Rationale and design of the PRAETORIAN-DFT trial: A prospective randomized CompArative trial of SubcutanEous ImplanTable CardiOverter-DefibrillatoR ImplANtation with and without DeFibrillation testing

Validation of the PRAETORIAN score in a large subcutaneous implantable cardioverter-defibrillator collective: Usefulness in clinical routine

BACKGROUND

To assess the risk of unsuccessful conversion of ventricular fibrillation during defibrillation testing (DFT) with the subcutaneous implantable cardioverter-defibrillator (S-ICD), the PRAETORIAN score has been proposed.

OBJECTIVE

The purpose of this study was to validate the PRAETORIAN score in a large S-ICD collective.

METHODS

A retrospective single-center analysis of S-ICD patients receiving intraoperative DFT was performed. DFT was performed using a stepwise protocol with 65-J standard polarity, change of polarity, increase to 80 J, and repositioning if necessary. If all DFTs failed, we switched to a transvenous ICD.

RESULTS

Overall, 398 patients were analyzed (268 male [67.3%]; mean age 42.4 ± 15.9 years; mean body mass index [BMI] 25.9 ± 4.8 kg/m2). Successful DFT with the first ICD shock was observed in 264 patients (66.3%). One hundred fourteen patients were defibrillated with the second (n = 104) or third (n = 10) DFT after changing shock polarity and/or shock energy. Overall, 20 patients needed at least 3 DFT (ie, 80 J and/or re-positioning). The majority (n = 88 [65.7%]) of DFT failures occurred before 2015 with the first-generation S-ICD. PRAETORIAN score was an independent predictor of DFT failure (odds ratio [OR] 1.007; 95% confidence interval [CI] 1.003-1.011 P ≤.001), while whereas BMI alone was not (P = .31). Presence of hypertrophic cardiomyopathy (HCM) (OR 2.6; 95% CI 1.3-4.4; P = .004) was predictive for at least 1 unsuccessful DFT in our multivariate regression analysis.

CONCLUSION

PRAETORIAN score proved to be a useful and valid predictive tool for successful DFT, whereas BMI only had a limited role. Patients with HCM were at increased risk for DFT failure or needed higher DFT energy.

Review of the National Institute for Health and Care Excellence guidelines on the management of atrial and ventricular arrhythmias

The National Institute for Health and Care Excellence (NICE) guidelines present a synopsis of extensive internal evidence and technology reviews, with a particular focus on clinical efficacy and cost-effectiveness within the NHS in England. This approach has delivered a novel perspective on arrhythmia management, with important distinctions from other policymakers' recommendations. For example, when compared with the European Society of Cardiology (ESC) and the American Heart Association (AHA)/Heart Rhythm Society (HRS)/American College of Cardiology (ACC) guidelines on atrial fibrillation (AF), NICE advocates unique strategies regarding arrhythmia detection, stroke and bleeding risk stratification, and rhythm control (NICE CG 196). Likewise, for patients at risk of sudden cardiac death, NICE TA314 not only recommends device therapy based on New York Heart Association class and ECG findings, but also incorporates quality-adjusted life year data from analysis of key randomised controlled trials.This review examines the NICE guidelines, together with those from the AHA/HRS/ACC and ESC, on the management of AF and ventricular arrhythmias and highlights the key common features and discrepancies between these important documents.

Predictive value of the PRAETORIAN score for defibrillation test success in patients with subcutaneous ICD: A subanalysis of the PRAETORIAN-DFT trial

BACKGROUND

The PRAETORIAN score estimates the risk of failure of subcutaneous implantable cardioverter-defibrillator (S-ICD) therapy by using generator and lead positioning on bidirectional chest radiographs. The PRospective randomized compArative trial of subcutanEous implanTable cardiOverter-defibrillatoR ImplANtation with and without DeFibrillation Testing (PRAETORIAN-DFT) investigates whether PRAETORIAN score calculation is noninferior to defibrillation testing (DFT) with regard to first shock efficacy in spontaneous events.

OBJECTIVE

This prespecified subanalysis assessed the predictive value of the PRAETORIAN score for defibrillation success in induced ventricular arrhythmias.

METHODS

This multicenter investigator-initiated trial randomized 965 patients between DFT and PRAETORIAN score calculation after de novo S-ICD implantation. Successful DFT was defined as conversion of induced ventricular arrhythmia in <5 seconds from shock delivery within 2 attempts. Bidirectional chest radiographs were obtained after implantation. The predictive value of the PRAETORIAN score for DFT success was calculated for patients in the DFT arm.

RESULTS

In total, 482 patients were randomized to undergo DFT. Of these patients, 457 (95%) underwent DFT according to protocol, of whom 445 (97%) had successful DFT and 12 (3%) had failed DFT. A PRAETORIAN score of ≥90 had a positive predictive value of 25% for failed DFT, and a PRAETORIAN score of <90 had a negative predictive value of 99% for successful DFT. A PRAETORIAN score of ≥90 was the strongest independent predictor for failed DFT (odds ratio 33.77; confidence interval 6.13-279.95; P < .001).

CONCLUSION

A PRAETORIAN score of <90 serves as a reliable indicator for DFT success in patients with S-ICD, and a PRAETORIAN score of ≥90 is a strong predictor for DFT failure.

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

BACKGROUND

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.

OBJECTIVE

The purpose of this study was to acutely assess the defibrillation efficacy of parallel and transverse configurations in patients receiving an S-ICD.

METHODS

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.

RESULTS

This study enrolled 35 patients (28 males (80%); mean age 51 ± 17 years; left ventricular ejection fraction 40% ± 15%; body mass index 26 ± 4 kg/m2; prior myocardial infarction 46%; congestive heart failure 49%; cardiomyopathy 63%). 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.

CONCLUSION

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.

Real-world evidence for the use of subcutaneous implantable cardioverter-defibrillators in China: A single-center experience

BACKGROUND

Subcutaneous implantable cardioverter-defibrillators (S-ICDs) have been shown to be non-inferior to transvenous ICDs in the prevention of sudden cardiac death (SCD), but there is still a lack of evidence from clinical trials in China. We investigated whether S‑ICD implantation in the Chinese population is safe and feasible and should be promoted in the future.

METHODS

Consecutive patients undergoing S‑ICD implantation at our center were enrolled in this retrospective study. Data were collected within the median follow-up period of 554 days. Data concerning patient selection, implantation procedures, complications, and episodes of shock were analyzed.

RESULTS

In total, 70.2% of all 47 patients (median age = 39 years) were included for secondary prevention of SCD with different etiologies. Vector screening showed that 98% of patients were with > 1 appropriate vector in all postures. An intraoperative defibrillation test was not performed on six patients because of the high risk of disease deterioration, while all episodes of ventricular fibrillation induced post implantation were terminated by one shock. As expected, no severe complications (e.g., infection and device-related complications) were observed, except for one case of delayed healing of the incision. Overall, 15 patients (31.9%) experienced appropriate shocks (AS) with all episodes terminated by one shock. Two patients (4.3%) experienced inappropriate shocks (IAS) due to noise oversensing, resulting in a high Kaplan-Meier IAS-free rate of 95.7%.

CONCLUSION

Based on appropriate patient selection and standardized implantation procedures, this real-world study confirmed the safety and efficacy of S‑ICD in Chinese patients, indicating that it may help to promote the prevention of SCD in China.

Postapproval Study of a Subcutaneous Implantable Cardioverter-Defibrillator System

BACKGROUND

The 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.

OBJECTIVES

The 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.

METHODS

Patients 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.

RESULTS

A 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%.

CONCLUSIONS

In 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).

Subcutaneous Implantable Cardioverter Defibrillator: A Contemporary Overview

The difference between subcutaneous implantable cardioverter defibrillators (S-ICDs) and transvenous ICDs (TV-ICDs) concerns a whole extra thoracic implantation, including a defibrillator coil and pulse generator, without endovascular components. The improved safety profile has allowed the S-ICD to be rapidly taken up, especially among younger patients. Reports of its role in different cardiac diseases at high risk of SCD such as hypertrophic and arrhythmic cardiomyopathies, as well as channelopathies, is increasing. S-ICDs show comparable efficacy, reliability, and safety outcomes compared to TV-ICD. However, some technical issues (i.e., the inability to perform anti-bradycardia pacing) strongly limit the employment of S-ICDs. Therefore, it still remains only an alternative to the traditional ICD thus far. This review aims to provide a contemporary overview of the role of S-ICDs compared to TV-ICDs in clinical practice, including technical aspects regarding device manufacture and implantation techniques. Newer outlooks and future perspectives of S-ICDs are also brought up to date.

Successful defibrillation testing in patients undergoing elective subcutaneous implantable cardioverter-defibrillator generator replacement

AIMS

After implantation of a subcutaneous implantable cardioverter-defibrillator (S-ICD), a defibrillation test (DFT) is performed to ensure that the device can effectively detect and terminate the induced ventricular arrhythmia. Data on DFT efficacy at generator replacement are scarce with a limited number of patients and conflicting results. This study evaluates conversion efficacy during DFT at elective S-ICD generator replacement in a large cohort from our tertiary centre.

METHODS AND RESULTS

Retrospective data of patients who underwent an S-ICD generator replacement for battery depletion with subsequent DFT between February 2015 and June 2022 were collected. Defibrillation test data were collected from both implant and replacement procedures. PRAETORIAN scores at implant were calculated. Defibrillation test was defined unsuccessful when two conversions at 65 J failed. A total of 121 patients were included. The defibrillation test was successful in 95% after the first and 98% after two consecutive tests. This was comparable with success rates at implant, despite a significant rise in shock impedance (73 ± 23 vs. 83 ± 24 Ω, P < 0.001). Both patients with an unsuccessful DFT at 65 J successfully converted with 80 J.

CONCLUSION

This study shows a high DFT conversion rate at elective S-ICD generator replacement, which is comparable to conversion rates at implant, despite a rise in shock impedance. Evaluating device position before generator replacement may be recommended to optimize defibrillation success at generator replacement.

Indications and management of implantable cardioverter-defibrillator therapy in childhood hypertrophic cardiomyopathy

Sudden cardiac death is the most common mode of death during childhood and adolescence in hypertrophic cardiomyopathy, and identifying those individuals at highest risk is a major aspect of clinical care. The mainstay of preventative therapy is the implantable cardioverter-defibrillator, which has been shown to be effective at terminating malignant ventricular arrhythmias in children with hypertrophic cardiomyopathy but can be associated with substantial morbidity. Accurate identification of those children at highest risk who would benefit most from implantable cardioverter-defibrillator implantation while minimising the risk of complications is, therefore, essential. This position statement, on behalf of the Association for European Paediatric and Congenital Cardiology (AEPC), reviews the currently available data on established and proposed risk factors for sudden cardiac death in childhood-onset hypertrophic cardiomyopathy and current approaches for risk stratification in this population. It also provides guidance on identification of individuals at risk of sudden cardiac death and optimal management of implantable cardioverter-defibrillators in children and adolescents with hypertrophic cardiomyopathy.

Opportunities and drawbacks of the subcutaneous defibrillator across different clinical settings

INTRODUCTION

The subcutaneous implantable cardioverter-defibrillator (S-ICD) is an established therapy for the prevention of sudden cardiac death (SCD) and an alternative to a transvenous implantable cardioverter-defibrillator system in selected patients. Beyond randomized clinical trials, many observational studies have described the clinical performance of S-ICD across different subgroups of patients.

AREAS COVERED

Our review aimed to describe the opportunities and drawbacks of the S-ICD, focusing on their use in special populations and across different clinical settings.

EXPERT OPINION

The choice to implant S-ICD should be based on the patient's tailored approach, which takes into account the adequate S-ICD screening at rest or during stress, the infective risk, the ventricular arrhythmia susceptibility, the progressive nature of the underlying disease, the work or sports activity, and the risk of lead-related complications.

Intermuscular two-incision technique for implantation of the subcutaneous implantable cardioverter defibrillator: a 3-year follow-up

PURPOSE

The aim of the present study was to evaluate the outcome of patients underwent subcutaneous implantable cardioverter defibrillator (S-ICD) implantation with the intermuscular (IM) two-incision technique during 3-year follow-up.

METHODS

the study population consisted of 105 consecutive patients (79 male; median 50 [13-77] years) underwent S-ICD implantation with the IM two-incision technique. The composite primary end point of the study consisted of device-related complications and inappropriate shocks (IAS). Secondary end points included the individual components of the primary end point, death from any cause, appropriate therapy, major adverse cardiac events, hospitalization for heart failure, and heart transplantation.

RESULTS

According to the PRAETORIAN score, the risk of conversion failure was classified as low in 99 patients (94.3%), intermediate in 6 (5.7%).Ventricular fibrillation was successfully converted at ≤65 J in 97.4% of patients. During a median follow-up of 39 (16-53) months, 10 patients (9.5%) experienced device-related complications, and 9 (8.5%) patients reported IAS. Lead-associated complications were the most common (5 patients, 4.7%), including 2 cases of lead failure (1.9%). Pocket complications were reported in 2 patients (1.9%). Extra-cardiac oversensing (3.8%) represented the leading cause of IAS. No T-wave oversensing episodes were recorded. Twelve patients (11.4%) experienced appropriate shocks. Eight patients (7.6%) died during follow-up. IAS or device-related complications did not impact on mortality.

CONCLUSIONS

The overall device-related complications and IAS rates over 3 years of follow-up were 9.5% and 8.5%, respectively. According to our findings, the IM two-incision technique allows for optimal positioning of the device achieving a low PRAETORIAN score with a high conversion rate. IM two-incision technique allows low incidence of pocket complications, shifting the type of complications towards lead-related complications, which represent the most common complications. The IM two-incision technique would not seem to impact the occurrence of IAS. Management of complications are safe without impact on the outcome.

Perioperative Safety and Early Patient and Device Outcomes Among Subcutaneous Versus Transvenous Implantable Cardioverter Defibrillator Implantations : A Randomized, Multicenter Trial

BACKGROUND

Implantable cardioverter defibrillators (ICDs) improve survival in patients at risk for cardiac arrest, but are associated with intravascular lead-related complications. The subcutaneous ICD (S-ICD), with no intravascular components, was developed to minimize lead-related complications.

OBJECTIVE

To assess key ICD performance measures related to delivery of ICD therapy, including inappropriate ICD shocks (delivered in absence of life-threatening arrhythmia) and failed ICD shocks (which did not terminate ventricular arrhythmia).

DESIGN

Randomized, multicenter trial. (ClinicalTrials.gov: NCT02881255).

SETTING

The ATLAS trial.

PATIENTS

544 eligible patients (141 female) with a primary or secondary prevention indication for an ICD who were younger than age 60 years, had a cardiogenetic phenotype, or had prespecified risk factors for lead complications were electrocardiographically screened and 503 randomly assigned to S-ICD (251 patients) or transvenous ICD (TV-ICD) (252 patients). Mean follow-up was 2.5 years (SD, 1.1). Mean age was 49.0 years (SD, 11.5).

MEASUREMENTS

The primary outcome was perioperative major lead-related complications.

RESULTS

There was a statistically significant reduction in perioperative, lead-related complications, which occurred in 1 patient (0.4%) with an S-ICD and in 12 patients (4.8%) with TV-ICD (-4.4%; 95% CI, -6.9 to -1.9; P = 0.001). There was a trend for more inappropriate shocks with the S-ICD (hazard ratio [HR], 2.37; 95% CI, 0.98 to 5.77), but no increase in failed appropriate ICD shocks (HR, 0.61 (0.15 to 2.57). Patients in the S-ICD group had more ICD site pain, measured on a 10-point numeric rating scale, on the day of implant (4.2 ± 2.8 vs. 2.9 ± 2.2; P < 0.001) and 1 month later (1.3 ± 1.8 vs. 0.9 ± 1.5; P = 0.035).

LIMITATION

At present, the ATLAS trial is underpowered to detect differences in clinical shock outcomes; however, extended follow-up is ongoing.

CONCLUSION

The S-ICD reduces perioperative, lead-related complications without significantly compromising the effectiveness of ICD shocks, but with more early postoperative pain and a trend for more inappropriate shocks.

PRIMARY FUNDING SOURCE

Boston Scientific.

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.

A real‐world experience of subcutaneous and transvenous implantable cardiac defibrillators—comparison with the PRAETORIAN study

Background

Methods

Results

Conclusion

The “Defibrillation Testing, Why Not?” survey. Testing of subcutaneous and transvenous defibrillators in the Italian clinical practice

Background

Defibrillation testing (DT) can be omitted in patients undergoing transvenous implantable cardioverter–defibrillator (T-ICD) implantation, but it is still recommended for patients at risk for a high defibrillation threshold and for ICD generator changes. Moreover, DT is still recommended on implantation of subcutaneous ICD (S-ICD). The aim of the present survey was to analyze the current practice of DT during T-ICD and S-ICD implantations.

Methods

In March 2021, an ad hoc questionnaire on the current performance of DT and the standard practice adopted during testing was completed at 72 Italian centers implanting S-ICD and T-ICD.

Results

48 (67%) operators reported never performing DT during de-novo T-ICD implantations, while no operators perform it systematically. The remaining respondents perform it for patients at risk for a high defibrillation threshold. DT is never performed at T-ICD generator change. At the time of de-novo S-ICD implantation, DT is never performed by 9 (13%) operators and performed systematically by 48 (66%). The remaining operators frequently omit DT in patients with more severe systolic dysfunction. DT is not performed at S-ICD generator change by 92% of operators. DT is conducted by delivering a first shock energy of 65 J by 60% of operators, while the remaining 40% test lower energy values.

Conclusions

In current clinical practice, most operators omit DT at T-ICD implantation, even when still recommended in the guidelines. DT is also frequently omitted at S-ICD implantation, and a wide variability exists among operators in the procedures followed during DT.

Non-transvenous ICD therapy: current status and beyond

Subcutaneous implantable cardioverter/defibrillators (S-ICDs) have been developed to offer ICD treatment to patients without venous access to the heart and to overcome complications associated with transvenous leads, particularly lead fracture/insulation defects and endocarditis. Several studies and registries have demonstrated the feasibility and safety of S‑ICD in different groups of patients. Further developments in S‑ICD technology involve the combination with devices that can provide anti-bradycardia and anti-tachycardia pacing if needed. The extravascular ICD (EV-ICD) is a new system that similarly offers ICD therapy without a transvenous lead but uses a substernal instead of a subcutaneous lead to facilitate detection of ventricular fibrillation and to provide anti-tachycardia and also temporary anti-bradycardia pacing. The first animal but also clinical data on EV-ICDs have been published. This review discusses the current state, potential advantages and limitations, and future research of both S‑ICD and EV-ICD.

A 10 J shock impedance in sinus rhythm correlates with a 65 J defibrillation impedance during subcutaneous defibrillator implantation using an intermuscular technique

INTRODUCTION

Defibrillation testing (DT) is recommended during the subcutaneous defibrillator (S-ICD) placement. We sought to compare 10 J shock impedance in sinus rhythm (SR) with 65 J defibrillation impedance and evaluate device position on a postimplant chest X-ray (CXR) using an intermuscular (IM) technique.

METHODS

Consecutive S-ICD implantations between 12/2019 and 12/2020 at The Ohio State University were reviewed. All implantations were performed using a two-incision IM technique. Standard DT with 65 J shock and 10 J shock in SR were performed unless contraindicated. The PRAETORIAN score was calculated based on CXR.

RESULTS

A total of 37 patients (age: 47.2 ± 15.8 years old, male: n = 26 [70.3%], body mass index: 30.1 ± 6.7 kg/m² ) underwent IM S-ICD implantation, and of those, 27 (73%) underwent both 65 J shock and 10 J shock in SR. The coefficient of determination (R² ) between 10 J shock impedance and 65 J shock impedance was 0.84. The mean of an impedance difference was 1.6 ± 4.8 Ω (minimum - 11 and maximum 8). Postimplant CXR was available for 33 out of 37 patients (89.2%). The PRAETORIAN score was less than 90 in all patients and the mean score was 32.7 ± 8.8.

CONCLUSION

We demonstrated that 10 J shock impedance in SR correlated well with 65 J defibrillation impedance during IM S-ICD implantation. An IM implantation technique provides excellent generator location on postimplant CXR. The IM technique combined with 10 J shock in SR may be sufficient to predict and ensure the defibrillation efficacy of the S-ICD.

Non-traditional implantable cardioverter-defibrillator configurations and insertion techniques: a review of contemporary options

Implantable cardioverter-defibrillators (ICDs) have revolutionized the treatment of acquired or inherited cardiac diseases associated with a high risk of sudden cardiac death due to ventricular tachyarrhythmias. Contemporary ICD devices offer reliable arrhythmia detection and discrimination algorithms and deliver highly efficient tachytherapies. Percutaneously inserted transvenous defibrillator coils with pectoral generator placement are the first-line approach in the majority of adults due to their extensively documented clinical benefit and efficiency with comparably low periprocedural implantation risks as well as the option of providing pain-free tachycardia treatment via anti-tachycardia pacing (ATP), concomitant bradycardiaprotection, and incorporation in a cardiac resynchronization therapy if indicated. Yet, expanding ICD indications particularly among younger and more complex patient groups as well as the increasingly evident long-term consequences and complications associated with intravascular lead placements promoted the development of alternative ICD configurations. Most established in daily clinical practice is the subcutaneous ICD but other innovative extravascular approaches like epicardial, pericardial, extra-pleural, and most recently substernal defibrillator coil placements have been introduced as well to overcome shortcomings associated with traditional devices and allow for individualized treatment strategies tailored to the patients characteristics and needs. The review aims to provide practical solutions for common complications encountered with transvenous ICD systems including restricted venous access, high defibrillation/fibrillation thresholds (DFTs), and recurrent device infections. We summarize the contemporary options for non-traditional extravascular ICD configurations outlining indications, advantages, and disadvantages.

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.

Pregnancy in patients with implantable cardiac defibrillators

The number of patients of reproductive age with inherited and congenital heart disease receiving implantable cardiac defibrillators (ICD) is steadily increasing. Safely and effectively coordinating pregnancy in this high-risk cohort is important to optimise maternal-foetal outcomes. As members of the multidisciplinary team caring for pregnant patients with indications for ICD, cardiologists and electrophysiologists should be aware of the considerations and nuances involved in managing these patients. This article reviews the pathophysiology of arrhythmias, ICD implantation considerations, novel minimal fluoroscopy techniques and subcutaneous ICD. In addition, antenatal and device management during pregnancy and delivery are discussed.

Innovations in Cardiac Implantable Electronic Devices

Cardiac implantable electronic devices (CIEDs) are essential for the management of a variety of cardiac conditions, including tachyarrhythmias, bradyarrhythmias, and medically refractory heart failure (HF). Recent advancements in CIED technology have led to innovative solutions that overcome shortcomings associated with traditional devices or address unmet needs. Leadless pacemakers, subcutaneous implantable cardioverter defibrillators (ICDs), and extravascular ICDs eliminate lead-related complications common with conventional pacemakers or ICDs. Conduction system pacing (His bundle pacing and left bundle branch pacing) is a more physiologic method of pacing and avoids the deleterious consequences associated with long-term right ventricular pacing. For HF-related devices, cardiac contractility modulation is an emerging therapy that bridges a gap for many patients ineligible for cardiac resynchronization therapy and has been shown to improve HF symptoms and decrease hospitalizations and mortality in select patients. Implantable pulmonary artery pressure monitors help guide HF management and reduce hospitalizations. Lastly, new phrenic nerve stimulating devices are being utilized to treat central sleep apnea, a common comorbidity associated with HF. While further long-term studies are still underway for many of these new technologies, it is anticipated that these devices will become indispensable therapeutics in the expanding cardiovascular armamentarium.

Implantation technique and optimal subcutaneous defibrillator chest position: a PRAETORIAN score-based study

Aims

The traditional technique for subcutaneous implantable cardioverter-defibrillator (S-ICD) implantation involves three incisions and a subcutaneous pocket. Recently, a two-incision and intermuscular (IM) technique has been adopted. The PRAETORIAN score is a chest radiograph-based tool that predicts S-ICD conversion testing. We assessed whether the S-ICD implantation technique affects optimal position of the defibrillation system according to the PRAETORIAN score.

Methods and results

We analysed consecutive patients undergoing S-ICD implantation. The χ2 test and regression analysis were used to determine the association between the PRAETORIAN score and implantation technique. Two hundred and thirteen patients were enrolled. The S-ICD generator was positioned in an IM pocket in 174 patients (81.7%) and the two-incision approach was adopted in 199 (93.4%). According to the PRAETORIAN score, the risk of conversion failure was classified as low in 198 patients (93.0%), intermediate in 13 (6.1%), and high in 2 (0.9%). Patients undergoing the two-incision and IM technique were more likely to have a low (&lt;90) PRAETORIAN score than those undergoing the three-incision and subcutaneous technique (two-incision: 94.0% vs. three-incision: 78.6%; P = 0.004 and IM: 96.0% vs. subcutaneous: 79.5%; P = 0.001). Intermuscular plus two-incision technique was associated with a low-risk PRAETORIAN score (hazard ratio 3.76; 95% confidence interval 1.01–14.02; P = 0.04). Shock impedance was lower in PRAETORIAN low-risk patients than in intermediate-/high-risk categories (66 vs. 96 Ohm; P = 0.001). The PRAETORIAN score did not predict shock failure at 65 J.

Conclusion

In this cohort of S-ICD recipients, combining the two-incision technique and IM generator implantation yielded the lowest PRAETORIAN score values, indicating optimal defibrillation system position.

Clinical trial registration

http://clinicaltrials.gov/ Identifier: NCT02275637.

The subcutaneous ICD for prevention of sudden cardiac death: Current evidence and future directions

Despite major advances in medical therapy, sudden cardiac death remains an important cause of cardiovascular mortality. In order to improve the risk-benefit balance of transvenous implantable cardioverter-defibrillator (ICD) systems, a totally subcutaneous ICD (S-ICD) system was developed and approved for use in Europe in 2009. The currently available S-ICD system has undergone several important hardware- and software-related modifications and improvements over the last 10 years aimed at further improving its efficacy and safety. The results of the PRAETORIAN trial, that is, the first randomized comparison of S-ICD versus transvenous ICDs, of the prospective UNTOUCHED study, and the overall consistent observational data underline that current generation S-ICD systems may be a valid alternative in patients with an ICD indication in whom bradycardia pacing or cardiac resynchronization therapy is not required due to a lower risk of system-related problems. This review summarizes the key differences between the two systems, improvements in hardware components and algorithms over time, as well as most recent clinical evidence regarding the efficacy and safety of the S-ICD.

Defibrillation testing during implantation of the subcutaneous implantable cardioverter-defibrillator: a necessary standard or becoming redundant?

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.

Recent Developments in Cardiology Procedures for Adult Congenital Heart Disease: The Anesthesiologist's Perspective

Many children born today with congenital heart disease can expect to live long into adulthood. Improvements in surgical technique and anesthetic and perioperative care have significantly increased the number of survivors. Unfortunately, as these patients progress through life they frequently require further interventions. Although surgical intervention may be required frequently, these patients can be managed in the cardiac catheterization or electrophysiology laboratory. Surgical correction of tetralogy of Fallot can leave patients with pulmonary valve dysfunction later in life. A percutaneous approach is now available for these patients, which can obviate the need for resternotomy. During deployment of the valve, anesthesiologists should be aware that compression of coronary arteries can occur. Adult congenital heart disease (ACHD) patients often require pacemaker/implantable cardioverter- defibrillator (ICD) insertion or ablation therapy. These patients may have altered cardiac anatomy, which can make endovascular procedures extremely challenging. Recent developments have made these procedures safer and more efficient. A number of congenital cardiac conditions can also be associated with orofacial abnormalities. ACHD patients, as a result, can present with challenging airways. The catheterization laboratory may not be the optimum environment for the anesthesiologist to manage a difficult airway. The requirement of transesophageal echocardiography for some cath eterization procedures needs to be considered when deciding on an airway management plan. Knowledge of the underlying cardiac anatomy and the planned procedure is advised when providing anesthesia for this complex patient group outside the theater setting.

Approaches to Minimizing Periprocedural Complications During Subcutaneous Implantable Cardioverter-defibrillator Placement

The subcutaneous implantable cardioverter-defibrillator (S-ICD) is the latest option among devices clinically available for the prevention of sudden cardiac death, with experience from previous trials and postmarketing studies supporting the feasibility and safety of this kind of system. The extracardiac positioning of the S-ICD obviates the need for transvenous leads, which translates into lower incidence rates of lead-related complications and systemic infections. This review will highlight the results of pertinent studies related to the perioperative management of S-ICDs and review potential approaches to minimizing the risk of complications such as hematoma at the pulse generator location, unsuccessful defibrillation due to suboptimal S-ICD lead and generator positioning, and postoperative pain. An extensive literature search using PubMed was conducted to identify relevant articles.