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Background: Recurrent ventricular tachycardia (VT) after prior endocardial catheter ablation(s) presents challenges in the setting of prior cardiac surgery where percutaneous epicardial access may not be feasible., Objective: The purpose of this study was to compare the outcomes of cryothermal vs radiofrequency ablation in direct surgical epicardial access procedures., Methods: We performed a retrospective study of consecutive surgical epicardial VT ablation cases. Surgical cases using cryothermal vs radiofrequency ablation were analyzed and outcomes were compared., Results: Between 2009 and 2022, 43 patients underwent either a cryothermal (n = 17) or a radiofrequency (n = 26) hybrid epicardial ablation procedure with direct surgical access. Both groups were similarly matched for age, sex, etiology of VT, and comorbidities with a high burden of refractory VT despite previous endocardial and/or percutaneous epicardial ablation procedures. The surgical access site was lateral thoracotomy (76.5%) in the cryothermal ablation group compared with lateral thoracotomy (42.3%) and subxiphoid approach (38.5%) in the radiofrequency group, with the remainder in both groups performed via median sternotomy. The ablation time was significantly shorter in those undergoing cryothermal ablation vs radiofrequency ablation (11.54 ± 15.5 minutes vs 48.48 ± 23.6 minutes; P < .001). There were no complications in the cryothermal ablation group compared with 6 patients with complications in the radiofrequency group. Recurrent VT episodes and all-cause mortality were similar in both groups., Conclusion: Hybrid surgical VT ablation with cryothermal or radiofrequency energy demonstrated similar efficacy outcomes. Cryothermal ablation was more efficient and safer than radiofrequency in a surgical setting and should be considered when surgical access is required., (Copyright © 2023 Heart Rhythm Society. All rights reserved.)

Patients with repaired tetralogy of Fallot are at elevated risk for ventricular arrhythmia and sudden cardiac death. Over the past decade, the pathogenesis and natural history of ventricular tachycardia has become increasingly understood, and catheter ablation has emerged as an effective treatment modality. Concurrently, there has been great progress in the development of a versatile array of transcatheter valves that can be placed in the native right ventricular outflow tract for the treatment of long-standing pulmonary regurgitation. Although such valve platforms may eliminate the need for repeat cardiac operations, they may also impede catheter access to the myocardial substrates responsible for sustained macro-reentrant ventricular tachycardia. This manuscript provides the rationale and design of a recently devised multicenter study that will examine the clinical outcomes of a uniform, preemptive strategy to eliminate ventricular tachycardia substrates before transcatheter pulmonary valve implantation in patients with tetralogy of Fallot., Competing Interests: Declaration of Competing Interest Drs. Aboulhosn and Levi report a relation with Edwards Lifesciences Corp. that includes consulting or advisory and with Medtronic Inc. that includes consulting or advisory. The remaining authors have no competing interests to declare., (Published by Elsevier Inc.)

Introduction: Cryoablation in open-chest surgical interventions for ventricular arrhythmias has been reported with reasonable procedural outcomes. However, the characteristics of cryoablation lesions on the ventricular myocardium are not well defined. The purpose of the present study was to determine the tissue and vascular effects of a linear epicardial cryoablation probe in a porcine animal model., Methods: Five adult Yorkshire swine underwent median sternotomy and application of linear cryoablation lesions using a malleable aluminum linear cryoablation probe of varying duration (2, 3, 4, and 5 min), including one lesion placed intentionally over the left anterior descending coronary (LAD) artery. Histological analysis was performed., Results: Maximum lesion depth was approximately 1.0 cm with 3 min freezes, with no significant increase in depth achieved with longer lesions. No transmural lesions were achieved. No large vessel epicardial coronary artery injuries were seen to the LAD; however, surprisingly, remote isolated interventricular septal injury was seen in all animals, suggestive of possible compromise of smaller coronary arterial vessels., Conclusion: Single application freezes with an aluminum linear cryoablation probe can create homogeneous ablative lesions over the ventricular myocardium with a maximum depth of approximately 1.0 cm. No large vessel injury occurred with direct lesion application of the LAD; however, small coronary vessels may be at risk., (© 2023 Wiley Periodicals LLC.)

Background: Positron emission tomography computed tomography (PET-CT) is not routinely used for premature ventricular complexes (PVCs). Whether specific clinical factors are associated with abnormal PET-CT results is not clear., Methods: The treatment courses and baseline characteristics of consecutive patients in a single center between 2012 and 2021, age > 18 years old, and who received 18 F-fluorodeoxyglucose (FDG) PET-CT imaging for evaluation of PVCs were retrospectively analyzed., Results: A total of 102 patients was included. Of these, 27 patients (26.4%) had abnormal PET-CT and 61 (59.8%) had normal imaging. Abnormal PET-CT findings were associated with non-sustained ventricular tachycardia (NSVT) (95.2% vs. 52.6%, p = 0.001), higher number of PVC morphologies (2.29 ± 0.7 vs. 1.31 ± 0.6, p < 0.001), greater PVC coupling interval dispersion (72.47 ± 66.4 ms vs. 13.42 ± 17.9 ms, p < 0.001), and greater likelihood of fast heart rate dependent PVCs (78.5% vs. 38.2%, p = 0.017). Fourteen (51.8%) patients had an abnormal PET-CT and abnormal late gadolinium enhancement (LGE). Patients with abnormal PET-CT were more frequently treated with immunosuppression (81.4% vs. 3.2%, p < .0001) than with catheter ablation (11.1% vs. 45.9%, p = 0.002) compared to the normal PET-CT group. Over a median follow-up of 862 days (IQR 134, 1407), PVC burden decreased in both groups [from 23 ± 16% to 9 ± 10% (p < 0.001) in abnormal PET-CT group and from 21 ± 15% to 7 ± 10% (p < 0.001) in normal PET-CT group]., Conclusions: Abnormal PET-CT findings were more commonly associated with NSVT, multiform PVCs, greater PVC coupling interval dispersion, and fast heart rate dependent PVCs. LGE was not sensitive for detecting inflammation. Immunosuppression was effective in managing PVCs with abnormal PET-CT., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

The left ventricular summit corresponds to the epicardial side of the basal superior free wall, extending from the base of the left coronary aortic sinus. The summit composes the floor of the compartment surrounded by the aortic root, infundibulum, pulmonary root, and left atrial appendage. The compartment is filled with thick adipose tissue, carrying the coronary vessels. Thus, the treatment of ventricular tachycardia originating from the summit is challenging, and three-dimensional understanding of this complicated region is fundamental. We revisit the clinical anatomy of the left ventricular summit with original images from the Wallace A. McAlpine collection., Competing Interests: Disclosure The authors have nothing to disclose., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Background: Mapping techniques to identify diseased myocardial substrate during ventricular tachycardia ablation procedures remain limited., Objective: We hypothesized that tissue derivative of the voltage with respect to time (dV/dt), the slope of the unipolar ventricular electrogram registered by local ventricular activation, represents a unique parameter for identifying potential arrhythmogenic tissue in the ischemic scar border zone., Methods: Using high-resolution electrical mapping, we examined dV/dt characteristics in the border zone of animals after chronic myocardial infarction (MI)., Results: Minimum dV/dt (dV/dt min ) in MI animals was less than that in control animals (-344.7 ± 68.7 in controls vs -174.2 ± 104.5 in MI; P < .001) and related to ventricular fibrosis. In MI animals, dV/dt min values were divided into high (≤-200 μV/ms) and low (>-200 μV/ms) dV/dt min . Low dV/dt min regions harbored arrhythmogenic substrates that were characterized by (1) high responsiveness to sympathetic stimulation, (2) presence of late potentials, and (3) lower unipolar and bipolar voltage amplitudes., Conclusion: Our data indicate that dV/dt min is a unique parameter for identifying arrhythmogenic myocardium and may add a useful metric to conventional mapping strategies., (Copyright © 2022. Published by Elsevier Inc.)

Background: Recurrent ventricular tachycardia (VT) due to dilated cardiomyopathy (DCM) is difficult to treat, and long-term outcome data are limited., Objectives: The aim of this study was to identify predictors of mortality or heart transplantation (HTx) and VT recurrence., Methods: Consecutive patients with DCM accepted for radiofrequency catheter ablation (RFCA) of VT at 9 centers were prospectively enrolled and followed., Results: Of 281 consecutive patients (mean age 60 ± 13 years, 85% men, mean left ventricular ejection fraction [LVEF] 36% ± 12%), 35% had VT storm, 20% had incessant VT, and amiodarone was unsuccessful in 68%. During follow-up of 21 months (IQR: 6-30 months), 67 patients (24%) died or underwent HTx, and 138 (49%) had VT recurrence (45 within 30 days, defined as early); the 4-year rate of VT recurrence or mortality or HTx was 70%. Independent predictors of mortality or HTx were early VT recurrence (HR: 2.92; 95% CI: 1.37-6.21; P < 0.01), amiodarone at discharge (HR: 3.23; 95% CI: 1.43-7.33; P < 0.01), renal dysfunction (HR: 1.92; 95% CI: 1.01-3.64; P = 0.046), and LVEF (HR: 1.36; 95% CI: 1.0-1.84; P = 0.052). LVEF ≤32% identified patients at risk for mortality or HTx (area under the curve: 0.75). Mortality or HTx per 100 person-years was 40.4 events after early, compared with 14.2 events after later VT recurrence and 8.5 events with no VT recurrence after RFCA (P < 0.01 for both). Patients with early recurrence and LVEFs ≤32% had a 1-year rate of mortality or HTx of 55%. VT recurrence was predicted by prior implantable cardioverter-defibrillator shocks, basal anteroseptal VT origin, and procedural failure but not LVEF., Conclusions: Patients with DCM needing RFCA for VT are a high-risk group. Following RFCA, approximately one-half remain free of VT recurrence. Early VT recurrence with LVEF ≤32% identifies those at very high risk for mortality or HTx, and screening for mechanical support or HTx should be considered. Late VT recurrence after RFCA does not predict worse outcome., Competing Interests: Funding Support and Author Disclosures This study was partially supported by an investigator-initiated grant (IIS-310) from Biosense Webster (a Johnson & Johnson company). Dr Zeppenfeld has received research grants from Biosense Webster to the Department of Cardiology at Leiden University Medical Center. Dr Wijnmaalen has received research grants from Biosense Webster to the Department of Cardiology at Leiden University Medical Center. Dr Berruezo is a stockholder in ADAS3D; and has received research grants from Biosense Webster and Biotronik. Dr Vaseghi is an educational consultant for Biosense Webster; and holds founder shares in NeuCures. Dr de Riva has received research grants from Biosense Webster to the Department of Cardiology at Leiden University Medical Center. Dr Piorkowski is chief medical officer of Abbott EP. Dr Stevenson has received speaker honoraria from Abbott, Boston Scientific, Biotronik, Johnson & Johnson, and Medtronic; and has received a research grant from Thermedical. 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.)

Introduction: Patients with prior cardiac surgery may represent a subgroup of patients with ventricular tachycardia (VT) that may be more difficult to control with catheter ablation., Methods: We evaluated 1901 patients with ischemic and nonischemic cardiomyopathy who underwent VT ablation at 12 centers. Clinical characteristics and VT radiofrequency ablation procedural outcomes were assessed and compared between those with and without prior cardiac surgery. Kaplan-Meier analysis was used to estimate freedom from recurrent VT and survival., Results: There were 578 subjects (30.4%) with prior cardiac surgery identified in the cohort. Those with prior cardiac surgery were older (66.4 ± 11.0 years vs. 60.5 ± 13.9 years, p < .01), with lower left ventricular ejection fraction (30.2 ± 11.5% vs. 34.8 ± 13.6%, p < .01) and more ischemic heart disease (82.5% vs. 39.3%, p < .01) but less likely to undergo epicardial mapping or ablation (9.0% vs. 38.1%, p<.01) compared to those without prior surgery. When epicardial mapping was performed, a significantly greater proportion required surgical intervention for access (19/52 [36.5%] vs. 14/504 [2.8%]; p < .01). Procedural complications, including epicardial access-related complications, were lower (5.7% vs. 7.0%, p < .01) in patients with versus without prior cardiac surgery. VT-free survival (75.1% vs. 74.1%, p = .805) and survival (86.5% vs. 87.9%, p = .397) were not different between those with and without prior heart surgery, regardless of etiology of cardiomyopathy. VT recurrence was associated with increased mortality in patients with and without prior cardiac surgery., Conclusion: Despite different clinical characteristics and fewer epicardial procedures, the safety and efficacy of VT ablation in patients with prior cardiac surgery is similar to others in this cohort. The incremental yield of epicardial mapping in predominant ischemic cardiomyopathy population prior heart surgery may be low but appears safe in experienced centers., (© 2020 Wiley Periodicals LLC.)

Background Cardiac sympathetic denervation (CSD) has been used as a bailout strategy for refractory ventricular tachycardia (VT). Risk of VT recurrence in patients with scar-related monomorphic VT referred for CSD and the extent to which CSD can modify this risk is unknown. We aimed to quantify arrhythmia recurrence risk and impact of CSD in this population. Methods and Results Adjusted competing risk time to event models were developed to adjust for risk of VT recurrence and sustained VT/implantable cardioverter-defibrillator shocks after VT ablation based on patient comorbidities at the time of VT ablation. Adjusted VT and implantable cardioverter-defibrillator shock recurrence rates were estimated for the subgroup who subsequently required CSD after ablation. The expected adjusted recurrence rates were then compared with the observed rates after CSD. Data from 381 patients with scar-mediated monomorphic VT who underwent VT ablation were analyzed, excluding patients with polymorphic VT. Sixty eight patients underwent CSD for recurrent VT. CSD reduced the expected adjusted VT recurrence rate by 36% (expected rate of 5.61 versus observed rate of 3.58 per 100 person-months, P =0.01) and the sustained VT/implantable cardioverter-defibrillator shock rates by 34% (expected rate of 4.34 versus observed 2.85 per 100 person-months, P =0.03). The median number of sustained VT/implantable cardioverter-defibrillator shocks in the year before versus the year after CSD was reduced by 90% (10 versus 1, P <0.0001). Conclusions Patients referred for CSD for refractory scar-mediated monomorphic VT are at a higher risk of VT recurrence after ablation as compared with those not requiring CSD, mostly because of their cardiac comorbidities. CSD significantly reduced both the expected risk of recurrences and VT burden.

Aims: Catheter ablation is an effective treatment for post-infarction ventricular tachycardia (VT). However, some patients may experience a worsened arrhythmia phenotype after ablation. We aimed to determine the prevalence and prognostic impact of arrhythmia exacerbation (AE) after post-infarction VT ablation., Methods and Results: A total of 1187 consecutive patients (93% men, median age 68 years, median ejection fraction 30%) who underwent post-infarction VT ablation at six centres were included. Arrhythmia exacerbation was defined as post-ablation VT storm or incessant VT in patients without prior similar events. During follow-up (median 717 days), 426 (36%) patients experienced VT recurrence. Events qualifying as AE occurred in 67 patients (6%). Median times to VT recurrence with and without AE were 238 [interquartile range (IQR) 35-640] days and 135 (IQR 22-521) days, respectively (P = 0.25). Almost half of the patients (46%) who experienced AE experienced it within 6 months of the index procedure. Patients with AE had had longer ablation times during the ablation procedures compared to the rest of the patients (median 42 vs. 34 min, P = 0.02). Among patients with VT recurrence, the risk of death or heart transplantation was significantly higher in patients with than without AE (hazard ratio 1.99, 95% CI 1.28-3.10; P = 0.002) after adjusting for age, gender, ejection fraction, cardiac resynchronization therapy, post-ablation non-inducibility, and post-ablation amiodarone use., Conclusion: Arrhythmia exacerbation after ablation of infarct-related VT is infrequent but is independently associated with an adverse long-term outcome among patients who experience a VT recurrence. The mechanisms and mitigation strategies of AE after catheter ablation require further investigation., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2020. For permissions, please email: journals.permissions@oup.com.)

Introduction: Cardiac sympathetic denervation (CSD) is utilized for the management of ventricular tachycardia (VT) in structural heart disease when refractory to radiofrequency ablation (RFA) or when patient/VT characteristics are not conducive to RFA., Methods: We studied consecutive patients who underwent CSD at our institution from 2009 to 2018 with VT requiring repeat RFA post-CSD. Patient demographics, VT/procedural characteristics, and outcomes were assessed., Results: Ninety-six patients had CSD, 16 patients underwent RFA for VT post-CSD. There were 15 male and 1 female patients with mean age of 54.2 ± 13.2 years. Fourteen patients had nonischemic cardiomyopathy. A mean of 2.0 ± 0.8 RFAs for VT was unsuccessful before the patient undergoing CSD. The median time between CSD and RFA was 104 days (interquartile range [IQR] = 15-241). The clinical VT cycle length was significantly increased after CSD both spontaneously on ECG and/or ICD interrogation (355 ± 73 ms pre-CSD vs. 422 ± 94 ms post-CSD, p = .001) and intraprocedurally (406 ± 86 ms pre-CSD vs. 457 ± 88 ms post-CSD, p = .03). Two patients had polymorphic and 14 had monomorphic VT (MMVT) pre-CSD, and all patients had MMVT post-CSD. The proportion of mappable, hemodynamically stable VTs increased from 35% during pre-CSD RFA to 58% during post-CSD RFA (p = .038). At median follow-up of 413 days (IQR = 43-1840) after RFA, eight patients had no further VT., Conclusion: RFA for recurrent MMVT post-CSD is a reasonable treatment option with intermediate-term clinical success in 50% of patients. Clinical VT cycle length was significantly increased after CSD with associated improvement in mappable, hemodynamically tolerated VT during RFA., (© 2020 Wiley Periodicals LLC.)

Background: Autonomic modulation is finding an increasing role in the treatment of ventricular arrhythmias. Renal denervation (RDN) has been described as a treatment modality for refractory ventricular tachycardia (VT) in case series., Objective: The purpose of this study was to evaluate RDN as an adjunctive therapy to cardiac sympathetic denervation (CSD) for ablation refractory VT., Methods: Patients who underwent RDN after radiofrequency ablation and CSD procedures at our center from 2012 to 2019 were evaluated., Results: Ten patients underwent RDN after CSD (9 bilateral and 1 left-sided only) with a median follow-up of 23 months. The mean age was 59.9 ± 10.4 years, and 9/10 (90%) were men. All had cardiomyopathy with a mean ejection fraction of 33% ± 11% (20% ischemic). Four (40%) underwent CSD during the same hospitalization as that for RDN. Patients who underwent RDN as adjunctive therapy to CSD had a decrease in all implantable cardioverter-defibrillator therapies (shocks + antitachycardia pacing [ATP]) from 29.5 ± 25.2 to 7.1 ± 10.1 comparing 6 months pre-RDN to 6 months post-RDN (P = .028). Implantable cardioverter-defibrillator shocks were significantly decreased from 7.0 ± 6.1 to 1.7 ± 2.5 comparing 6 months pre-RDN to 6 months post-RDN (P = .026). This benefit was driven by a decrease in therapies for 6 patients who had a staged procedure, not performed during the same hospitalization (28.5 ± 24.3 to 1.0 ± 1.2; P = .043)., Conclusion: RDN demonstrates the potential benefit when VT recurs after radiofrequency ablation and CSD. The benefit is seen in patients who undergo a staged procedure. The need for acute RDN after CSD portends a poor prognosis., (Copyright © 2019 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Recurrences of atrial fibrillation (AF) after ablation have been attributed to conduction gaps and nontransmural ablation lesions., Objective: The purpose of this study was to assess the feasibility of adjunctive percutaneous mapping of the epicardial regions of the left atrium to characterize the transmural extent of substrate and ablation lesions., Methods: Between 2014 and 2018, combined epicardial and endocardial mapping of AF was performed in 18 patients via an inferior subxiphoid percutaneous approach (16 with previously failed ablation procedures and 2 patients with long-standing persistent AF) at 2 centers. Epicardial substrate mapping was compared with endocardial mapping to assess transmural uniformity., Results: Of 18 patients, 4 (22%) demonstrated nontransmural atrial low-voltage regions with relative epicardial sparing in the left atrial posterior wall. Transmural isolation of the posterior wall was achieved after an endocardial "box" lesion set in 6/9 (67%), guided by epicardial voltage data, while epicardial and endocardial dissociation during AF was observed in 1 patient. In 3 patients, epicardial capture along the endocardial pulmonary vein lesion set despite endocardial capture loss and bidirectional block was observed. Two cases of mitral flutter were terminated from the epicardium. A balloon was positioned in the pericardial space in 6 patients for esophageal protection during ablation., Conclusion: A percutaneous epicardial approach for mapping and ablation of the left atrium is feasible in the electrophysiology laboratory during endocardial catheter ablation for AF and may be useful as an adjunctive approach in refractory cases. High-density epicardial mapping can provide direct evidence of nonuniform lesion and substrate transmurality of the human left atrium before and after ablation., (Copyright © 2019 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Persistent left superior vena cava (PLSVC) is one of the most frequently reported congenital anomalies and may be an important source of trigger of atrial fibrillation (AF)., Methods: This was a multicenter retrospective experience including 28 patients with PLSVC who were referred for catheter ablation for drug-refractory symptomatic AF. Pulmonary vein and PLSVC isolation were performed (3.5-mm open irrigated tip ablation catheter at maximum power of 20 W, maximum temperature 43 °C with flow rate of 17 ml/min). Clinical outcomes such as complications and long-term freedom from AF were measured., Results: The mean age of the population was 61 ± 8 years, 21% were females, and AF duration was 60 ± 33 months. Sixty-one percent paroxysmal AF (17/28), 25% (7/28) persistent AF, and 14% (4/28) had long-standing persistent AF. There were no major complications that required any intervention. PLSVC isolation was achieved in 96% (27/28). Freedom from AF at 1 year without antiarrhythmic drugs was seen in 75% (21/28) of patients., Conclusions: In PLSVC patients with AF, segmental isolation of PLSVC appears to be feasible and safe and can translate into favorable clinical outcomes.

Background: Several distinct risk factors for arrhythmia recurrence and mortality following ventricular tachycardia (VT) ablation have been described. The effect of concurrent risk factors has not been assessed so far; thus, it is not yet possible to estimate these risks for a patient with several comorbidities. The aim of the study was to identify specific risk groups for mortality and VT recurrence using the Survival Tree (ST) analysis method., Methods: In 1251 patients 16 demographic, clinical and procedure-related variables were evaluated as potential prognostic factors using ST analysis using a recursive partitioning algorithm that searches for relationships among variables. Survival time and time to VT recurrence in groups derived from ST analysis were compared by a log-rank test. A random forest analysis was then run to extract a variable importance index and internally validate the ST models., Results: Left ventricular ejection fraction, implantable cardioverter defibrillator/cardiac resynchronization device, previous ablation were, in hierarchical order, identified by ST analysis as best predictors of VT recurrence, while left ventricular ejection fraction, previous ablation, Electrical storm were identified as best predictors of mortality. Three groups with significantly different survival rates were identified. Among the high-risk group, 65.0% patients were survived and 52.1% patients were free from VT recurrence; within the medium- and low-risk groups, 84.0% and 97.2% patients survived, 72.4% and 88.4% were free from VT recurrence, respectively., Conclusions: Our study is the first to derive and validate a decisional model that provides estimates of VT recurrence and mortality with an effective classification tree. Preprocedure risk stratification could help optimize periprocedural and postprocedural care.

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.)

Background: Idiopathic ventricular ectopy (VE) shows predilection to sites within the left ventricular (LV) base such as the outflow tract/aortic sinuses, LV summit, and areas adjacent to the aortomitral continuity. We characterize VE arising from the inferior septum of the LV base that was successfully managed by LV endocardial ablation from the inferoseptal recess of the LV., Objective: The purpose of this study was to determine the incidence, electrocardiographic (ECG) findings, electrophysiological findings, and anatomical features associated with VE arising from the basal inferoseptal process of the LV (ISP-LV) ablated using an LV endocardial approach via the inferoseptal recess of the LV., Methods: A total of 425 consecutive patients undergoing VE ablation between January 1, 2012 and December 31, 2016 at 3 centers were evaluated. Demographic characteristics, ECG findings, and procedural data were analyzed for patients with ISP-LV VEs., Results: Seven (1.5%) had a site of origin from the ISP-LV. Common ECG findings were a right bundle branch block concordant pattern or an atypical left bundle branch block early transition pattern, suggestive of a basal origin with a left superior axis, a biphasic QRS complex in lead aVR, and a small s wave in lead V 6 . Earliest activation was seen in an area below the outflow tract accessed from the inferoseptal recess inferior to the His bundle. In 3 cases, transient junctional rhythm was seen during ablation. All cases were ablated successfully with no complications., Conclusion: VE arising from the ISP-LV represents a distinct subset of idiopathic arrhythmia and can be successfully treated by endocardial catheter ablation from the inferoseptal recess. They share common surface ECG and electrophysiological findings with special anatomical features that need recognition for successful catheter ablation., (Copyright © 2018 Heart Rhythm Society. 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.)

Background: There is limited experience of surgical epicardial access in the contemporary era of ventricular tachycardia ablation after cardiac surgery., Objectives: The purpose of this study was to describe our institutional experience with surgical epicardial access and the influence of surgical approach and compare outcomes with those of a propensity-matched percutaneous epicardial access control group., Methods: We performed a retrospective study of consecutive surgical epicardial ventricular tachycardia (VT) ablation cases from a single center. Surgical cases were propensity-matched to percutaneous epicardial ablation controls and short-term and long-term outcomes were compared., Results: Between 2004 and 2016, 38 patients underwent 40 surgical epicardial access procedures (subxiphoid, n = 22; thoracotomy, n = 18). The commonest indication was prior coronary artery bypass grafting (45%), valve surgery (22%), or ventricular assist device (VAD) (10%). The mean procedure time was 444 minutes (standard deviation, 107 minutes). Mapped epicardial geometry area was 149 cm 2 (interquartile range 182 cm 2 ), which comprised 36% of the mapped epicardial geometric area of a percutaneous control group. Subxiphoid access gave preferential access to the inferior and inferolateral left ventricular segments and was less frequently able to access the anterior, anterolateral, and apical segments compared with a thoracotomy approach. When compared with results from a propensity-matched percutaneous-access group, short-term outcomes, complication rates, and 1-year survival free from a combined end point of VT recurrence, death, or transplantation were not statistically different., Conclusions: Surgical epicardial access after cardiac surgery for ablation of VT in patients with careful preprocedure evaluation can be performed with acceptable safety with no statistical difference in long-term outcomes compared with a propensity-matched percutaneous epicardial cohort. The region of left ventricular epicardium that can be mapped is limited compared with that of percutaneous cases and is determined by the surgical approach., (Copyright © 2017 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Infrequent intraprocedural premature ventricular complexes (PVCs) may impede radiofrequency catheter ablation (RFA) outcome, and pharmacologic induction is unpredictable., Objective: The purpose of this study was to determine whether PVC circadian variation could help predict drug response., Methods: Consecutive patients referred for RFA with detailed Holter monitoring and frequent monomorphic PVCs were included. Patients were divided into 3 groups based on hourly PVC count relationship to corresponding mean heart rate (HR) during each of the 24 hours on Holter: fast-HR-dependent PVC (F-HR-PVC) type for a positive correlation (Pearson, P <.05), slow-HR-dependent PVC (S-HR-PVC) type for a negative correlation, and independent-HR-PVC (I-HR-PVC) when no correlation was found., Results: Fifty-one of the 101 patients (50.5%) had F-HR-PVC, 39.6% I-HR-PVC, and 9.9% S-HR-PVC; 30.7% had infrequent intraprocedural PVC requiring drug infusion. The best predictor of infrequent PVC was number of hours with PVC count <120/h on Holter (area under the curve 0.80, sensitivity 83.9%, specificity 74.3%, for ≥2 h). Only F-HR-PVC patients responded to isoproterenol. Isoproterenol washout or phenylephrine infusion was successful for the 3 S-HR-PVC patients, and no drug could increase PVC frequency in the 12 I-HR-PVC patients. Long-term RFA success rate in patients with frequent PVCs at baseline (82.9%) was similar to those with infrequent PVC who responded to a drug (77.8%; P = .732) but significantly higher than for those who did not respond to any drug (15.4%; P <.0001)., Conclusion: A simple analysis of Holter PVC circadian variability provides incremental value to guide pharmacologic induction of PVCs during RFA and predict outcome. Patients with infrequent I-HR-PVC had the least successful outcomes from RF ablation., (Copyright © 2017 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Pericardial adhesions can prevent epicardial access and restrict catheter movement during mapping and ablation of ventricular tachycardia (VT). The incidence of adhesions in patients without prior cardiac surgery or clinically evident pericarditis is not known., Objective: To describe the incidence of pericardial adhesions and explore their impact in patients without prior cardiac surgery or pericarditis., Methods: A retrospective search of our ablation database containing patients who underwent epicardial ablation for VT was undertaken. Adhesions were diagnosed with routine contrast pericardiography after pericardial entry. Demographics and long-term outcomes were compared between patients with and without adhesions., Results: Between 2004 and 2016, successful epicardial entry was achieved in 188 of 192 attempts (98%). In 155 first-time epicardial access attempts, pericardial adhesions were diagnosed in 13 (8%). When comparing baseline demographics, there was no significant difference. However, adhesions tended to occur more frequently with severe renal impairment (2% of patients without adhesions vs 15% of patients with adhesions, P = .07). No patient with a structurally normal heart had adhesions present. Adhesions were associated with limited epicardial mapping (3% of patients without adhesions vs 85% of patients with adhesions, P < .001) and lower short-term procedural success (68% of patients without adhesions vs 46% of patients with adhesions, P = .02), but complication rates were similar. The presence of adhesions did not translate into lower VT-free survival (P = .64) or freedom from a combined end point of VT recurrence, death, or transplant at 1 year (P = .93)., Conclusion: Adhesions may be unexpectedly encountered in patients without prior cardiac surgery or pericarditis. When present, they can limit mapping and may be associated with lower short-term success. Larger studies are required to determine their impact on long-term outcomes., (Copyright © 2017 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Objective: The purpose of this study was to evaluate the characteristics and outcome of patients undergoing ablation after electrical storm (ES)., Methods: Clinical and procedural characteristics, ventricular tachycardia (VT) recurrence, and mortality rates from 1940 patients undergoing VT ablation were compared between patients with and without ES., Results: The group of 677 patients with ES (34.9%) were older, were more frequently men, and had a lower ejection fraction, more advanced heart failure, and a higher prevalence of cardiovascular comorbidities as compared with those without ES (86.1% patients with ES had ≥2 comorbidities vs 71.4%; P < .001). Patients with ES had more inducible VTs (2.5 ± 1.8 vs 1.9 ± 1.9; P < .001), required longer procedures (296.1 ± 119.1 minutes vs 265.7 ± 110.3 minutes; P < .001), and had a higher in-hospital mortality (42 deaths [6.2%] vs 18 deaths [1.4%]; P < .001). At 1-year follow-up, patients with ES experienced a higher risk of VT recurrence and mortality (32.1% vs 22.6% and 20.1% vs 8.5%; long-rank, P < .001 for both). Among patients with ES, those without any inducible VT after ablation had a higher survival rate (86.3%) than did those with nonclinical VTs only (72.9%), those with clinical VTs inducible at programmed electrical stimulation (51.2%), and not-tested patients (65.0%) (long-rank, P < .001 for all). In multivariate analysis, ES remained an independent predictor of in-hospital mortality, VT recurrence, and 1-year mortality (P < .001)., Conclusion: Patients with ES have a high risk of VT recurrence and mortality. Patient and procedure characteristics are consistent with advanced cardiac disease and longer and more complex procedures. In patients with ES, acute procedural success is associated with a significant reduction in VT recurrence and improved 1-year survival., (Copyright © 2017 Heart Rhythm Society. 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.)

Background: Successful ventricular tachycardia (VT) ablation is associated with improved survival in patients with heart failure. However, the safety and efficacy of VT ablation in the elderly, a population with higher competing nonsudden death risk and comorbidities, have not been well defined., Methods and Results: The International Ventricular Tachycardia Center Collaborative Study Group registry of 2061 patients who underwent VT ablation at 12 international centers was analyzed. Kaplan-Meier analysis was used to estimate survival of patients ≥70 years with and without VT recurrence. Of the 2049 patients who met inclusion criteria, 681 (33%) patients were ≥70 years of age (mean age, 75±4 years). Among these, 92% were men, 71% had ischemic VT, and 42% had VT storm at presentation. Mean (±SD) left ventricular ejection fraction was 30±11%. Compared with patients <70 years, patients ≥70 years had higher in-hospital (4.4% versus 2.3%; P =0.01) and 1-year mortality (15% versus 11%; P =0.002) but a similar incidence of VT recurrence at 1 year (26% versus 25%; P =0.74) and time to VT recurrence (280 versus 289 days; P =0.20). Absence of VT recurrence during follow-up was strongly associated with improved survival in patients ≥70 years., Conclusion: VT ablation in the elderly is feasible and reasonably safe with a modestly higher in-hospital and 1-year mortality, with similar rates of VT recurrence at 1 year compared with younger patients. Successful VT ablation, that is, lack of VT recurrence, is strongly associated with improved survival even in this elderly subgroup., (© 2017 American Heart Association, Inc.)

Objectives: This study hypothesizes that post-extrasystolic potentiation reflects left ventricle contractile reserve and therefore may predict an improvement of premature ventricular contraction (PVC)-induced cardiomyopathy after PVC ablation., Background: Post-extrasystolic potentiation is a physiologic phenomenon of blood pressure accentuation after a PVC beat., Methods: We performed a retrospective study of patients with a PVC burden of ≥10% PVC/24 h and left ventricular ejection fraction (LVEF) of <50% who underwent successful ablation between January 1, 2009, to June 30, 2015. Subjects were classified as having reversible (a final LVEF ≥50%) or irreversible (final LVEF <50%) LV dysfunction on a follow-up echocardiogram. A reference (control) group with ≥10% PVC but normal LV function was also identified., Results: Sixty-one patients (age 68 ± 11 years, 98% male) were studied: 30 with preserved and 31 with reduced LVEF. During median follow-up of 9.4 months, the LVEF of 17 of 31 reduced EF patients improved (reversible) but 14 did not (irreversible). The post-PVC beat systolic blood pressure (SBP) (mm Hg) increase ranged from 12.1 in control subjects (LVEF >50%) to 11.5 in reversible patients to 5 in irreversible patients. In multivariate analysis, the independent predictors of reversible LV function were post-PVC SBP rise (odds ratio [OR]: 4.61; 95% confidence interval [CI]: 1.45 to 15.83 per 5-mm Hg increase; p < 0.001), post-PVC pulse pressure change (OR: 5.2; 95% CI: 2.3 to 18.6 per 5-mm Hg increase; p < 0.001), and PVC QRS duration (OR: 2.78; 95% CI: 1.63 to 10.94 per 10-ms increase; p < 0.001)., Conclusions: In patients with LV dysfunction and frequent PVC, post-PVC SBP accentuation may be a marker for subsequent recovery of LVEF after ablation in presumed PVC-induced cardiomyopathy., (Published by Elsevier Inc.)

Background: Data evaluating repeat radiofrequency ablation (>1RFA) of ventricular tachycardia (VT) are limited., Objective: The purpose of this study was to determine the safety and outcomes of VT >1RFA in patients with structural heart disease., Methods: Patients with structural heart disease undergoing VT RFA at 12 centers with data on prior RFA history were included. Characteristics and outcomes were compared between first-time (1RFA) and >1RFA patients., Results: Of 1990 patients, 740 had >1RFA (mean 1.4 ± 0.9, range 1-10). >1RFA vs 1RFA patients did not differ with regard to age (62 ± 13 years vs 62 ± 13 years), left ventricular ejection fraction (33% ± 13% vs 34% ± 13%), or sex (88% vs 87% men), but they more often were nonischemic (53% vs 41%), had implantable cardioverter-defibrillator shocks (70% vs 63%) or VT storm (38% vs 33%), and had been treated with amiodarone (55% vs 48%) or ≥2 antiarrhythmic drugs (22% vs 14%). >1RFA procedures were longer (300 ± 122 minutes vs 266 ± 110 minutes), involved more epicardial access (41% vs 21%), induced VTs (2.4 ± 2.2 vs 1.9 ± 1.6) and only unmappable VTs (15% vs 9%), and VT was more often inducible after RFA (42% vs 33%, all P <.03). Total complications were higher for >1RFA vs 1RFA (8% vs 5%, P <.01), mostly related to pericardial effusion (2.4% vs 1.3%, P = .07) and venous thrombosis (0.8% vs 0.2%, P = .06). VT recurrence was higher for >1RFA vs 1RFA (29% vs 24%, P <.001). Survival was worse for >1RFA vs 1RFA if VT recurred (67% vs 78%, P = .003) but was equivalent if successful (93% vs 92%, P = .96)., Conclusion: Patients requiring repeat VT ablation differ significantly from those undergoing first-time ablation. Despite more challenging ablation characteristics, VT-free survival after repeat ablations is encouraging. Mortality is comparable if VT does not recur after RFA at specialized centers., (Copyright © 2017 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: In patients referred for radiofrequency catheter ablation (RFCA) of ventricular tachycardia (VT) in the setting of structural heart disease, early post-procedural mortality (EM) has not been previously investigated., Objectives: The purpose of this study was to evaluate EM after catheter ablation of scar-related VT., Methods: Associations between clinical and procedural variables and EM (within 31 days of the procedure) were tested in patients with structural heart disease undergoing RFCA of VT at 12 international centers., Results: Of 2,061 patients (mean age 62 ± 13 years; left ventricular ejection fraction [LVEF] 34 ± 13%; 53% ischemic etiology), EM occurred in 100 (5%; 95% confidence interval [CI]: 4% to 6%). A total of 54 (3%) patients died before hospital discharge (median 9 days after the procedure; 25% for refractory VT), including 12 (0.6%) after a major procedure-related complication. In multivariable analysis, the following factors were found to be significantly associated with EM: LVEF (odds ratio [OR] per percent decrease: 1.12; 95% CI: 1.05 to 1.20; p < 0.001), chronic kidney disease (OR: 2.73; 95% CI: 1.10 to 6.80; p = 0.030), presentation with VT storm (OR: 3.61; 95% CI: 1.37 to 9.48; p = 0.009), and presence of unmappable VTs (OR: 5.69; 95% CI: 1.37 to 23.69; p = 0.017). Recurrent VT was also associated with an increased risk of subsequent death (hazard ratio: 7.19; 95% CI: 5.57 to 9.28; p < 0.001) and EM (hazard ratio: 11.45; 95% CI: 7.47 to 17.59; p < 0.001)., Conclusions: In a contemporary cohort of patients with scar-related VT undergoing RFCA, EM occurred in 5% of cases. Clinical and procedural variables indicating poorer clinical status (low LVEF, chronic kidney disease, VT storm, and unmappable VTs) and post-procedural VT recurrence may predict EM. Identification of such features may prompt early consideration for hemodynamic support or other care to help mitigate later potential complications., (Copyright © 2017 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.)

Ablation of ventricular tachycardia (VT) in the setting of structural heart disease, previously reserved for highly experienced specialized centers, is being performed at more centers internationally as cardiac electrophysiologists gain advanced training. Interventional cardiac electrophysiologists need a high level of anatomic knowledge to guide a procedure that can carry significant risk. Understanding cardiac anatomy improves the chance of procedural success and also the likelihood of appropriate decision making if complications are encountered. This article focuses on selected anatomic regions where complex anatomy can be an impediment to successful VT ablation., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Background: Ventricular tachycardia (VT) radiofrequency ablation has been associated with reduced VT recurrence and mortality, although it is typically not considered among New York Heart Association class IV (NYHA IV) heart failure patients. We compared characteristics and VT radiofrequency ablation outcomes of those with and without NYHA IV in the International VT Ablation Center Collaboration., Methods and Results: NYHA II-IV patients undergoing VT radiofrequency ablation at 12 international centers were included. Clinical variables, VT recurrence, and mortality were analyzed by NYHA IV status using Kaplan-Meier analysis and Cox proportional hazard models. There were significant differences between NYHA IV (n=111) and NYHA II and III (n=1254) patients: NYHA IV had lower left ventricular ejection fraction; more had diabetes mellitus, kidney disease, cardiac resynchronization implantable cardioverter-defibrillator, and VT storm despite greater antiarrhythmic drug use (P<0.01). NYHA IV subjects required more hemodynamic support, were inducible for more and slower VTs, and were less likely to undergo final programmed stimulation. There was no significant difference in acute complications. In-hospital deaths, recurrent VT, and 1-year mortality were higher in the NYHA IV group, in the context of greater baseline comorbidities. Importantly, NYHA IV patients without recurrent VT had similar survival compared with NYHA II and III patients with recurrent VT (68% versus 73%). Early VT recurrence (≤30 days) was significantly associated with mortality, especially in NYHA IV patients., Conclusions: Despite greater baseline comorbidities, VT radiofrequency ablation can be safely performed among NYHA IV patients. Early VT recurrence is significantly associated with subsequent mortality regardless of NYHA status. Elimination of recurrent VT in NYHA IV patients may reduce mortality to a level comparable to NYHA II and III with arrhythmia recurrence., (© 2017 American Heart Association, Inc.)

Background: Recurrence of ventricular tachycardia (VT) after ablation in patients with previous myocardial infarction is associated with adverse prognosis. However, the impact of the timing of VT recurrence on outcomes is unclear., Methods and Results: We analyzed data from a multicenter collaborative database of patients who underwent catheter ablation for infarct-related VT. Multivariable Cox regression analyses investigated the effect of the timing of VT recurrence on the composite outcome of death or heart transplantation using VT recurrence as a time-varying covariate. A total of 1412 patients were included (92% men; age: 66.7±10.7 years), and 605 patients (42.8%) had a recurrence after median 116 days (188 [31.1%] within 1 month, 239 [39.5%] between 1 and 12 months, and 178 [29.4%] after 12 months). At median follow-up of 670 days, 375 patients (26.6%) experienced death or heart transplantation. The median time from recurrence to death or heart transplantation was 65 and 198.5 days in patients with recurrence ≤30 days and >30 days post ablation, respectively. The adjusted hazard ratio (95% confidence interval) for the effect of VT recurrence occurring immediately post ablation on death or heart transplantation was 3.45 (2.33-5.11) in reference to no recurrence. However, the magnitude of this effect decreased statistically significantly (P<0.001) as recurrence occurred later in the follow-up period. The respective risk estimates for VT recurrence at 30 days, 6 months, 1 year, and 2 years were 3.36 (2.29-4.93), 2.94 (2.09-4.14), 2.50 (1.85-3.37), and 1.81 (1.37-2.40)., Conclusions: VT recurrence post ablation is associated with a mortality risk that is highest soon after the ablation and decreases gradually thereafter., (© 2016 American Heart Association, Inc.)

Importance: Significant differences have been described between women and men regarding presentation, mechanism, and treatment outcome of certain arrhythmias. Previous studies of ventricular tachycardia (VT) ablation have not included sufficient women for meaningful comparison., Objective: To compare outcomes between women and men with structural heart disease undergoing VT ablation., Design, Setting, and Participants: Investigator-initiated, multicenter, observational study performed between 2002 and 2013, conducted by the International VT Ablation Center Collaborative Group, consisting of 12 high-volume ablation centers. Consecutive patients with structural heart disease undergoing VT ablation were studied. Structural heart disease was defined as left ventricular ejection fraction less than 55%, hypertrophic cardiomyopathy, or right ventricular cardiomyopathy, with scar confirmed during electroanatomic mapping., Exposures: Catheter ablation., Main Outcomes and Measures: Ventricular tachycardia-free survival and transplant-free survival were compared between women and men. Cox proportional hazard modeling was performed., Results: Of 2062 patients undergoing ablation, 266 (12.9%) were women. Mean (SD) age was 62.4 (13.3) years and 1095 (53.1%) had ischemic cardiomyopathy. Compared with men, women were younger, with higher left ventricular ejection fraction and less VT storm. Despite this, women had higher rates of 1-year VT recurrence following ablation (30.5% vs 25.3%; P = .03). This difference was only partially explained by higher prevalence of nonischemic cardiomyopathy among women and was actually most pronounced among those with ischemic cardiomyopathy., Conclusions and Relevance: In 12 high-volume ablation centers, women with structural heart disease have worse VT-free survival following ablation than men. Whether this is owing to differences in referral pattern, arrhythmia substrate, or undertreatment requires further study.

Background: Catheter ablation in the right ventricular outflow tract (RVOT) may modify the electrophysiologic substrate for recurrent ventricular tachycardia/ventricular fibrillation (VT/VF) in patients with Brugada syndrome (BrS)., Objective: The purpose of this study was to investigate the mechanism and arrhythmogenic substrate of VT/VF and to evaluate the long-term outcomes of catheter ablation in patients with BrS., Methods: Eleven consecutive patients with BrS referred to 2 academic medical centers underwent combined epicardial-endocardial electroanatomic mapping. Catheter ablation was performed in regions of localized conduction slowing. Transmural dispersion of late activation was calculated as the difference between the latest activation between epicardium and endocardium, and low-voltage areas were analyzed., Results: Eleven patients met diagnostic criteria for BrS (spontaneous type 1, n = 9; Na channel provocation = 2). All patients were found to have a localized region in the anterior epicardial RVOT with conduction slowing evidenced by prolonged electrogram duration (78.79 ± 19.87 ms vs 58.93 ± 10.11 ms in epicardial right ventricle, and 59.87 ± 12.61 ms in endocardial RVOT, P <.005, respectively) with variable low voltage (0.97 ± 0.48 mV; median scar area 19.8 ± 25.9 cm 2 ). Epicardial ablation resulted in normalization of spontaneous type 1 Brugada ECG pattern in all patients, and 73% were free from VT/VF at 25 ± 11 months., Conclusion: Prolonged electrograms localized to epicardial RVOT with variable low voltage were identified in all patients with BrS. J-point and ST-segment elevation correlated with greater transmural dispersion of late activation and was independent of total low-voltage area. Despite normalization of spontaneous type 1 pattern in all patients after ablation, recurrence was still observed, suggesting the implantable cardioverter-defibrillator as the cornerstone therapy for BrS., (Copyright © 2016 Heart Rhythm Society. All rights reserved.)

Although considerable progress has been made in developing ablation approaches to cure atrial fibrillation (AF), outcomes are still suboptimal, especially for persistent and long-lasting persistent AF. In this topical review, we review the arrhythmia mechanisms, both reentrant and nonreentrant, that are potentially relevant to human AF at various stages/settings. We describe arrhythmia mapping techniques used to distinguish between the different mechanisms, with a particular focus on the detection of rotors. We discuss which arrhythmia mechanisms are likely to respond to ablation, and the challenges and prospects for improving upon current ablation strategies to achieve better outcomes., Competing Interests: None, (Copyright © 2016 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: The effects of varying the wavefront of activation on ventricular scar characterization has not been systematically assessed., Methods and Results: Patients referred for ablation of scar-related ventricular tachycardia underwent voltage maps during a minimum of 2 wavefronts of activation. The bipolar and unipolar low-voltage areas were compared, and direct electrogram analysis was performed in regions where discrepancies were seen. Concordance between wavefronts was measured by calculating percentage of overlap between maps. Sixty endocardial voltage maps (360±147 points) were performed in 29 patients during 2 distinct wavefronts, with 3 wavefronts in 7 patients. With median bipolar and unipolar low-voltage areas of 37 and 116 cm(2), respectively, 22% and 14% variability in median scar area was observed with a different activation wavefront. Concordance between wavefronts was lower in patients with mixed scar compared to those with dense scar (52% [interquartile range, 29%-70%] versus 84% [interquartile range, 71%-87%]), with septal scars exhibiting the lowest concordance [(27% (interquartile range, 21%-56%)]. Among 16 critical sites for ventricular tachycardia, 3 (18%) were in a discordant region of scar, with one of the wavefronts showing voltage >1.5 mV., Conclusions: Significant differences in bipolar and unipolar low-voltage characterization of scar were observed with different ventricular activation wavefronts, particularly in septal locations and in patients without dense scar. In patients with a paucity of dense, low-voltage regions identified during substrate mapping, an alternate activation wavefront may increase the sensitivity to detect arrhythmogenic substrate and critical sites for ventricular tachycardia., (© 2016 American Heart Association, Inc.)

Catheter ablation of ventricular tachycardia (VT) has evolved in recent years, especially in patients with ischemic heart disease. Data from prospective studies show that VT catheter ablation reduces the risk of recurrent VT; however, there is a paucity of data on the effect of VT catheter ablation on mortality and patient-centered outcomes such as quality of life. Performing randomized clinical trials of VT catheter ablation can be fraught with challenges, and, as a result, several prior trials of VT catheter ablation had to be stopped prematurely. The main challenges are inability to blind the patient to therapy to obtain a traditional control group, high crossover rates between the 2 arms of the study, patient refusal to participate in trials in which they have an equal chance of receiving a "pill" vs an invasive procedure, heterogeneity of mapping and ablation techniques as well as catheters and equipment, rapid evolution of technology that may make findings of any long trial less relevant to clinical practice, lack of consensus on what constitutes acute procedural and long-term success, and presentation of patients to electrophysiologists late in the course of their disease. In this article, a panel of experts on VT catheter ablation and/or clinical trials of VT catheter ablation review challenges faced in conducting prior trials of VT catheter ablation and offer potential solutions for those challenges. It is hoped that the proposed solutions will enhance the feasibility of randomized clinical trials of VT catheter ablation., (Copyright © 2016 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Introduction: The safety of ventricular tachycardia (VT) ablation in patients with laminated left ventricular (LV) thrombus has not been examined., Methods: Patients with laminated LV thrombus on transthoracic echocardiogram who underwent scar-mediated VT ablation at two centers from 2010 to 2013 were retrospectively analyzed. All patients had failed medical therapy. Acute procedural outcomes, complications, and clinical outcomes at 1 year were assessed., Results: Eight patients (four ischemic, four nonischemic cardiomyopathy) underwent VT ablation in the presence of laminated intracavitary thrombus. Six out of eight (75%) had electrical storm (ES). The mapping and ablation approach was LV endocardial-only in three patients, epicardial-only in two, combined epicardial-RV endocardial in two, and combined epicardial-LV endocardial in one. Major complication (ischemic stroke) occurred in one patient 9 days post-procedure. There was no procedural mortality. Complete acute procedural success (noninducibility of any VT after ablation) was achieved in five (63%), and partial success (ablation of only clinical VT) in an additional three (37%). At 1 year, freedom from VT and survival were achieved in six (75%) and seven (88%) patients, respectively., Conclusion: Initial data suggest that ablation of VT in the presence of intracavitary thrombus is feasible, is associated with a similar success rate to historical studies in patients without thrombus, and has an acceptable risk of complications given the high-risk nature of patients with ES. Further data are needed; however, the presence of a laminated thrombus should not necessarily preclude ablation in patients who have failed medical therapy for VT in whom ablation is otherwise indicated., (© 2015 Wiley Periodicals, Inc.)

Background: New approaches to ablation of atrial fibrillation (AF) include focal impulse and rotor modulation (FIRM). Studies of this technology with short-term follow-up have shown favorable outcomes., Objective: The purpose of this study was to characterize the long-term results of FIRM ablation in a cohort of patients treated at 2 academic medical centers., Methods: All FIRM-guided ablation procedures (n = 43) at UCLA Medical Center and Virginia Commonwealth University Medical Center performed between January 2012 and October 2013 were included for analysis. During AF, FIRM software constructed phase maps from unipolar atrial electrograms to identify putative AF sources. These sites were targeted for ablation, along with pulmonary vein isolation in 77% of patients., Results: AF was paroxysmal in 56%, and 67% had prior AF ablation. All patients had rotors identified (mean 2.6 ± 1.2 per patient, 77% in LA). Prespecified acute procedural end-point was achieved in 47% of patients (n = 20): AF termination in 4, organization in 7, >10% slowing of AF cycle length in 9. Acute complications occurred in 4 patients (9.3%). At 18 ± 7 months of follow-up, 37% were free from documented recurrent AF after a 3-month blanking period; 21% were free from documented atrial tachyarrhythmias and off antiarrhythmic drugs. Multivariate analysis did not reveal any significant predictors of AF recurrence, including pattern of AF, acute procedural success, or prior failed ablation., Conclusion: Long-term clinical results after FIRM ablation in this cohort of patients showed poor efficacy, different from previously published studies. Randomized studies are needed to evaluate the efficacy and clinical utility of this ablation approach for treating AF., (Copyright © 2016 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Catheter ablation is frequently used as a palliative option to reduce shock burden in patients with ventricular tachycardia (VT). A risk prediction tool that accurately predicts short-term survival could improve patient selection for VT ablation., Objective: The objective of the study is to assess utility of the Seattle Heart Failure Model (SHFM) to predict 6-month mortality in patients undergoing VT ablation., Methods: Data on patients who underwent VT ablation at 2 tertiary institutions were retrospectively compiled. The SHFM score at the time of ablation, including 2 added VT variables, was used to predict 6-month mortality. The predicted number of deaths was compared to the observed number to assess model calibration. Model discrimination of those who died within 6 months was assessed by both K- and C-statistics., Results: Mean age of the 243 patients was 63 ± 12 years; 89% were male. Mean SHFM score for the cohort was 1.3 ± 1.3. The Kaplan-Meier probability of death within 6 months was 14% (34 patients). The number of deaths estimated by the SHFM at 6 months was 31 (13%) giving a predicted to observed ratio of 0.91 (95% CI 0.64-1.30). The K-statistic for 6-month mortality predictions was 0.77 (95% CI 0.73-0.81), whereas the C-statistic was 0.84 (95% CI 0.78-0.92). Patients with an SHFM score ≥4.0 had an estimated positive predictive value of 80% (95% CI 28%-99%) for dying within 6 months of VT ablation., Conclusion: The SHFM was well calibrated to a sample of patients who underwent VT ablation and provided good discrimination of short-term deaths. This model could be useful as a prognostic tool to improve patient selection for VT ablation., (Published by Elsevier Inc.)

Background: The impact of catheter ablation of ventricular tachycardia (VT) on all-cause mortality remains unknown., Objective: The purpose of this study was to examine the association between VT recurrence after ablation and survival in patients with scar-related VT., Methods: Analysis of 2061 patients with structural heart disease referred for catheter ablation of scar-related VT from 12 international centers was performed. Data on clinical and procedural variables, VT recurrence, and mortality were analyzed. Kaplan-Meier analysis was used to estimate freedom from recurrent VT, transplant, and death. Cox proportional hazards frailty models were used to analyze the effect of risk factors on VT recurrence and mortality., Results: One-year freedom from VT recurrence was 70% (72% in ischemic and 68% in nonischemic cardiomyopathy). Fifty-seven patients (3%) underwent cardiac transplantation, and 216 (10%) died during follow-up. At 1 year, the estimated rate of transplant and/or mortality was 15% (same for ischemic and nonischemic cardiomyopathy). Transplant-free survival was significantly higher in patients without VT recurrence than in those with recurrence (90% vs 71%, P<.001). In multivariable analysis, recurrence of VT after ablation showed the highest risk for transplant and/or mortality [hazard ratio 6.9 (95% CI 5.3-9.0), P<.001]. In patients with ejection fraction <30% and across all New York Heart Association functional classes, improved transplant-free survival was seen in those without VT recurrence., Conclusion: Catheter ablation of VT in patients with structural heart disease results in 70% freedom from VT recurrence, with an overall transplant and/or mortality rate of 15% at 1 year. Freedom from VT recurrence is associated with improved transplant-free survival, independent of heart failure severity., (Copyright © 2015 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Epicardial mapping and ablation via a percutaneous subxiphoid technique has been instrumental in improving the working understanding of complex myocardial scars in various arrhythmogenic substrates. Endocardial ablation alone may not be sufficient in patients with ischemic cardiomyopathy, dilated cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, hypertrophic cardiomyopathy, and Chagas disease to prevent recurrent ventricular tachycardia. Multiple observational studies have demonstrated greater freedom from recurrence with adjunctive epicardial ablation compared with endocardial ablation alone. While epicardial ablation is performed predominantly at tertiary referral centers, knowledge of the technical approach, clinical indications, and potential complications is imperative to maximizing clinical success and patient safety. In 1996, Sosa and colleagues modified the pericardiocentesis technique to enable percutaneous access to the pericardial space for mapping and catheter ablation of ventricular tachycardia.1 Originally developed for patients with epicardial scarring due to chagasic cardiomyopathy and patients with ischemic cardiomyopathy refractory to endocardial ablationm,2,3 this approach has since become an essential part of the armamentarium for the treatment of ventricular tachycardia. Myocardial scars are three-dimensionally complex with varying degrees of transmurality, and the ability to map and ablate the epicardial surface has contributed to a greater understanding of scar-related VT in postinfarction cardiomyopathy and nonischemic substrates including idiopathic dilated cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, hypertrophic cardiomyopathy, and chagasic cardiomyopathy. In this review, we highlight the percutaneous approach and discuss clinical indications and potential complications.

Background: Accessory pathways can lie near or within the coronary sinus (CS). Radiofrequency catheter ablation of accessory pathways is a well-established treatment option, but this procedure can cause damage to adjacent coronary arteries., Objective: The purpose of this study was to evaluate the anatomic relationship between the coronary arteries and the CS., Methods: Retrospective data of patients who underwent catheter ablation of supraventricular tachycardia between June 2011 and August 2013 was reviewed. In addition, detailed analysis of coronary computed tomographic angiography (CTA) data from 50 patients was performed., Results: Between June 2011 and August 2013, 427 patients underwent catheter ablation of supraventricular tachycardia, of whom 105 (age 28 ± 17 years, 60% male) had accessory pathway-mediated tachycardia. Of these, 23 patients had accessory pathways near the CS, and 60% (N = 14) underwent concurrent coronary angiography. In 4 patients, the posterolateral (inferolateral) branch (PLA) of the right coronary artery was in close proximity to the CS, and 2 patients (18%) had stenosis of the PLA at the site of ablation. On CTA at their closest proximity, the PLA was 1.9 ± 1.3 mm and the left circumflex artery (LCx) was 2.0 ± 0.8 mm from the body of the CS, in right and left coronary artery-dominant patients, respectively. CS ostium and PLA were 3.6 ± 1.9 mm apart. In left-dominant patients, LCx and CS ostium were 3.8 ± 1.2 mm apart., Conclusion: The PLA and LCx are in close proximity to the anteroinferior aspect of the CS ostium and proximal CS. The relationship of the CS and coronary arteries should be evaluated before ablation at these sites., (Copyright © 2015 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Background: Ablation has become an important option for treatment of ventricular tachycardia (VT). The influence of procedure duration on outcomes remains unexamined., Objective: The purpose of this study was to determine the influence of procedure duration on outcomes and complications over an 8-year period, Methods: Patients referred for scar-mediated VT ablation from 2004 to 2011 were retrospectively analyzed. Procedure duration was defined as the time from the insertion of catheters through the femoral vein to the time of their withdrawal. Procedure duration was analyzed in relationship with baseline and intraoperative covariates, acute procedural outcomes, complications, and 6-month clinical outcomes., Results: One hundred forty-eight patients underwent VT ablation with mean procedure duration of 5.7 ± 1.8 hours. VT recurrence and survival at 6 months were 46% and 82%, respectively, and were not associated with procedure duration. Hospital mortality increased with intraoperative intraaortic balloon pump insertion (adjusted odds ratio [OR] 13.7, 95% confidence interval [CI] 2.35-79.94, P = .004) and was improved with successful ablation of the clinical VT as a procedural end-point (adjusted OR 0.13, 95% Cl 0.03-0.54, P = .005). The association between procedure duration and hospital mortality remained after adjusting for significant baseline variables (adjusted OR 1.75, 95% CI 1.14-2.68, P = .0098) and intraoperative variables (adjusted OR 1.6, 95% CI 1.12-2.29, P = .0104)., Conclusion: Hospital mortality was significantly increased by unsuccessful clinical VT ablation as a procedural end-point and intraoperative intraaortic balloon pump insertion. However, after adjusting for significant baseline and intraoperative covariates, procedure duration still was associated with increased hospital mortality. Procedure duration had no impact on VT recurrence and survival at 6 months., (Copyright © 2015 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)