventional Epicardial Access.

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 (EpiCO2) 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 EpiCO2 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 EpiCO2 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 EpiCO2). There was no difference in success rate whether the ConvEpi or EpiCO2 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 EpiCO2 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%] EpiCo2; 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, EpiCO2 was associated with a reduction in bleeding ≥80 mL (OR: 0.27; 95% CI: 0.08-0.89; P = 0.03). CONCLUSIONS: EpiCO2 access is associated with lower rates of major complication and bleeding when compared with ConvEpi access.

Long-Term Freedom From Ventricular Arrhythmias in ARVC With Endocardial Only Ablation: Predictors of Success.

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.

Electrophysiologic diagnosis of narrow and wide complex tachyarrhythmias.

Establishing the precise mechanism of cardiac arrhythmias in the electrophysiology laboratory is one of the main requisites for a successful and safe ablation. This article provides an organized approach to the differential diagnosis of narrow and wide complex tachycardias based on the analysis of electrical activation patterns, followed by specific pacing maneuvers in each case.

Evaluation of organized atrial arrhythmias after cryptogenic stroke.

Background: Long-term rhythm monitoring to detect atrial fibrillation (AF) following a cryptogenic stroke (CS) is well established. However, the burden of organized atrial arrhythmias in this population is not well defined. Objective: The purpose of this study was to assess the incidence and risk factors for organized atrial arrhythmias in patients with CS. Methods: We evaluated all patients with CS who received an insertable cardiac monitor (ICM) between October 2014 and April 2020. All ICM transmissions categorized as AF, tachycardia, or bradycardia were reviewed. We evaluated the time to detection of organized AF and the combination of either organized atrial arrhythmia or AF. Results: A total of 195 CS patients with ICMs were included (51% men; mean age 66 ± 12 years; mean CHA2DS2-VASC score 4.6). Over mean follow-up of 18.9 ± 11.2 months, organized atrial arrhythmias lasting ≥30 seconds were detected in 45 patients (23%), of whom 62% did not have AF. Seventeen patients had both organized atrial arrhythmia and AF, and another 21 patients had AF only. Compared to those with normal left atrial size, patients with left atrial enlargement had a higher adjusted risk for development of atrial arrhythmias (mild left atrial enlargement: hazard ratio 1.99; 95% confidence interval 1.06-3.75; moderate/severe left atrial enlargement: hazard ratio 3.06; 95% confidence interval 1.58-5.92). Conclusion: Organized atrial arrhythmias lasting ≥30 seconds are detected in nearly one-fourth of CS patients. Two-thirds of these patients did not have AF. Further studies are required to evaluate the impact of organized atrial arrhythmias on recurrent stroke risk.

Risk of atrial arrhythmias in patients with ventricular tachycardia in arrhythmogenic right ventricular cardiomyopathy.

BACKGROUND: In arrhythmogenic right ventricular cardiomyopathy (ARVC), risk of atrial arrhythmias (AAs) persists after ventricular tachycardia (VT) ablation. OBJECTIVE: The purpose of this study was to determine the type, prevalence, outcome, and risk correlates of AA in ARVC in patients undergoing VT ablation. METHODS: Prospectively collected procedural and clinical data on ARVC patients undergoing VT ablation were analyzed. Risk score for typical atrial flutter was determined from univariate logistic regression analysis. RESULTS: Of 119 consecutive patients with ARVC and VT ablation, 40 (34%) had AA: atrial fibrillation (AF) in 31, typical isthmus-dependent atrial flutter (AFL) in 27, and atrial tachycardia/atypical flutter (AT) in 10. Seventeen patients (43%) with AA experienced inappropriate defibrillator therapy, with 15 patients experiencing shocks. Ablation was performed for typical AFL in 21 (53%), AT in 5 (13%), and pulmonary vein isolation for AF in 4 (10%) patients and prevented AA in 78% and all AFL during additional mean follow-up of 65 months. Risk score for typical flutter included age >40 years (1 point), ≥moderate right ventricular dysfunction (2 points), ≥moderate tricuspid regurgitation (2 points), ≥moderate right atrial dilation (2 points), and right ventricular volume >250 cc (3points), with score >4 identifying 50% prevalence of typical flutter. CONCLUSION: AAs are common in patients with ARVC and VT, can result in inappropriate implantable cardioverter-defibrillator shocks, and typically are controlled with atrial ablation. A risk score can be used to identify patients at high risk for typical AFL who may be considered for isthmus ablation at the time of VT ablation.

Utility of Very High-Output Pacing to Identify VT Circuits in Patients Manifesting Traditionally Inexcitable Scar.

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.

Identifying Origin of Nonpulmonary Vein Triggers Using 2 Stationary Linear Decapolar Catheters: A Novel Algorithm.

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.

Sinus rhythm electrocardiographic abnormalities, sites of origin, and ablation outcomes of ventricular premature depolarizations initiating ventricular fibrillation.

BACKGROUND: Ventricular fibrillation (VF) can be initiated by ventricular premature depolarizations (VPDs) in the absence of obvious structural abnormalities. OBJECTIVE: The purpose of this study was to determine the prevalence of 12-lead electrocardiographic (ECG) sinus rhythm reduced QRS amplitude, QRS fractionation (QRSf), and early repolarization (ER) pattern, and the outcome of catheter ablation and VPD anatomic distribution in patients with VPDs initiating VF. METHODS: We compared a cohort with no apparent structural heart disease and VPDs initiating VF (group 1; n = 42) to a reference cohort (group 2; n = 61) of patients with no structural heart disease and symptomatic unifocal VPDs. RESULTS: A reduced QRS amplitude (<0.55 mV) in aVF (59% vs 10%; P <.001), QRSf in ≥2 contiguous leads (50% vs 16%; P <.001), and ER pattern (21.4% vs 1.6%; P = .01) were more common in group 1 than in group 2. At least 1 abnormal ECG finding was present in 34 group 1 patients (81%) vs 17 group 2 patients (28%) (P <.001). VPD origin included right ventricular and left ventricular distal Purkinje system and moderator band/papillary muscles in 83% of group 1 patients vs 18% of group 2 patients (P <.001). VF was eliminated with a single ablation procedure in 77% of group 1 patients with at least 2 years of follow-up. CONCLUSION: A reduced QRS amplitude (<0.55 mV) in aVF, QRSf in ≥2 contiguous leads, and/or an ER pattern are frequently observed in patients with VPDs initiating VF. VPDs initiating VF typically originate from the distal Purkinje system and papillary muscles and can be successfully eliminated with catheter ablation.

Presence of sinus rhythm at time of ablation in patients with persistent atrial fibrillation undergoing pulmonary vein isolation is associated with improved long-term arrhythmia outcomes.

BACKGROUND: Adverse structural and electrical remodeling underlie persistent atrial fibrillation (PersAF). Restoration of sinus rhythm (SR) prior to ablation in PersAF may improve the underlying substrate, thus improving arrhythmia outcomes. The aim of this study was to evaluate if the presence of SR at time of ablation is associated with improved long-term arrhythmia outcomes of a limited catheter ablation (CA) strategy in PersAF. METHODS: Patients with PersAF undergoing pulmonary vein isolation at our institution from 2014-2018 were included. We compared patients who presented for ablation in SR (by cardioversion and/or antiarrhythmic drugs [AADs]) to those who presented in AF. Primary outcome of interest was freedom from atrial arrhythmias (AAs) on or off AADs at 1 year after single ablation. Secondary outcomes included freedom from AAs on or off AADs overall, freedom from AAs off AADs at 1 year, and time to recurrent AF. RESULTS: Five hundred seventeen patients were included (322 presented in AF, 195 SR). The primary outcome was higher in those who presented for CA in SR as compared to AF (85.6% vs. 77.0%, p = 0.017). Freedom from AAs off AAD at 12 months was also higher in those presenting in SR (59.0% vs. 44.4%; p = 0.001) and time to recurrent AF was longer (p = 0.008). Presence of SR at CA was independently associated with the primary outcome at 12 months (OR 1.77; 95% CI 1.08-2.90) and overall (OR 1.89; 95% CI 1.26-2.82). CONCLUSIONS: Presence of SR at time of ablation is associated with improved long-term arrhythmia outcomes of limited CA in PersAF.

Impact of Left Ventricular Papillary Muscle Ventricular Arrhythmia Ablation on Mitral Valve Function.

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.

Longitudinal electrocardiographic assessment in Brugada syndrome.

Background: The type 1 electrocardiographic (ECG) pattern diagnostic of Brugada syndrome (BrS) can be dynamic. Limited studies have rigorously evaluated the temporal stability of the Brugada ECG pattern. Objective: We sought to evaluate fluctuations of the Brugada pattern in serial resting ECGs from BrS patients managed within a large health care system. Methods: In our cohort of BrS patients with at least 2 standard, resting ECGs recorded on separate clinical encounters, we evaluated serial changes in the Brugada pattern and categorized patients into 1 of 3 groups: dynamic was defined as the presence of both type 1 and non-type 1 patterns in available ECGs; the provoked-only group was defined as having a non-type 1 Brugada pattern across resting ECGs; and the persistent group was defined as having a type 1 pattern on all ECGs. We also evaluated the clinical risk in this cohort according to the Shanghai risk score. Results: In 72 patients with BrS (mean age 46 ± 15 years, 69% male), 828 standard, resting ECGs were recorded over a median duration of 30.2 (interquartile range 6.3-68.1) months. The dynamic group comprised 50 (69% of the cohort) patients, the provoked-only group consisted of 17 patients (24% of the cohort), and the persistent group included 5 patients. No significant differences were detected in the total number of ECGs evaluated during the follow-up period between any of the groups. Only sinus node dysfunction and a prior cardiac arrest were associated with the persistent type 1 group. The majority of patients had a low annualized risk of lethal arrhythmic events. Conclusion: Most BrS patients have a dynamic Brugada pattern noted on longitudinal, resting ECGs. Expert consensus statements should provide clarity on the frequency of obtaining resting ECGs in patients suspected of having BrS during follow-up.

Utility of Prolonged Duration Endocardial Ablation for Ventricular Arrhythmias Originating From the Left Ventricular Summit.

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.

Characterization of the right ventricular substrate participating in postinfarction ventricular tachycardia.

BACKGROUND: The right ventricle (RV) is uncommonly implicated in postinfarction ventricular tachycardia (VT). The prevalence and features of the RV substrate participating in postinfarction VT are undefined. OBJECTIVES: The purpose of this study was to characterize critical right ventricular substrate (CRVS) involvement in patients with postinfarction VT. METHODS: We retrospectively reviewed 1279 patients with postinfarction VT undergoing catheter ablation at our center from January 2000 through May 2020. Cases with CRVS defined by conclusive demonstration of participation in VT with activation, entrainment, and/or pacemapping during sinus rhythm were identified. RESULTS: CRVS was identified in 27 of 1279 patients (2.1%): age 65 ± 13 years, 96% male, median left ventricular (LV) ejection fraction 25%, and 93% with left bundle branch block (LBBB) morphology VT. CRVS was identified by RV activation and/or entrainment mapping (n = 19) or by the presence of low-voltage abnormal electrograms with excellent pacemap for the targeted VT and noninducibility after ablation (n = 8). VT termination during RV ablation occurred in 15 patients. After median follow-up of 20 months (interquartile range 9-53 months) and median of 2 procedures (interquartile range 1-3), 22 of 27 patients (80%) had no VT recurrence and 11 (41%) died. CONCLUSION: The RV contains critical substrate elements of postinfarction VT in at least 2.1% of cases. RV mapping should be considered in cases in which LV mapping fails to demonstrate adequate targets, particularly in patients with LBBB morphology VT.

Effect of Transcutaneous Magnetic Stimulation in Patients With Ventricular Tachycardia Storm: A Randomized Clinical Trial.

IMPORTANCE: Autonomic neuromodulation provides therapeutic benefit in ventricular tachycardia (VT) storm. Transcutaneous magnetic stimulation (TcMS) can noninvasively and nondestructively modulate a patient's nervous system activity and may reduce VT burden in patients with VT storm. OBJECTIVE: To evaluate the safety and efficacy of TcMS of the left stellate ganglion for patients with VT storm. DESIGN, SETTING, AND PARTICIPANTS: This double-blind, sham-controlled randomized clinical trial took place at a single tertiary referral center between August 2019 and July 2021. The study included 26 adult patients with 3 or more episodes of VT in 24 hours. INTERVENTIONS: Patients were randomly assigned to receive a single session of either TcMS that targeted the left stellate ganglion (n = 14) or sham stimulation (n = 12). MAIN OUTCOMES AND MEASURES: The primary outcome was freedom from VT in the 24-hour period following randomization. Key secondary outcomes included safety of TcMS on cardiac implantable electronic devices, as well as burden of VT in the 72-hour period following randomization. RESULTS: Among 26 patients (mean [SD] age, 64 [13] years; 20 [77%] male), a mean (SD) of 12.7 (10.3) episodes of VT occurred within the 24 hours preceding randomization. Patients had recurrent VT despite taking a mean (SD) of 2.0 (0.6) antiarrhythmic drugs (AADs), and 11 patients (42%) required mechanical hemodynamic support at the time of randomization. In the 24-hour period after randomization, VT recurred in 4 of 14 patients (29% [SD 47%]) in the TcMS group vs 7 of 12 patients (58% [SD 51%]) in the sham group (P = .20). In the 72-hour period after randomization, patients in the TcMS group had a mean (SD) of 4.5 (7.2) episodes of VT vs 10.7 (13.8) in the sham group (incidence rate ratio, 0.42; P < .001). Patients in the TcMS group were taking fewer AADs 24 hours after randomization compared with baseline (mean [SD], 0.9 [0.8] vs 1.8 [0.4]; P = .001), whereas there was no difference in the number of AADs taken for the sham group (mean [SD], 2.3 [0.8] vs 1.9 [0.5]; P = .20). None of the 7 patients in the TcMS group with a cardiac implantable electronic device had clinically significant effects on device function. CONCLUSIONS AND RELEVANCE: In this randomized clinical trial, findings support the potential for TcMS to safely reduce the burden of VT in the setting of VT storm in patients with and without cardiac implantable electronic devices and inform the design of future trials to further investigate this novel treatment approach. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT04043312.

Isolated critical epicardial arrhythmogenic substrate abnormalities in patients with arrhythmogenic right ventricular cardiomyopathy and ventricular tachycardia.

BACKGROUND: Ventricular tachycardia (VT) substrate abnormalities in arrhythmogenic right ventricular cardiomyopathy (ARVC) typically involve both the right ventricular (RV) endocardium (ENDO) and epicardium (EPI). OBJECTIVE: The purpose of this study was to examine the prevalence, electrophysiological features, and outcomes of catheter ablation of VT in patients with isolated epicardial substrate (IES) abnormalities. METHODS: We studied 71 consecutive patients with VT who met Task Force criteria for ARVC and underwent detailed ENDO and EPI mapping. Patients with critical IES demonstrated (1) confluent EPI bipolar abnormal electrograms (EGMs) and (2) no or minor (<5.0 cm2) RV ENDO low bipolar voltage. Induced VTs were localized using activation mapping, entrainment mapping, and/or pacemapping. RESULTS: Twelve patients (17%) had IES. Extensive EPI bipolar low-voltage area (Bi-LVA; 74 ± 40 cm2) and EGM abnormalities were identified in all patients. Uni-ENDO LVA (<5.5 mV) was seen in 11 of 12 patients (92%) (41 ± 25 cm2) and corresponded to EPI RV bipolar abnormalities. A median of 2 VTs (range 1-7; cycle length 288 ± 68 ms) were induced and localized to the EPI. EPI ablation resulted in noninducibility of all targeted VTs. Preablation cardiac magnetic resonance (CMR) imaging was performed in 10 of 12 patients with RV dyskinesis and/or late gadolinium enhancement in only 4 of 10 patients. During follow-up of 56 ± 46 months, 9 of 12 patients (75%) remained VT-free. CONCLUSION: In patients with ARVC and VT, substrate abnormalities can uncommonly be isolated to the RV EPI. Detection of critical IES may be limited with CMR imaging but suggested by ENDO unipolar EGM abnormalities. EPI ablation eliminates VT in these patients and typically results in long-term VT-free survival.

Substrate Characterization and Outcome of Catheter Ablation of Ventricular Tachycardia in Patients With Nonischemic Cardiomyopathy and Isolated Epicardial Scar.

BACKGROUND: The substrate for ventricular tachycardia (VT) in left ventricular (LV) nonischemic cardiomyopathy may be epicardial. We assessed the prevalence, location, endocardial electrograms, and VT ablation outcomes in LV nonischemic cardiomyopathy with isolated epicardial substrate. METHODS: Forty-seven of 531 (9%) patients with LV nonischemic cardiomyopathy and VT demonstrated normal endocardial (>1.5 mV)/abnormal epicardial bipolar low-voltage area (LVA, <1.0 mV and signal abnormality). Abnormal endocardial unipolar LVA (≤8.3 mV) and endocardial bipolar split electrograms and predictors of ablation success were assessed. RESULTS: Epicardial bipolar LVA (27.3 cm2 [interquartile range, 15.8-50.0]) localized to basal (40), mid (8), and apical (3) LV with basal inferolateral LV most common (28/47, 60%). Of 44 endocardial maps available, 40 (91%) had endocardial unipolar LVA (24.5 cm2 [interquartile range, 9.4-68.5]) and 29 (67%) had characteristic normal amplitude endocardial split electrograms opposite the epicardial LVA. At mean of 34 months, the VT-free survival was 55% after one and 72% after multiple procedures. Greater endocardial unipolar LVA than epicardial bipolar LVA (hazard ratio, 10.66 [CI, 2.63-43.12], P=0.001) and number of inducible VTs (hazard ratio, 1.96 [CI, 1.27-3.00], P=0.002) were associated with VT recurrence. CONCLUSIONS: In patients with LV nonischemic cardiomyopathy and VT, the substrate may be confined to epicardial and commonly basal inferolateral. LV endocardial unipolar LVA and normal amplitude bipolar split electrograms identify epicardial LVA. Ablation targeting epicardial VT and substrate achieves good long-term VT-free survival. Greater endocardial unipolar than epicardial bipolar LVA and more inducible VTs predict VT recurrence.

Impact of left atrial posterior wall isolation on arrhythmia outcomes in patients with atrial fibrillation undergoing repeat ablation.

BACKGROUND: It remains unclear whether additional left atrial posterior wall isolation (LAPWI) beyond pulmonary vein reisolation (PVRI) is beneficial in atrial fibrillation (AF) patients undergoing repeat ablation. OBJECTIVE: We sought to assess impact of LAPWI on arrhythmia outcomes in patients undergoing repeat AF ablation. METHODS: All AF patients that underwent repeat ablation between January 2016 and December 2018 were included. Those undergoing PVRI only served as control, whereas those undergoing LAPWI (with or without PVRI) were the study group. Primary endpoint was freedom from atrial arrhythmias (AA) off antiarrhythmic drugs (AADs) at 1 year follow-up. Secondary endpoint was freedom from AA on/off AADs at 1 year follow-up. RESULTS: One hundred ninety-six patients (61% paroxysmal AF, 39% persistent AF) participated; 93 underwent PVRI and 103 underwent LAPWI±PVRI. Patients in the LAPWI group were older, had more hypertension and persistent AF, and had lower rates of PV reconnection (52.4% vs 100%, P < .001). LAPWI was performed empirically in 79.6% and to target triggers in 20.4%. It was accomplished by linear lesions across the LA floor and roof alone in 65% and additional LAPW lesions in 35%. The primary and secondary endpoints were similar between patients undergoing LAPWI and those undergoing PVRI (43.7% vs 69.9%, P = .50 and 66% vs 77.4%, P = .36, respectively). There was no difference in adverse events between the 2 groups. CONCLUSION: LAPWI did not improve freedom from atrial arrhythmias on or off AADs at 1 year beyond PVRI in AF patients undergoing repeat ablation. Differences in patient demographics and AF type may underlie the observed lack of benefit of LAPWI, and further study is warranted.