Longevity of the Subcutaneous Implantable Defibrillator: Long-Term Follow-Up of the European Regulatory Trial Cohort

Subcutaneous air entrapment after subcutaneous implantable cardioverter defibrillator implantation evaluated by computed tomography

BACKGROUND

Inappropriate shock (IAS) caused by subcutaneous air entrapment (AE) in an early period after subcutaneous implantable cardioverter defibrillator (S-ICD) implantation has been reported, however, no detailed data on air volume are available. We evaluated the subcutaneous air volume after implantation and its absorption rate one week after implantation.

METHODS

Patients who underwent S-ICD implantation in our hospital received chest CT scans immediately after implantation and followed up 1 week later. The total subcutaneous air volume, air around the generator, the distal electrode, and the proximal electrode within 3 cm were calculated using a three-dimensional workstation. Fat areas at the level of the lower edge of the generator were also analyzed.

RESULT

Fifteen patients received CT immediately after implantation. The mean age was 45.6 ± 17.9 (66.7% of men), and the mean body mass index was 24.3 ± 3.3. The three-incision technique was applied in seven patients and two-incision technique was in the latter eight patients. The mean total subcutaneous air volume was 18.54 ± 7.50 mL. Air volume around the generator, the distal electrode, and the proximal electrode were 11.05 ± 5.12, 0.72 ± 0.72, and 0.88 ± 0.87 mL, respectively. Twelve patients received a follow-up CT 1 week later. The mean total subcutaneous air was 0.25 ± 0.45 mL, showing a 98.7% absorption rate.

CONCLUSION

Although subcutaneous air was observed in all patients after S-ICD implantation, most of the air was absorbed within 1 week, suggesting a low occurrence of AE-related IAS after a week postoperation.

Initial Experience With Intercostal Insertion of an Extravascular ICD Lead Compatible With Existing Pulse Generators

BACKGROUND

This study assessed safety and feasibility of a novel extravascular 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. Currently available or investigational, extravascular-ICDs include a subcutaneous or subxiphoid lead connected to customized extravascular-ICD PGs.

METHODS

This novel extravascular-ICD (AtaCor Medical Inc, San Clemente, CA) employs a unique intercostal implant technique and is designed to function with commercial DF-4 ICD PGs. In this nonrandomized, single-center, acute study, 36 de novo or replacement ICD (transvenous ICD) patients enrolled to receive a concomitant extravascular-ICD lead inserted through an intercostal space along the left parasternal margin. extravascular-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 up or down in 5 to 10 joule increments depending on the success and limitations of the generator used.

RESULTS

Successful 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). Furthermore, 24 of 27 (89%) of patients tested with a left, mid-axillary intermuscular PG had successful VF conversion with defibrillation energies at least 10 J below the maximum delivered output of the device. All evaluable episodes (n=93) were automatically sensed, detected, and shocked. No serious device-related intraoperative adverse events were observed.

CONCLUSIONS

This first-in-human study documented the safe and reliable placement of a novel extravascular ICD lead with effective sensing and defibrillation of induced ventricular fibrillation using commercial DF-4 ICD PGs.

Substernal Extravascular Implantable Cardioverter-Defibrillator System Infections in Large Animals

The extravascular implantable cardioverter-defibrillator (EV ICD) with lead implantation in the substernal space may provide clinical advantages over transvenous and subcutaneous systems. This is the first reported examination of substernal infection in large animals implanted with the EV ICD system.The system was implanted in 13 large animals (canine, porcine, and ovine). The porcine were co-implanted with a transvenous cardiac resynchronization therapy with defibrillator (CRT-D) system. Infection was promoted through a cadence of immunosuppressive monitors and study interventions. The animals were monitored for clinical presentation of infection over 12-18 weeks, and cultures were collected to confirm infection. Treatment was bifurcated: 1) some infections were treated only with antibiotics ( "antibiotics only" ), whereas 2) some infections were treated with system removal and antibiotics ( "antibiotics + explant" ). Histopathology was conducted at the study closure.Five infections were confirmed over the course of the study, four of which involved infection of the EV ICD system and one infection of only the concomitantly implanted transvenous CRT-D system without EV ICD-related infection. Among the four EV ICD infections, two of two infections treated with antibiotics only did not resolve whereas two of two infections treated with antibiotics + explant resolved, as shown by histology. The transvenous CRT-D system infection progressed to septicemia and endocarditis, requiring early study discontinuation. No EV ICD-related infection progressed to blood stream infection, and the sternal bone did not become infected when infection was present in the substernal tissues.The study findings suggest that EV ICD-related infections are treatable with system removal and antibiotic therapy.

The development of the extravascular defibrillator with substernal lead placement: A new Frontier for device-based treatment of sudden cardiac arrest

INTRODUCTION

The extravascular implantable cardioverter-defibrillato (EV ICD) system with substernal lead placement is a novel nontransvenous alternative to current commercially available ICD systems. The EV ICD provides defibrillation and pacing therapies without the potential long-term complications of endovascular lead placement but requires a new procedure for implantation with a safety profile under evaluation.

METHODS

This paper summarizes the development of the EV ICD, including the preclinical and clinical evaluations that have contributed to the system and procedural refinements to date.

RESULTS

Extensive preclinical research evaluations and four human clinical studies with >140 combined acute and chronic implants have enabled the development and refinement of the EV ICD system, currently in worldwide pivotal study.

CONCLUSION

The EV ICD may represent a clinically valuable solution in protecting patients from sudden cardiac death while avoiding the long-term consequences of transvenous hardware. The EV ICD offers advantages over transvenous and subcutaneous systems by avoiding placement in the heart and vasculature; relative to subcutaneous systems, EV ICD requires less energy for defibrillation, enabling a smaller device, and provides pacing features such as antitachycardia and asystole pacing in a single system.

Three-Year Extraction Experience of a Novel Substernal Extravascular Defibrillation Lead in Sheep

Background

The extravascular implantable cardioverter‐defibrillator (EV ICD) with lead implantation in the substernal space may provide an alternative to transvenous and subcutaneous systems. This is the first‐reported chronic extraction experience for EV ICD leads. The aim of the study is to evaluate the chronic encapsulation and extractability of EV ICD leads.

Methods

Two EV ICD leads and one transvenous lead were implanted in each of 24 mature sheep. A subset of animals was evaluated yearly for histology and lead extractability. Extractions were performed using simple traction or extraction tools. Histology evaluated the encapsulating tissue.

Results

At 1 year, extraction was performed successfully for two of five EV ICD leads with traction alone using ≤3.1 kg‐force (kgf) and the remainder extracted successfully with extraction tools; no transvenous leads were removed with traction alone. At 2 years, no EV ICD or transvenous leads were extracted with traction alone, while at 3 years, one of eight EV ICD leads and two of four transvenous leads were extracted with traction (0.8 and ≤2.3 kgf, respectively). There was one observation of hemopericardium resulting in tamponade with EV ICD extraction but without injury to cardiovascular structures and related to the unique implant tract. Among transvenous leads, inversion of the ventricle with loss of cardiac output resulted in abandonment of traction for two animals.

Conclusions

Chronic extraction of EV ICD leads from the substernal space was successfully performed using traction and simple tools through 3 years in sheep with one observation of hemopericardium that did not originate from cardiovascular injury.

The Role of Subcutaneous ICDs in the Prevention of Sudden Cardiac Death

The ICD is an important therapy in the prevention of sudden cardiac death. The transvenous-ICD (TV-ICD) has been the primary device used for this purpose. However, mechanical and infectious complications occur with traditional TV-ICDs increasing morbidity and mortality. The subcutaneous-ICD (S-ICD) system was developed to circumvent some of these complications, but S-ICDs have their inherent set of limitations as well. These include inappropriate shock delivery, lack of bradycardia, antitachycardia or CRT pacing therapy and shorter device longevity. The S-ICD is now included in guidelines as an acceptable alternative to TV-ICDs among patients without pacing indications. This review discusses the rationale for S-ICDs by reviewing studies including the PRAETORIAN, PAS and UNTOUCHED trials.

The extravascular implantable cardioverter-defibrillator: characterization of anatomical parameters impacting substernal implantation and defibrillation efficacy

Aims

The aim of this study is to provide a thorough, quantified assessment of the substernal space as the site of extravascular implantable cardioverter-defibrillator (ICD) lead placement using computed tomography (CT) scans and summarizing adverse events and defibrillation efficacy across anatomical findings. Subcutaneous ICDs are an alternative to transvenous defibrillators but have limitations related to ICD lead distance from the heart. An alternative extravascular system with substernal lead placement has the potential to provide defibrillation at lower energy and pacing therapies from a single device.

Methods and results

A multi-centre, non-randomized, retrospective analysis of 45 patient CT scans quantitatively and qualitatively assessing bony, cardiac, vascular, and other organ structures from two human clinical studies with substernal lead placement. Univariate logistic regression was used to evaluate 15 anatomical parameters for impact on defibrillation outcome and adjusted for multiple comparisons. Adverse events were summarized. Substernal implantation was attempted or completed in 45 patients. Defibrillation testing was successful in 37 of 41 subjects (90%) using ≥10 J safety margin. There were two intra-procedural adverse events in one patient, including reaction to anaesthesia and an episode of transient atrial fibrillation during ventricular fibrillation induction. Anatomical factors associated with defibrillation failure included large rib cage width, myocardium extending very posteriorly, and a low heart position in the chest (P-values <0.05), though not significant adjusting for multiple comparisons.

Conclusion

Retrospective analysis demonstrates the ability to implant within the substernal space with low intra-procedural adverse events and high defibrillation efficacy despite a wide range of anatomical variability.

Comparative Effectiveness of Implantable Defibrillators for Asymptomatic Brugada Syndrome: A Decision-Analytic Model

Background Optimal management of asymptomatic Brugada syndrome (BrS) with spontaneous type I electrocardiographic pattern is uncertain. Methods and Results We developed an individual-level simulation comprising 2 000 000 average-risk individuals with asymptomatic BrS and spontaneous type I electrocardiographic pattern. We compared (1) observation, (2) electrophysiologic study (EPS)-guided implantable cardioverter-defibrillator (ICD), and (3) upfront ICD, each using either subcutaneous or transvenous ICD, resulting in 6 strategies tested. The primary outcome was quality-adjusted life years (QALYs), with cardiac deaths (arrest or procedural-related) as a secondary outcome. We varied BrS diagnosis age and underlying arrest rate. We assessed cost-effectiveness at $100 000/QALY. Compared with observation, EPS-guided subcutaneous ICD resulted in 0.35 QALY gain/individual and 4130 cardiac deaths avoided/100 000 individuals, and EPS-guided transvenous ICD resulted in 0.26 QALY gain and 3390 cardiac deaths avoided. Compared with observation, upfront ICD reduced cardiac deaths by a greater margin (subcutaneous ICD, 8950; transvenous ICD, 6050), but only subcutaneous ICD improved QALYs (subcutaneous ICD, 0.25 QALY gain; transvenous ICD, 0.01 QALY loss), and complications were higher. ICD-based strategies were more effective at younger ages and higher arrest rates (eg, using subcutaneous devices, upfront ICD was the most effective strategy at ages 20-39.4 years and arrest rates >1.37%/year; EPS-guided ICD was the most effective strategy at ages 39.5-51.3 years and arrest rates 0.47%-1.37%/year, and observation was the most effective strategy at ages >51.3 years and arrest rates <0.47%/year). EPS-guided subcutaneous ICD was cost-effective ($80 508/QALY). Conclusions Device-based approaches (with or without EPS risk stratification) can be more effective than observation among selected patients with asymptomatic BrS. BrS management should be tailored to patient characteristics.

Complications related to elective generator replacement of the subcutaneous implantable defibrillator

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%.

Subcutaneous implantable cardioverter defibrillator: Can it overtake its transvenous counterpart

Over the past decade, the emergence of the subcutaneous implantable cardioverter defibrillator (S-ICD) has provided cardiologists with an option to provide both primary or secondary prevention treatment of sudden cardiac death (SCD) without the associated risks that come with the use of intracardiac leads. S-ICD may prove to be a useful option in those who are young, have thromboembolic risk, immunodeficiency states, unfavorable anatomy due to adult congenital heart disease (ACHD). This article reviews the existing literature to determine whether S-ICD can prove to be a safe alternative in comparison to Transvenous implantable cardioverter defibrillator (TV-ICD) and in which patient population should S-ICD be considered over TV-ICD.

Subcutaneous Implantable Cardioverter Defibrillators: An Overview of Implantation Techniques and Clinical Outcomes

Sudden Cardiac Death (SCD) is a significant health problem worldwide. Multiple randomized controlled trials have shown that Implantable Cardioverter Defibrillators (ICDs) are effective life-saving management option for individuals at risk of SCD in both primary and secondary prevention. Although the conventional transvenous ICDs (TV-ICDs) are safe and effective, there are potential complications associated with its use, including localized pocket or wound infection or systematic infection, a vascular access related complication such as pneumothorax, and venous thrombosis, and lead related complications such as dislodgement, malfunction, and perforation. Furthermore, transvenous leads placement may not be feasible in certain patients like those with venous anomaly or occlusion, or with the presence of intracardiac shunts. Transvenous leads extraction, when needed, is associated with considerable morbidity & mortality and requires significant skills and costs. Totally subcutaneous ICD (S-ICD) is designed to afford the same life-saving benefit of the conventional TV-ICDs while avoiding the shortcomings of the TV-leads and to simplify the implant techniques and hence expand the use of ICDs in clinical practice. It becomes commercially available after receiving CE mark in 2009, and its use increased significantly after its FDA approval in 2012. This review aims to give an overview of the S-ICD system components, implantation procedure, clinical indications, safety, efficacy, and future directions.

Subcutaneous implantable cardioverter-defibrillator implantation for ventricular fibrillation caused by coronary artery spasm: a case report

BACKGROUND

Coronary artery spasm usually has a good prognosis, except when it induces lethal ventricular arrhythmias. Implantable cardioverter-defibrillator (ICD) implantation in addition to optimal medical therapy including prescription of coronary vasodilators and smoking cessation is a therapeutic option for coronary artery spasm patients who present with lethal ventricular arrhythmia. Subcutaneous ICDs are now available as an alternative to conventional transvenous ICDs.

CASE SUMMARY

We report the first case of a 50-year-old Japanese male without any structural heart disease who presented with ventricular fibrillation caused by coronary artery spasm, and underwent subcutaneous ICD implantation for secondary prevention of sudden cardiac death (SCD). We attributed his aborted SCD to coronary artery spasm based on findings of cardiac catheterization including acetylcholine provocation test and cardiac electrophysiological study. During the 1 year of follow-up, the patient discharged on calcium channel blockers and nicorandil has been free of angina, ventricular arrhythmias, and appropriate ICD therapy.

DISCUSSION

Coronary artery spasm patients with aborted SCD may be good candidates for implantation of subcutaneous ICDs, because most of them have no need for concomitant bradycardia therapy, cardiac resynchronization therapy, or anti-tachycardia pacing therapy.

The Subcutaneous Implantable Cardioverter-Defibrillator: New Insights and Expanding Populations

Implantable cardioverter defibrillators (ICDs) have become a mainstay of treatment in patients at risk for sudden cardiac death. The majority of contemporary ICDs are implanted transvenously; however, this approach carries acute procedural and long-term risks. The subcutaneous ICD (S-ICD) was developed, in part, to circumvent some of these adverse events or as an alternative option in patients unable to undergo transvenous implantation. Early promising trials evaluating the S-ICD were small and focused on niche populations. More recently, larger trials included broader populations with worse heart failure and co-morbidities that may be more representative of typical ICD recipients. These studies have consistently demonstrated positive results. This review describes the S-ICD system, implantation, and the safety and efficacy of the device.

Safety, Efficacy and Evidence Base for Use of the Subcutaneous Implantable Cardioverter Defibrillator

The trans-venous implantable cardioverter defibrillator (TV-ICD) is effective in treating life-threatening ventricular arrhythmia and reduces mortality in high-risk patients. However, there are significant short- and long-term complications that are associated with intravascular leads. These shortcomings are mostly relevant in young patients with long life expectancy and low risk of death from non-arrhythmic causes. Drawbacks of trans-venous leads recently led to the development of the entirely subcutaneous implantable cardioverter defibrillator (S-ICD). The S-ICD does not require vascular access or permanent intravascular defibrillation leads. Therefore, it is expected to overcome many complications associated with conventional ICDs. This review highlights data on safety and efficacy of the S-ICD and is envisioned to help in identifying the role of this device in clinical practice.

Longevity of Cardiovascular Implantable Electronic Devices

Battery depletion is the most common reason for device reoperation, which is associated with significant patient morbidity and mortality. This article describes the history of pacing and defibrillation power supplies and the factors that determine the longevity of pacing and defibrillator generators with a special emphasis on factors that can be adjusted or controlled by the implanting and following physician. Optimization of longevity is attained through device selection; shock minimization; avoidance of prolonged radiofrequency telemetry; selection of higher impedance vectors; avoidance of long pulse duration when possible; and avoidance of unnecessary feature activation, such as continuous electrogram storage.

Systematic Review of Defibrillation Threshold Testing at De Novo Implantation

Background—

Recent results from the largest multicenter randomized trial (Shockless IMPLant Evaluation [SIMPLE]) on defibrillation threshold (DFT) testing suggest that while shock testing seems safe, it does not reduce the risk of failed shocks or prolong survival. A contemporary systematic review of DFT versus no-DFT testing at the time of implantable cardioverter–defibrillator implantation was performed to evaluate the current evidence and to assess the impact of the SIMPLE study.

Methods and Results—

Electronic searches were performed using 6 databases from their inception to March 2014. Relevant studies investigating implant DFT were identified. Data were extracted and analyzed according to predefined clinical end points. Predefined outcomes for interrogation were all-cause mortality, composite end point of implantable cardioverter–defibrillator efficacy (arrhythmic deaths and ineffective shocks), and composite safety end point (the sum of complications recorded at 30 days). Meta-analysis was performed including 13 studies and 9740 patients. No significant differences between DFT versus no-DFT cohorts were found in terms of all-cause mortality (risk ratio, 0.90; 95% confidence interval, 0.71–1.15; P =0.41), composite efficacy outcome (risk ratio, 1.24; 95% confidence interval, 0.65–3.37; P =0.51), and 30-day postimplant complications (risk ratio, 1.18; 95% confidence interval, 0.87–1.60; P =0.29). No significant difference was found in the trends observed when the results of the SIMPLE study were excluded or included.

Conclusions—

This systematic review of contemporary data suggests a modest average effect of DFT, if any, in terms of mortality, shock efficacy, or safety. Therefore, DFT testing should no longer be compulsory during de novo implantation. However, DFT testing may still be clinically relevant in specific patient populations.