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INTRODUCTION Before ablation, predicting the site of origin (SOO) of outflow tract ventricular arrhythmia (OTVA), can inform patient consent and facilitate appropriate procedural planning. We set out to determine if OTVA variability can accurately predict SOO. METHODS Consecutive patients with a clear SOO identified at OTVA ablation had their prior 24-h ambulatory ECGs retrospectively analysed (derivation cohort). Percentage ventricular ectopic (VE) burden, hourly VE values, episodes of trigeminy/bigeminy, and the variability in these parameters were evaluated for their ability to distinguish right from left-sided SOO. Effective parameters were then prospectively tested on a validation cohort of consecutive patients undergoing their first OTVA ablation. RESULTS High VE variability (coefficient of variation ≥0.7) and the presence of any hour with

Intramural septal substrate presents a challenge in patients undergoing ventricular tachycardia ablation, in terms of both accurate mapping and ablation with unipolar radiofrequency energy. We present the first use of the novel 2-F octapolar catheter in accurately defining intramural septal scar and facilitating bipolar ablation. (Level of Difficulty: Advanced.), Central Illustration

Background A major predictor of eligibility of subcutaneous implantable cardiac defibrillators (S-ICD) is the T:R ratio. The eligibility cut-off of the T:R ratio incorporates a safety margin to accommodate for fluctuations of ECG signal amplitudes. We introduce a deep learning-based tool that accurately measures the degree of T:R ratio fluctuations and explore its role in S-ICD screening. Methods Patients were fitted with Holters for 24 h to record their S-ICD vectors. Our tool was used to assess the T:R ratio over the duration of the recordings. Multiple T:R ratio cut-off values were applied, identifying patients at high risk of T-wave oversensing (TWO) at each of the proposed values. The purpose of our study is to identify the ratio that recognises patients at high risk of TWO while not inappropriately excluding true S-ICD candidates. Results Thirty-seven patients (age 54.5 + / − 21.3 years, 64.8% male) were recruited. Fourteen patients had heart-failure, 7 hypertrophic cardiomyopathy, 7 had normal hearts, 6 had congenital heart disease, and 3 had prior inappropriate S-ICD shocks due to TWO. 54% of patients passed the screening at a T: R of 1:3. All patients passed the screening at a T: R of 1:1. The only subgroup to wholly pass the screening utilising all the proposed ratios are the participants with normal hearts. Conclusion We propose adopting prolonged screening to select patients eligible for S-ICD with low probability of TWO and inappropriate shocks. The appropriate T:R ratio likely lies between 1:3 and 1:1. Further studies are required to identify the optimal screening thresholds.

Percutaneous catheter ablation is an effective and safe therapy that can eliminate ventricular tachycardia, reducing the risks of both recurrent arrhythmia and shock therapies from a defibrillator. Successful ablation requires accurate identification of arrhythmic substrate and the effective delivery of energy to the targeted tissue. A thorough pre-procedural assessment is needed before considered 3D electroanatomical mapping can be performed. In contemporary practice, this must combine traditional electrophysiological techniques, such as activation and entrainment mapping, with more novel physiological mapping techniques for which there is an ever-increasing evidence base. Novel techniques to maximise energy delivery to the tissue must also be considered and balanced against their associated risks of complication. This review provides a comprehensive appraisal of contemporary practice and the evidence base that supports recent developments in mapping and ablation, while also considering potential future developments in the field.

A major predictor of eligibility of subcutaneous implantable cardiac defibrillators (S-ICD) is the T:R ratio. The eligibility cut-off of the T:R ratio incorporates a safety margin to accommodate for fluctuations of ECG signal amplitudes. We introduce a deep learning-based tool that accurately measures the degree of T:R ratio fluctuations and explore its role in S-ICD screening.Patients were fitted with Holters for 24 h to record their S-ICD vectors. Our tool was used to assess the T:R ratio over the duration of the recordings. Multiple T:R ratio cut-off values were applied, identifying patients at high risk of T-wave oversensing (TWO) at each of the proposed values. The purpose of our study is to identify the ratio that recognises patients at high risk of TWO while not inappropriately excluding true S-ICD candidates.Thirty-seven patients (age 54.5 + / - 21.3 years, 64.8% male) were recruited. Fourteen patients had heart-failure, 7 hypertrophic cardiomyopathy, 7 had normal hearts, 6 had congenital heart disease, and 3 had prior inappropriate S-ICD shocks due to TWO. 54% of patients passed the screening at a T: R of 1:3. All patients passed the screening at a T: R of 1:1. The only subgroup to wholly pass the screening utilising all the proposed ratios are the participants with normal hearts.We propose adopting prolonged screening to select patients eligible for S-ICD with low probability of TWO and inappropriate shocks. The appropriate T:R ratio likely lies between 1:3 and 1:1. Further studies are required to identify the optimal screening thresholds.

Haemodialysis patients who require defibrillator therapy are expected to benefit from the entirely avascular subcutaneous defibrillator (S-ICD), but haemodialysis is associated with dynamic changes in R and T wave amplitude which can impact S-ICD eligibility. A continuous assessment of S-ICD eligibility during haemodialysis has not previously been performed.Continuous surface ECG recordings were obtained from a cohort of patients undergoing maintenance haemodialysis, but without an indication for an ICD. Automated vector screening was retrospectively performed at one-minute intervals throughout the dialysis session. Variations in S-ICD eligibility were calculated and in vectors with high degrees of variation, the underlying mechanism was identified.72 vector recordings (mean duration 254.1 ± 6.0 min) were obtained from 24 patients (mean age 64.3 ± 5.5 years, 68% male). At the start of haemodialysis 47 vectors were S-ICD eligible (65.2%). At the end of session, all of these vectors had remained eligible, and an additional 6 vectors had also become eligible (73.6%). High vector score variability was observed in 7 patients and the commonest cause was a progressive change in R:T ratio (71.5%).In a haemodialysis population, a single haemodialysis session can be associated with a potential change in S-ICD eligibility in 8.4% of vectors, with up to 12.5% of vectors showing high degrees of variability, most commonly due to variations in R:T ratio. In an S-ICD population with similar characteristics S-ICD screening prior to haemodialysis would be expected to more accurately identify vectors that retain eligibility.

Pre-implant ECG screening is performed to ensure that S-ICD recipients have at least one suitable sensing vector, yet cardiac over-sensing remains the commonest cause of inappropriate shock therapy in the S-ICD population. One explanation would be the presence of dynamic variations in ECG morphology that result in variations in vector eligibility.Adult ICD patients had a 24-h ambulatory ECG performed using a digital Holter positioned to record all three S-ICD vectors. Using an S-ICD simulator, automated screening was then performed at one-minute intervals. In vectors with a mean vector score 100 (the accepted value for a passing vector when screened on a single occasion), the percentage of all screening assessments that passed, eligible vector time (EVT), was calculated. EVT was compared statistically to QRS duration, corrected time to peak T (pTc) and mean vector score.Ambulatory monitoring was performed in 14 patients (mean age 63.7 ± 5.2 years, 71.4% male) with 42 vectors analysed. In 19 vectors the mean vector score was 100. Within this "passing" cohort EVT varied between 42.7% and 100%. In 7/19 (37%) the EVT was 75%. A negative correlation was found between QRS duration and EVT (Pearson correlation -.60, p = .007). No correlation was found between EVT and mean vector score or pTc.Vector eligibility is dynamic. When "passing" vectors are subjected to repeated screening, 37% are found to be ineligible, more than a quarter of the time. Further investigation is required to determine the clinical significance of these findings.

Aims Approximately 5.7% of potential subcutaneous implantable cardioverter-defibrillator (S-ICD) recipients are ineligible by virtue of their vector morphology, with higher rates of ineligibility observed in some at-risk groups. Mathematical vector rotation is a novel technique that can generate a personalized sensing vector, one with maximal R:T ratio, using electrocardiogram (ECG) signal recorded from the present S-ICD location. Methods and results A cohort of S-ICD ineligible patients were identified through ECG screening of ICD patients with no ventricular pacing requirement and their personalized vectors were generated using ECG signal from a Holter monitor. Subcutaneous ICD eligibility in this cohort was then recalculated. In a separate cohort, episodes of arrhythmia were recorded in patients undergoing arrhythmia induction, and arrhythmia detection in standard S-ICD vectors was compared to rotated vectors using an S-ICD simulator. Ninety-two participants (mean age 64.9 ± 2.7 years) underwent screening and 5.4% were found to be S-ICD ineligible. Personalized vector generation increased the R:T ratio in these vectors from 2.21 to 7.21 (4.54–9.88, P < 0.001) increasing the cohort eligibility from 94.6% to 100%. Rotated S-ICD vectors also showed high ventricular fibrillation (VF) detection sensitivity (97.8%), low time to VF detection (6.1 s), and excellent tachycardia discrimination (sensitivity 96%, specificity 88%), with no significant differences between rotated and standard vectors. Conclusion In S-ICD ineligible patients, mathematical vector rotation can generate a personalized vector that is associated with a significant increase in R:T ratio, resulting in universal device eligibility in our cohort. Ventricular fibrillation detection efficacy, time to VF detection, and tachycardia discrimination were not affected by vector rotation.

Background At our institution, Cardiac Implantable Electronic Devices (CIEDs) are routinely checked after elective direct current cardioversion procedures (DCCV) to ensure that the leads and generator have not been damaged. Anecdotally, this was perceived to be an unnecessary intervention. A comprehensive assessment of the impact of DCCV on device parameters and programming would allow either a change in practice to be safely undertaken, or to justify this ongoing use of resources. Method We retrospectively evaluated the routine post procedure device checks performed on consecutive patients with CIEDs undergoing elective DCCV at our institution between 2013 and 2019. Lead parameters (impedance, high voltage impedance, amplitude and capture threshold) recorded immediately post DCCV, were compared to the previous recorded values for each device. Atrial threshold and P wave amplitudes were not assessed as they would have been significantly altered by conversion of atrial dysrhythmia to sinus rhythm, rather than by the procedure itself. Where values could not be determined at either of the two device checks (pre or post DCCV), for example no R wave amplitude due to absence of underlying rhythm, this parameter was excluded from the data set. Values before and after DCCV were compared using a paired samples t test. Lead thresholds were assessed in volts, provided the pre and post DCCV checks used the same pulse width. The incidence of programming changes as a direct result of DCCV was also calculated. Results A total of 53 patients were identified for analysis (60.3% male, mean age 73 +/- 15 years). All patients underwent an elective DCCV receiving up to 3 shocks (starting at 150J) with defibrillation pads placed in conventional positions (either anterior-posterior or anterolateral) >8cm from the CIED generator. Device types were dual chamber pacemaker 51%, single chamber pacemaker 11%, CRT-D 11%, DR-ICD 9%, CRT-P 8%, VR-ICD 6% and S-ICD 4%. CIED manufacturers were Medtronic 66%, Boston Scientific 21%, Abbott 11%, and Microport (Sorin) 2%. The mean time between pre DCCV and post DCCV device checks was 4.7 +/- 2.7 months. The mean changes in lead parameters (presented with 95% confidence intervals) were as follows; impedance -7.4 ohms (-22.0 to +7.3, p=0.32, n=90), high voltage impedance -0.2 ohms (-3.7 to +3.4, p=0.92, n=17), amplitude -0.1 mV (-0.7 to + 0.6, p=0.80, n=38) and lead threshold -0.01 V (-0.07 to +0.04, p=0.64, n=57). The incidence of device reprogramming as a result of DCCV was found to be 0% (n=53). Conclusion DCCV is not associated with statistically significant changes in lead impedance, amplitude or threshold across a range of CIED devices. DCCV is not associated with a need for alterations in device programming post procedure. Providing the standard protocol and pad positions (anterior-posterior or anterolateral, >8cm from CIED generator) for DCCV in patients with CIEDs are followed, there is therefore no requirement for a routine CIED check post DCCV. Conflict of Interest None

Introduction Establishing the frequency and nature of arrhythmias in hemodialysis (HD) is an important step in improving outcomes of these patients. We undertook this systematic review and meta-analysis to characterize arrhythmia frequency in maintenance HD patients. Methods We identified studies on arrhythmias in adult patients on maintenance HD detected via implantable loop recorders (ILRs). Studies included were in English and reported ILR-detected arrhythmia incidence in HD patients. Data were extracted by one author using electronic spreadsheets and verified by a second author. Random effects models were used for pooled inferences. The I2 statistic was used to quantify heterogeneity. Results Five studies qualified for inclusion (317 patients). The overall estimates for the annualized rate of death and sudden cardiac death (SCD) was 0.14 (95% confidence interval [CI]: 0.11–0.18) and 0.06 (95% CI: 0.03–0.10), respectively. Across all 5 studies, the combined annualized rate of patients experiencing at least 1 bradycardia/asystole event was 0.19 (95% CI: 0.11–0.33) but heterogeneity was high (I2 = 79.8%). The average annualized rate of sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) episodes (0.02, 95% CI: 0.01–0.05) was significantly lower (P < 0.001) than the rate of bradycardia/asystole reported in the same patients. Incidence of atrial fibrillation (AF) varied significantly across the studies (from 0.07 to 0.83 patients per year) reflecting variable definitions (new-onset vs. total number of episodes). Conclusion The incidence of arrhythmias among chronic HD patients is high, with bradycardia/asystole occurring more frequently than ventricular arrhythmias. Additional studies to refine estimates particularly of AF are needed., Graphical abstract

The British Heart Rhythm Society’s Clinical Practice Guidelines on the Management of Patients Developing QT Prolongation on Antipsychotic Medication are written for heart rhythm consultants, primary care physicians, specialist registrars, nurses and physiologists who may be requested to review ECGs or advise on cases where antipsychotic-induced QT prolongation is suspected or proven. The guidance is adapted from the latest Maudsley Prescribing Guidelines in Psychiatry, published in 2018.

Permanent cardiac pacemakers have traditionally comprised a surgically implanted subcutaneous pulse generator affixed to at least one transvenous pacing lead. Despite technological advances, implant-related complications and transvenous-lead failure rates have remained high. The Micra Transcatheter Pacing System is a miniaturized single chamber pacemaker that is implanted directly into the right ventricle, eliminating the subcutaneous pocket and creating a leadless pacemaker system. Registry data show an extremely high implant success rate, significantly lower major complication rates than transvenous pacemakers, stable pacing parameters and reliable battery performance. In this review we summarize the available clinical literature and highlight the promising efficacy and safety of the Micra Transcatheter Pacing System.

Background Implantable cardioverter defibrillators (ICDs) can provide effective therapies for life-threatening ventricular arrhythmia (VA), whilst inappropriate and unnecessary therapies can cause physiological and psychological morbidity. The evidence base which underpins optimal ICD programming evolves rapidly. At our institution we introduced standardised programming for both primary (type 1) and secondary (type 2) prevention ICDs, utilising increased detection times and higher therapy zones in line with current best available evidence [figures 1 and 2]. In this study we retrospectively compared the inappropriate and unnecessary therapy rates of ICD patients who were switched from patient tailored to standardised programming during routine follow-up. Methods A total of 200 patients, who had been routinely switched from patient tailored to standardised programming, were identified for analysis (mean age 72 years, 86% male, 75% primary prevention, 35% CRT, 64% coronary disease). Electronic records and physiologist follow-up reports were used to retrospectively analyse; episodes of VA, symptoms experienced, and therapies delivered. Therapies during the nine months prior to standardisation were compared statistically to the nine month period immediately following standardisation. Inappropriate therapies were defined as ATP or shock delivery in the absence of VA. For all episodes where symptom status could be established, unnecessary therapy rates were calculated as the percentage of ATP or shock therapies which were delivered during asymptomatic VA episodes. Results There were a total of 1807 episodes of treated VA; 1300 occurring prior to standardisation (1230 ATP, 70 shocks) and 507 post (490 ATP, 17 shocks). Standardisation reduced the number of inappropriate ATP episodes from 59 to 1, and inappropriate shocks from 8 to 0. Standardisation reduced unnecessary ATP rates from 98.5% (n=1075) to 5.9% (n=456), whilst unnecessary shocks rates were reduced from 87.3% (n=55) to 41.2% (n=17). Conclusions The application of standardised programming, using longer detection times and higher treatment zones, to patients undergoing ICD follow-up, significantly reduces the delivery of both inappropriate and unnecessary ATP and shocks.

OBJECTIVE: At our tertiary cardiothoracic centre, cardiac MRI and thoracic CT scans are performed in patients with implanted LINQ devices. The degree of foreign body artefact associated with the LINQ device, and its clinical importance, has not previously been assessed. A case series review was therefore performed with a simultaneous review of patient safety and data loss events, secondary to the MRI environment. METHODS: A local database search identified LINQ device patients who underwent thoracic CT or cardiac MRI scans between March 2014 and December 2016. Images were reviewed by two radiologists, recording the presence of subcutaneous and intrathoracic artefact, and its clinical significance. Furthermore a specialist in cardiac rhythm management reviewed all LINQ data downloads undertaken before and after MRI scanning, and a search of the trust incident reporting system was performed. RESULTS: Minor subcutaneous artefact was present on all scans. Intrathoracic artefact was observed in 25.6% of thoracic CT scans and 33.3% of cardiac MRIs; however no clinically significant artefact was observed. Device downloads were only performed by 53.8% of patients prior to their MRI scan and 56.5% after their MRI scan. No adverse patient safety or data loss events were noted. CONCLUSION: The LINQ device does not produce clinically significant artefact, even when artefact extends into the intrathoracic space, which occurs in a third of MRIs and a quarter of CTs. MRI scanning of the LINQ device is safe with no evidence of inappropriate data loss. ADVANCES IN KNOWLEDGE: This is the first published case series of CT and MRI scanning in LINQ patients and the first performed quantification of artefact related to the LINQ device.

Implantable cardiac devices have an increasingly important role. Pacemakers remain the only effective treatment for symptomatic bradycardia; cardiac resynchronisation therapy is a proven treatment for heart failure; and implantable cardioverter defibrillators (ICD) are superior to medical therapy in prevention of sudden cardiac death. Our ageing population has led to a rising number of device implants. Physicians in all specialties increasingly encounter patients with cardiac devices and require an understanding of their capabilities and functions. The rising prevalence of implantable devices has been matched by a parallel expanse in device technology. Leadless devices have become a reality and represent the future of device therapy. The absence of a transvenous lead offers a significant clinical advantage because of many well established issues related to lead complications. The leadless pacemaker and subcutaneous ICD are significant new products that are currently not well recognised or understood by general physicians.

Bedside vascular ultrasound machines are increasingly available. They are used to facilitate safer vascular access across a number of different specialties. In the electrophysiology laboratory however, where patients are frequently anticoagulated and require the insertion of multiple venous sheaths, anatomical landmark techniques predominate. Despite the high number of vascular complications associated with electrophysiological procedures and the increasing evidence to support its use in electrophysiology, ultrasound remains underutilised. A new standard of care is required. A comprehensive technical report, providing a detailed explanation of this important technique, will provide other electrophysiology centres with the knowledge and justification for adopting ultrasound guidance as their standard practice. We review the increasing body of evidence which demonstrates that routine ultrasound usage can substantially improve the safety of femoral venous access in the electrophysiology laboratory. We offer a comprehensive technical report to guide operators through the process of ultrasound-guided venous access, with a specific focus on the electrophysiology laboratory. Additionally, we detail a novel technique which utilises real-time colour Doppler ultrasound to accurately identify needle tip location during venous puncture. The use of vascular ultrasound to guide femoral venous cannulation is rapid, inexpensive and easily learnt. Ultrasound is readily available and offers the potential to significantly reduce vascular complications in the unique setting of the electrophysiology laboratory. Ultrasound guidance to achieve femoral venous access should be the new standard of care in electrophysiology.

Introduction All patients with a cardiac pacemaker require regular routine follow up. At an interval of no greater than twelve months battery longevity and lead parameters require assessment. This is usually undertaken in secondary care, by a trained cardiac physiologist, in a clinic setting. At University Hospital Southampton 2878 patients undergo routine pacemaker follow up. Pacemaker prevalence increases with patient age. Many patients with pacemakers are frail with multiple co-morbidities and a high percentage are reliant on hospital transport. Hospital attendance for this cohort can be challenging and costly. The pacemaker clinic has a high DNA (did not attend) rate. In 2012, 285 appointment slots were not utilised (around 15% of total appointments). Two-thirds of our pacemaker patients have a remote compatible Medtronic device. A single Medtronic carelink express monitor, placed in a convenient community location, would allow multiple patients to undergo remote monitoring. We hypothesise that this would increase patient satisfaction with pacemaker follow up, reduce wasted appointment time, minimise expenditure on hospital transport, decrease carbon footprint, and increase availability of on-site clinics and physiologists. We hypothesise that this would be a safe and effective method of conducting pacemaker follow up. Method A Medtronic carelink express monitor was placed in a community health centre and a pilot group of 90 patients were invited to partake in community follow up. Patients were instructed on how to use the monitoring device and 57 patients were successfully enrolled. Patients were given an indication of when pacemaker follow up was required, but exact attendance time was entirely at their discretion. The carelink monitor was unmanned. Information was sent wirelessly to the hospital and assessed at a virtual follow up clinic. Results 100% of patients successfully utilised the remote device with a virtual DNA rate of 0%. No patients required extra assistance in using the equipment at the time of download. The average time to assess a download was 6 min, compared to 15 min for an on-site appointment. There were no adverse events during the follow up period. Average patient travel time and distance for follow up was reduced. Hospital transport was not required for any patient. The feedback from patients was positive and based around ease of travel, length of travel and stay, and flexibility to attend. Conclusions and Implications This pilot study demonstrates the feasibility and benefits of remote pacemaker monitoring from a community location. This model could be replicated in the future by other Trusts.

In recent years, there has been a significant evolution in the field of cardiovascular implantable electronic devices (CIEDs). Pacemakers can now be leadless, implantable cardioverter defibrillators can be entirely subcutaneous and implantable loop recorders have become miniaturized. Driven by technological advances and an ageing population implant numbers have also steadily increased. These highly prevalent systems are all radio-opaque and are frequently observed on chest radiographs, yet the devices are neither well recognized nor understood. We present a pictorial review of CIEDs; describing the chest radiograph appearances of both newer generation systems and their traditional predecessors. Furthermore, we discuss the clinical role of chest radiography in both CIED implantation and follow up, with the aim of improving understanding in this important and expanding field. Finally, we present a collection of interesting and challenging radiographs, where multiple CIED systems have been implanted.