Non-invasive stereotactic arrhythmia radiotherapy for ventricular tachycardia: results of the prospective STARNL-1 trial.

AIMS: Stereotactic arrhythmia radiotherapy (STAR) is suggested as potentially effective and safe treatment for patients with therapy-refractory ventricular tachycardia (VT). However, the current prospective knowledge base and experience with STAR is limited. In this study we aimed to prospectively evaluate the efficacy and safety of STAR. METHODS AND RESULTS: The StereoTactic Arrhythmia Radiotherapy in the Netherlands no.1 was a pre-post intervention study to prospectively evaluate efficacy and safety of STAR. In patients with therapy-refractory VT, the pro-arrhythmic region was treated with a 25 Gy single radiotherapy fraction. The main efficacy measure was a reduction in the number of treated VT-episodes by ≥50%, comparing the 12 months before and after treatment (or end of follow-up, excluding a 6-week blanking period). The study was deemed positive when ≥50% of patients would meet this criterion. Safety evaluation included left ventricular ejection fraction, pulmonary function, and adverse events. Six male patients with an ischaemic cardiomyopathy were enrolled, and median age was 73 years (range 54-83). Median left ventricular ejection fraction was 38% (range 24-52). The median planning target volume was 187 mL (range 93-372). Four (67%) patients completed the 12-month follow-up, and two patients died (not STAR related) during follow-up. The main efficacy measure of ≥50% reduction in treated VT-episodes at the end of follow-up was achieved in four patients (67%). The median number of treated VT-episodes was reduced by 87%. No reduction in left ventricular ejection fraction or pulmonary function was observed. No treatment related serious adverse events occurred. CONCLUSIONS: STAR resulted in a ≥ 50% reduction in treated VT-episodes in 4/6 (67%) patients. No reduction in cardiac and pulmonary function nor treatment-related serious adverse events were observed during follow-up. CLINICAL TRIAL REGISTRATION: Netherlands Trial Register-NL7510.

The genetic basis of apparently idiopathic ventricular fibrillation: a retrospective overview.

AIMS: During the diagnostic work-up of patients with idiopathic ventricular fibrillation (VF), next-generation sequencing panels can be considered to identify genotypes associated with arrhythmias. However, consensus for gene panel testing is still lacking, and variants of uncertain significance (VUS) are often identified. The aim of this study was to evaluate genetic testing and its results in idiopathic VF patients. METHODS AND RESULTS: We investigated 419 patients with available medical records from the Dutch Idiopathic VF Registry. Genetic testing was performed in 379 (91%) patients [median age at event 39 years (27-51), 60% male]. Single-gene testing was performed in 87 patients (23%) and was initiated more often in patients with idiopathic VF before 2010. Panel testing was performed in 292 patients (77%). The majority of causal (likely) pathogenic variants (LP/P, n = 56, 15%) entailed the DPP6 risk haplotype (n = 39, 70%). Moreover, 10 LP/P variants were found in cardiomyopathy genes (FLNC, MYL2, MYH7, PLN (two), TTN (four), RBM20), and 7 LP/P variants were identified in genes associated with cardiac arrhythmias (KCNQ1, SCN5A (2), RYR2 (four)). For eight patients (2%), identification of an LP/P variant resulted in a change of diagnosis. In 113 patients (30%), a VUS was identified. Broad panel testing resulted in a higher incidence of VUS in comparison to single-gene testing (38% vs. 3%, P < 0.001). CONCLUSION: Almost all patients from the registry underwent, albeit not broad, genetic testing. The genetic yield of causal LP/P variants in idiopathic VF patients is 5%, increasing to 15% when including DPP6. In specific cases, the LP/P variant is the underlying diagnosis. A gene panel specifically for idiopathic VF patients is proposed.

Long-term success of a multi-electrode substrate mapping and ablation strategy versus a classic single tip mapping and ablation strategy for ventricular tachycardia ablation in patients with ischemic cardiomyopathy.

INTRODUCTION: Over the past years, mapping and ablation techniques for the treatment of ventricular tachycardia (VT) have evolved rapidly. High Density (HD) substrate mapping is now routine and pre-procedural imaging is increasingly used. The additional value of these techniques for long-term VT-free survival is not clear. METHODS: We compared baseline and procedural characteristics, procedural success, safety and outcome of mapping and ablation of ventricular tachycardia in patients with ischemic heart disease between two groups. (1) Low Density (LD) group: VT mapping and ablation with a 4 mm single tip catheter (2) HD group: HD substrate mapping with the Pentaray (Biosense Webster, USA) or HD Grid (Abbott, USA) catheter and ablation with a 4 mm single tip catheter. RESULTS: VT ablation was performed in 133 patients (71 patients in LD group and 62 patients in HD group). The median follow-up was 5.0 years in LD group and 2.0 years in HD group. One-, two-, and five-year VT recurrence rates were 47%, 56%, and 65% in the LD group versus 39%, 50%, and 55% in the HD group (log-rank test for VT recurrence p = .70). One-, two-, and five-year ICD shock recurrence rates were 14%, 18%, and 24% in the LD group versus 8%, 15%, and 19% in the HD group (log-rank test for ICD-shock p = .79). All-cause mortality, cardiac (non-arrhythmic), and arrhythmic death, were similar in both groups. Severe procedural complications (tamponade, stroke, or procedural death) occurred in four patients (5%, 1 vascular, 3 tamponade) in the LD group versus two patients (3%, both tamponade) in the HD group (NS). In univariate and multivariable analysis, only a higher LVEF was significantly associated with VT-free survival. HD mapping was not significantly associated with VT-free survival. Anterior infarct location and age were significantly associated with ICD recurrent shock in both univariate and multivariable analyses. CONCLUSIONS: In patients with ischemic cardiomyopathy, a HD substrate mapping, and ablation strategy did not lead to higher VT-free survival and shock-free survival compared to a single tip mapping and ablation strategy. In this study, only LVF is an independent predictor for VT recurrence. Anterior infarct location and age predict recurrent ICD shocks.

High-density mapping for ablation of atypical atrial flutters - procedural characteristics related to outcome.

BACKGROUND: High-density (HD) mapping is increasingly used to characterize arrhythmic substrate for ablation of atypical atrial flutters (AAFl). However, results on clinical outcomes and factors that are associated with arrhythmia recurrence are scarce. METHODS: Single-center, prospective, observational cohort study that enrolled patients with catheter ablation for AAFl using a HD mapping system and a grid-shaped mapping catheter. Procedural characteristics, rates of atrial flutter recurrence, and factors that were associated with atrial flutter recurrence were evaluated. RESULTS: Sixty-one patients with a total of 94 AAFl were included in the cohort. HD mapping was used to successfully identify the flutter circuit of 80/94 AAFl. The circuit was not identified for 14/94 AAFl in 11 patients. Critical isthmuses were identified and ablated in 29 patients (48%). Acute procedural success was achieved in 52 patients (85%), and 37 patients (61%) remained free from atrial flutter recurrence during a follow up of 1.3 [1.0-2.1] years. Atrial flutter recurrence was univariably associated with presence of a non-identified flutter circuit (HR:2.6 95% CI [1.1-6.3], p = .04) and critical isthmus-targeted ablation (HR:0.4 [0.15-0.90], p = .03). In multivariable regression analyses, critical isthmus ablation remained significant (HR:0.4 [0.16-0.97], p = .04), whereas presence of a non-identified flutter did not (HR:2.4 [0.96-5.8], p = .06). CONCLUSION: HD mapping was successfully used to identify the majority of AAFl circuits. Ablation resulted in freedom from atrial flutter recurrence in 61% of the cohort. Successful identification of all flutter circuits and critical isthmuses appears to be beneficial for long-term outcomes.

Predictors of appropriate implantable cardiac defibrillator therapy in cardiac sarcoidosis.

BACKGROUND: Cardiac sarcoidosis (CS) is associated with an increased risk for sudden cardiac death. An implantable cardiac defibrillator (ICD) is recommended in a subgroup of CS patients. However, the recommendations for primary prevention differ between guidelines. The purpose of the study was to evaluate the efficacy and safety of ICDs in CS and to identify predictors of appropriate therapy. METHODS: A retrospective cohort study was performed in CS patients with an ICD implantation between 2010 and 2019. Primary outcome was appropriate ICD therapy. Independent predictors were calculated using Cox proportional hazard analysis. RESULTS: 105 patients were included. An ICD was implanted for primary prevention in 79%. During a median follow-up of 2.8 years, 34 patients (32.4%) received appropriate ICD therapy of whom 24 (22.9%) received an appropriate shock. Three patients (2.9%) received an inappropriate shock due to atrial fibrillation. Independent predictors of appropriate therapy included prior ventricular arrhythmias (hazard ratio [HR]: 10.5 [95% confidence interval (CI): 5.0-21.9]) and right ventricular late gadolinium enhancement (LGE) (HR: 3.6 [95% CI: 1.7-7.6]). Within the primary prevention group, right ventricular LGE (HR: 5.7 [95% CI: 1.6-20.7]) was the only independent predictor of appropriate therapy. Left ventricular ejection fraction did not differ between patients with and without appropriate therapy (44.4% vs. 45.6%, p = .70). CONCLUSION: In CS patients with an ICD, a high rate of appropriate therapy was observed and a low rate of inappropriate shocks. Prior ventricular arrhythmias and right ventricular LGE were independent predictors of appropriate therapy.

Persistent phrenic nerve palsy after atrial fibrillation ablation: Follow-up data from The Netherlands Heart Registration.

BACKGROUND: Persistent phrenic nerve palsy (PNP) is an established complication of atrial fibrillation (AF) ablation, especially during cryoballoon and thoracoscopic ablation. Data on persistent PNP reversibility is limited because most patients recover <24 h. This study aims to investigate persistent PNP recovery, freedom of PNP-related symptoms after AF ablation and identify baseline variables associated with the occurrence and early PNP recovery in a large nationwide registry study. METHODS: In this study, we used data from the Netherlands Heart Registration, comprising data from 9549 catheter and thoracoscopic AF ablations performed in 2016 and 2017. PNP data was available of 7433 procedures, and additional follow-up data were collected for patients who developed persistent PNP. RESULTS: Overall, the mean age was 62 ± 10 years, and 67.7% were male. Fifty-four (0.7%) patients developed persistent PNP and follow-up was available in 44 (81.5%) patients. PNP incidence was 0.07%, 0.29%, 1.41%, and 1.25%, respectively for patients treated with conventional-RF, phased-RF, cryoballoon, and thoracoscopic ablation respectively. Seventy-one percent of the patients fully recovered, and 86% were free of PNP-related symptoms after a median follow-up of 203 (113-351) and 184 (82-359) days, respectively. Female sex, cryoballoon, and thoracoscopic ablation were associated with a higher risk to develop PNP. Patients with PNP recovering ≤180 days had a larger left atrium volume index than those with late or no recovery. CONCLUSION: After AF ablation, persistent PNP recovers in the majority of patients, and most are free of symptoms. Female patients and patients treated with cryoballoon or thoracoscopic ablation are more prone to develop PNP.

Loss of cardiac synchronization due to automatic sense testing.

In the latest generation Biotronik cardiac resynchronization devices, cardiac resynchronization therapy (CRT) may be inadvertently interrupted due to automatic sense testing. This issue can easily be recognized during device interrogation by the "CRT interrupt warning."To avoid CRT interruption, both understanding of the algorithm and correct device programming are critical. The automatic sense testing algorithm has no built-in protection to avoid CRT interrupted pacing. When implanting this generation of devices programming needs to be adequate to avoid the occurrence of this phenomenon.

Dielectric imaging for electrophysiology procedures: The technology, current state, and future potential.

Electroanatomic mapping systems have become an essential tool to guide the identification and ablation of arrhythmic substrate. Recently, a novel guiding system for electrophysiology procedures was introduced that uses dielectric sensing to perform high resolution anatomical imaging. Dielectric imaging systems use electrical fields to differentiate anatomic structures based on their conductivity and permittivity. This technique enables non-fluoroscopic, noncontact mapping of anatomic structures, assessment of pulmonary vein occlusion state during cryoballoon ablation, and has the potential to assess for additional tissue characterization including tissue thickness and tissue type. This article elaborates on the functioning and potential of dielectric imaging systems and provides two cases to illustrate the clinical impact for electrophysiology procedures.

Efficacy and safety of the GOLD FORCE multicentre randomized clinical trial: multielectrode phased radiofrequency vs. irrigated radiofrequency single-tip catheter with contact force ablation for treatment of symptomatic paroxysmal atrial fibrillation.

AIMS: Pulmonary vein isolation (PVI) for atrial fibrillation (AF) has become increasingly safe and effective with the evolution of single-tip ablation catheters aided by contact force sensing (ST-CF) and single-shot devices such as the second-generation pulmonary vein ablation catheter (PVAC) Gold multi-electrode array. The multicentre randomized GOLD FORCE trial was conducted to evaluate non-inferiority of safety and efficacy of PVAC Gold PVI compared to ST-CF ablation for paroxysmal AF. METHODS AND RESULTS: The primary efficacy endpoint documented AF recurrence ≥30 s was assessed by time-to-first-event analysis after a 90-day blanking period using repeated 7-day Holters. Secondary endpoints include acute success and procedural characteristics. Safety endpoints included procedural complications, stroke/transient ischaemic attack (TIA), tamponade, bleeding, and access site complications. Two hundred and eight patients underwent randomization and PVI (103 assigned to PVAC Gold, 105 to ST-CF). Acute success rates were 95% and 97% for PVAC Gold and ST-CF, respectively. At 12 months, AF recurrence was observed in 46.6% of the PVAC Gold group and in 26.2% of the ST-CF group [absolute efficacy difference 20.4% (95% confidence interval, CI 7.5-33.2%), hazard ratio 2.05 (95% CI 1.28-3.29), P = 0.003]. PVAC Gold had significantly shorter procedure and ablation times. Complication rates were 5.7% and 4.9% for PVAC Gold and ST-CF, respectively (P = 0.782). CONCLUSION: In this multicentre randomized clinical trial, ablation with ST-CF and PVAC Gold ablation catheters non-inferiority for efficacy was not met. AF recurrence was significantly more frequent in the PVAC Gold group compared to single-tip contact force group. Both groups had similarly low rates of adverse events. PVAC Gold ablation had significantly shorter procedure and ablation times.

Complications in pulmonary vein isolation in the Netherlands Heart Registration differ with sex and ablation technique.

AIMS: Pulmonary vein isolation (PVI) has become a cornerstone of the invasive treatment of atrial fibrillation. Severe complications are reported in 1-3% of patients. This study aims to compare complications and follow-up outcome of PVI in patients with atrial fibrillation. METHODS AND RESULTS: The data were extracted from the Netherlands Heart Registration. Procedural and follow-up outcomes in patients treated with conventional radiofrequency (C-RF), multielectrode phased RF (Ph-RF), or cryoballoon (CB) ablation from 2012 to 2017 were compared. Subgroup analysis was performed to identify variables associated with complications and repeat ablations. In total, 13 823 patients (69% male) were included. The reported complication incidence was 3.6%. Patients treated with C-RF developed more cardiac tamponades (C-RF 0.8% vs. Ph-RF 0.3% vs. CB 0.3%, P ≤ 0.001) and vascular complications (C-RF 1.7% vs. Ph-RF 1.2% vs. CB 1.3%, P ≤ 0.001). Ph-RF was associated with fewer bleeding complications (C-RF: 1.0% vs. Ph-RF: 0.4% vs. CB: 0.7%, P = 0.020). Phrenic nerve palsy mainly occurred in patients treated with CB (C-RF: 0.1% vs. Ph-RF: 0.2% vs. CB: 1.5%, P ≤ 0.001). In total, 18.4% of patients were referred for repeat ablation within 1 year. Female sex, age, and CHA2DS2-VASc were independent risk factors for cardiac tamponade and bleeding complications, with an adjusted OR for female patients of 2.97 (95% CI 1.98-4.45) and 2.02 (95% CI 1.03-4.00) respectively. CONCLUSION: The reported complication rate during PVI was low. Patients treated with C-RF ablation were more likely to develop cardiac tamponades and vascular complications. Female sex was associated with more cardiac tamponade and bleeding complications.

ICD implantation for secondary prevention in patients with ventricular arrhythmia in the setting of acute cardiac ischemia and a history of myocardial infarction.

INTRODUCTION: In patients with a prior myocardial infarction (MI) but preserved left ventricular (LV) function, sustained ventricular arrhythmias (VAs) may arise in the setting of an acute coronary syndrome (ACS). It is unknown whether an implantable cardioverter-defibrillator (ICD) is mandatory in these patients as VA might be triggered by a reversible cause. The purpose of this study is to analyze the benefit of ICD therapy in this patient population. METHODS: We conducted a retrospective observational study in ICD recipients implanted from 2008 to 2011. The study group consisted of patients with sustained VA in the setting of an ACS, with a history of MI, but with left ventricular ejection fraction (LVEF) greater than 35 (group A). The two control groups consisted of patients admitted with VA with a history of MI, but without ACS at presentation, either with LVEF greater than 35% (group B) or ≤35% (group C). The primary endpoint was the number of patients with appropriate ICD therapy (antitachycardia pacing or shock). RESULTS: A total of 291 patients were included with a mean follow-up of 5.3 years. Appropriate ICD therapy occurred in 45.6% of the patients in group A vs 51.6% and 60.4% in groups B and C (P = .11). In group A, 31.1% received an appropriate ICD shock vs 34.7% and 44.3% in control groups B and C (P = .12). CONCLUSION: On the basis of these data, ICD implantation seems warranted in patients with history of MI presenting with VA in the setting of an ACS, despite preserved LV function and adequate revascularization. Further trials, preferably randomizes, should be performed to address these findings.

Left atrial catheter ablation in patients with previously implanted left atrial appendage closure devices.

AIMS: Left atrial appendage closure (LAAC) is increasingly used as an alternative to oral anticoagulation (OAC) for stroke prevention in atrial fibrillation (AF) patients. Feasibility and safety of left atrial (LA) catheter ablation (CA) in patients with previously implanted LAAC devices have not been well studied. We report on the feasibility, safety, and efficacy of LA CA in the presence of a previously implanted LAAC device. METHODS AND RESULTS: In this prospective cohort study consecutive patients that underwent LA CA with a previously implanted Watchman device were included. Periprocedural characteristics and long-term clinical follow-up were evaluated. Twenty-three LA CA procedures were performed in 19/162 AF patients with previously implanted Watchman devices [47% male, age 63.9 ± 6.2 years, CHA2DS2-VASc 4.0 (3.0-5.0); HASBLED 3.0 (2.0-4.0); 63% paroxysmal]. Left atrial CA was performed with irrigated radiofrequency (RF; n = 20, 87%) or phased RF (n = 3, 13%) in a mean of 18 months after LAAC implantation (range 4-80 months). Targets of CA consisted of pulmonary vein isolation (n = 19, 83%), superior vena cava isolation (n = 13, 57%), and additional linear lesions (n = 8, 35%). Procedures were carried out under vitamin K antagonist (VKA; n = 6, 26%), non-VKA OAC (NOAC; n = 8, 35%), or single antiplatelet therapy alone (n = 9, 39%). Left atrial CA was successful without any signs of interference from the device. Procedure-related complications were not observed. During a mean follow-up of 28 months, 11 patients (58%) had AF recurrence. CONCLUSION: Left atrial CA after LAAC appears to be feasible, effective, and safe in this single centre cohort. Previously implanted Watchman device should not be a reason to relinquish CA in symptomatic AF patients, even in patients on single antiplatelet therapy alone.

Effects of epicardial versus transvenous left ventricular lead placement on left ventricular function and cardiac perfusion in cardiac resynchronization therapy: A randomized clinical trial.

INTRODUCTION: Optimal left ventricular (LV) lead position in patients undergoing cardiac resynchronization therapy (CRT) is crucial to achieve an optimal effect on hemodynamics. Due to various difficulties, up to 30% of transvenous LV lead placements fail, or a suboptimal position is achieved. Surgical epicardial LV lead placement could be performed at a position anticipated to be the optimal site. This could have a more favorable effect, which may be expressed by increased improvement in left ventricular ejection fraction (LVEF) and cardiac perfusion. The objective of this trial is to compare transvenous versus epicardial LV lead placement in CRT in a randomized fashion METHODS AND RESULTS: Fifty-two patients were randomized to either epicardial or transvenous approach. All patients received an ICD with CRT. Patients were followed for 6 months after device implant. Primary endpoint was the degree of change in cardiac perfusion measured by myocardial perfusion scintigraphy. LVEF equally improved in both groups, from 24% to 36% in the transvenous group versus 25% to 35% in the epicardial group (P = 0.797). Cardiac perfusion, expressed as summed stress score, improved in both groups without a significant difference as well (P = 0.727). Complication rate was similar, respectively 6 and 7 patients had any complication. Admission time was significantly longer in the epicardial group with 2 (2-7) versus 3 (2-32) days (P <0.001). CONCLUSION: Epicardial LV lead placement does not result in additional improvement of LVF or myocardial perfusion compared to the conventional transvenous in CRT.

Effect of alcohol dosage on long-term outcomes after alcohol septal ablation in patients with hypertrophic cardiomyopathy.

OBJECTIVES: The aim of this study is to assess the long-term effects of alcohol dosage in alcohol septal ablation (ASA) on mortality and adverse arrhythmic events (AAE). BACKGROUND: ASA can be performed to reduce left ventricular outflow tract (LVOT) obstruction in patients with hypertrophic cardiomyopathy (HCM). However, the effect of alcohol dosage on long-term outcomes is unknown. METHODS: This retrospective cohort study includes 296 HCM patients (age 60 ± 22 years, 58% male) who underwent ASA because of symptomatic LVOT obstruction. Twenty-nine patients (9.8%) were excluded because the alcohol dosage could not be retrieved. Primary endpoints were all-cause mortality and AAE. RESULTS: During 6.3 ± 3.7 years of follow-up, all-cause mortality and AAE rates were similar in patients who received ≤2.0 mL (n = 142) and >2.0 mL (n = 121) alcohol during ASA. Age was the only independent predictor of mortality (HR 1.1 95% CI 1.0-1.1, P < 0.001). Predictors of AAE were maximum CK-MB >240 U/L (HR 3.3 95% CI 1.5-7.2, P = 0.003), and sudden cardiac death survivor (HR 5.9 95% CI 1.7-20.3, P = 0.004). There was a mild to moderate correlation between CK-MB levels and amount of alcohol (Spearman's ρ 0.39, P < 0.001), cross-sectional area of the target septal branch ostium/ostia (Spearman's ρ 0.19, P = 0.003), and maximum ventricular wall thickness (Spearman's ρ 0.17, P = 0.006). CONCLUSIONS: Alcohol dosage appears not to have a long-term effect on mortality and AAE. A larger infarct size created by ASA increases the risk of AAE, and extended monitoring of these patients is advised. © 2016 Wiley Periodicals, Inc.

Inappropriate Shock Due to T-Wave Oversensing by a Subcutaneous ICD after Alcohol Septal Ablation for Hypertrophic Cardiomyopathy.

A 53-year-old female patient with hypertrophic obstructive cardiomyopathy (HOCM) was admitted for alcohol septal ablation (ASA). A subcutaneous internal cardioverter defibrillator (S-ICD) was implanted for primary prevention. After ASA, the patient developed a right bundle branch block, and the S-ICD delivered a total of five inappropriate shocks due to T-wave oversensing (TWOS). TWOS is a relatively frequent cause of inappropriate shocks in S-ICD patients. After invasive treatment for HOCM, there is a risk of developing intraventricular conduction delay and subsequent changes in QRS and T-wave morphology. This should be taken into consideration when ICD indication is evaluated in HOCM patients.

First-in-Human Experience With Ultra-Low Temperature Cryoablation for Monomorphic Ventricular Tachycardia.

Ultra-low temperature cryoablation (ULTC) using near-critical nitrogen (-196ºC) has been shown to produce durable, contiguous, transmural lesions in ventricles of animal models. This report summarizes acute experience with ULTC in the first-ever 13 patients with recurrent monomorphic ventricular tachycardias (VTs) of both ischemic cardiomyopathy and nonischemic etiologies enrolled in the CryoCure-VT (Cryoablation for Monomorphic Ventricular Tachycardia; NCT04893317) clinical trial. After an average of 9.6 ± 4.6 endocardial ULTC lesions per patient, no clinical ventricular tachycardias were inducible in 91% of patients. Two procedure-related serious adverse events recorded in 2 patients resolved post-procedurally without clinical sequelae. Further investigation of both acute and chronic outcomes is warranted and ongoing.

Dielectric response as a novel marker for ablation lesion quality: Relation to conventional ablation parameters.

Background: The tissue response viewer (TRV) is a novel marker for ablation lesion quality that aims to classify lesions into transmural or nontransmural lesions (high or low dielectric response, HDR or LDR) using dielectric-based tissue assessment. The objective of this study was to gain insight in the TRV by relating its outcomes to conventional ablation parameters. Methods: Patients that had repeat ablation for atrial fibrillation with a dielectric imaging-based mapping system were enrolled. All ablation data were downloaded from the mapping system and analyzed to explore associations between TRV outcomes and other ablation parameters. Results: The cohort included 24 patients, in which 58 pulmonary veins and 8 superior vena cavas were targeted. A total of 388 energy applications were applied, resulting in 639 ablation points. The system classified 36% of ablation points as HDR and 44% as LDR. The system did not provide a dielectric response in 20%. The system's ability to provide a dielectric response was related to longer ablation duration and absence of dragging ablation. HDR (versus LDR) was multivariably associated with longer energy applications, higher mean ablation power, and lower wall thickness. Greater impedance drop was univariably associated with HDR. Conclusion: Outcomes of the TRV are associated with conventional ablation parameters (e.g., duration and power) but also local wall thickness. Catheter stability seems important for successful lesion assessment with the TRV. Further reduction of missing outcomes and validation of the tool are warranted before widespread use.

Importance of Systematic Diagnostic Testing in Idiopathic Ventricular Fibrillation: Results From the Dutch iVF Registry.

BACKGROUND: Idiopathic ventricular fibrillation (iVF) is a diagnosis of exclusion. Systematic diagnostic testing is important to exclude alternative causes for VF. The early use of "high yield" testing, including cardiac magnetic resonance (CMR), exercise testing, and sodium channel blocker provocation, has been increasingly recognized. OBJECTIVES: The purpose of this study was to investigate the importance and consistency of systematic diagnostic testing in iVF. METHODS: This study included 423 iVF patients from 11 large secondary and tertiary hospitals in the Netherlands. Clinical characteristics and diagnostic testing data were ascertained. RESULTS: IVF patients experienced the index event at a median age of 40 years (IQR: 28-52 years), and 61% were men. The median follow-up time was 6 years (IQR: 2-12 years). Over the years, "high yield" diagnostic tests were increasingly performed (mean 68% in 2000-2010 vs 75% in 2011-2021; P < 0.001). During follow-up, 38 patients (9%) originally labeled as iVF received an alternative diagnosis. Patients in whom "high-yield" diagnostic tests were consistently performed during the initial work-up received an alternative diagnosis less frequently during follow-up (HR: 0.439; 95% CI: 0.219-0.878; P = 0.020). Patients who received an alternative diagnosis during follow-up had a worse prognosis in terms of cardiac death (P = 0.012) with a trend toward more implantable cardioverter-defibrillator therapy (P = 0.055). CONCLUSIONS: Although adherence to (near) complete diagnostic testing in this population of iVF patients increased over the years, patients with iVF still undergo varying levels of diagnostic evaluation. The latter leads to initial underdiagnosis of alternative conditions and is associated with a worse prognosis. Our results underscore the importance of early systematic diagnostic assessment in patients with apparent iVF.

Interobserver variability in target definition for stereotactic arrhythmia radioablation.

Background: Stereotactic arrhythmia radioablation (STAR) is a potential new therapy for patients with refractory ventricular tachycardia (VT). The arrhythmogenic substrate (target) is synthesized from clinical and electro-anatomical information. This study was designed to evaluate the baseline interobserver variability in target delineation for STAR. Methods: Delineation software designed for research purposes was used. The study was split into three phases. Firstly, electrophysiologists delineated a well-defined structure in three patients (spinal canal). Secondly, observers delineated the VT-target in three patients based on case descriptions. To evaluate baseline performance, a basic workflow approach was used, no advanced techniques were allowed. Thirdly, observers delineated three predefined segments from the 17-segment model. Interobserver variability was evaluated by assessing volumes, variation in distance to the median volume expressed by the root-mean-square of the standard deviation (RMS-SD) over the target volume, and the Dice-coefficient. Results: Ten electrophysiologists completed the study. For the first phase interobserver variability was low as indicated by low variation in distance to the median volume (RMS-SD range: 0.02-0.02 cm) and high Dice-coefficients (mean: 0.97 ± 0.01). In the second phase distance to the median volume was large (RMS-SD range: 0.52-1.02 cm) and the Dice-coefficients low (mean: 0.40 ± 0.15). In the third phase, similar results were observed (RMS-SD range: 0.51-1.55 cm, Dice-coefficient mean: 0.31 ± 0.21). Conclusions: Interobserver variability is high for manual delineation of the VT-target and ventricular segments. This evaluation of the baseline observer variation shows that there is a need for methods and tools to improve variability and allows for future comparison of interventions aiming to reduce observer variation, for STAR but possibly also for catheter ablation.

Safety of pulmonary vein isolation and left atrial complex fractionated atrial electrograms ablation for atrial fibrillation with phased radiofrequency energy and multi-electrode catheters.

AIMS: Recently, a multi-electrode catheter system using phased radiofrequency (RF) energy was developed specifically for atrial fibrillation (AF) ablation: the pulmonary vein ablation catheter (PVAC), the multi-array septal catheter (MASC), and the multi-array ablation catheter (MAAC). Initial results of small trials have been promising: shorter procedure times and low adverse event rates. In a large single-centre registry, we evaluated the adverse events associated with multi-electrode ablation catheter procedures with PVAC alone, or combined with MASC and MAAC. METHODS AND RESULTS: In all, 634 consecutive patients with AF had 663 procedures with multi-electrode ablation catheters, 502 patients with the PVAC alone, 128 patients with PVAC/MASC/MAAC, 29 redo procedures with the PVAC or PVAC/MASC/MAAC, and 4 patients had a complicated transseptal puncture. Major and minor adverse events during 6 month follow-up were registered. In 15 cases (2.3%), major adverse events were seen within the first month after the procedure. These included complicated transseptal puncture (4), stroke (2), transient ischaemic attack (5), acute coronary syndrome (2), femoral pseudoaneurysm (1), and arteriovenous fistulae (1). Minor adverse events were seen in 10.7% at 6 months, mostly due to femoral haematoma (3.9%), and non-significant PV stenosis (5.2%). There was no difference in the occurrence of major adverse events between PVAC alone, or PVAC/MASC/MAAC ablation. CONCLUSION: Ablation with phased RF and multi-electrode catheters is accompanied by a major adverse event rate of 2.3% within 1 month and a minor event rate of 10.7% at 6 months.