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Conduction system pacing (CSP) has emerged as a more physiological alternative to right ventricular pacing and is also being used in selected cases for cardiac resynchronization therapy. His bundle pacing was first introduced over two decades ago and its use has risen over the last five years with the advent of tools which have facilitated implantation. Left bundle branch area pacing is more recent but its adoption is growing fast due to a wider target area and excellent electrical parameters. Nevertheless, as with any intervention, proper technique is a prerequisite for safe and effective delivery of therapy. This document aims to standardize the procedure and to provide a framework for physicians who wish to start CSP implantation, or who wish to improve their technique.

Conduction system pacing (CSP) has emerged as a more physiological alternative to right ventricular pacing and is also being used in selected cases for cardiac resynchronization therapy. His bundle pacing was first introduced over two decades ago and its use has risen over the last years with the advent of tools which have facilitated implantation. Left bundle branch area pacing is more recent but its adoption is growing fast due to a wider target area and excellent electrical parameters. Nevertheless, as with any intervention, proper technique is a prerequisite for safe and effective delivery of therapy. This document aims to standardize the procedure and to provide a framework for physicians who wish to start CSP implantation, or who wish to improve their technique. A synopsis is provided in this print edition of EP-Europace. The full document may be consulted online, and a ‘Key Messages’ App can be downloaded from the EHRA website.

Implantable cardioverter defibrillators (ICDs) improve survival in patients at risk for cardiac arrest, but are associated with intravascular lead-related complications. The subcutaneous ICD (S-ICD), with no intravascular components, was developed to minimize lead-related complications.To assess key ICD performance measures related to delivery of ICD therapy, including inappropriate ICD shocks (delivered in absence of life-threatening arrhythmia) and failed ICD shocks (which did not terminate ventricular arrhythmia).Randomized, multicenter trial. (ClinicalTrials.gov: NCT02881255).The ATLAS trial.544 eligible patients (141 female) with a primary or secondary prevention indication for an ICD who were younger than age 60 years, had a cardiogenetic phenotype, or had prespecified risk factors for lead complications were electrocardiographically screened and 503 randomly assigned to S-ICD (251 patients) or transvenous ICD (TV-ICD) (252 patients). Mean follow-up was 2.5 years (SD, 1.1). Mean age was 49.0 years (SD, 11.5).The primary outcome was perioperative major lead-related complications.There was a statistically significant reduction in perioperative, lead-related complications, which occurred in 1 patient (0.4%) with an S-ICD and in 12 patients (4.8%) with TV-ICD (-4.4%; 95% CI, -6.9 to -1.9;At present, the ATLAS trial is underpowered to detect differences in clinical shock outcomes; however, extended follow-up is ongoing.The S-ICD reduces perioperative, lead-related complications without significantly compromising the effectiveness of ICD shocks, but with more early postoperative pain and a trend for more inappropriate shocks.Boston Scientific.

Atrial low voltage area (LVA) catheter ablation has emerged as a promising strategy for ablation of persistent atrial fibrillation (AF). It is unclear if catheter ablation of atrial LVA increases treatment success rates in patients with persistent AF.The primary aim of this trial is to assess the potential benefit of adjunctive catheter ablation of atrial LVA in addition to pulmonary vein isolation (PVI) in patients with persistent AF, when compared to PVI alone. The secondary aims are to evaluate safety outcomes, the quality of life and the healthcare resource utilization.A multicenter, prospective, parallel-group, 2-arm, single-blinded randomized controlled trial is under way (NCT03347227). Patients who are candidates for catheter ablation for persistent AF will be randomly assigned (1:1) to either PVI alone or PVI + atrial LVA ablation. The primary outcome is 18-month documented event rate of atrial arrhythmia (AF, atrial tachycardia or atrial flutter) post catheter ablation. Secondary outcomes include procedure-related complications, freedom from atrial arrhythmia at 12 months, AF burden, need for emergency department visits/hospitalization, need for repeat ablation for atrial arrhythmia, quality of life at 12 and 18 months, ablation time, and procedure duration.Characterization of Arrhythmia Mechanism to Ablate Atrial Fibrillation (COAST-AF) is a multicenter randomized trial evaluating ablation strategies for catheter ablation. We hypothesize that catheter ablation of atrial LVA in addition to PVI will result in higher procedural success rates when compared to PVI alone in patients with persistent AF.

Purpose Patients with right bundle branch block (RBBB) are less likely to respond to cardiac resynchronization therapy (CRT). We aimed to assess whether patients with RBBB respond to CRT with biventricular fusion pacing. Methods Consecutive patients with RBBB at a single tertiary care center, who were implanted with a CRT device capable of biventricular fusion pacing using SyncAV programming, were assessed and compared to a historical cohort of CRT patients with RBBB. QRSd was measured and compared during intrinsic conduction, nominal CRT pacing and manual electrocardiogram-based optimized SyncAV programming. Left ventricular ejection fraction (LVEF) was also compared before and 6 months after CRT. Results We included 8 consecutive patients with RBBB (group 1) who were able to undergo SyncAV programming and 16 patients with RBBB (group 2) from a historical cohort. In group 1, compared to mean intrinsic conduction QRSd (155 ± 13 ms), mean nominally-paced QRSd was 156 ± 15 ms (ΔQRSd 1.3 ± 11.6; p = 0.77) and SyncAV-optimized paced QRSd was 135 ± 14 ms (ΔQRSd −20.0 ± 20.4; p = 0.03 and ΔQRSd −21.3 ± 16.3; p = 0.008; compared to intrinsic conduction and nominal pacing respectively). In group 2, mean QRSd with nominal pacing was 160 ± 24 ms (ΔQRSd 3.8 ± 33.4; p = 0.66 compared to intrinsic conduction). In group 1, baseline LVEF was 22.1 ± 11.5 and after 6 months of follow-up was 27.8 ± 8.6 (p = 0.047). In group 2, the baseline LVEF was 27.2 ± 10.6 and after 6 months of follow-up was 25.0 ± 10.0 (p = 0.45). Conclusions CRT programed to allow biventricular fusion pacing significantly improved electrical synchrony and LVEF in patients with RBBB. Larger studies are required to confirm these findings.

Background: The Hearts in Rhythm Organization (HiRO) is a team of Canadian inherited heart rhythm and cardiomyopathy experts, genetic counsellors, nurses, researchers, patients, and families dedicated to the detection of inherited arrhythmias and cardiomyopathies, provision of best therapies, and protection from the tragedy of sudden cardiac arrest. Methods: Recently, existing disease-specific registries were merged into the expanded National HiRO Registry, creating a single common data set for patients and families with inherited conditions that put them at risk for sudden death in Canada. Eligible patients are invited to participate in the registry and optional biobank from 20 specialized cardiogenetics clinics across Canada. Results: Currently, there are 4700 participants enrolled in the National HiRO Registry, with an average of 593 participants enrolled annually over the past 5 years. The capacity to enable knowledge translation of research findings is built into HiRO’s organizational infrastructure, with 3 additional working groups (HiRO Clinical Care Committee, HiRO Active Communities Committee, and HiRO Annual Symposium Committee), supporting the organization’s current goals and priorities as set alongside patient partners. Conclusion: The National HiRO Registry aims to be an integrated research platform to which researchers can pose novel research questions leading to a better understanding, detection, and clinical care of those living with inherited heart rhythm and cardiomyopathy conditions and ultimately to prevent sudden cardiac death. Résumé: Contexte: La Hearts in Rhythm Organization (HiRO) est une équipe d’experts canadiens en matière de rythmes cardiaques et de cardiomyopathies héréditaires, de conseillers en génétique, d’infirmières, de chercheurs, de patients et de familles qui se consacrent à la détection des arythmies et des cardiomyopathies héréditaires, à la mise en place des meilleures thérapies et à la protection contre la tragédie que représente une mort subite d’origine cardiaque. Méthodes: Récemment, les registres existants relatifs à des maladies spécifiques ont été fusionnés en un registre national élargi de l’HiRO, créant ainsi un ensemble de données commun unique à destination des patients et leurs familles, atteints de maladies héréditaires, qui sont à risque de mort subite au Canada. Les patients admissibles sont invités à s’associer au registre et à la biobanque facultative regroupant 20 cliniques spécialisées en cardiogénétique au Canada. Résultats: Actuellement, 4 700 participants sont inscrits au registre national de l’HiRO, avec une moyenne de 593 participants inscrits chaque année au cours des cinq dernières années. La capacité à favoriser l’application des connaissances issues de la recherche fait partie de la structure organisationnelle de l’HiRO, avec trois groupes de travail supplémentaires (comité des soins cliniques de l’HiRO, comité des communautés cctives de l’HiRO et comité du symposium annuel de l’HiRO), soutenant les objectifs et les priorités actuels de l’organisation tels qu’ils ont été fixés en partenariat avec les patients. Conclusion: Le registre national de l’HiRO vise à devenir une plateforme de recherche intégrée au sein de laquelle les chercheurs peuvent exposer des questions de recherche inédites permettant de mieux comprendre, détecter et soigner les personnes atteintes de troubles du rythme cardiaque et de cardiomyopathie héréditaires et, à terme, de prévenir la mort subite d’origine cardiaque.

Background The leadless Micra transcatheter-pacing system (Micra-TPS) is implanted via a femoral approach using a 27-French introducer sheath. The Micra Transcutaneous Pacing Study excluded patients with inferior vena cava (IVC) filters. Objective To examine the feasibility and safety of Micra-TPS implantation through an IVC filter. Methods This multicenter retrospective study included patients with an IVC filter who underwent a Micra-TPS implantation. Data for clinical and IVC filter characteristics, preprocedure imaging, and procedural interventions were collected. The primary outcome was a successful leadless pacemaker (LP) implantation via a femoral approach in the presence of an IVC filter. Periprocedural and delayed clinical complications were also evaluated. Results Of the 1528 Micra-TPS implants attempted, 23 patients (1.5%) had IVC filters. The majority (69.6%) of IVC filters were permanent. Six (26.1%) patients underwent preprocedural imaging to assess for filter patency. One patient's filter was retrieved before LP implantation. The primary outcome was achieved in 21 of 22 patients (95.5%) with an existing IVC filter. An occluded IVC precluded LP implantation in one patient. Difficulty advancing the stiff guidewire or the 27-Fr sheath was encountered in five patients. These cases required repositioning of the wire (n = 2), gradual sheath upsizing (n = 2), or balloon dilation of the filter (n = 1). Postprocedure fluoroscopy revealed intact filters in all cases. During a median 6-month follow-up, there were no clinical complications related to the filter or the Micra-TPS. Conclusion This multicenter experience demonstrates the feasibility and safety of Micra-TPS implantation via an IVC filter without acute procedural or delayed clinical complications.

Catheter ablation (CA) was developed as a potentially curative procedure through electrical isolation of the pulmonary veins to isolate the main triggers of atrial fibrillation (AF). When successful, CA has clearly been shown to decrease AF recurrence and symptoms, and improve quality of life. With advancing technology, increased procedural success, and lower complication risk, CA is being used at much higher rates, with broader indications and in a diverse AF population. Symptomatic paroxysmal AF that is refractory to antiarrhythmic drugs is currently the indication for CA with the best evidence. CA for AF as first-line therapy is reserved for highly selected symptomatic patients with paroxysmal AF. Current studies have not shown an improvement in mortality or quality of life with CA as first-line therapy. In patients with persistent AF who are symptomatic despite medical therapy, CA is a reasonable therapeutic option. Although recent trials have suggested that CA reduced mortality and hospitalizations in patients with heart failure and reduced ejection fraction, the evidence is not conclusive. Therefore, current guidelines recommend CA for similar indications to patients without heart failure, but large trials comparing CA with strict rate control will be reported in the near future. Ongoing studies will assess whether CA of AF reduces major adverse cardiovascular events and whether stopping anticoagulation in the long term is possible after CA. The purpose of this review is to outline the current and evolving indications for CA of AF and the underlying evidence supporting these indications.

Background: Atrial fibrillation (AF) and heart failure (HF) frequently coexist and can be challenging to treat. Pharmacologically based rhythm control of AF has not proven to be superior to rate control. Ablation-based rhythm control was compared with rate control to evaluate if clinical outcomes in patients with HF and AF could be improved. Methods: This was a multicenter, open-label trial with blinded outcome evaluation using a central adjudication committee. Patients with high-burden paroxysmal (>4 episodes in 6 months) or persistent (duration Results: From December 1, 2011, to January 20, 2018, 411 patients were randomly assigned to ablation-based rhythm control (n=214) or rate control (n=197). The primary outcome occurred in 50 (23.4%) patients in the ablation-based rhythm-control group and 64 (32.5%) patients in the rate-control group (hazard ratio, 0.71 [95% CI, 0.49–1.03]; P =0.066). Left ventricular ejection fraction increased in the ablation-based group (10.1±1.2% versus 3.8±1.2%, P =0.017), 6-minute walk distance improved (44.9±9.1 m versus 27.5±9.7 m, P =0.025), and NT-proBNP demonstrated a decrease (mean change –77.1% versus –39.2%, P P =0.0036), as did the AF Effect on Quality of Life score (least-squares mean difference of 6.2 [95% CI, 1.7–10.7]; P =0.0005). Serious adverse events were observed in 50% of patients in both treatment groups. Conclusions: In patients with high-burden AF and HF, there was no statistical difference in all-cause mortality or HF events with ablation-based rhythm control versus rate control; however, there was a nonsignificant trend for improved outcomes with ablation-based rhythm control over rate control. Registration: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT01420393.

Aims Genetic testing is recommended in specific inherited heart diseases but its role remains unclear and it is not currently recommended in unexplained cardiac arrest (UCA). We sought to assess the yield and clinical utility of genetic testing in UCA using whole-exome sequencing (WES). Methods and results Survivors of UCA requiring external defibrillation were included from the Cardiac Arrest Survivor with Preserved Ejection fraction Registry. Whole-exome sequencing was performed, followed by assessment of rare variants in previously reported cardiovascular disease genes. A total of 228 UCA survivors (mean age at arrest 39 ± 13 years) were included. The majority were males (66%) and of European ancestry (81%). Following advanced clinical testing at baseline, the likely aetiology of cardiac arrest was determined in 21/228 (9%) cases. Whole-exome sequencing identified a pathogenic or likely pathogenic (P/LP) variant in 23/228 (10%) of UCA survivors overall, increasing the proportion of ‘explained’ cases from 9% only following phenotyping to 18% when combining phenotyping with WES. Notably, 13 (57%) of the 23 P/LP variants identified were located in genes associated with cardiomyopathy, in the absence of a diagnosis of cardiomyopathy at the time of arrest. Conclusions Genetic testing identifies a disease-causing variant in 10% of apparent UCA survivors. The majority of disease-causing variants was located in cardiomyopathy-associated genes, highlighting the arrhythmogenic potential of such variants in the absence of an overt cardiomyopathy diagnosis. The present study supports the use of genetic testing including assessment of arrhythmia and cardiomyopathy genes in survivors of UCA.

Optimal programming of cardiac resynchronization therapy (CRT) has not yet been fully elucidated. A novel algorithm (SyncAV) has been developed to improve electrical synchrony by fusion of the triple wavefronts: intrinsic, right ventricular (RV)-paced, and left ventricular (LV)-paced.Consecutive patients at a single tertiary care center with a previously implanted CRT device with SyncAV algorithm (programmable negative AV hysteresis) were evaluated. QRS duration (QRSd) was measured during 1) intrinsic conduction, 2) existing CRT pacing as chronically programmed by treating physician, 3) using the device-based QuickOpt™ algorithm for optimization of AV and VV delays, and 4) ECG-based optimized SyncAV programming. The paced QRSd was assessed and compared to intrinsic conduction and between the different modes of programming.Of 64 consecutive, potentially eligible patients who underwent assessment, 34 patients who were able to undergo SyncAV programming were included. Mean intrinsic conduction QRSd was 163 ± 24 ms. In comparison, the mean QRSd was 152 ± 25 ms (-11.1 ± 19.0) during existing CRT pacing, 160 ± 25 ms (-4.1 ± 25.2) using the QuickOpt™ algorithm and 138 ± 23 (-24.9 ± 17.2) using ECG-based optimized SyncAV programming. SyncAV optimization resulted in significant reductions in QRSd compared to existing CRT pacing (P = 0.02) and QuickOpt™ (P 0.001). Of the 32% of patients who did not have QRS narrowing with existing CRT, 72% experienced QRS narrowing with SyncAV.ECG-based atrio-ventricular delay optimization using SyncAV significantly improved electrical synchrony in patients with a previously implanted CRT. Further studies are needed to assess the impact on long-term outcomes.

Research teams developing biobanks and/or genomic databases must develop policies for the disclosure and reporting of potentially actionable genomic results to research participants. Currently, a broad range of approaches to the return of results exist, with some studies opting for non-disclosure of research results while others follow clinical guidelines for the return of potentially actionable findings from sequencing. In this review, we describe current practices and highlight decisions a research team must make when designing a return of results policy, from informed consent to disclosure practices and clinical validation options. The unique challenges of returning incidental findings in cardiac genes, including reduced penetrance and the lack of clinical screening standards for phenotype-negative individuals are discussed. Lastly, the National Hearts in Rhythm Organization (HiRO) Registry approach is described to provide a rationale for the selective return of field-specific variants to those participating in disease-specific research. Our goal is to provide researchers with a resource when developing a return of results policy tailored for their research program, based on unique factors related to study design, research team composition and availability of clinical resources.

Background: Following an unexplained cardiac arrest, clinical genetic testing is increasingly becoming standard of care. Periodic review of variant classification is required, as reinterpretation can change the diagnosis, prognosis, and management of patients and their relatives. Methods: This study aimed to develop and validate a standardized algorithm to facilitate clinical application of the 2015 American College of Medical Genetics and Association for Molecular Pathology guidelines for the interpretation of genetic variants. The algorithm was applied to genetic results in the Cardiac Arrest Survivors With Preserved Ejection Fraction Registry, to assess the rate of variant reclassification over time. Variant classifications were then compared with the classifications of 2 commercial laboratories to determine the rate and identify sources of variant interpretation discordance. Results: Thirty-one percent of participants (40 of 131) had at least 1 genetic variant with a clinically significant reclassification over time. Variants of uncertain significance were more likely to be downgraded (73%) to benign than upgraded to pathogenic (27%; P =0.03). For the second part of the study, 50% (70 of 139) of variants had discrepant interpretations (excluding benign variants), provided by at least 1 team. Conclusions: Periodic review of genetic variant classification is a key component of follow-up care given rapidly changing information in the field. There is potential for clinical care gaps with discrepant variant interpretations, based on the interpretation and application of current guidelines. The development of gene- and disease-specific guidelines and algorithms may provide an opportunity to further standardize variant interpretation reporting in the future. Registration: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT00292032.

BACKGROUND Following an unexplained cardiac arrest, patients and family members typically undergo a comprehensive series of investigations to identify the underlying cause of arrest, with a diagnosis identified in more than half of cardiac arrest survivors. However, the long-term arrhythmic outcomes among cardiac arrest survivors remains unclear. METHODS AND RESULTS The Cardiac Arrest Survivors with Preserved Ejection Fraction Registry (CASPER) prospectively enrolls cardiac arrest survivors and their first-degree relatives (FDR) across 16 Canadian centers. Patient demographics, cardiac investigations, working diagnoses, and follow-up events are recorded. Those with a history of significant coronary artery disease or manifest cause of cardiac arrest are excluded. Arrhythmic events, including implantable cardioverter-defibrillator (ICD) shock or anti-tachycardia pacing (ATP) are recorded. Patients with at least one follow-up visit were included. Hazard ratios for arrhythmic events were calculated using Cox proportional hazards models. 741 patients were enrolled, with a median age of 42 years (interquartile range [IQR] 29-53), 56% being male, and mostly Caucasian (82%). Patients included cardiac arrest suvivors/probands (n=480, 66%) and first-degree relatives (n=243, 34%). In addition to baseline investigations, patients undertook signal-averaged ECG (56%), exercise testing (70%), extended monitoring (50%), cardiac MRI (62%), and provocative testing with procainamide (39%), adrenaline (31%) or an electrophysiologic study (14%). After excluding 18 patients with ongoing diagnosis adjudication, the working diagnoses of probands and FDRs are reported in the Table. Working diagnoses among probands were divided into three categories, including unexplained/idiopathic (after comprehensive investigations, n=351), structural/cardiomyopathy (including arrhythmogenic right ventricular cardiomyopathy and others, n=64), and electrical/channelopathy (including Long QT Syndrome, Brugada Syndrome, and others, n=65). During a median follow-up of 3.3 years (IQR 1.7-5.9), 69 patients (9%) suffered an ICD shock or ATP with a median time-to-event of 1.0 years (IQR 0.5-2.8). Probands had a significantly higher rate of events (hazard ratio [HR] 16.9, 95% confidence interval [CI] 4.1-69.0, p CONCLUSION In a cohort of unexplained cardiac arrest survivors and first-degree relatives, probands had a significant rate of recurrent events. Probands with structural/cardiomyopathy diagnoses had twice the risk of arrhythmia recurrence. Patients with structural diagnoses may be more likely to have arrhythmic events in follow-up, potentially due to a progressive disease process compared to other diagnoses.

Background The defibrillator lead is the weakest part of the transvenous (TV) implantable cardioverter defibrillation (ICD) system and a frequent cause of morbidity. Lead dislodgement, cardiac perforation, insertion-related trauma including pneumothorax and vascular injury, are common early complications of TV-ICD implantation. Venous occlusion, tricuspid valve dysfunction, lead fracture and lead insulation failure are additional, later complications. The introduction of a totally sub-cutaneous ICD (S-ICD) may reduce these lead-related issues, patient morbidity, hospitalizations and costs. However, such benefits compared to the TV-ICD have not been demonstrated in a randomized trial. Design ATLAS (Avoid Transvenous Leads in Appropriate Subjects) is a multi-centered, randomized, open-label, parallel group trial. Patients younger than 60 years are eligible. If older than 60 years, patients are eligible if they have an inherited heart rhythm disease, or risk factors for ICD-related complication, such as hemodialysis, a history of ICD or pacemaker infection, heart valve replacement, or severe pulmonary disease. This study will determine if using an S-ICD compared to a TV-ICD reduces a primary composite outcome of perioperative complications including pulmonary or pericardial perforation, lead dislodgement or dysfunction, tricuspid regurgitation and ipsilateral venous thrombosis. Five hundred patients will be enrolled from 14 Canadian hospitals, and data collected to both early- (at 6 months) and mid-term complications (at 24 months) as well as mortality and ICD shock efficacy. Summary The ATLAS randomized trial is comparing early- and mid-term vascular and lead-related complications among S-ICD versus TV-ICD recipients who are younger or at higher risk of ICD-related complications.

Aims Randomized trials suggest reductions in all-cause mortality and heart failure (HF) rehospitalizations with catheter ablation (CA) in patients with atrial fibrillation (AF) and HF. Whether these results can be replicated in a real-world population with long-term follow-up or varies over time is unknown. We sought to evaluate the long-term effectiveness of CA in reducing the incidence of all-cause mortality, HF hospitalizations, stroke, and major bleeding in AF–HF patients. Methods and results In a cohort of patients newly diagnosed with AF–HF in Quebec, Canada (2000–2017), CA patients were matched 1:2 to controls on time and frequency of hospitalizations. Confounders were controlled for using inverse probability of treatment weighting. Multivariable Cox models adjusted for the presence of cardiac electronic implantable devices and medication use during follow-up, and the effect of time since CA was modelled with B-splines. For non-fatal outcomes, the Lunn–McNeil approach was used to account for the competing risk of death. Among 101 933 AF–HF patients, 451 underwent CA and were matched to 899 controls. Over a median follow-up of 3.8 years, CA was associated with a statistically significant reduction in all-cause mortality [hazard ratio 0.4 (95% confidence interval 0.2–0.7)], but no difference in stroke or major bleeding. The hazard of HF rehospitalization for CA patients, relative to non-CA patients, varied with time since CA (P = 0.01), with a reduction in HF rehospitalizations until approximately 3 years post-CA. Conclusion Compared with matched non-CA patients, CA was associated with a long-term reduction in all-cause mortality and a reduction in HF rehospitalizations until 3 years post-CA.

Femoral venous access is required for most electrophysiology procedures. Limited data are available regarding post-procedure venous thromboembolism (VTE), specifically deep vein thrombosis (DVT) and pulmonary embolism (PE). Potential preventative strategies are unclear. We aimed to survey Canadian centers regarding incidence of VTE and strategies for prevention of VTE after procedures that do not require post-procedure anticoagulation. An online survey was distributed to electrophysiologists representing major Canadian EP centers. Participants responded regarding procedural volume, incidence of VTE post-procedure, and their practice regarding pharmacological and non-pharmacological peri-procedural VTE prophylaxis. The survey included 17 centers that performed a total of 6062 procedures in 2016. Ten patients (0.16%) had VTE (including 9 DVTs and 6 PEs) after diagnostic electrophysiology studies and right-sided ablation procedures excluding atrial flutter. Five centers (41.6%) administered systemic intravenous heparin during both diagnostic electrophysiology studies and right-sided ablation procedures. For patients taking oral anticoagulants, 10 centers (58.8%) suspend therapy prior to the procedure. Two centers (11.8%) routinely prescribed post-procedure pharmacologic prophylaxis for VTE. Four centers (23.5%) used compression dressings post-procedure and all prescribed bed rest for a maximum of 6 h. Of the variables collected in the survey, none were found to be predictive of VTE. VTE is not a common complication of EP procedures. There is significant variability in the strategies used to prevent VTE events. Future research is required to evaluate strategies to reduce the risk of VTE that may be incorporated into EP practice guidelines.

Background Catheter ablation (CA) is an established therapy for atrial fibrillation (AF). Studies regarding long-term real-world outcomes post-CA have inconsistently accounted for oral anticoagulation (OAC). Objectives To describe patterns of OAC use post-CA and to compare the OAC-adjusted long-term risk of stroke and major bleeding in AF patients with and without CA. Methods A population-based cohort of AF patients was constructed in Quebec and Ontario, Canada (1999-2014). Propensity score matching was performed to determine the incidence rates of stroke and major bleeding among those undergoing CA, adjusted for time-dependent OAC use. Results From the entire cohort, 6391 patients were identified as having undergone CA as compared to 482 977 patients who did not. Of these, 1240 patients with government medical insurance undergoing CA were matched with 2427 patients without CA. Post-CA, 78%, 65%, and 61% remained on an OAC at 1, 2, and 5 years, while 75%, 71%, and 68% of patients not undergoing CA were on OACs at 1, 2, and 5 years. At follow-up, there was no statistically significant difference for stroke (adjusted hazard ratio [HR], 0.88; 95% CI, 0.63 to 1.21) or major bleeding (adjusted HR, 0.88; 95% CI, 0.73 to 1.06). Conclusion No evidence was found that CA significantly decreases the risk of stroke or major bleeding when adjusting for OAC use over time. It may be prudent to continue anticoagulation post-CA based on patient-risk profile until randomized trials demonstrate both reduced stroke rates with CA, and improved safety (balancing stroke and bleeding risk) with OAC discontinuation post-CA.

Objectives This study sought to evaluate the predictive value of noninducibility on long-term outcomes. Background The traditional endpoint for catheter ablation of ventricular tachycardia (VT) is noninducibility of VT by programmed stimulation; however, the definition of inducibility remains variable and its prognostic value limited by nonstandardized periprocedural antiarrhythmic drug therapy and implantable cardioverter-defibrillator programming in prior observational studies. The VANISH trial randomized patients with prior myocardial infarction and VT to ablation (with an endpoint of noninducibility of VT ≥300 ms after ablation) versus antiarrhythmic drug escalation. Methods Patients enrolled in the VANISH study randomized to catheter ablation were included. The relationship between post-ablation inducibility and the primary composite endpoint (death, VT storm >30 days, or appropriate implantable cardioverter-defibrillator shock >30 days) was assessed using a time-to-event analysis, adjusting for other clinical and procedural characteristics. Results A total of 129 patients from the ablation arm were included in the primary analysis, of which 51 were noninducible post-ablation compared with 78 who had inducible VT or in whom inducibility testing was not performed. There were no significant baseline characteristic or procedural differences except for increased implantable cardioverter-defibrillator shocks before randomization in the noninducible group. In multivariate analysis, inducibility significantly increased the risk of death, appropriate shock, or VT storm after 30 days (HR: 1.87; p = 0.017). Conclusions Inducibility of any VT post-ablation was associated with an increased risk of the composite endpoint in the VANISH trial. A randomized trial is required to confirm whether more aggressive ablation targeting faster induced VTs (

Background Femoral venous access for catheter introduction represents the cornerstone of electrophysiology (EP) procedures. Limited data are available regarding postprocedure VTE. The aim of this systematic review is to determine the incidence of DVT and pulmonary embolism (PE) associated with femoral vein catheterization during EP procedures. Methods An electronic search was conducted for studies documenting the incidence of DVT and PE after EP procedures. Studies were classified as atrial fibrillation (AF) or non-AF ablation procedures. Results Two thousand eight-hundred sixty-four studies were evaluated, 16 of which were included in the analysis. The incidence of DVT after AF and non-AF ablations reached as high as 0.33% and 2.38%, respectively, with a pooled incidence of 0% (95% CI, 0%-0.0003%) and 0.24% (95% CI, 0.08%-0.39%), respectively. The incidence of PE was 0.29% after AF ablation and ranged from 0% to 1.67% for non-AF procedures; the pooled incidence after non-AF ablations was 0.12% (95% CI, 0%-0.25%). Asymptomatic DVT was documented in up to 21.2% of patients. Hematomas occurred in 1.05% of AF ablations (95% CI, 0.30%-1.8%) and 0.3% of non-AF ablations (95% CI, 0.09%-0.51%). Conclusions A lower incidence of symptomatic DVT and PE was observed after AF ablations as opposed to non-AF ablations, likely due to the use of routine periprocedural anticoagulation. Asymptomatic DVTs appear to be common, although their significance is unclear. Future studies are required to weigh the risk of hematoma against the risk of VTE associated with the use of prophylactic anticoagulation after non-AF ablation procedures.

The differential diagnosis between benign syncope common in a young population and life-threatening arrhythmic ones represents a major challenge in the management of patients with inherited arrhythmias (IAs) [(1)][1]. In this population, ventricular arrhythmias can often be hemodynamically tolerated

Background: Current guidelines are relatively general regarding the type of patient with heart failure (HF) who should be considered for catheter ablation (CA) of atrial fibrillation (AF). The aim of the present study was to identify clinical predictors and sex differences for treatment with CA in the AF-HF population. Methods: A population-based AF-HF cohort was created using the Quebec administrative data (2000-2017). Patients were followed from the date of diagnosis of both diseases to the date of CA or death. Predictors for CA, represented by time-varying covariates, were assessed in a multivariable Cox model that accounted for the competing risk of death. Results: Among 101,931 patients with AF-HF with medication information (median age, 80.7 years; interquartile range [IQR], 73.9-86.3; 51.4% were female, median CHA2DS2-VASc, 4; IQR, 3-4), only 432 (0.4%) underwent CA after a median of 0.8 years (IQR, 0.1-2.7). Independent of multiple comorbidities and advanced age, which were associated with a lower likelihood of CA, women were approximately half as likely to undergo a CA (26% were women; adjusted hazard ratio, 0.6; 95% confidence interval, 0.4-0.7). Prior use of direct-acting oral anticoagulants and antiarrhythmics, and the presence of an implantable cardioverter-defibrillator were also predictors for CA treatment (P < 0.05 for all). Conclusion: In a real-world population, CA was infrequently used to treat AF among patients with HF, and the likelihood of CA was further reduced in women. Because patients with CA had few comorbidities, future studies need to be conducted to determine whether CA can be beneficial in subjects whose clinical characteristics are more representative of the AF-HF population. Résumé: Contexte: Les lignes directrices actuelles abordent de façon relativement générale les cas d’insuffisance cardiaque (IC) où les patients devraient être considérés comme des candidats à l’ablation par cathéter (AC) pour le traitement de la fibrillation auriculaire (FA). La présente étude visait à cerner les prédicteurs cliniques et les différences entre les sexes dans le contexte de l’AC au sein de la population atteinte de FA et d’IC. Méthodologie: Une cohorte populationnelle de patients atteints de FA et d’IC a été constituée à partir de données administratives du Québec (2000-2017). Le suivi des patients allait de la date du diagnostic des deux affections à la date de l’AC ou du décès. Les prédicteurs d’AC, représentés par des covariables temporalisées, ont été évalués dans un modèle de Cox multivarié tenant compte du risque concurrent de décès. Résultats: Sur 101 931 patients atteints de FA et d’IC dont la médication était documentée (âge médian : 80,7 ans; intervalle interquartile [IIQ] : 73,9-86,3; proportion de patients de sexe féminin : 51,4 %; score CHA2DS2-VASc médian : 4; IIQ : 3-4), seulement 432 (0,4 %) ont subi une AC au bout d’un laps de temps médian de 0,8 an (IIQ : 0,1-2,7). Indépendamment des maladies concomitantes multiples et de l’âge avancé, associés à une moindre probabilité d’AC, les femmes étaient environ deux fois moins susceptibles de subir une AC (proportion de patients de sexe féminin : 26 %; rapport des risques instantanés corrigé : 0,6; intervalle de confiance à 95 % : de 0,4 à 0,7). Les antécédents de traitement par des anticoagulants oraux à action directe et des antiarythmiques, ainsi que la présence d’un défibrillateur cardioverteur implantable étaient également des prédicteurs d’AC (p < 0,05 dans tous les cas). Conclusion: Au sein d’une population en contexte réel, l’AC a été rarement pratiquée pour traiter la FA chez des patients atteints d’IC. En outre, la probabilité d’une AC était moindre chez les femmes. Étant donné que les patients ayant subi une AC présentaient peu de maladies concomitantes, d’autres études devront être menées pour déterminer si l’AC peut être salutaire chez les personnes présentant des caractéristiques cliniques plus représentatives de la population atteinte de FA et d’IC.

Background Atrial fibrillation (AF) and heart failure (HF) are common co-existing conditions. Randomized trial data suggests a reduction in all-cause mortality with catheter ablation (CA) in selected patients, however, whether these results are replicable in a real-world population and persist in the long-term remains to be shown. Purpose To evaluate the long-term effectiveness of CA in AF-HF patients in reducing the incidence of: a) all-cause mortality b) HF hospitalizations, and c) major morbidities (stroke/transient ischemic attack (TIA) and major bleeding). Methods A population-based administrative cohort was created of AF-HF patients with government prescription coverage in Quebec, Canada (1999–2015). Patients who underwent CA (cases) were matched 1:2 to controls using risk-set sampling. Cases were matched on time in the cohort and frequency of hospitalizations. Measured time-invariant confounders were controlled for using inverse probability of treatment weighting (IPTW) and included age, sex, clinical characteristics, presence of cardiac implantable electronic devices, and medication use. Multivariable Cox models adjusted the association of CA with the outcomes for the time varying confounders of the presence of an implantable cardioverter defibrillator (ICD) or cardiac resynchronization therapy (CRT), anticoagulation use (warfarin or direct oral anticoagulation), and any antiarrhythmic (AAD) use during follow-up. For non-fatal outcomes, the competing risk of death was accounted for using the Lunn-McNeil approach. Results Of the 87,676 AF-HF patients, 298 underwent CA and were matched to 591 controls. After IPTW, the distribution of covariates was balanced between cases and controls [age 65.6±11.0 vs 61.6±11.6; women 24% vs 20%; CHA2DS2-Vasc score 3.2±2.3 vs 2.9±2.1; CA vs non-CA, respectively; standardized mean differences Conclusion In a matched population-based AF-HF cohort, CA was associated with a reduced risk of all-cause mortality compared to patients who did not undergo CA. Although no difference in the risk of HF hospitalizations, stroke/TIA, and major bleeding was detected between CA and non-CA patients, larger studies are warranted. Acknowledgement/Funding Canadian Institute of Health Research; Fonds de recherché du Quebec-Santé, Clinical Research Scholar Award (V. Essebag) and Doctoral Award (M. Samuel)

Background: Oral anticoagulant use is common among patients undergoing pacemaker or defibrillator surgery. BRUISE CONTROL (Bridge or Continue Coumadin for Device Surgery Randomized Controlled Trial; NCT00800137) demonstrated that perioperative warfarin continuation reduced clinically significant hematomas (CSH) by 80% compared with heparin bridging (3.5% versus 16%). BRUISE-CONTROL-2 (NCT01675076) observed a similarly low risk of CSH when comparing continued versus interrupted direct oral anticoagulant (2.1% in both groups). Using patient level data from both trials, the current study aims to: (1) evaluate the effect of concomitant antiplatelet therapy on CSH, and (2) understand the relative risk of CSH in patients treated with direct oral anticoagulant versus continued warfarin. Methods: We analyzed 1343 patients included in BRUISE-CONTROL-1 and BRUISE-CONTROL-2. The primary outcome for both trials was CSH. There were 408 patients identified as having continued either a single or dual antiplatelet agent at the time of device surgery. Results: Antiplatelet use (versus nonuse) was associated with CSH in 9.8% versus 4.3% of patients ( P P =0.0071). In multivariable analysis, adjusting for antiplatelet use, there was no significant difference in CSH observed between direct oral anticoagulant use compared with continued warfarin (odds ratio, 0.858; 95% CI, 0.375–1.963; P =0.717). Conclusions: Concomitant antiplatelet therapy doubled the risk of CSH during device surgery. No difference in CSH was found between direct oral anticoagulant versus continued warfarin. In anticoagulated patients undergoing elective or semi-urgent device surgery, the patient specific benefit/risk of holding an antiplatelet should be carefully considered. Clinical Trial Registration: URL: https://www.clinicaltrials.gov . Unique identifiers: NCT00800137, NCT01675076.

Introduction Catheter ablation (CA) has been increasingly used to treat atrial fibrillation (AF) in patients with heart failure (HF), however, its safety at the population-level has not yet been evaluated. To assess the safety of CA in AF-HF patients, the frequency and potential risk factors for adverse events (AEs) within 30 days post-CA were determined. Methods A population-based cohort of AF-HF patients who underwent CA in Quebec, Canada (2000-2017) was constructed using administrative databases. Major AEs included all-cause mortality, cerebrovascular accident (CVA), pericardial effusion requiring drainage (PERD), vascular AEs, hemorrhage/hematoma, and pulmonary embolism. Univariate logistic regression models were employed to assess potential risk factors for major AEs. Results Of 700 AF-HF patients who underwent CA (median age 64.5 years [interquartile range, IQR, 56.2-71.0], 22.0% female, and median CHA2 DS2 -Vasc 3 [IQR, 2-4]), 14 (2.0%) patients developed 16 major AEs within 30 days of CA. Hemorrhage/hematoma was the most frequent major AE (four patients; 0.6%) followed by all-cause mortality, CVA/TIA, PERD, and vascular AEs (three patients each; 0.4%). Coronary artery disease (odds ratio [OR], 3.9 [95% confidence interval, CI, 1.2-12.3]) and age ≥65 years (OR, 3.1 [95% CI, 1.1-9.8]) were identified predictors for the composite outcome of major AEs. More than half of the patients (57.2%) underwent a second CA within a median of 0.8 (IQR, 0.2-2.2) years from the date of first CA. Conclusion CA performed in the AF-HF population portends a relatively low incidence of major AEs. A larger study is required to determine whether certain patient factors are independently associated with a higher risk of post-CA AEs.

BACKGROUND Cardiac resynchronization therapy (CRT) reduces morbidity and mortality in heart failure with reduced ejection fraction (HFrEF). CRT efficacy is greater in left bundle branch block (LBBB). This study aimed to determine if strict LBBB criteria predict an improved QRS duration and left ventricular ejection fraction (LVEF) response after CRT. METHODS HFrEF patients who received a CRT device at a single quaternary center were included. Patients were divided into three groups based on baseline QRS morphology. Group 1 consisted of patients with strict LBBB. Group 2 had conventional LBBB, and group 3 had non-LBBB morphology. Outcomes assessed included change in QRS duration after CRT, change in LVEF, and all-cause mortality. RESULTS In 231 patients, 56% of patients were in group 1, 29% were in group 2, and 15% were in group 3. Patients with strict LBBB had a significant reduction in QRS duration (-20.9 ± 12.4 ms) compared to conventional LBBB (6.7 ± 19.4 ms; P

A significant proportion of patients’ experience recurrence of atrial fibrillation (AF) despite pulmonary venous isolation (PVI), especially those with persistent AF. Isolation of the left atrial appendage (LAA) may reduce AF recurrence. The aim of this study was to assess the efficacy of LAA isolation in addition to PVI compared with PVI alone. We conducted a comprehensive search of electronic databases, up to April 21st, 2017, for all studies comparing the effect LAA electrical isolation or ligation in addition to PVI, as opposed to PVI alone, on the recurrence of atrial fibrillation after catheter ablation. We used random‐effects meta‐analysis models to summarize the studies. One RCT and four observational studies enrolling 781 patients were retained. Four studies assessed the added effect of LAA catheter ablation, and one study evaluated the effect of LAA ligation with the aim of LAA electrical isolation. Four studies exclusively enrolled patients with persistent atrial fibrillation and one study predominantly enrolled patients with persistent atrial fibrillation. Follow‐up ranged from 12 to 15 months. The addition of LAA isolation to PVI reduced AF recurrence compared with the latter alone (odds ratio (OR) = 0.19; 95% confidence intervals (CI) = 0.10‐0.37; P

The unpredictable nature and potentially catastrophic consequences of ventricular arrhythmias (VAs) have obligated physicians to search for therapies to prevent sudden cardiac death (SCD). At present, a low left ventricular ejection fraction (LVEF) has been used as a risk factor to predict SCD in patients with structural heart disease and has been consistently adopted as the predominant, and sometimes sole, indication for implantable cardioverter defibrillator (ICD) therapy. Although the ICD remains the mainstay life-saving therapy for SCD, it does not modify the underlying arrhythmic substrate and may be associated with adverse effects from perioperative and long-term complications. Preventative pharmacological therapy has been associated with limited benefits, but anti-arrhythmic medications have significant side effects profiles. Catheter ablation of VAs has greatly evolved over the last few decades. Substrate mapping in sinus rhythm has allowed haemodynamically unstable VAs to be successfully treated. Both LVEF as an indication for ICD therapy and electro-anatomical mapping for substrate modification identify static components of underlying myocardial arrhythmogenicity. They do not take into account dynamic factors, such as the mechanisms of arrhythmia initiation and development of new anatomical or functional lines of block, leading to the initiation and maintenance of VAs. Dynamic factors are difficult to evaluate and consequently are not routinely used in clinical practice to guide treatment. However, progress in the treatment of VAs should consider and integrate dynamic factors with static components to fully characterize the myocardial arrhythmic substrate.

BACKGROUND Little is known about the relationship between daily atrial fibrillation (AF) burden and quality of life (QOL). We sought to determine the influence of atrial tachycardia (AT) or AF burden on measures of QOL and symptoms. METHODS AND RESULTS We retrospectively analyzed patients with dual-chamber pacemakers from the Atrial Septal Pacing Efficacy Clinical Trial (ASPECT), Atrial Therapy Efficacy and Safety Trial (ATTEST), and aTRial arrhythmias dEtected by implaNted Device diagnostics Study (TRENDS) trials. All patients underwent at least one QOL evaluation. We predefined four AF burden groups: no AT/AF (group 1), ≤30 minutes (group 2), 30 minutes-2 hours (group 3), and >2 hours (group 4) per day. We compared QOL measures using the 12-item Short-Form Health Survey (SF-12; standard 4 week recall) and the AF Symptom Checklist (SC) severity and frequency between groups 2-4 to those in group 1. A total of 798 patients were analyzed (age 72 ± 11 years, 447 male [56%]). SC frequency and severity and SF-12 physical and mental scores worsened significantly when patients in group 4 were compared to patients with no AF. There were no statistically significant differences for any of the measures when comparing group 2 or 3 patients to group 1. By linear regression, only the 2-hour-cutoff had a significant impact on QOL as measured by SC frequency (+3.15, P < 0.001), severity (+3.23, P < 0.001), SF-12 physical score (-2.42, P = 0.013), and SF-12 mental score (-2.11, P = 0.021). CONCLUSION A daily AT/AF burden of more than 2 hours had significant impact on QOL. This might influence the choice of appropriate cut-off points to determine the success of an AF treatment.

This study sought to evaluate the predictive value of noninducibility on long-term outcomes.The traditional endpoint for catheter ablation of ventricular tachycardia (VT) is noninducibility of VT by programmed stimulation; however, the definition of inducibility remains variable and its prognostic value limited by nonstandardized periprocedural antiarrhythmic drug therapy and implantable cardioverter-defibrillator programming in prior observational studies. The VANISH trial randomized patients with prior myocardial infarction and VT to ablation (with an endpoint of noninducibility of VT ≥300 ms after ablation) versus antiarrhythmic drug escalation.Patients enrolled in the VANISH study randomized to catheter ablation were included. The relationship between post-ablation inducibility and the primary composite endpoint (death, VT storm30 days, or appropriate implantable cardioverter-defibrillator shock30 days) was assessed using a time-to-event analysis, adjusting for other clinical and procedural characteristics.A total of 129 patients from the ablation arm were included in the primary analysis, of which 51 were noninducible post-ablation compared with 78 who had inducible VT or in whom inducibility testing was not performed. There were no significant baseline characteristic or procedural differences except for increased implantable cardioverter-defibrillator shocks before randomization in the noninducible group. In multivariate analysis, inducibility significantly increased the risk of death, appropriate shock, or VT storm after 30 days (HR: 1.87; p = 0.017).Inducibility of any VT post-ablation was associated with an increased risk of the composite endpoint in the VANISH trial. A randomized trial is required to confirm whether more aggressive ablation targeting faster induced VTs (300 ms) can improve outcomes.

Background— The resynchronization-defibrillation for ambulatory heart failure trial (RAFT) study demonstrated that adding cardiac resynchronization therapy (CRT) in selected patients requiring de novo implantable cardiac defibrillators (ICD) reduced mortality as compared with ICD therapy alone, despite an increase in procedure-related adverse events. Data are lacking regarding the management of patients with ICD therapy who develop an indication for CRT upgrade. Methods and Results— Participating RAFT centers provided data regarding de novo CRT-D (CRT with ICD) implant, upgrade to CRT-D during RAFT (study upgrade), and upgrade within 6 months after presentation of study results (substudy). Substudy centers enrolled 1346 (74.9%) patients in RAFT, including 644 de novo, 80 study upgrade, and 60 substudy CRT attempts. The success rate (initial plus repeat attempts) was 95.2% for de novo versus 96.3% for study upgrade and 90.0% for substudy CRT attempts ( P =0.402). Acute complications occurred among 26.2% of de novo versus 18.8% of study upgrade and 3.4% of substudy CRT implantation attempts ( P Conclusions— Among a broad group of implant physicians, CRT upgrades were performed in patients with an ICD in situ with no difference in implant success rate and a reduced acute complication rate as compared with a de novo CRT implant. Decisions to upgrade were influenced by predictors of benefit in subgroup analyses of the RAFT study and other trials.

Background Intracardiac thrombi arising in the left atrial appendage (LAA) are the principal cause of stroke in nonvalvular atrial fibrillation (AF). Predicting the presence of LAA thrombi is of vital importance in stratifying patients that would need further LAA imaging prior to cardioversion or AF ablation. Methods We comprehensively searched PubMed from its inception to November 2017 for randomized controlled trials, cohort and case control studies, as well as for case series on LAA thrombi risk factors, imaging, prevention, and anticoagulation management in atrial fibrillation. Results A systematic review of the literature identified 106 articles that investigated the presence of LAA thrombi in AF patients. We classified the articles according to topic and reported on: (1) risk factors; (2) diagnostic imaging modalities; (3) prevention strategies before cardioversion; (4) prevention strategies before AF ablation; and (5) management of detected LAA thrombi. Conclusions Integration of clinical, biomarker, and imaging risk factors can improve overall prediction for the presence of LAA thrombi, translating into improved patient selection for imaging. The gold standard for the diagnosis of LAA thrombi remains transesophageal echocardiography, although intracardiac ultrasound, cardiac computed tomography, and cardiovascular magnetic imaging are promising alternative modalities. When LAA thrombi are discovered, the treatment regimen remains variable, although direct oral anticoagulants might have efficacy similar to vitamin K antagonists. Future trials will help further elucidate direct oral anticoagulant use for the treatment of LAA thrombi.

Aims The purpose of this study was to evaluate the outcomes of purely substrate-guided ventricular tachycardia (VT) ablation in patients with non-ischaemic dilated cardiomyopathy (NIDCM) and ischaemic cardiomyopathy (ICM) and the impact of acute procedural success on long-term outcome. Methods and results One hundred and forty-two patients (65 ± 12 years old, 72% male) with ICM ( n = 87) and with NIDCM ( n = 55) underwent substrate-guided VT ablation. The ablation approach involved eliminating all LP regions and ablating all scar border zone regions with 10 or more out of 12 pace-matching. All patients were followed with regular implantable defibrillator interrogations for mean 641 ± 301 days. Complete acute success (no inducible VT) was achieved in 60 patients with ICM (69%) and in 29 patients with NIDCM (53%) ( P = 0.03). Partial success (elimination of clinical VT only) was obtained in nine patients with ICM (10%) and in four patients with NIDCM (7%) ( P = 0.14). Procedural failure (clinical VT still inducible) occurred in 18 patients within the ICM group (21%) and in 22 patients of the NIDCM (40%) ( P = 0.04). Overall, 51 patients presented with recurrence of ventricular arrhythmias: 23 in the group with ICM (26%) and 28 in the group with NIDCM (51%) ( P = 0.03). Long-term success was related to acute procedural outcome. Conclusions Substrate-guided ablation is an effective approach in the treatment of VT with long-term outcome directly related to acute procedural success. Success rates are significantly lower in patients with NIDCM compared with those with ICM.