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Background: Bradyarrhythmias are adequately treated with pacemakers. There are different pacing modes (single-chamber, dual-chamber, cardiac resynchronisation therapy [CRT] and conduction system pacing [CSP]) and a choice between leadless or transvenous pacemakers. The expected pacing need is important for determining optimal pacing mode and device type. This study aimed to evaluate atrial pacing (AP) and ventricular pacing (VP) percentages over time for the most common pacing indications. Methods: Included patients were aged ≥18 years with a dual-chamber rate-modulated [DDD(R)] pacemaker implantation and ≥1 year of follow-up at a tertiary centre between January 2008 and January 2020. Baseline characteristics, AP and VP at yearly follow-up visits up to 6 years after implantation were retrieved from the medical records. Results: A total of 381 patients were included. Primary pacing indications were incomplete atrioventricular block (AVB) in 85 (22%), complete AVB in 156 (41%) and sinus node dysfunction (SND) in 140 (37%) patients. Mean age at implantation was 71±14, 69±17 and 68±14 years, respectively (p=0.23). Median follow-up was 42 months (25–68 months). Overall, AP was highest in SND with median 37% (7%–75%) versus 7% (1%–26%) in incomplete AVB and 3% (1%–16%) in complete AVB (p

Aims Remote monitoring (RM) for implantable cardioverter-defibrillators (ICDs) is advocated for the potential of early detection of disease progression and device dysfunction. While studies have examined the effect of RM on clinical outcomes in carefully selected populations of heart failure patients implanted with ICDs from a single vendor, there is a paucity of data in real-world patients. We aimed to assess the long-term effect of RM in a representative ICD population using real-world data. Methods and results This is an observational retrospective longitudinal study of 1004 patients implanted with an ICD or cardiac resynchronization therapy device (CRT-D) from all device vendors between 2010 and 2021. Patients started on RM (N = 403) within 90 days following de novo device implantation and yearly in-office visits were compared with patients with only bi-yearly in-office follow-up (non-RM, N = 601). In a propensity score matched cohort of 430 patients (mean age 61.4 ± 14.3 years, 26.7% female), all-cause mortality at 4-year was 12.6% in the RM and 27.7% in the non-RM group [hazard ratio (HR) 0.52, 95% confidence interval (CI) 0.32–0.82; P = 0.005]. No difference in inappropriate ICD-therapy (HR 1.90, 95% CI 0.86–4.21; P = 0.122) was observed. The risk of appropriate ICD-therapy (HR 1.71, 95% CI 1.07–2.74; P = 0.026) was higher in the RM group. Conclusion Remote monitoring was associated with a reduction in long-term all-cause and cardiac mortality compared with traditional office visits in a real-world ICD population.

Structured AbstractObjectivesThis study assessed safety and feasibility of a novel extravascular (EV) implantable cardioverter-defibrillator (ICD) lead when inserted anteriorly through a rib space and connected to various commercially available ICD pulse generators (PGs) placed in either a left mid-axillary or left pectoral pocket.BackgroundCurrently available or investigational, EV-ICDs include a subcutaneous or subxiphoid lead connected to customized EV-ICD PGs. This novel EV-ICD (AtaCor Medical, Inc, San Clemente, CA) employs a unique intercostal implant technique and is designed to function with commercial DF-4 ICD PGs.MethodsIn this non-randomized, single-center, acute study, 36 de novo or replacement transvenous (TV) ICD patients enrolled to receive a concomitant EV-ICD lead inserted through an intercostal space along the left parasternal margin. EV-ICD leads were connected to DF-4 compatible ICD PGs positioned in either a left mid-axillary or pectoral pocket for acute sensing and defibrillation testing. Defibrillation testing started at 30 Joules (J) and stepped down in 10 J increments following conversion success and stepped up in 5 J increments following conversion failure.ResultsSuccessful acute defibrillation using ≤ 35 J was noted in 100% of left mid-axillary PG subjects (n=27, mean 16.3 ± 8.6 J) and 83% of left pectoral PG subjects (n=6, mean 21.0 ± 8.4 J). All evaluable episodes (n=93) were automatically sensed, detected, and shocked. No serious device-related intraoperative adverse events were observed.ConclusionsThis first-in-human study documented safe and reliable placement of a novel extravascular ICD lead with effective sensing and defibrillation of induced ventricular fibrillation using commercial DF-4 ICD pulse generators.Condensed AbstractThis study assessed feasibility of intercostal implantation of a novel extravascular implantable cardioverter-defibrillator (ICD) lead designed to function with commercial DF-4 pulse generators (PGs). Lead placement was successful in 33 of 36 attempts (94%). Acute defibrillation with ≤35 J was successful in 27 of 27 left mid-axillary PG subjects (100%) and 5 of 6 left pectoral PG subjects (83%). All evaluable episodes (n=93) were automatically detected. No serious device-related intraoperative adverse events were observed. This study demonstrates feasibility of a novel extravascular ICD lead with effective sensing and defibrillating of induced ventricular fibrillation using commercial DF-4 PGs.

We aimed to evaluate the effect of defibrillator component positioning on high-voltage impedance. In two human specimens with BMI 19.1 kg/m and 31.4 kg/m , shocks were administered with a subcutaneous implantable cardioverter-defibrillator (S-ICD) and an automated external defibrillator placed in various positions. High-voltage impedance increased with more fat tissue between the defibrillator components, or with air in the subcutaneous pocket of the S-ICD. High-voltage impedance was lowest when defibrillator components were placed anteriorly, but due to adjacent positioning, the electrical current will not be transmitted through the myocardium and effective defibrillation is unlikely. In conclusion, positioning of defibrillator components greatly affects high-voltage impedance, but the course of the current should always be considered.

Background: The Apple Watch (AW) is the first commercially available wearable device with built-in electrocardiogram (ECG) electrodes to perform a single-lead ECG to detect atrial fibrillation (AF). Methods: Patients with AF who were scheduled for electrical cardioversion (ECV) were included in this study. The AW ECGs were obtained pre-ECV and post-ECV. In case of an unclassified recording, the AW ECG was obtained up to 3 times. The 12-lead ECG was used as the reference standard. Sensitivity, specificity, and kappa coefficient were calculated. Results: In total, 74 patients were included. Mean age was 67.1 ± 12.3 years and 20.3% were female. In total 65 AF and 64 sinus rhythm measurements were obtained. The first measurement with the AW showed a sensitivity of 93.5% and specificity of 100% (κ = 0.94). A second measurement resulted in a sensitivity of 94.6% and specificity of 100% (κ = 0.95). A third measurement resulted in a sensitivity of 93% and a specificity of 96.5% (κ = 0.90). Adjudication of unclassified recordings by a physician reduced the total unclassified recordings from 27.9% to 1.6%, but also reduced the accuracy. The kappa coefficient for unclassified single-lead ECGs was 0.58. Conclusion: The single-lead ECG of the AW shows a high accuracy for identifying AF in a clinical setting. Repeating the recording once decreases the total of unclassified recordings; however, a third recording resulted in a lower accuracy and the occurrence of false-positive measurements. Unclassified results of the AW can be reduced by physicians’ interpretation of the single-lead ECG; however, the interrater agreement is only moderate.

BackgroundPatients with an implantable cardioverter-defibrillator (ICD) are at a high risk of malignant ventricular arrhythmias. The use of remote ICD monitoring, wearable devices, and patient-reported outcomes generate large volumes of potential valuable data. Artificial intelligence–based methods can be used to develop personalized prediction models and improve early-warning systems.ObjectiveThe purpose of this study was to develop an integrated web-based personalized prediction engine for ICD therapy.MethodsThis international, multicenter, prospective, observational study consists of 2 phases: (1) a development study and (2) a feasibility study. We plan to enroll 400 participants with an ICD (with or without cardiac resynchronization therapy) on remote monitoring: 300 participants in the development study and 100 in the feasibility study. During 12-month follow-up, electronic health record data, remote monitoring data, accelerometry-assessed physical behavior data, and patient-reported data are collected. By using machine- and deep-learning approaches, a prediction engine is developed to assess the risk probability of ICD therapy (shock and antitachycardia pacing). The feasibility of the prediction engine as a clinical tool, the SafeHeart Platform, is assessed during the feasibility study.ResultsDevelopment study recruitment commenced in 2021. The feasibility study starts in 2022.ConclusionSafeHeart is the first study to prospectively collect a multimodal data set to construct a personalized prediction engine for ICD therapy. Moreover, SafeHeart explores the integration and added value of detailed objective accelerometer data in the prediction of clinical events. The translation of the SafeHeart Platform to clinical practice is examined during the feasibility study.

Background: Cardiac implantable electronic device (CIED) infections have a high morbidity and mortality and are an indication of device extraction. As a replacement, leadless pacemakers (LPs) may be preferable due to a low infection risk, but mid-term data on reinfections is lacking. Moreover, early LP reimplantation in pacemaker-dependent patients would circumvent the need for temporary pacemakers. Methods: We included all patients with LP implantation as a replacement for an infected CIED, between January 2013 and December 2021. The occurrence of reinfection was assessed during standard follow-up visits. Results: Twenty-nine patients (mean age 81 ± 9 years) were included, of which 21 (73%) had a pocket infection, 7 (24%) endocarditis, and 1 (3%) a systemic infection without endocarditis. All LP implantations were successful. LPs were implanted before extraction (n = 4, 13%), simultaneously with extraction (n = 5, 17%) and after extraction (n = 20, 70%). No reinfection occurred during the follow-up of median 32 months (IQR 13-66 months). Repeat blood cultures obtained in 9 (30%) patients and transthoracic echocardiography in all 7 patients with pacemaker endocarditis were negative for reinfection. In a subset of 6 LPs extracted during follow-up due to early battery depletion, prophylactically after the battery advisory or due to non-capture (median 36 months (range 0-67 months) post-implantation), histopathologic examination of tissues around the LPs showed no signs of infection. Conclusions: After replacing infected CIEDs for an LP, no reinfections occurred in over 2.5 years follow-up. These results confirm that in case of CIED infection, the LP is an appealing replacement device. LP implantation before CIED extraction is feasible.

Background The subcutaneous implantable cardioverter-defibrillator (S-ICD) is developed to overcome lead-related complications and systemic infections, inherent to transvenous ICD (TV-ICD) therapy. The PRAETORIAN trial demonstrated that the S-ICD is non-inferior to the TV-ICD with regard to the combined primary endpoint of inappropriate shocks and complications. This prespecified secondary analysis evaluates all complications in the PRAETORIAN trial. Methods and results The PRAETORIAN trial is an international, multicentre, randomized trial in which 849 patients with an indication for ICD therapy were randomized to receive an S- ICD (N = 426) or TV-ICD (N = 423) and followed for a median of 49 months. Endpoints were device-related complications, lead-related complications, systemic infections, and the need for invasive interventions. Thirty-six device-related complications occurred in 31 patients in the S-ICD group of which bleedings were the most frequent. In the TV-ICD group, 49 complications occurred in 44 patients of which lead dysfunction was most frequent (HR: 0.69; P = 0.11). In both groups, half of all complications were within 30 days after implantation. Lead-related complications and systemic infections occurred significantly less in the S-ICD group compared with the TV-ICD group (P < 0.001, P = 0.03, respectively). Significantly more complications required invasive interventions in the TV-ICD group compared with the S-ICD group (8.3% vs. 4.3%, HR: 0.59; P = 0.047). Conclusion This secondary analysis shows that lead-related complications and systemic infections are more prevalent in the TV-ICD group compared with the S-ICD group. In addition, complications in the TV-ICD group were more severe as they required significantly more invasive interventions. This data contributes to shared decision-making in clinical practice.

We strongly recommend to limit ATP therapy to a single sequence and first observe the efficacy in the individual patient. After a positive effect of ATP is established, ATP programming may be safely extended.

Aims Subcutaneous-implantable cardiac defibrillators (S-ICDs) are used increasingly to prevent sudden cardiac death in young patients. This study was set up to gain insight in the indications for S-ICD, possible complications, and their predictors and follow-up results. Methods and results A multicentre, observational, retrospective, non-randomized, standard-of-care registry on S-ICD outcome in young patients with congenital heart diseases (CHDs), inherited arrhythmias (IAs), idiopathic ventricular fibrillation (IVF), and cardiomyopathies (CMPs). Anthropometry was registered as well as implantation technique, mid-term device-related complications, and incidence of appropriate/inappropriate shocks (IASs). Data are reported as median (interquartile range) or mean ± standard deviation. Eighty-one patients (47% CMPs, 20% CHD, 21% IVF, and 12% IA), aged 15 (14–17) years, with body mass index (BMI) 21.8 ± 3.8 kg/m2, underwent S-ICD implantation (primary prevention in 59%). This was performed with two-incision technique in 81% and with a subcutaneous pocket in 59%. Shock and conditional zones were programmed at 250 (200–250) and 210 (180–240) b.p.m., respectively. No intraoperative complications occurred. Follow up was 19 (6–35) months: no defibrillation failure occurred, 17% of patients received appropriate shocks, 13% of patients received IAS (supraventricular tachycardias 40%, T-wave oversensing 40%, and non-cardiac oversensing 20%). Reprogramming, proper drug therapy, and surgical revision avoided further IAS. Complications requiring surgical revision occurred in 9% of patients, with higher risks in patients with three-incision procedures [hazard ratio (HR) 4.3, 95% confidence interval (95% CI) 0.5–34, P = 0.038] and BMI < 20 (HR 5.1, 95% CI 1–24, P = 0.031). Conclusion This multicentre European paediatric registry showed good S-ICD efficacy and safety in young patients. Newer implantation techniques and BMI > 20 showed better outcome.

BACKGROUND: The extravascular implantable cardioverter-defibrillator (ICD) has a single lead implanted substernally to enable pause-prevention pacing, antitachycardia pacing, and defibrillation energy similar to that of transvenous ICDs. The safety and efficacy of extravascular ICDs are not yet known. METHODS: We conducted a prospective, single-group, nonrandomized, premarket global clinical study involving patients with a class I or IIa indication for an ICD, all of whom received an extravascular ICD system. The primary efficacy end point was successful defibrillation at implantation. The efficacy objective would be met if the lower boundary of the one-sided 97.5% confidence interval for the percentage of patients with successful defibrillation was greater than 88%. The primary safety end point was freedom from major system- or procedure-related complications at 6 months. The safety objective would be met if the lower boundary of the one-sided 97.5% confidence interval for the percentage of patients free from such complications was greater than 79%. RESULTS: A total of 356 patients were enrolled, 316 of whom had an implantation attempt. Among the 302 patients in whom ventricular arrhythmia could be induced and who completed the defibrillation testing protocol, the percentage of patients with successful defibrillation was 98.7% (lower boundary of the one-sided 97.5% confidence interval [CI], 96.6%; P

Background: Leadless pacemakers (LPs) can mitigate conventional pacemaker complications related to the transvenous leads and subcutaneous pocket surrounding the pulse generator. Although single-chamber leadless pacing has been established, multichamber pacing requires wireless bidirectional communication across multiple LPs to maintain synchrony. This preclinical study demonstrates the chronic performance of implant-to-implant (i2i) communication that achieves synchronous, dual-chamber pacing with 2 LPs. Methods: The i2i communication modality employs subthreshold electrical signals conducted between implanted LPs through the blood and myocardial tissue on a beat-by-beat basis. Right atrial and right ventricular LPs were implanted in 9 ovine subjects. The i2i transmission performance was evaluated 13 weeks after implant. Results: Right atrial and right ventricular LPs were implanted successfully and without complication in 9 ovine subjects. A total of 8715±457 right atrial-to-right ventricular and right ventricular-to-right atrial transmissions were sent per hour, with a success rate of 99.2±0.9%. Of periods with i2i communication failure when DDD pacing was not possible, 97.3±1.8% were resolved within 6 s. Conclusions: For the first time, synchronized, dual-chamber pacing has been demonstrated in a chronic preclinical feasibility study by 2 leadless pacemakers using beat-to-beat, wireless communication, achieving a success rate of 99.2%.

Background The subcutaneous implantable cardioverter-defibrillator (S-ICD) is an alternative to conventional transvenous ICD (TV-ICD) therapy to reduce lead complications. Objective To evaluate outcomes in channelopathy vs patients with structural heart disease in the EFFORTLESS-SICD Registry and with a previously reported TV-ICD meta-analysis in channnelopathies. Methods The EFFORTLESS registry includes 199 patients with channelopathies (Brugada syndrome 83, long QT syndrome 24, idiopathic ventricular fibrillation 78, others 14) and 786 patients with structural heart disease. Results Channelopathy patients were younger (39 ± 14 years vs 51 ± 17 years; P < .001) with left ventricular ejection fraction 59% ± 9% vs 41% ± 18% (P < .001). The complication rate (follow-up: 3.2 ± 1.5 years vs 3.0 ± 1.5 years) was similar: 13.6% vs 11.2% (P = .42). Appropriate shocks rates were 9.5% vs 10.8% (P = .70), with shocks for monomorphic ventricular tachycardia being 2.0% vs 6.9% (P < .02) and for polymorphic ventricular tachycardia/ventricular fibrillation (VT/VF) 8.0% vs 5.7% (P = .30). Conversion effectiveness of VT/VF episodes was similar: 36 of 37 (97.3%) vs 151 of 155 (97.4%, P = .59). VT/VF storm event (2% vs 0.9%, P = .33) and lower inappropriate shock (IAS) (8.5% vs 12.5%, P = .12) rates were statistically similar between channelopathy and non-channelopathy patients, with 45.5% channelopathy vs 31.4% non-channelopathy patients managed with a conditional zone > 200 beats per minute (P = .0002). Annualized appropriate shock, IAS, and complication rates appear to be lower for the S-ICD vs meta-analysis TV-ICD patients, particularly lead complications. Conclusion EFFORTLESS demonstrates similar S-ICD efficacy and a nonsignificant, lower rate of IAS in channelopathy patients as compared to structural heart disease. Comparable IAS rates were achieved with the device programmed to higher rates for channelopathy patients., Graphical abstract

Introduction The third‐generation subcutaneous implantable cardioverter‐defibrillator (S‐ICD) (EMBLEM™ A219, Boston Scientific) contains a new diagnostic tool to detect atrial fibrillation (AF) in S‐ICD patients, without the use of an intracardiac lead. This is the first study to evaluate the performance of the S‐ICD AF monitor (AFM). Methods The AFM algorithm analyzes a subcutaneous signal for the presence of AF, similar to the signals collected by implantable and wearable diagnostic devices. The AFM algorithm combines heart rate (HR) scatter analysis with an HR histogram. The algorithm was tested against publicly available electrocardiogram databases (simulated performance). Real‐world performance of the algorithm was evaluated by using the S‐ICD LATITUDE remote monitoring (RM) database. Results The simulated performance of the AFM algorithm resulted in a sensitivity of 95.0%, specificity of 100.0%, and positive predictive value (PPV) of 100.0%. To evaluate the real‐world performance of the AFM, 7744 S‐ICD devices were followed for up to 30 months by RM, whereof 99.5% had the AFM enabled. A total of 387 AF episodes were randomly chosen for adjudication, resulting in a PPV of 67.7%. The main cause of misclassification was atrial and ventricular ectopy. Conclusion The AFM exhibited a very high sensitivity and specificity in a simulated setting, designed to maximize PPV in order to minimize the clinical burden of reviewing falsely detected AF events. The real‐world performance of the AFM, enabled in 99.5% of S‐ICD patients, is a PPV of 67.7%.

Aims To guarantee uninterrupted function of the subcutaneous implantable cardioverter-defibrillator (S-ICD), the pulse generator needs to be surgically replaced before the battery is depleted. The risks related to this replacement substantially impact long-term outcome for S-ICD recipients, as the majority will undergo one or several of these procedures in their lifetime. We aim to describe the procedural characteristics of the replacement procedure and to provide an insight in the complications associated with these replacements. Methods and results In this retrospective analysis, data from replacement procedures and follow-up visits were collected from all patients who underwent elective S-ICD generator replacement in our tertiary centre from June 2014 until November 2019. Original device position was assessed using the PRAETORIAN score. Complications were defined as those requiring surgical intervention, systemic antibiotic treatment, or device extraction. Seventy-two patients were included, with a median follow-up of 1.9 years (IQR 0.6–3.3 years) after replacement. Battery depletion occurred after 5.9 ± 0.7 years. The pulse generator was repositioned in patients with a PRAETORIAN score ≥90 to minimize the defibrillation threshold. Although there was an increase in impedance compared to the implant procedure, first shock conversion rate during defibrillation testing was 91.4% with a success rate of 100% after multiple attempts. Two patients developed a complication after, respectively, 9 and 21 months, resulting in a complication rate of 1.4% per year. Conclusion With a median follow-up of 1.9 years, this study shows a low complication rate after S-ICD replacement, with a first shock conversion rate of 91.4%.

Since the publication of the SIMPLE and NORDIC trials, defibrillation testing (DFT) is rarely performed during routine implantation of transvenous implantable cardioverter-defibrillators (ICD). However, the results of these trials cannot be extrapolated to the later introduced subcutaneous ICD (S-ICD) and a class I recommendation to perform DFT during the implantation of these devices remains in the current guidelines. Due to the high conversion success rate of DFT on one hand, and the risk of complications on the other, a significant number of physicians omit DFT in S‑ICD recipients. Several retrospective analyses have assessed the safety of the omission of DFT and report contradicting results and recommendations. It is known that implant position, as well as device factors and patient characteristics, influence defibrillation success. A better comprehension of these factors and their relationship could lead to more reliable and safer alternatives to DFT. An ongoing randomised clinical trial, which is expected to end in 2023, is the first study to implement a method that assesses implant position to identify patients who are likely to fail their DFT.

Introduction: Permanent transvenous pacemaker therapy is an essential management option in patients with symptomatic bradyarrhythmias, but harbors a concomitant risk of serious complications. As most complications are lead- or pocket-related, intracardiac leadless pacemaker therapy has the potential to positively impact patient outcome. Since the first leadless pacemaker implant in 2012, many studies have been conducted to evaluate the effectiveness, safety, and applicability of this novel pacing approach.Areas covered: This review will cover the current status of leadless pacemaker technology. Available safety and efficacy outcomes, current area of indication, and end-of-life management will be evaluated. Furthermore, future perspectives for clinical practice and new pacing modalities are discussed.Expert opinion: The first-generation leadless pacemakers are a promising innovation that provide safe and efficient single-chamber pacing therapy without the use of transvenous pacemaker leads. Yet, broad implementation of this technology is hampered by limitations of the current leadless devices, such as end-of-life management and its single-chamber pacing indication. Further innovations such as leadless dual-chamber pacing therapy, leadless cardiac synchronization therapy, energy-harvesting leadless pacemakers, communicating leadless pacemakers with subcutaneous implantable cardiac defibrillators, and minimally invasive completely extracardiac pacemakers are currently being developed that have the potential to become major game changers in pacing therapy.

Background Since the introduction of the subcutaneous implantable-defibrillator (S-ICD) knowledge of factors elevating the defibrillation threshold (DFT), have increased. Optimal device positioning most likely results in a decrease in DFT. The PRAETORIAN score is a tool to systematically evaluate S-ICD implant position and predict conversion success by estimating the DFT on a chest X-ray. The objective of this study is to determine DFT in de novo S-ICD patients. Methods De novo S-ICD patients were enrolled with DFT testing using a single 30 J shock or a prespecified step-down protocol. Chest X-rays were obtained and implant position was evaluated using the PRAETORIAN score. Results Fifteen patients, age 47 (±18) years and body mass index (BMI) 25(±3) kg/m2 , underwent conversion testing with a single 30 J shock. Fourteen patients (93%) converted successfully. Implant position was optimal in all patients, PRAETORIAN score of 30 (100%). Twelve patients were available for analysis in the step-down DFT cohort, age 46 years (±15), left ventricular ejection fraction 50% (±15%) and a median BMI of 25.7 kg/m2 (range 23.8-29.1 kg/m2 ). No complications occurred during DFT testing. Mean DFT was 29 J (±12 J). Time to shock was 11 seconds (±2 seconds) for a 20 J shock compared with 17 seconds in case of a 70 J shock output. Nearly all patients were implanted with optimal device positioning with the lowest possible PRAETORIAN score of 30 (92%). Conclusion DFT in S-ICD patients with optimal device positioning is lower than previously reported. Conversion testing using a low shock output reduced time to therapy by 6 seconds on average.

Background: Leadless pacemakers (LPs) have proven safe and effective, but device revisions remain necessary. Either replacing the LP or implanting a new adjacent LP is feasible. Replacement seems more appealing, but encapsulation and tissue adhesions may hamper the safety and efficacy of LP retrieval. Objective: We determined the incidence and cellular characteristics of tissue adherent to retrieved LPs and the potential implications for end-of-life strategy. Methods: All 15 consecutive successful Nanostim LP retrievals in a tertiary center were included. We assessed the histopathology of adherent tissue and obtained clinical characteristics. Results: Adherent tissue was present in 14 of 15 retrievals (93%; median implantation duration 36 months; range 0–96 months). The tissue consisted of fibrosis (n = 2), fibrosis and thrombus (n = 9), or thrombus only (n = 3). In short-term retrievals (

Aims This study was performed to develop and externally validate prediction models for appropriate implantable cardioverter-defibrillator (ICD) shock and mortality to identify subgroups with insufficient benefit from ICD implantation. Methods and results We recruited patients scheduled for primary prevention ICD implantation and reduced left ventricular function. Bootstrapping-based Cox proportional hazards and Fine and Gray competing risk models with likely candidate predictors were developed for all-cause mortality and appropriate ICD shock, respectively. Between 2014 and 2018, we included 1441 consecutive patients in the development and 1450 patients in the validation cohort. During a median follow-up of 2.4 (IQR 2.1–2.8) years, 109 (7.6%) patients received appropriate ICD shock and 193 (13.4%) died in the development cohort. During a median follow-up of 2.7 (IQR 2.0–3.4) years, 105 (7.2%) received appropriate ICD shock and 223 (15.4%) died in the validation cohort. Selected predictors of appropriate ICD shock were gender, NSVT, ACE/ARB use, atrial fibrillation history, Aldosterone-antagonist use, Digoxin use, eGFR, (N)OAC use, and peripheral vascular disease. Selected predictors of all-cause mortality were age, diuretic use, sodium, NT-pro-BNP, and ACE/ARB use. C-statistic was 0.61 and 0.60 at respectively internal and external validation for appropriate ICD shock and 0.74 at both internal and external validation for mortality. Conclusion Although this cohort study was specifically designed to develop prediction models, risk stratification still remains challenging and no large group with insufficient benefit of ICD implantation was found. However, the prediction models have some clinical utility as we present several scenarios where ICD implantation might be postponed.

Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Boston Scientific OnBehalf EFFORTLESS Registry Introduction Patients (pts) implanted with transvenous (TV) implantable cardioverter-defibrillator (ICD) experience complications (Cx) associated with TV leads and inappropriate shocks (IAS) for atrial fibrillation (AF) or other supraventricular tachycardias (SVT). The EFFORTLESS S-ICD Registry is a 5-year (yr) follow-up (f/u) study of pts implanted with the subcutaneous ICD (S-ICD). Purpose To report on the 5-yr outcomes of pts with a wide range of S-ICD indications implanted with early generation devices. Methods Pts were enrolled at 43 centers February 2011-December 2014. Kaplan-Meier Cx, appropriate shock (AS), and IAS rates are reported. Results 994 pts (495 retrospective) were enrolled in the EFFORTLESS study and 984 pts (28% female, 48 ± 17 yrs, BMI 27 ± 6 kg/m2, ejection fraction 43 ± 18%) underwent S-ICD implantation. Mean study f/u was 4.4 ± 1.6 yrs. The pt cohort had diverse etiologies: 31% ischemic heart disease, 19% non-ischemic cardiomyopathy, 11% hypertrophic cardiomyopathy, 17% channelopathies, and 20% of pts miscellaneous. Total system- and procedure-related Cx (table) were 9.4% at 5 yrs. AS and IAS rates at 5 yrs were 15.9% and 16.9%, respectively and the IAS rates for AF/SVT and t wave oversensing were 3.1% and 5.8%, respectively. More pts experienced Cx and IAS in the first yr than in yrs 2-5 altogether (8.7 vs 8.2%), the most common as a result of discomfort/erosion (38%), IAS (26%), system infection (9%), and premature battery depletion (9%). Of these late Cx, 74% were experienced by retrospective pts. Spontaneous conversion efficacy for the first shock and final shocks was 89.7% and 97.7%. Of the 91 (9.2%) deaths reported, none were associated with the S-ICD system or procedure. Cause of death was cardiac for 40 pts, non-cardiac for 40 pts, other for 4 pts, and unknown for 7 pts. Only 20 (2.0%) pts had their S-ICD replaced for a TV device for pacing: 4 bradycardia, 7 anti-tachycardia, and 9 for biventricular pacing. Conclusions The EFFORTLESS registry provides 5-year follow-up for a diverse, large, multinational S-ICD registry. Complications primarily occurred in the first year but remained low through 5 years. Inappropriate shock rates were typically observed in older generation devices prior to introduction of the SMART Pass filter. Replacement for TV-ICD due to the need for pacing was rare. Outcome 30 day 1 yr 2 yr 3 yr 4 yr 5yr Annual Complications (Kaplan-Meier) 2.0 5.3 6.8 7.6 8.6 9.4 1.9 IAS, overall (Kaplan-Meier) 1.7 8.7 11.6 13.1 14.6 16.9 3.4 IAS, t wave oversensing 3.4 5.8 1.2

Funding Acknowledgements Type of funding sources: None. Background Routine defibrillation testing during implant and replacement of the subcutaneous implantable cardioverter-defibrillator (S-ICD) is recommended per current guidelines. Recently, concerns have been raised about an increase in shock impedance and consequent shock failure during defibrillation testing in S-ICD patients undergoing a generator replacement. Purpose We aim to describe the defibrillation success rate in relation to the shock impedance in patients undergoing S-ICD generator replacement in our large tertiary center. Methods In this retrospective analysis, data from replacement procedures were collected from all patients who underwent an S-ICD generator replacement in our center from June 2014 to December 2020. Defibrillation testing was performed with at least one shock of ≤65J, and a successful shock was defined as terminating the ventricular arrhythmia within 5 seconds after the shock. Results A total of 133 patients underwent an S-ICD generator replacement, 5.8 ± 0.9 years after initial implant. Reasons for replacement were: reaching of elective replacement indicator (n = 119), early battery depletion (n = 9), complaints of generator pocket (n = 3) and device malfunction (n = 2). Defibrillation testing was performed in 111 patients (86.5%) undergoing a replacement procedure. Shock impedance data from both the implant and replacement procedure were available in 101 patients. The median shock impedance of these patients during their replacement procedure was significantly higher than during their implant, 79Ω (IQR 66-94) and 66Ω (IQR 57.5-81) respectively (Z = -5.552, p Conclusion In this large retrospective analysis, we have shown a first shock success rate during S-ICD generator replacement of 94.6%, which is similar to the success rate of defibrillation testing after initial implant. After multiple attempts, defibrillation testing success rate was 100%. Even though the median shock impedance during replacement was significantly higher than during the initial implant, there was no difference in impedance increase in patients with a successful shock compared to patients with an unsuccessful shock. Abstract Figure. Defibrillation success

Funding Acknowledgements Type of funding sources: None. Background Implantable cardioverter-defibrillator (ICD) therapy is associated with the risk of inappropriate shocks (IAS). IAS, defined as any shock on a different rhythm than VT or VF, cause psychological stress, decrease the quality of life and may provoke ventricular arrhythmias. In the subcutaneous ICD (S-ICD) the majority of IAS are caused by T-wave oversensing (TWOS), often during exercise. Exercise-optimized programming during an exercise ECG test (X-ECG) after implantation has shown to be successful in reducing IAS in patients known with TWOS. In recent years, new discrimination algorithms in the latest generation S-ICDs have significantly reduced the risk of TWOS. The benefit of performing an X-ECG in these latest generation S-ICDs to reduce IAS is unclear. Purpose We aim to describe the effect of exercise-optimized programming after S-ICD implantation on inappropriate shock rate in the latest generation S-ICDs. Methods In this retrospective multicenter study, data were collected from two experienced S-ICD hospitals in the Netherlands. All patients underwent an S-ICD implantation of second or third generation between February 2015 and December 2020. Patients younger than 21 years were excluded. Patients with an X-ECG after implantation were compared with patients without X-ECG after implantation. Total number of patients with IAS and cause of the first IAS were evaluated. Results In total, 262 patients were included in the X-ECG group and 61 in the no X-ECG group. The median follow-up time was 22 months in the X-ECG group (IQR 9-33) and 23 months in the no X-ECG group (IQR 12-33, P = 0.9). Mean age was 51 ± 15 years and 61 ± 15 years respectively (P< 0.001). Primary prevention indication was similar in both groups (56% for the X-ECG group versus 49% for the no X-ECG group, P = 0.4). A total of 8 patients (3.1%) experienced IAS in the X-ECG group; 3 first shocks (1.15%) were due to TWOS, 2 (0.8%) were given on a SVT and 3 (1.15%) on other non-cardiac activity. In the no X-ECG group, 6 patients (9.8%) experienced IAS; 1 first shock (1.6%) was due to TWOS, 4 (6.6%) were given on a SVT and 1 (1.6%) on other non-cardiac activity. Patients with an X-ECG had a significantly lower risk of IAS compared to patients in the no X-ECG group (hazard ratio 0.32; 95% CI 0.1 to 0.9; P = 0.027). The Kaplan-Meier estimate of IAS-free survival for the X-ECG group was 61 months (95% CI 59 to 62) and 50 months (95% CI 46 to 55) for the no X-ECG group. Results are shown in the figure. Conclusion This study shows that, in the latest generation S-ICDs, exercise-optimized programming after S-ICD implantation results in a significantly lower risk of IAS in adults. Patients with an X-ECG after S-ICD implantation were younger, which may have affected the outcome. Further prospective data with more equal groups is necessary. Until then, we recommend considering exercise testing after S-ICD implantation in the latest generation S-ICDs. Abstract Figure.

Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): Eurostars Introduction Patients at a high risk of sudden cardiac death (SCD) benefit from an implantable cardioverter defibrillator (ICD). However, they remain at a high risk of (inappropriate) shocks, heart failure, mortality and psychological distress. Consumer-level wearable accelerometry as method for recording physical behaviour (PB) has gained popularity over the past years, but so far the clinical potential is largely underinvestigated. The identification of patterns in PB and the association with clinical outcomes may provide a means to improve ICD therapy. Purpose This review addresses the evidence concerning PB in ICD patients and aims to characterise PB patterns associated with clinical outcomes. Methods A systematic review of studies focussing on accelerometer-assessed PB in patients older than 18 years equipped with an ICD, or patients at a high risk of SCD (e.g. advanced heart failure) was performed. PB could be assessed using a wearable accelerometer or an embedded accelerometer in the ICD (i.e. device-measured physical activity (D-PA)). Papers presenting quantitative data in English language peer reviewed journals published between January 2000 and September 2020 were identified via the OVID MEDLINE and OVID EMBASE databases. A study protocol describing study selection, data charting and summarisation of results was developed apriori. Study selection was conducted by two independent reviewers and a third reviewer in case of disagreement. Results A total of 4219 studies were identified, of which 51 were deemed appropriate for this review. Of these studies, 29 examined D-PA (n = 169.742 patients), 19 examined wearable accelerometery (n = 1.601) and 3 validated wearable accelerometry against D-PA (n = 106). The main findings were that (i) a low level of physical activity (PA) after implantation of the ICD and (ii) a decline in physical activity were both associated with an increased risk of ICD shocks, hospitalization and mortality. Second, PB was affected by cardiac factors (e.g. onset of atrial arrhythmias, ICD shocks) and non-cardiac factors (e.g. seasonal differences, pandemic lockdown). Third, PB was related to left ventricular ejection fraction, physical and cognitive function and quality of life. The evidence regarding wearable accelerometry compared to D-PA was scarce and heterogeneous. Conclusion This review demonstrated the potential of PB as an identifier of clinical deterioration in an ICD population. Accelerometer-assessed PB data could improve early warning systems and facilitate preventive and pro-active strategies, especially considering the nature of PB as modifiable risk factor. We suggest two directions for future research: (i) prospective collection of wearable accelerometry data in an ICD population to identify the most clinically relevant behavioural metrics (ii) investigation of preventive measures that can be undertaken once changes in PB are observed. Abstract Figure. Accelerometry-derived physical behaviour

Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Boston Scientific and Abbott Background One of the presumed advantages of leadless pacemaker (LP) therapy is that tricuspid regurgitation (TR) occurrence and severity would be less than with conventional pacemakers due to the absence of leads. However, TR and mitral regurgitation (MR) may also worsen due to chronic right ventricular (RV) pacing per se. Purpose To determine whether a novel LP is associated with increased TR and MR severity in a chronic canine model and to evaluate predictors of TR and MR worsening. Methods Healthy canine subjects were implanted with a novel LP programmed at a lower rate of 80/min. TR and MR were assessed by transthoracic echocardiography (TTE) prior to implant, at 90 days and at 18 months after implant. Further were assessed percentage of pacing, presence of pacing during TTE, and wall motion abnormalities (WMA) observed during TTE, indicating ventriculo-ventricular dyssynchronous pacing. Paired t-tests were performed to compare TR and MR severity before and after implant. Univariable and multivariable generalized estimating equation (GEE) models were used to evaluate factors predictive of increased TR and MR severity. Paired t-tests were used to evaluate whether the increase of TR and MR differed between subgroups where pacing or WMA were observed or not. Results An LP was implanted in 73 subjects. TR and MR severity at 90 days (n = 55) were significantly increased from baseline (p = 0.02 and 0.001, confidence intervals [CIs] 0.05-0.64 and 0.20-0.75, respectively); at 18 months (n = 37) TR severity remained significantly increased but MR did not (p = 0.01 and 0.62, CI [0.09, 0.69] and [-0.15, 0.25], respectively). Multivariable GEE (figure) showed that WMA and absence of TR at baseline are significant predictors for increased TR, while WMA and a shorter RV long axis are significant predictors for increased MR. Subgroup analysis demonstrated that TR and MR at day 90 were only significantly increased in subjects with observed pacing or WMA (n = 29; p = 0.0014 and p Conclusion In absence of pacing, the novel EMPOWER LP was not associated with increased TR and MR severity in a canine model. When pacing was observed TR and MR did increase. Increased MR severity did not persist at 18 months. Abstract Figure 1

Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Boston Scientific and Abbott Background Leadless pacemaker (LP) fixation mechanism exposure (FE) by penetration of the epicardial surface has been described. Previously reported animal model studies showed FE for 7/10 Micra LPs, versus 4/10 CapSureFix Novus RV pacing leads (both Medtronic). However, it is unknown whether FE causes pericardial effusion or pericarditis or does not have clinical significance. Purpose To determine the incidence of FE of a novel LP in a chronic animal model and its association with acute or chronic pericardial effusion. Methods Canine subjects were implanted with novel LPs (Boston Scientific) in an ongoing study. Acute pericardial effusion was assessed by post-procedural transthoracic echocardiography (TTE). Chronic pericardial effusion was assessed by TTE 90 days after implantation and post-mortem assessed pericardial fluid colour (PFC) and volume (PFV). FE was assessed visually at necropsy. Mann-Whitney U tests and chi-squared tests were used to determine whether greater PFV, more haemorrhagic PFC or LP implantation location differed significantly between subjects with and without FE. Results Results to date are reported. Canine subjects (n = 71) were chronically implanted with LPs. Due to 14 in-vivo retrievals, data is shown of 57 subjects with LPs in situ at necropsy. Pre-deployment radiocontrast injection confirmed LP position (RV apex n = 41; RV apicoseptal n = 16), and mechanical stability and electrical testing confirmed adequate talon fixation after deployment. Necropsy after median 94 days (IQR 91-540) demonstrated FE in 11 cases (19%) (figure). No acute nor chronic pericardial effusion was seen on TTE. Mean PFV for animals with and without FE was 1.8 and 1.6 cc, respectively. FE did not show an association with PFV or colour (p= 0.53 and p = 0.83, respectively). For two animals, PFV and PFC are not available; FE was not observed in either of these cases. LP implantation location was not associated with incidence of FE (p = 1.00). Conclusion Fixation mechanism exposure by the talons of a novel leadless pacemaker was observed in 19% of animals implanted and was not associated with acute or chronic pericardial effusion. Abstract Figure 1

Background: Suboptimal positioning of the subcutaneous implantable cardioverter-defibrillator (S-ICD) increases the defibrillation threshold and risk of conversion failure. Objective: Our objective is to develop a tool to evaluate the implant position and predict defibrillation success of the S-ICD: the PRAETORIAN score. Methods: The PRAETORIAN score is based on clinical and computer modeling knowledge of determinants affecting the defibrillation threshold: subcoil fat, subgenerator fat, and anterior positioning of the S-ICD generator. The score evaluates these determinants on the postoperative anterior-posterior and lateral chest radiographs and has 3 categories: 30–

Background: Conventional cardiac device infections are increasing in incidence, causing significant morbidity and mortality. Leadless pacemaker (LP) therapy may provide new opportunities for the management of pacemaker (PM) infections as it does not require implantation of transvenous leads and a pectoral pocket. Objective: We sought to evaluate the effect of early and late LP implantation in patients diagnosed with device infection. Methods: Patients receiving an LP at our center after conventional PM lead extraction due to infection between December 2013 and November 2017 were included. Results: A total of 17 patients (mean age 77.4 ± 7.77 years) underwent LP implantation (ie, 11 with Nanostim leadless cardiac pacemaker [Abbott, Chicago, IL] and 6 with Micra transcatheter pacing system [Medtronic, Minneapolis, MN]) after successful PM system explantation. In 9 PM-dependent patients, a temporary transvenous pacing system was placed as a bridge to permanent LP implantation. Early LP implantation was performed in 6 patients (1 week). All patients experienced no LP infection during a mean follow-up of 16 ± 12 months, including 7 patients with a history of recurrent device infections with a mean follow-up of 20 ± 14 months. Conclusion: Early and late LP placement after infected conventional pacing system explantation was a viable option in our case series. This therapy may provide an alternative strategy in the management of device infection, if confirmed by subsequent prospective randomized trials, particularly for patients who are PM dependent or have a history of recurrent device infections.

Transvenous temporary cardiac pacing therapy (TV-TP) is widely used to treat life-threatening arrhythmias. Yet aggregated evidence on TV-TP is limited. We conducted a systematic scoping review to evaluate indications, access routes and complications of TV-TP, as well as permanent pacemaker therapy (PPM) following TV-TP. Clinical studies concerning TV-TP were identified in Ovid MEDLINE. Case studies and studies lacking complication rates were excluded. To assess complication incidence over time, differences in mean complication rates between 10-year intervals since the introduction of TV-TP were evaluated. We identified 1398 studies, of which 32 were included, effectively including 4546 patients. Indications varied considerably; however TV-TP was most commonly performed in atrioventricular block (62.7%). The preferred site of access was the femoral vein (47.2%). The mean complication rate was 36.7%, of which 10.2% were considered serious. The incidence of complications decreased significantly between 10-year interval groups, but remained high in the most recent time period (22.9%) (analysis of variance; p