Subcutaneous Implantable Cardioverter-defibrillator System Research Articles

Incidence, implications, and management of sense-B-noise failure in subcutaneous cardioverter-defibrillator patients: insights from a large multicentre registry.

Subcutaneous implantable cardioverter-defibrillators (S-ICDs) offer potentially distinct advantages over transvenous defibrillator systems. Recent randomized trials showed significantly lower lead failure rates than transvenous ICD. Still, S-ICDs remain associated with the risk of inappropriate shocks (IAS). While previous studies have reported varying causes of IAS, this study explores a rare cause of IAS, referred to as 'sense-B-noise.' It was recently described in case series, but its incidence has not been studied in a large cohort of S-ICD patients. We retrospectively reviewed data from patients implanted with S-ICD models 1010, A209, and A219 between October 2009 and July 2023 across nine centres in Europe and the USA. The analysis concentrated on determining the incidence and understanding the implications of sense-B-noise events. Sense-B-noise represents a rare manifestation of distinct electrogram abnormalities within the primary and alternate sensing vectors. Data were collected from medical records, device telemetry, and manufacturer reports for investigation. This registry is registered on clinicaltrials.gov (NCT05713708). Subcutaneous implantable cardioverter-defibrillator devices of the 1158 patients were analysed. The median follow-up time for all patients was 46 (IQR 23-64) months. In 107 patients (9.2%) ≥1 IAS was observed during follow-up. Sense-B-noise failure was diagnosed in six (0.5 and 5.6% of all IAS) patients, in all patients, the diagnosis was made after an IAS episode. Median lead dwell time in the affected patients was 23 (2-70) months. To resolve the sense-B-noise defect, in three patients reprogramming to the secondary vector was undertaken, and two patients underwent system removal with subsequent S-ICD reimplantation due to low amplitude in the secondary vector. In one patient, the secondary vector was initially programmed, and subsequently, an S-ICD system exchange was performed due to T-wave-oversensing IAS episodes. This multicentre analysis' findings shed light on a rare but clinically highly significant adverse event in S-ICD therapy. To our knowledge, we provide the first systematic multicentre analysis investigating the incidence of sense-B-noise. Due to being difficult to diagnose and limited options for resolution, management of sense-B-noise is challenging. Complete system exchange may be the only option for some patients. Educating healthcare providers involved in S-ICD patient care is crucial for ensuring accurate diagnosis and effective management of sense-B-noise issues.

Clinical practice and outcome of S-ICD replacement: results from the multicenter rhythm detect registry

Abstract Background Subcutaneous implantable cardioverter-defibrillator (S-ICD) therapy is expanding rapidly. However, there are few data on the S-ICD replacement procedure. Objective The aim of this analysis was to describe the procedure and outcome of S-ICD replacement in clinical practice. Methods From 2013 to 2022, consecutive patients undergoing de-novo implantation of an S-ICD were enrolled at 66 Italian centers of the Rhythm Detect Registry. We analyzed consecutive patients who required S-ICD replacement. Results 319 S-ICD generators (49 Cameron, 270 Emblem) were replaced for battery depletion. All the procedures were performed in electrophysiology laboratories, by one or two expert operators. In 118 (37%) cases, the replacement was performed as outpatient procedure. The procedure was performed under local anesthesia with or without conscious sedation in 297 patients (93%). The previous S-ICD generator was in an intermuscular pocket in 195 (61%) patients, and in a subcutaneous pocket in the remaining 124 (39%). 39 (31%) generators were shifted from subcutaneous to intermuscular pocket, and their PRAETORIAN score improved from 43±20 to 34±13 (p=0.007). In most cases (308 (97%)), the defibrillation test was not performed after replacement, but the overall PRAETORIAN score was very low (37±28). The S-ICD system was successfully replaced in all patients and no complications were reported; the procedure duration was 39±16 min and was comparable in the case of generator re-implanted in the same pocket or in case of shift to a new pocket. Conclusions S-ICD replacement was safe and easy to perform, with no peri-operative complications. In clinical practice the replacement procedure is often an opportunity to optimize the position of the generator

Left ventricular assist device in the presence of subcutaneous implantable cardioverter defibrillator: data from a multicenter experience

Abstract Background Left ventricular assist devices (LVADs) are an increasingly used strategy for the management of patients with advanced heart failure (HF).Subcutaneous implantable cardioverter defibrillator (S-ICD) might be a viable alternative to conventional ICDs, with a lower risk of short- and long-term of device-related complications and infections. Purpose:The aim of this multicenter study was to evaluate the outcomes and management of S-ICD recipients who underwent LVAD implantation. Methods:The study population included patients with an S-ICD who underwent LVAD implantation for advanced HF despite optimal medical therapy. Results:The study population included 30 patients (25 male;median age 45 [38-52] years).The HeartMate III was the most common LVAD type. Median follow-up in the setting of concomitant use of S-ICDs and LVADs was 7 months (1-20).There were no reports of inability to interrogate S-ICD systems in this population.Electromagnetic interference (EMI) occurred in 21 (70%) patients.The primary sensing vector was the one most significantly involved in determining EMI.Twenty-seven patients (90%) remained eligible for S-ICD implantation with at least one optimal sensing vector.The remaining 3 patients (10%) were ineligible for S-ICD after attempts of reprogramming of sensing vectors. Six patients (20%) experienced inappropriate shocks due to EMI. Six patients (20%) experienced appropriate shocks.No S-ICD extraction because of need for antitachycardia pacing,ineffective therapy or infection was reported. Conclusions: Concomitant use of LVAD and S-ICD is feasible in most patients. However, the potential risk of EMI oversensing, IS,and undersensing in the post-operative period following LVAD implantation should be considered.Careful screening for EMI should be performed in all sensing vectors after LVAD implantation.

Subcutaneous cardioverter defibrillator implanted intermuscularly in patients with end-stage renal disease requiring hemodialysis: 5-year follow-up.

The aim of the present study was to evaluate the long-term safety and effectiveness of the subcutaneous implantable cardioverter defibrillator (S-ICD) when implanted intermuscularly in patients with end-stage renal disease and hemodialysis. This study is a retrospective analysis of 21 consecutive patients implanted with S-ICDs at three experienced centers in Germany with comorbid renal insufficiency requiring hemodialysis, as well as being at risk of sudden cardiac death. The S-ICD was placed intermuscularly in all patients. Follow-ups (FUs) were performed every 6months. The mean ± standard deviation FU duration was 60.0 ± 11.4months, with a range of 39 to 78months. There were no deaths due to arrhythmia, or device-associatedinfections and complications. Four patients (19.1%) died during FU due to respiratory insufficiency during dialysis, systolic heart failure, septic infection of the urogenital tract, and colorectal cancer, respectively. There were six non-device-related hospitalizations with a duration of 12.7 ± 5.1days and a hospitalization rate of 4.1 per 100 patient years. In the long-term FU of this small population of seriously compromised hemodialysis patients at risk of sudden cardiac death, the intermuscularly implanted S-ICD system was safe and effective. No arrhythmic complications, device-associated infections, or complications compromised survival. These data are encouraging and support testing in a larger group of similarly compromised patients.

Left ventricular assist device in the presence of subcutaneous implantable cardioverter defibrillator: Data from a multicenter experience

BackgroundLeft ventricular assist devices (LVADs) are an increasingly used strategy for the management of patients with advanced heart failure (HF). Subcutaneous implantable cardioverter defibrillator (S-ICD) might be a viable alternative to conventional ICDs with a lower risk of short- and long-term of device-related complications and infections.The aim of this multicenter study was to evaluate the outcomes and management of S-ICD recipients who underwent LVAD implantation. MethodsThe study population included patients with a preexisting S-ICD who underwent LVAD implantation for advanced HF despite optimal medical therapy. ResultsThe study population included 30 patients (25 male; median age 45 [38–52] years).The HeartMate III was the most common LVAD type. Median follow-up in the setting of concomitant use of S-ICDs and LVADs was 7 months (1–20).There were no reports of inability to interrogate S-ICD systems in this population. Electromagnetic interference (EMI) occurred in 21 (70%) patients. The primary sensing vector was the one most significantly involved in determining EMI. Twenty-seven patients (90%) remained eligible for S-ICD implantation with at least one optimal sensing vector. The remaining 3 patients (10%) were ineligible for S-ICD after attempts of reprogramming of sensing vectors. Six patients (20%) experienced inappropriate shocks (IS) due to EMI. Six patients (20%) experienced appropriate shocks. No S-ICD extraction because of need for antitachycardia pacing, ineffective therapy or infection was reported. ConclusionsConcomitant use of LVAD and S-ICD is feasible in most patients. However, the potential risk of EMI oversensing, IS and undersensing in the post-operative period following LVAD implantation should be considered. Careful screening for EMI should be performed in all sensing vectors after LVAD implantation.

Abstract 18178: Should We Screen for S-ICD Vectors in Hypertrophic Cardiomyopathy Post-Myectomy?

Case Description: We describe a 40 year old Asian male with hypertrophic cardiomyopathy (HCM) who presented after an inappropriate shock from his subcutaneous ICD (S-ICD) but was otherwise asymptomatic. The device was placed 4 months ago for secondary prevention of sudden cardiac death (SCD). He underwent a septal myectomy 2 months prior to presentation for severe LVOT obstruction. EKG showed sinus rhythm with new post-myectomy LBBB. Troponins were normal. Device interrogation revealed a wide complex rhythm consistent with sinus tachycardia with LBBB and evidence of T-wave oversensing (TWOS). The S-ICD was turned off and no further arrythmias were seen on continuous telemetry. Subsequent vector rescreening reflected ineligibility for S-ICD, most likely due to altered QRS morphology post-myectomy. Accordingly, the S-ICD system was extracted and a dual chamber transvenous ICD was placed. Patient noted to be doing well at 3 months follow up. Discussion: S-ICD is a safe and effective alternate to transvenous ICDs to prevent SCD in patients with HCM, especially those with a long life-expectancy. The pre-implant automated screening tool generates 3 sensing vectors. Screening is done to ensure at least 1 vector with suitable EKG morphology as low amplitude vectors and low R:T ratios increase risk of oversensing. However, post-surgical changes can alter the QRS morphology as seen above. This can significantly impact the screening process. Currently, there are no guidelines for rescreening. We propose rescreening in the setting of significant QRS changes (especially post-operatively) to reduce the risk of oversensing and undersensing in high risk populations.

How likely is the sense-B-noise to affect patients with subcutaneous implantable cardioverter-defibrillators and can we solve that problem in every case?

Sense-B-noise is a newly reported possible cause of inappropriate shocks in patients with subcutaneous implantable cardioverter-defibrillators (S-ICDs). The nature of that noise is unknown, it is not related to mechanical failure of the S-ICD system. Reprogramming to the secondary sensing vector is suggested by the producer as a possible solution. We analyzed the medical records of S-ICD recipients from two university clinical centers (Gdansk and Szczecin, Poland). Our aim was to determine the rate of sense-B-noise, and whether the secondary sensing vector would be available for reprogramming if such a problem occurred in our patients. The sense-B-noise issue affected three patients in our cohort (3%), which corresponds to the incidence of 0.012 events per patient-year of follow-up. The primary vector was permanently used in 47 patients (52%), secondary in 28 (31%), and alternate in 16 (17%), respectively. Therefore, the total number of patients potentially vulnerable to sense-B noise (with the primary or alternate vector programmed permanently) was 63 (69%). Among those 63 patients, 51 individuals (81%) had also the secondary vector available for permanent use. The sense-B-noise affected 3% of patients in our cohort, with an incidence of 0.012 per patient-year of follow-up. Most patients potentially vulnerable to sense-B noise could be reprogrammed to the secondary sensing vector, if necessary. Further investigation of the sense-B-noise issue is needed.

Impact of Age on Subcutaneous Implantable Cardioverter-Defibrillator in a Large Patient Cohort: Mid-Term Follow-Up

BackgroundThe subcutaneous implantable cardioverter-defibrillator (S-ICD) is an accepted alternative to transvenous (TV) ICD to provide defibrillation therapy to treat life-threatening ventricular tachyarrhythmias in high-risk patients. S-ICD outcomes by age group have not been reported. ObjectivesIn this study, the authors sought to report S-ICD outcomes in different age groups in a multicenter S-ICD post-approval study (PAS) involving the largest cohort of patients ever reported. MethodsPatients were prospectively enrolled in the S-ICD PAS and stratified based on age: young, aged 15-34 years; adult, aged 35-69 years; and elderly, aged ≥70 years. Patient characteristics and clinical outcomes through 3 years of follow up after implantation were compared. ResultsThe S-ICD PAS enrolled 1,637 patients. Elderly patients were more likely to receive an S-ICD as a replacement of a TV-ICD (15.1% elderly vs 12.3% adult vs 7.4% young). Secondary prevention indication decreased with age (32.7% young vs 22.2% adult vs 20.5% elderly). Mortality rate was significantly higher in the elderly group (24.0% elderly vs 13.0% adult vs 7.4% young; P < 0.0001), whereas the complication rate did not differ significantly (12.3% young vs 11.3% adult vs 8.1% elderly). Rates of appropriate shock (12.7% young vs 13.0% adult vs 13.8% elderly) and inappropriate shock (7.8% young vs 9.1% adult vs 8.8% elderly) rates did not differ between groups (P = 0.96 and P = 0.98, respectively). ConclusionsImplant complications and appropriate and inappropriate shock rates were similar among age groups. S-ICD for secondary prevention was more common in the young group. Replacing a TV-ICD for an S-ICD increases with age. (S-ICD System Post-Approval Study; NCT01736618)

Acute human defibrillation performance of a subcutaneous implantable cardioverter-defibrillator with an additional coil electrode

The subcutaneous implantable cardioverter-defibrillator (S-ICD) delivers 80 J shocks from an 8 cm left-parasternal coil to a 59 cm3 left lateral pulse generator (PG). A system that defibrillates with lower energy could significantly reduce PG size. Computer modeling and animal studies suggested that a second shock coil either parallel to the left-parasternal coil or transverse from the xiphoid to the PG pocket would significantly reduce the defibrillation threshold. The purpose of this study was to acutely assess the defibrillation efficacy of parallel and transverse configurations in patients receiving an S-ICD. Testing was performed in patients receiving a conventional S-ICD system. Success at 65 J was required before investigational testing. A second electrode was temporarily inserted from the xiphoid incision connected to the PG with an investigational Y-adapter. Phase 1 (n = 11) tested the parallel configuration. Phase 2 (n = 21) tested both parallel and transverse configurations in random order. This study enrolled 35 patients (76% male; mean age 52 ± 17 years; left ventricular ejection fraction 40% ± 15%; body mass index 26 ± 4 kg/m2; prior myocardial infarction 50%; congestive heart failure 53%; cardiomyopathy 56%). Compared to the conventional S-ICD system, mean shock impedance decreased for both parallel (69 ± 15 Ω vs 86 ± 20 Ω; n = 33; P < .001) and transverse (56 ± 14 Ω vs 81 ± 21 Ω; n = 20; P < .001) configurations. Shock success rates at 20, 30, and 40 J were 55%, 79%, 97%, and 25%, 70%, 90% for parallel and transverse configurations, respectively. Defibrillation threshold testing was well tolerated with no serious adverse events. Adding a second shock coil, particularly in the parallel configuration, significantly reduced the impedance and had a high likelihood of defibrillation success at energies ≤40 J. This may enable the development of a smaller S-ICD.

Postapproval Study of a Subcutaneous Implantable Cardioverter-Defibrillator System

BackgroundThe subcutaneous implantable cardioverter-defibrillator (S-ICD) was developed to avoid complications related to transvenous implantable cardioverter-defibrillator (TV-ICD) leads. Device safety and efficacy were demonstrated previously with atypical clinical patients or limited follow-up. ObjectivesThe S-ICD PAS (Subcutaneous Implantable Cardioverter-Defibrillator System Post Approval Study) is a real-world, multicenter, registry of U.S. centers that was designed to assess long-term S-ICD safety and efficacy in a diverse group of patients and implantation centers. MethodsPatients were enrolled in 86 U.S. centers with standard S-ICD indications and were observed for up to 5 years. Efficacy endpoints were first and final shock efficacy. Safety endpoints were complications directly related to the S-ICD system or implantation procedure. Endpoints were assessed using prespecified performance goals. ResultsA total of 1,643 patients were prospectively enrolled, with a median follow-up of 4.2 years. All prespecified safety and efficacy endpoint goals were met. Shock efficacy rates for discrete episodes of ventricular tachycardia or ventricular fibrillation were 98.4%, and they did not differ significantly across follow-up years (P = 0.68). S-ICD–related and electrode-related complication-free rates were 93.4% and 99.3%, respectively. Only 1.6% of patients had their devices replaced by a TV-ICD for a pacing need. Cumulative all-cause mortality was 21.7%. ConclusionsIn the largest prospective study of the S-ICD to date, all study endpoints were met, despite a cohort with more comorbidities than in most previous trials. Complication rates were low and shock efficacy was high. These results demonstrate the 5-year S-ICD safety and efficacy for a large, diverse cohort of S-ICD recipients. (Subcutaneous Implantable Cardioverter-Defibrillator [S-ICD] System Post Approval Study [PAS]; NCT01736618)

Procedure, management, and outcome of subcutaneous implantable cardioverter-defibrillator extraction in clinical practice.

Subcutaneous implantable cardioverter-defibrillator (S-ICD) therapy is expanding rapidly. However, there are few data on the S-ICD extraction procedure and subsequent patient management. The aim of this analysis was to describe the procedure, management, and outcome of S-ICD extractions in clinical practice. We enrolled consecutive patients who required complete S-ICD extraction at 66 Italian centres. From 2013 to 2022, 2718 patients undergoing de novo implantation of an S-ICD were enrolled. Of these, 71 required complete S-ICD system extraction (17 owing to infection). The S-ICD system was successfully extracted in all patients, and no complications were reported; the median procedure duration was 40 (25th-75th percentile: 20-55) min. Simple manual traction was sufficient to remove the lead in 59 (84%) patients, in whom lead-dwelling time was shorter [20 (9-32) months vs. 30 (22-41) months; P = 0.032]. Hospitalization time was short in the case of both non-infectious [2 (1-2) days] and infectious indications [3 (1-6) days]. In the case of infection, no patients required post-extraction intravenous antibiotics, the median duration of any antibiotic therapy was 10 (10-14) days, and the re-implantation was performed during the same procedure in 29% of cases. No complications arose over a median of 21 months. The S-ICD extraction was safe and easy to perform, with no complications. Simple traction of the lead was successful in most patients, but specific tools could be needed for systems implanted for a longer time. The peri- and post-procedural management of S-ICD extraction was free from complications and not burdensome for patients and healthcare system. URL: http://clinicaltrials.gov/Identifier: NCT02275637.

Defibrillation testing during S-ICD implantation: How relevant? Results from a multicenter study

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Defibrillation testing (DFT) is still recommended in patients with subcutaneous implantable cardioverter-defibrillator (S-ICD) to ensure proper detection of ventricular fibrillation and confirm effective defibrillation. Given the significant risk of complications, recent studies, are reconsidering the interest of the DFT in S-ICD. The purpose of this study was to assess the clinical "real-life" outcomes of DFT over a mid-term follow-up period after third-generation S-ICD implantation. Methods and Results 368 patients (pts) (47.9 ± 15.5 years old; male 72.8%) implanted with Generation 3 S-ICD system were included in this retrospective multicenter registry-based study. Mean left ventricular ejection fraction (LVEF) was 40.8% (primary prevention 56.1%). For 99.2% pts, S-ICD implantation was performed using the two-incision technique and intermuscular positioning of the generator was performed for all pts. 81% pts underwent ICD testing during implantation. Reasons for not performing DFT were: very low LVEF (3.5%), intracardiac thrombus (2.4%) and VF induction failure. In 2.2% (8 pts) DFT was unsuccessful, causes were: induction of ventricular tachycardias with rates falling below the shock zone for 3 pts while shocks were ineffective for 5 pts. One patient required revision for contralateral lead implantation, while sensing vector reprogramming and shock polarity modification were efficient for the others. The mean impedance was 68.4 (±14.7) Ω and time to shock therapy ranged from 10 to 33 s, with a mean of 16.7 (±4) s. A total of 36 appropriate shocks (10.1%) have been observed after a FU period of 11.02±8.8 months (1.8 shocks per patient, several shocks for 12pts, failure of the first shock for 5 patients). 17 patients (4.6%) underwent S-ICD system extraction. The reasons were pocket site complication (7 pts), pacing indication for cardiac resynchronization therapy or bradycardia (3 pts), and S-ICD lead dysfunction (4 pts). Extraction after heart transplant was needed in 3 pts. Among the 4 pts explanted for system dysfunction, only one patient had a DFT during implantation. After a mean follow-up of 19±12.1 months, the mortality rate was 3.8% (no S-ICD-related deaths were reported). There was no significant difference between the 2 groups of pts with and without DFT testing (p=0.629). Conclusion The DFT remains for the moment highly recommended during S-ICD implantations. Results from randomized studies are still needed to confirm the relevance of DFT during S-ICD implantation.

A 25-year single-center experience with transvenous and subcutaneous ICD patients under thirty years of age

Abstract Funding Acknowledgements Type of funding sources: None. Background Young implantable cardioverter-defibrillator (ICD) recipients present high rate of inappropriate shocks and complications. Some of them seem to be underestimated. The subcutaneous ICD(S-ICD) system was developed to eliminate lead-related complications and was proved to be effective, avoiding intracardiac and endovascular adhesions. Aims To report on our clinical experience with transvenous (TV-ICD) and S-ICD therapy in patients under thirty years of age. Methods We reviewed database of ICD recipients in our institution between 1996 and 2022(25 years) and have chosen 125 pts consecutively implanted up to and including the age of 30 years. We retrospectively analyzed the rate of appropriate(AI) and inappropriate interventions(IS), lead complications rate, infection rate, mortality and treatment options. Results The study group: 84 TV-ICD(age: 6-30, BMI: 16,3-22,2) and 41 S-ICD( age: 15-30, BMI; 15,6-31,1) patients. The mean follow-up in analyzed groups was 159±48 and 40± 2 months respectively. Abnormal ventricular function: EF≤30 occurred in compared groups: 12/84(14%) and 5/41(12%) respectively, p=0,3. 24/84pts(28%) received ≥1 AI for VT/VF(ATP or shock) in TV-ICD and 4/40pts(10%) in S-ICD groups. 25/84 pts(30%) received one or multiple (IS) and 1/40pts(2,5%) in compared groups respectively, p=0,02. There were 18/84 (21.5%) ventricular lead dysfunctions(reimplantation of a new system) in TV-ICD and 0% in S-ICD groups, p=0,025. An infection rate (endocarditis or device pocket )was 8/84 (10%) in TV-ICD group with complete system removal and 1 pts (2,5%) wound infection(staphylococcus aureus) in S-ICD group successfully treated with antibiotics. 1 left ventricular assist device was implanted in end-stage heart failure S-ICD patient with good result. There were 2 S-ICD implantations as a concomitant device i.e. conversion of TV-ICD(with therapy OFF) to S-ICD due to ventricular lead dysfunction. 4(10%) pts required generator elective replacement due to early battery depletion in S-ICD group. In 2(5%)pts right sternal lead location was chosen due to better sensing results. Mortality rate was 6/84 pts (7%), caused by ventricular lead dysfunction, end-stage heart failure or heart transplantation fatal result in TV-ICD group. There was no death in S-ICD group. Conclusions TV- ICD implantation in children and young adults is a feasible and effective procedure in a 25-year follow-up but the rate of complications is high in this population. S-ICD recipients did not experienced lead failures or systematic infections. S-ICD appears to be a good therapy option and an alternative to TV-ICD in pediatric and young patients population, preventing from some serious lead complications and tricuspid valve regurgitation. The method and follow-up period effect is present between the TV-ICD and S-ICD in analyzed groups.

Capsulectomy: a safe and effective way to lower shock impedance in S-ICD replacement procedures

Abstract Funding Acknowledgements Type of funding sources: None. Background The safety and efficacy of the subcutaneous implantable cardioverter-defibrillator (S-ICD) has been proven in various clinical trials. Due to intermuscular device placement, higher shock energy is required for effective treatment of ventricular tachyarrhythmia. High shock impedance is a risk marker for ineffective defibrillation. Previous studies have shown reduced shock efficacy in device replacement procedures, possibly due to fibrous encapsulation of the device associated with dwelling time of the system. Therefore, in case of significant capsulation, capsulectomy became part of device replacement procedure in our center. In this study we analyzed the results of intraoperative testing before and after capsulectomy measured by results of high-voltage impedance. Purpose Aim of our study was to show that removal of the fibrous capsulation can help to reduce high voltage impedance without relevant perioperative adverse events at the device replacement procedure. Methods Between January 2018 and November 2022, a total of 68 consecutive patients underwent S-ICD device replacement in our center. Pre-operative high-voltage impedance was determined either through recent therapy deliveries or by a 10J test shock immediately before device replacement. Device replacement was performed according to international standards. In case of significant capsulation, additional capsulectomy was performed. Defibrillation testing was routinely performed by the end of the procedure in the absence of contraindications. Results Of 68 patients, 81% were male, mean age at device replacement was 55 ± 17 years. Most patients were implanted for primary prevention (69%). Defibrillation testing with 65 J at initial device implantation was successful in 87% of patients. Mean dwelling time of the S-ICD System was 61 months (±19 months). Shock impedance increased significantly to 98±33 Ω vs. 80±20 Ω (p=0.013) at initial implantation. Capsulectomy of the S-ICD pocket resulted in a significant decrease of high-voltage impedance to 83±23 Ω as compared to measurement prior to replacement (p=0.03). Defibrillation testing was successful in all patients. First shock efficacy with 65 J was 92%. No acute complications (defined as significant bleeding, prolongation of hospital stay, etc.) were observed in short term follow-up and patients could be discharged as planned. Conclusion Capsulectomy of S-ICD pocket appears to be a safe and effective way to reduce shock impedance which has proven to be a predictor of successful defibrillation in testing as well as in spontaneous episodes. Despite the additional step during device replacement, no complications were observed in our study. Randomized trials regarding defibrillation testing during first implantation are ongoing. Trials addressing the optimal device replacement strategy however are warranted.

Experience of using the of subcutaneous cardioverter-defibrillators in the world practice: review

The article provides a review of international clinical studies on the use of a subcutaneous implantable cardioverter-defibrillator (ICD) in comparison with classical intravenous defibrillation systems. Subcutaneous ICDs have shown themselves to be a worthy alternative to intravenous defibrillating systems for the primary prevention of sudden cardiac death, when the patient is not indicated for anti-tachy stimulation and anti-brady stimulation. World experience on the use of subcutaneous ICDs proves the safety and effectiveness of the functioning of the subcutaneous ICD system, excluding from the patient’s life the formidable risks associated with the implantation procedure and further functioning of the classical intravenous ICD system.

Sense-B-noise: an enigmatic cause for inappropriate shocks in subcutaneous implantable cardioverter defibrillators.

Subcutaneous implantable cardioverter defibrillators (S-ICDs) are well established. However, inappropriate shocks (IAS) remain a source of concern since S-ICDs offer very limited troubleshooting options. In our multicentre case series, we describe several patients who experienced IAS due to a previously unknown S-ICD system issue. We observed six patients suffering from this novel IAS entity. The IAS occurred exclusively in primary or alternate S-ICD sensing vector configuration (therefore called 'Sense-B-noise'). IAS were caused by non-physiologic oversensing episodes characterized by intermittent signal saturation, diminished QRS amplitudes, and disappearance of the artefacts after the IAS. Noise/oversensing could not be provoked by manipulation, X-ray did not show evidence for lead/header issues and impedance measurements were within normal limits. The pooled experience of our centres implies that up to ∼5% of S-ICDs may be affected. The underlying root cause was discussed extensively with the manufacturer but remains unknown and is under further investigation. Sense-B-noise is a novel cause for IAS due to non-physiologic signal oversensing, arising from a previously unknown S-ICD system issue. Sense-B-noise may be suspected if episodes of signal saturation in primary or alternate vector configuration are present, oversensing cannot be provoked, and X-ray and electrical measurements appear normal. The issue can be resolved by reprogramming the device to secondary sensing vector.

A new window on subcutaneous ICD system performance: Z-lead impedance change over time in devices with and without extracellular matrix envelope use

Abstract Background Device impedance for subcutaneous ICDs (S-ICDs) may rise over time reflecting changes in tissue electrical conduction due to fibrosis from the natural foreign body response, increasing the risk of defibrillation failure. A biologic envelope optimized for S-ICDs may mitigate fibrosis and encourages angiogenesis around the device possibly decreasing impedance rise over time. The S-ICD system performs routine low-voltage Z-lead (LVZ) impedance testing (impedance between shocking coil and can) that may provide insight into the impedance changes on device functionality and efficacy over time. Purpose Explore early and late impedance changes over time in S-ICDs implanted with and without envelopes using periodic LVZ measurements. Methods 30 patients received S-ICDs (15 with envelope) between 1/2017 and 3/2021, after excluding those with device complications, uncontrolled comorbidities, or recent cardiac surgery. Impedance data was recorded at initial implantation. LVZ impedance data was extracted from the wireless remote monitoring system, trended over 0–4 years post implant, and analyzed blinded to patient information. Results 24 patients (12 envelope) had evaluable implant and chronic data sets. Baseline clinical characteristics were similar between groups. Impedance in general was higher in the envelope group at initial implantation (LVZ mean 89 Ω vs 74 Ω) and throughout the first year. Comparing envelope to no envelope, the initial average shock impedance was 87.3±30.50 vs 66.7±10.40, followed by an average low-V impedance drop of 29 Ω vs 17 Ω during the first month, with a recovery to 109 Ω vs 91 Ω at 30 months post implant. After 30 months, impedance trends demonstrated a modest linear increase up to 48 months in the no envelope group in comparison with a modest decrease in the envelope group (sample sizes too small to determine significance) (Figure 1). Conclusion The results demonstrate periodic LVZ testing in the S-ICD monitoring system can reliably trend changes in system impedance over time. Impedance measurements within the first 6–7 months (and most markedly within the first 3 months) appear to be transiently lower than the values seen after this timepoint suggesting that early impedance measurements may not predict steady-state impedance. Further studies are needed to explore the impact of envelope use and the S-ICD impedance changes beyond 30 months. Funding Acknowledgement Type of funding sources: None.

Air entrapment as a cause of S-ICD inappropriate shocks.

The subcutaneous implantable cardioverter-defibrillator (S-ICD) is noninferior to the transvenous ICD concerning device-related complications or inappropriate shocks (IASs) in patients with an indication for defibrillator therapy and not in need of pacing. 1 Knops R.E. Olde Nordkamp L.R.A. Delnoy P.P.H.M. et al. Subcutaneous or transvenous defibrillator therapy. N Engl J Med. 2020; 383: 526-536 Crossref PubMed Scopus (149) Google Scholar The main causes of IAS in S-ICD recipients are T-wave oversensing, oversensing of ventricular tachycardia/ventricular fibrillation below the therapy zone, myopotentials, and low-amplitude signals. 2 Burke M.C. Aasbo J.D. El-Chami M.F. et al. 1-Year prospective evaluation of clinical outcomes and shocks. JACC Clin Electrophysiol. 2020; 6: 1537-1550 Crossref PubMed Scopus (15) Google Scholar ,3 Gold M.R. Lambiase P.D. El-Chami M.F. et al. Primary results from the Understanding Outcomes With the S-ICD in Primary Prevention Patients With Low Ejection Fraction (UNTOUCHED) trial. Circulation. 2021; 143: 7-17 Crossref PubMed Scopus (45) Google Scholar Subcutaneous air entrapment has recently been considered an underdiagnosed cause of early postimplant IAS, accounting for a part of oversensing of low-amplitude signals. 4 Chinitz J.S. Nadraus P. Darge A. Cacciabaudo J. Altman E.J. Inappropriate shocks within 24 hours after implantation of a subcutaneous defibrillator with a two-incision technique. J Innovations Card Rhythm Manag. 2016; 7: 2295-2298 Crossref Google Scholar ,5 Nishinarita R. Kishihara J. Matsuura G. et al. Early inappropriate shock in a subcutaneous cardiac defibrillator due to subcutaneous air. J Arrhythm. 2019; 35: 682-684 Crossref PubMed Scopus (2) Google Scholar Few data are available about the incidence, prevention, and management of postprocedural IAS due to subcutaneous air entrapment. We searched for case reports on IAS due to subcutaneous air entrapment published in PubMed, Google Scholar, Scopus, and EMBASE from 2012 to December 2021. For each of them, we analyzed the patients’ clinical characteristics, the S-ICD implantation technique, the timing and mode of IAS diagnosis, and the management of complications. A total 15 patients with S-ICD (66% male) with a median age of 55 years (interquartile range 17–75 years) were included. The indication for S-ICD implantation was primary prevention in 6 patients (40%) and secondary prevention in 9 patients (60%). A 3-incision technique was used in 7 patients (46.6%) and a 2-incision technique in 6 patients (40%). IAS was experienced on the same day of the procedure in 66.6% of cases and after discharging in 33.3%, always within 4 days of S-ICD implantation. Intraprocedural chest radiography was performed for checking the correct S-ICD system positioning in 40% of cases; in none of them, the presence of air entrapment has been reported. Subcutaneous air entrapment was diagnosed by postoperative chest radiography in 11 cases (73.3%), whereas the diagnosis was based on device interrogation and reproduction of the electrogram alterations by manipulation in 2 cases (13.3%). The most common localization of air entrapment was around the proximal electrode (46.6%, n = 7), followed by the distal electrode (26.6%, n = 4) and ICD generator (20.0%, n = 3); in 1 case, the precise localization was not investigated. Reprogramming the sensing vector and waiting the time necessary for oversensing resolution and air reabsorption were the most common strategies used to manage this complication (80.0%, n = 12). After 2 weeks, in 73.3% of patients, no further shocks occurred and chest radiography did not show residual air. Table 1 summarizes patients’ clinical characteristics, timing and management of IAS from 14 case reports/case series. On the basis of these data, the air entrapment should be considered an early complication (<24 hours) and an uncommon cause of IAS in S-ICD recipients, even if its epidemiology may be biased by misdiagnosing and underreporting. The relationship between air entrapment and S-ICD implantation technique is still controversial; however, a slightly increased incidence with the 3-incision technique was shown. The diagnosis should be made by performing a systematic approach including device interrogation, provocative maneuvers, and chest radiography. Reprogramming a different sensing vector or temporally switching off the S-ICD system, until air reabsorption, are part of the management of acute complications. Reassessing patients at 2 weeks with further device interrogation during provocative maneuvers may be useful. Value are presented as mean ± SD or n (%). DCM = dilatative cardiomyopathy; HCM = hypertrophic cardiomyopathy; IAS = inappropriate shock; ICD = implantable cardioverter-defibrillator; IHD = ischemic heart disease; PMs = physical maneuvers.

Real-Life Inter-Rater Variability of the PRAETORIAN Score Values.

(1) Background: The PRAETORIAN score is a tool developed for postoperative evaluation of the position of subcutaneous implantable cardioverter-defibrillator systems. The aim of our study was to evaluate the real-life inter-rater variability of the PRAETORIAN score, based on chest radiographs of S-ICD patients reviewed by independent clinical raters. (2) Methods: Postoperative chest X-rays of patients that underwent S-ICD implantation were evaluated by five clinical raters who gave values of the PRAETORIAN score. Ratings were then compared in a fully crossed manner to determine the inter-rater variability of the attributed scores. (3) Results: In total, 87 patients were included in the study. In the case of the most important final risk category of the PRAETORIAN score, the mean Light’s kappa was 0.804, the Fleiss’ kappa was 0.249, and the intraclass correlation was 0.38. The final risk category was identically determined by all five raters in 75.86% of patients, by four raters in 14.94%, and by three raters in 9.20% of patients. (4) Conclusions: The overall inter-rater variability of the PRAETORIAN score in a group of electrophysiologists experienced in S-ICD implantation, yet previously naive to the PRAETORIAN score, and self-trained in its utilization, was only modest in our study. Appropriate use of the score might require training of clinical raters.

How to better identify patients at high risk of inappropriate shocks before S-ICD implantation: Results from a multicenter experience

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Despite the recent improvements, inappropriate shocks (IAS) in patients implanted with subcutaneous implantable cardioverter-defibrillator (S-ICD) remain a challenge in "real-life" practice. The purpose of this study was to assess the preoperative predictive factors of IAS with the latest generation of S-ICD, with a particular focus on data obtained during the screening procedure. Methods Between January 2017 and March 2020, 300 patients implanted with Generation 3 S-ICD system for primary and secondary prevention were included in this multicentric study. Follow-up (FU) of at least 6 months and preoperative screening procedure data were mandatory for all patients. Results After a mean follow-up of 22.8 (±11.4) months, appropriate therapies occurred in 12.3% patients; while 26 patients (8.7%) experienced inappropriate therapies (incidence 4.9 per 100 patient-years). The total number of inappropriate shock episodes was 48; 9 patients experienced multiple episodes. Causes of IAS were: supraventricular arrhythmias (34.6%), cardiac (30.7%) and extra-cardiac noise oversensing (38.4%). In univariate analysis, availability of all 3 sensing vectors during preoperative screening significantly reduced inappropriate therapies occurrence (hazard ratio [HR], 0.32; 95% confidence interval [CI], 0.12-0.89, P=0.028). Clinical preoperative S-ICD inappropriate shocks predictors were: history of Supraventricular Tachycardia (SVT)(HR, 4.42; 95% CI, 1.45-13.47; P=0.009); overweight (BMI&amp;gt;25: HR, 1.93; 95% CI, 0.83-0.4.48; P=0.13); QRS duration (HR, 1.01; 95% CI, 0.1-1.03; P=0.14) and lower QRS/T wave ratio in lead I (for a threshold &amp;lt; 3: HR, 4.44; 95% CI, 1.88-10.48; P=0.001). By multivariate analysis, independent factors associated with IAS were: the availability of less than 3 sensing vectors during preoperative screening (p&amp;lt;0.05), a low QRS/T wave ratio in lead I (for a threshold &amp;lt;3; p&amp;lt;0.001), history of SVT (p&amp;lt;0.001) and overweight (BMI&amp;gt; 25; p&amp;lt;0.05). Conclusion Automatic preoperative screening data is of high interest as a predictor of IAS with a quantitative value. ECG specificities in association with other clinical factors should be taken into consideration to identify patients at high risk for IAS.