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Background: Early experience with a novel multielectrode saline-irrigated radiofrequency balloon (RFB) catheter with an integrated camera system found that it was safe and effective in performing single-shot pulmonary vein isolation (PVI) for atrial fibrillation., Objective: The purpose of this study was to further assess potential treatment risks by looking for subclinical events., Methods: The study was performed at 2 sites. Patients underwent PVI by RFB. A control group underwent conventional point-by-point radiofrequency ablation. Stroke scale questionnaire and brain magnetic resonance imaging (MRI) were performed before and after the ablation procedure, and esophageal endoscopy was performed after the procedure in RFB patients only., Results: We enrolled 27 patients in the RFB group and 15 patients in the control group. The RFB and control groups were well matched [predominantly male: 62% vs 53%; CHA 2 DS 2 -VASc score: 1.9 ± 1.3 vs 1.5 ± 1.6; mean age 60 years in both groups]. All patients underwent successful ablation and completed study assessments. Clinically silent, new MRI diffusion weighted imaging cerebral lesions were observed in 8 patients (30%) in the RFB group and 1 patient (7%) in the control group, and 11 susceptibility weighted imaging lesions in the RFB group and 1 in the control group. Endoscopy showed a minor thermal injury in 1 patient in the RFB group., Conclusion: An increased rate of clinically silent cerebral events was seen in the RFB group. A low rate of esophageal thermal injury was observed., (© 2021 Heart Rhythm Society. Published by Elsevier Inc.)

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Background: The risk of heart block during radiofrequency ablation of atrioventricular (AV) nodal reentrant tachycardia and septal accessory pathways is minimized by rapidly ceasing ablation in response to markers of risk, such as atrioventricular dissociation, fast junctional rhythm, PR interval prolongation, or 2 consecutive atrial or ventricular depolarizations. Currently this is done manually., Objectives: The objectives of this study were to build and test a control system able to monitor cardiac rhythm and automatically terminate ablation energy when required., Methods: The device was built from off-shelf componentry. Preclinical testing involved real-time input of electrogram/electrocardiogram data from 209 ablation procedures (20 patients) over slow (n = 19) and fast (n = 1) AV nodal pathways. The device response speed was compared with the human response speed. The device's ability to prevent heart block was tested in 5 sheep. First-in-human testing was then performed in 12 patients undergoing AV nodal reentrant tachycardia ablation., Results: Risk conditions necessitating shutoff of ablation (200 total; 111 preclinical and 89 first-in-human) were detected by the device with 100% sensitivity and 94% specificity, automatically terminating ablation while still allowing successful ablation in all patients. Device shutoff of ablation was always faster than human response (median difference 1.24 seconds). In each of 5 sheep, 40 consecutive attempts to cause heart block by ablating over the His bundle were unsuccessful because of automatic shutoff in response to rhythm change., Conclusion: Automated shutoff of ablation close to the AV node in response to markers of the risk of heart block is feasible with high accuracy as well as faster response than human response. The system may improve the safety of ablation near the AV node by preventing heart block., (Copyright © 2020 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)

Objectives: The aim of this study was to evaluate the safety and performance of an extravascular (EV) implantable cardioverter-defibrillator (ICD)., Background: Limitations of existing transvenous and subcutaneous ICD systems include lead reliability and morbidity issues associated with ICD lead implantation in the vasculature or lack of pacing therapies (e.g., antitachycardia pacing) in subcutaneous systems. The EV defibrillator uses a novel substernal lead placement to address these limitations., Methods: This was a prospective, nonrandomized, chronic pilot study conducted at 4 centers in Australia and New Zealand. Participants were 21 patients referred for ICD implantation. Patients received EV ICD systems. Data collection included major systemic and procedural adverse events, defibrillation testing at implantation, and sensing and pacing thresholds., Results: Among 20 patients who underwent successful implantation, the median defibrillation threshold was 15 J, and 90% passed defibrillation testing with a ≥10-J safety margin. Mean R-wave amplitude was 3.4 ± 2.0 mV, mean ventricular fibrillation amplitude was 2.8 ± 1.7 mV, and pacing was successful in 95% at ≤10 V. There were no intraprocedural complications. Two patients have undergone elective chronic system removal since hospital discharge. In the 15 patients presently implanted, the systems are stable in long-term follow-up., Conclusions: This first-in-human evaluation of an EV ICD demonstrated the feasibility of substernal lead placement, defibrillation, and pacing with a chronically implanted system. There were no acute major complications, and pacing, defibrillation, and sensing performance at implantation were successful in most patients. (Extravascular ICD Pilot Study [EV ICD]; NCT03608670)., Competing Interests: Author Relationship With Industry This work was sponsored in its entirety by Medtronic. Dr. Crozier is a consultant for and has received research support and fellowship support from Medtronic; and has received grants from Boston Scientific. Dr. O’Donnell is a consultant for Medtronic and Abbott. Dr. Haqqani is a consultant for Medtronic, Abbott, and Boston Scientific. Drs. Kotschet and Shaw are consultants for Medtronic. Dr. Denman has received grants from Medtronic and Boston Scientific. Ms. Portway, Mr. Sawchuk, Ms. Thompson, Dr. Sherfesee, Mr. Liang, Dr. Lentz, Mr. DeGroot, and Dr. Cheng are employees of Medtronic. The authors have reported that they have no relationships relevant to the contents of this paper to disclose., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

Aim: Christchurch, New Zealand, experienced two major earthquakes on 4th September 2010 and 22nd February 2011. Previous studies have demonstrated that earthquakes are associated with sudden cardiac deaths. Whilst myocardial ischemia would contribute to this, ventricular arrhythmia triggered by stress has also been suggested. We aim to study the impact of the two earthquakes on ventricular arrhythmia events., Methods: We conducted a retrospective review of all patients resident in the earthquake zone with implantable defibrillators. Ventricular arrhythmia requiring therapy and non-sustained events were recorded from the period of 30 days before thru 30 days after the two earthquakes. Weekly event rates were calculated and compared using log rank analysis. Results are expressed as mean (range), significance was determined at the <0.05 level., Results: For the 211 patients who were exposed to the 2010 earthquake, there was no difference in the proportion of patients free of therapy, either Shock or ATP (0.943 before and 0.933 after the earthquake, p = 0.85, ns). Similarly, there was no significant increase in events requiring therapy in the 236 patients exposed to the 2011 earthquake (0.957 before and 0.961 after the earthquake, p = 0.80, ns). We identified one patient who required multiple therapy for ventricular tachycardia immediately following both earthquakes., Conclusion: The two Christchurch earthquakes were not associated with an increase in the event rate of either sustained or non-sustained ventricular arrhythmias in our patients. We identified only a single patient who had arrhythmic storms immediately following the earthquakes., Competing Interests: The authors have declared that no competing interests exist.

Background: Catheter ablation for atrial fibrillation has potential to cause esophageal thermal injury. Esophageal temperature monitoring during ablation is commonly used; however, it has not eliminated thermal injuries, possibly because conventional sensors have poor spatial sampling and response characteristics. To enhance understanding of temperature dynamics that may underlie esophageal injury, we tested a high-resolution, intrabody, infrared thermography catheter to continuously image esophageal temperatures during ablation., Methods and Results: Atrial fibrillation ablation patients were instrumented with a flexible, 9F infrared temperature catheter inserted nasally (n=8) or orally (n=8) into the esophagus adjacent to the left atrium. Ablation was performed while the infrared catheter continuously recorded surface temperatures from 7680 points per second circumferentially over a 6-cm length of esophagus. Physicians were blinded to temperature data. Endoscopy was performed within 24 hours to document esophageal injury. Thermal imaging showed that most patients (10/16) experienced ≥1 events where peak esophageal temperature was >40°C. Three patients experienced temperatures >50°C; and 1 experienced >60°C. Analysis of temperature data for each subject's maximum thermal event revealed high gradients (2.3±1.4°C/mm) and rates of change (1.5±1.3°C/s) with an average length of esophageal involvement of 11.0±5.4 mm. Endoscopy identified 3 distinct thermal lesions, all in patients with temperatures >50°C; all resolved within 2 weeks., Conclusions: Infrared thermography provided dynamic, high-resolution mapping of esophageal temperatures during cardiac ablation. Esophageal thermal injury occurred with temperatures >50°C and was associated with large spatiotemporal gradients. Additional studies are warranted to determine the relationships between thermal parameters and esophageal injury., (© 2018 American Heart Association, Inc.)

Introduction: Adults with congenital heart disease (CHD) frequently have cardiac arrhythmias, many of which are best treated with radiofrequency ablation (RFA). We present our experience in this group., Methods: Retrospective chart based review of diagnosis, arrhythmia type, results of cardiac electrophysiological assessment, and procedural and long-term clinical success of radiofrequency ablation., Results: Forty-five patients were identified with CHD and arrhythmias undergoing RFA; including surgically repaired atrial septal defects (21), Ebstein's anomaly (12), repaired transposition of the great arteries (3), repaired Tetralogy of Fallot (4), repaired ventricular septal defect (3), repaired coarctation (1) and unrepaired anomalous pulmonary venous anatomy (1). Arrhythmias were atrial flutter (24), atrial fibrillation (1), atrial tachycardia (3), atrioventricular nodal re-entrant tachycardia (5), and atrioventricular re-entrant tachycardia (12). Procedural success was ultimately obtained in 36 patients, with 6 having unsuccessful ablation and 3 an undetermined result. Twelve patients required a repeat procedure. One patient required a third procedure and had insertion of permanent pacemaker and atrioventricular nodal ablation. With follow-up (range 2-264 months) 31 patients (69%) remained in sinus rhythm, 9 have developed atrial fibrillation, 3 are in atrial flutter or atrial tachycardia, 1 patient reports ongoing palpitations with no documented arrhythmia and 1 patient has died. Procedural complications were major venous access bleeding (2), transient heart block during slow pathway ablation with late complete heart block (1)., Conclusions: The majority of arrhythmias in adult patients with congenital heart defects can be successfully treated with radiofrequency ablation at a relatively low risk.

Background: We examined equity of access to implanted cardioverter defibrillators (ICDs) in New Zealand in 2010 by district health board (DHB), ethnicity and socioeconomic status., Methods: All new ICD recipients in 2010 were examined according to home district health board, ethnicity according to the national health database, and socioeconomic status using the NZDep index., Results: During 2010, 352 new ICDs were implanted nationwide, giving an overall implantation rate of 80.6/million. However, implant rates varied significantly across the 20 DHBs with the highest implant rate observed in Tairawhiti at 192.3/million, and the lowest at 22/million in the Nelson region. There was also significant variation in implant rate by ethnicity, with Maori ethnicity at an implant rate of 114/million, European patients at 83/million, Pacific Island patients at 47/million and Asian patients an implant rate of 32/million. There was no significant difference in number of implants by socioeconomic decile., Conclusions: The variance in implantation rate by district health board and by ethnicity suggests that access to ICD therapy is not equitable in New Zealand. Investigation into causes of inequity of access is required., (Copyright © 2012 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) and the Cardiac Society of Australia and New Zealand (CSANZ). Published by Elsevier B.V. All rights reserved.)

Background: There is little recent information regarding outcome and its determinants following cardioversion (CV) for atrial fibrillation (AF) or flutter. This study aims to help improve prediction of cardiac rhythm outcome following CV for AF., Methods: Cardiac rhythm at 6 weeks and 12 months was documented following elective (EC; n=496) or immediate (IC; n=52) cardioversion for AF or atrial flutter in a single referral centre., Results: 65 and 58% of IC patients remained in sinus rhythm (SR) 6 weeks and 1 year after CV (respectively) compared with 43% and 30% in EC patients (P<0.001). Independent positive predictors of SR 6 weeks after cardioversion included amiodarone therapy (OR 2.04 [1.28-3.33], P<0.01) and atrial flutter (OR 1.85 [1.09-3.13], P<0.05). Negative predictors included the need for >1 shock to achieve SR (OR 1.61 [1.12-2.37], P=0.011) and arrhythmia duration, (OR 0.96 [0.95-0.97], P<0.001). At 1 year, amiodarone, duration of arrhythmia and the need for >1 shock remained independent predictors of rhythm., Conclusions: The number of shocks required to achieve SR is a newly demonstrated independent predictor of rhythm outcome after elective CV.

Aims: To report the long-term results following percutaneous pulmonary vein ablation (PVA) for atrial fibrillation (AF) at Christchurch Hospital., Methods: A retrospective observational audit review of outcomes. The sample population included all patients identified as having undergone percutaneous radiofrequency ablation of multiple pulmonary veins at Christchurch Hospital, from the first procedure performed on 29 September 2001 until 15 December 2009., Results: A total of 187 patients underwent pulmonary vein ablation. The patient population was predominantly younger (mean age 51) and male (83%) with no important comorbidity. Following a single procedure only, the chance of remaining free of AF at 12 months was 0.74 for patients with paroxysmal AF (PAF) and 0.60 for patients with persistent AF (PsAF). 52 patients (28%) underwent a repeat procedure within 12 months of their index ablation owing to early recurrence of AF. 5-year survival free of clinical AF when analysed following these early repeat procedures, if required, was 0.74 and 0.56 for PAF and PsAF patients respectively. Complications occurred following 6% of procedures and were serious in 2.5%. New atrial flutter developed in 6% of patients., Conclusions: PVA is an effective treatment for AF, with better outcomes in patients with paroxysmal atrial fibrillation. However, as it carries a significant risk, we recommend that its application be reserved for patients with highly symptomatic, medication-refractory disease.