Subcutaneous implantable cardioverter-defibrillator and defibrillation testing: A propensity-matched pilot study

Differences in underlying cardiac substrate among S-ICD recipients and its impact on long-term device-related outcomes: Real-world insights from the iSUSI registry

BACKGROUND

Outcome comparisons among subcutaneous implantable cardioverter-defibrillator (S-ICD) recipients with nonischemic cardiomyopathies are scarce.

OBJECTIVE

The aim of this study was to evaluate differences in device-related outcomes among S-ICD recipients with different structural substrates.

METHODS

Patients enrolled in the i-SUSI (International SUbcutaneouS Implantable cardioverter defibrillator registry) project were grouped according to the underlying substrate (ischemic vs nonischemic) and subgrouped into dilated cardiomyopathy, hypertrophic cardiomyopathy, Brugada syndrome (BrS), arrhythmogenic right ventricular cardiomyopathy (ARVC). The main outcome of our study was to compare the rates of appropriate and inappropriate shocks and device-related complications.

RESULTS

Among 1698 patients, the most common underlying substrate was ischemic (31.7%), followed by dilated cardiomyopathy (20.5%), BrS (10.8%), hypertrophic cardiomyopathy (8.5%), and ARVC (4.4%). S-ICD for primary prevention was more common in the nonischemic cohort (70.9% vs 65.4%; P = .037). Over a median (interquartile range) follow-up of 26.5 (12.6-42.8) months, no differences were observed in appropriate shocks between ischemic and nonischemic patients (4.8%/y vs 3.9%/y; log-rank, P = .282). ARVC (9.0%/y; hazard ratio [HR] 2.492; P = .001) and BrS (1.8%/y; HR 0.396; P = .008) constituted the groups with the highest and lowest rates of appropriate shocks, respectively. Device-related complications did not differ between groups (ischemic: 6.4%/y vs nonischemic: 6.1%/y; log-rank, P = .666), nor among underlying substrates (log-rank, P = .089). Nonischemic patients experienced higher rates of inappropriate shocks than did ischemic S-ICD recipients (4.4%/y vs 3.0%/y; log-rank, P = .043), with patients with ARVC (9.9%/y; P = .001) having the highest risk, even after controlling for confounders (adjusted HR 2.243; confidence interval 1.338-4.267; P = .002).

CONCLUSION

Most S-ICD recipients were primary prevention nonischemic cardiomyopathy patients. Among those, patients with ARVC tend to receive the most frequent appropriate and inappropriate shocks and patients with BrS the least frequent appropriate shocks.

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

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.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 a preexisting 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 (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.

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.

Defibrillation threshold in elective subcutaneous implantable defibrillator generator replacements: Time to reduce the size of the pulse generator?

INTRODUCTION

The first step-down defibrillation studies in the subcutaneous implantable cardioverter-defibrillator (S-ICD) described a defibrillation threshold (DFT) of 32.5 ± 17.0 J and 36.6 ± 19.8 J. Therefore, the default shock output of the S-ICD was set at 80 J. In de novo implants, the DFT is lower in optimally positioned S-ICDs. However, a retrospective analysis raised concerns about a high DFT in S-ICD replacements, possibly related to fibrosis.

OBJECTIVE

We aimed to find the DFT in patients undergoing S-ICD generator replacement.

METHODS

This prospective study enrolled patients who underwent S-ICD generator replacement with subsequent defibrillation testing. A pre-specified defibrillation testing protocol was used to determine the DFT, defined as the lowest shock output that effectively terminated the induced ventricular arrhythmia.

RESULTS

A total of 45 patients were enrolled, 6.0 ± 2.1 years after initial implant. Mean DFT during replacement in the total cohort was 27.4 ± 14.3 J. In patients with a body mass index (BMI) 18.5-25 kg/m2 (N = 22, BMI 22.5 ± 1.6), median DFT was 20 J (IQR 17.5-30). In 18/22 patients, the DFT was ≤30 J and 5/22 patients were successfully defibrillated at 10 J. One patient with hypertrophic cardiomyopathy had a DFT of 65 J. In patients with a BMI >25 kg/m2 (N = 23, BMI 29.5 ± 4.2), median DFT was 30 J (IQR 20-40). In 15/23 patients, the DFT was ≤30 J and 4/23 patients had a successful defibrillation test at 10 J.

CONCLUSIONS

This study eases concerns about a high DFT after S-ICD generator replacement. The majority of patients had a DFT ≤30 J, regardless of BMI, suggesting that the shock output of the S-ICD could be safely reduced.

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.

The need for a subsequent transvenous system in patients implanted with subcutaneous implantable cardioverter-defibrillator

BACKGROUND

The absence of pacing capabilities may reduce the appeal of subcutaneous implantable cardioverter-defibrillator (S-ICD) devices for patients at risk for conduction disorders or with antitachycardia pacing (ATP)/cardiac resynchronization (CRT) requirements. Reports of rates of S-ICD to transvenous implantable cardioverter-defibrillator (TV-ICD) system switch in real-world scenarios are limited.

OBJECTIVE

The purpose of this study was to investigate the need for a subsequent transvenous (TV) device in patients implanted with an S-ICD and its predictors.

METHODS

All patients implanted with an S-ICD were enrolled from the multicenter, real-world iSUSI (International SUbcutaneouS Implantable cardioverter defibrillator) Registry. The need for a TV device and its clinical reason, and appropriate and inappropriate device therapies were assessed. Logistic regression with Firth penalization was used to assess the association between baseline and procedural characteristics and the overall need for a subsequent TV device.

RESULTS

A total of 1509 patients were enrolled (age 50.8 ± 15.8 years; 76.9% male; 32.0% ischemic; left ventricular ejection fraction 38% [30%-60%]). Over 26.5 [13.4-42.9] months, 155 (10.3%) and 144 (9.3%) patients experienced appropriate and inappropriate device therapies, respectively. Forty-one patients (2.7%) required a TV device (13 bradycardia; 10 need for CRT; 10 inappropriate shocks). Body mass index (BMI) >30 kg/m2 and chronic kidney disease (CKD) were associated with need for a TV device (odds ratio [OR] 2.57 [1.37-4.81], P = .003; and OR 2.67 [1.29-5.54], P = .008, respectively).

CONCLUSION

A low rate (2.7%) of conversion from S-ICD to a TV device was observed at follow-up, with need for antibradycardia pacing, ATP, or CRT being the main reasons. BMI >30 kg/m2 and CKD predicted all-cause need for a TV device.

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.

Combined Use of S-ICD and Absorbable Antibacterial Envelopes: A Proof-of-concept Study

BACKGROUND

Absorbable antibacterial envelopes (AAEs) are currently recommended in patients undergoing a transvenous ICD implantation in cases at high risk of infection, who are now preferably implanted with a subcutaneous ICD (S-ICD). Nevertheless, experiences using a combined approach with S-ICD and AAE have not been reported. The aim of our study was to evaluate this strategy in patients at very high risk of infection.

METHODS

Twenty-five patients were implanted with the S-ICD+AAE using our combined approach, restricted to patients who would fit our decisional flow algorithm identifying very high-risk patients. Patients were followed up 1 month after discharge and every 6 months thereafter. Complications were defined as device-related events requiring medical or surgical intervention for resolution and/or device reprogramming.

RESULTS

Twenty-five patients (92% males, mean age 58.5±14.1 years) were implanted with the S-ICD device and the AAE using our combined approach. The most common high-infective risk factors were diabetes requiring insulin treatment (80%) and CKD requiring hemodialysis (48%), with 7 (28%) patients presenting with more than 2 risk factors. A single mild early post-operative hematoma was observed that was managed conservatively with a spontaneous resolution. Despite a very high-risk cohort, only a single late pocket infection was detected and solved conservatively with antibiotic therapy.

CONCLUSIONS

The preliminary data of this proof-of-concept study show how a combined deployment of AAE and S-ICD in selected patients at very high risk of infection is a safe and feasible technique and may offer a reliable treatment option in specific and selected clinical settings.

Subcutaneous ICD for more and transvenous ICD for few?!

Implantable cardioverter defibrillators (ICDs) have been shown to reduce the risk of sudden cardiac death in primary or secondary prevention with thousands of ICDs implanted every year worldwide. Whilst ICD are more commonly implanted transvenously (TV), this approach carries high risk of peri- and post-procedural complications. Subcutaneous ICD (S-ICD) have been introduced to overcome the intravascular complications of TV system by placing all metalware outside the chest cavity for those with an indication for a defibrillator and no pacing requirements. In conclusion, a review of the current guidelines recommendations regarding S-ICD may be needed considering the emerging evidence which shows high efficacy and safety with contemporary devices and programming algorithms. A stronger recommendation may be developed for selective patients who have an indication for single-chamber ICD in the absence of negative screening, recurrent monomorphic ventricular tachycardia, cardiac resynchronization therapy, or pacemaker indication. These criteria encapsulate a large proportion (around 70%!) of all ICD eligible patients.