Six-year follow-up of the initial Dutch subcutaneous implantable cardioverter-defibrillator cohort: Long-term complications, replacements, and battery longevity

Trends in adoption of extravascular cardiac implantable electronic devices: the Dutch cohort

INTRODUCTION

Conventional implantable cardioverter-defibrillators (ICDs) and pacemakers carry a risk of pocket- and lead-related complications in particular. To avoid these complications, extravascular devices (EVDs) have been developed, such as the subcutaneous ICD (S-ICD) and leadless pacemaker (LP). However, data on patient or centre characteristics related to the actual adoption of EVDs are lacking.

OBJECTIVE

To assess real-world nationwide trends in EVD adoption in the Netherlands.

METHODS

Using the Netherlands Heart Registration, all consecutive patients with a de novo S‑ICD or conventional single-chamber ICD implantation between 2012-2020, or de novo LP or conventional single-chamber pacemaker implantation between 2014-2020 were included. Trends in adoption are described for various patient and centre characteristics.

RESULT

From 2012-2020, 2190 S‑ICDs and 10,683 conventional ICDs were implanted; from 2014-2020, 712 LPs and 11,103 conventional pacemakers were implanted. The general use has increased (S-ICDs 8 to 21%; LPs 1 to 8%), but this increase seems to have reached a plateau. S‑ICD recipients were younger than conventional ICD recipients (p < 0.001) and more often female (p < 0.001); LP recipients were younger than conventional pacemaker recipients (p < 0.001) and more often male (p = 0.03). Both S‑ICDs and LPs were mainly implanted in high-volume centres with cardiothoracic surgery on-site, although over time S‑ICDs were increasingly implanted in centres without cardiothoracic surgery (p < 0.001).

CONCLUSION

This nationwide study demonstrated a relatively quick adoption of innovative EVDs with a plateau after approximately 4 years. S‑ICD use is especially high in younger patients. EVDs are mainly implanted in high-volume centres with cardiothoracic surgery back-up, but S‑ICD use is expanding beyond those centres.

Transvenous versus subcutaneous implantable cardioverter defibrillators in young cardiac arrest survivors

Secondary prevention implantable cardioverter defibrillators (ICDs) are indicated in young patients presenting with aborted sudden cardiac death (SCD) because of ventricular arrhythmias. Transvenous-ICDs (TV-ICDs) are effective, established therapies supported by evidence. The significant morbidity associated with transvenous leads led to the development of the newer subcutaneous-ICD (S-ICD). This review discusses the clinical considerations when selecting an ICD for the young patient presenting with out-of-hospital cardiac arrest. The major benefits of TV-ICDs are their ability to pace (antitachycardia pacing [ATP], bradycardia support and cardiac resynchronisation therapy [CRT]) and the robust evidence base supporting their use. Other benefits include a longer battery life. Significant complications associated with transvenous leads include pneumothorax and tamponade during insertion and infection and lead failure in the long term. Comparatively, S-ICDs, by virtue of having no intravascular leads, prevent these complications. S-ICDs have been associated with a higher incidence of inappropriate shocks. Patients with an indication for bradycardia pacing, CRT or ATP (documented ventricular tachycardia) are seen as unsuitable for a S-ICD. If venous access is unsuitable or undesirable, S-ICDs should be considered given the patient is appropriately screened. There is a need for further randomised controlled trials to directly compare the two devices. TV-ICDs are an effective therapy for preventing SCD limited by significant lead-related complications. S-ICDs are an important development hindered largely by an inability to pace. Young patients stand to gain the most from a S-ICD as the cumulative risk of lead-related complications is high. A clinical framework to aid decision-making is presented.

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).

Incidence of premature battery depletion in subcutaneous cardioverter-defibrillator patients: insights from a multicenter registry

BACKGROUND

The subcutaneous ICD established its role in the prevention of sudden cardiac death in recent years. The occurrence of premature battery depletion in a large subset of potentially affected devices has been a cause of concern. The incidence of premature battery depletion has not been studied systematically beyond manufacturer-reported data.

METHODS

Retrospective data and the most recent follow-up data on S-ICD devices from fourteen centers in Europe, the US, and Canada was studied. The incidence of generator removal or failure was reported to investigate the incidence of premature S-ICD battery depletion, defined as battery failure within 60 months or less.

RESULTS

Data from 1054 devices was analyzed. Premature battery depletion occurred in 3.5% of potentially affected devices over an observation period of 49 months.

CONCLUSIONS

The incidence of premature battery depletion of S-ICD potentially affected by a battery advisory was around 3.5% after 4 years in this study. Premature depletion occurred exclusively in devices under advisory. This is in line with the most recently published reports from the manufacturer.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04767516 .

Infection in patients with subcutaneous implantable cardioverter-defibrillator: Results of the S-ICD Post Approval Study

BACKGROUND

Early subcutaneous implantable cardioverter-defibrillator (S-ICD) studies included atypical cohorts of patients who were younger with fewer comorbidities. Recent S-ICD studies included patient populations with more comorbidities.

OBJECTIVES

The goals of this study were to determine the incidence and predictors of S-ICD-related infection over a 3-year follow-up period and to use these results to develop an infection risk score.

METHODS

The S-ICD Post Approval Study is a US prospective registry of 1637 patients. Baseline demographic characteristics and outcomes with 3-year postimplantation follow-up were compared between patients with and without device-related infection. A risk score was derived from multivariable proportional hazards analysis of 22 variables.

RESULTS

Infection was observed in 55 patients (3.3%), with 69% of infections occurring within 90 days and a vast majority (92.7%) within 1 year of implantation. Late infections more likely involved device erosion; no infections occurred after year 2. The annual mortality rate postinfection was 0.6%/y. No lead extraction complications or bacteremia related to infection were observed. An infection risk score was created with diabetes, age, prior transvenous ICD implant, and ejection fraction as predictors. Patients with a risk score of ≥3 had an 8.8 hazard ratio (95% confidence interval 2.8-16.3) of infection compared with a 0 risk score.

CONCLUSION

Infection rates in the S-ICD Post Approval Study were similar to other S-ICD populations and not associated with systemic blood-borne infections. Late infection (>1 year) is uncommon and associated with system erosion. A high-risk infection cohort can be identified that may facilitate preventive measures.

Evolution of extravascular implantable cardioverter-defibrillator therapy for ventricular arrhythmias

Implantable cardioverter-defibrillators have become an established therapy for the prevention of sudden cardiac death due to life-threatening ventricular arrhythmias in the last decades. In all those years, the use of transvenous leads has proven to be the most vulnerable part of the system. The development of the completely subcutaneous implantable cardioverter-defibrillator opened a new era of device therapy outside of the vascular system. The next step, enabling extravascular devices with the option of antitachycardia pacing, is just around the corner. This may become an important option for all patients without a bradycardia pacing indication that are in need for antitachycardia pacing because of monomorphic ventricular tachycardia.

Effects and Complications of Subcutaneous Implantable Cardioverter-Defibrillator in the Prevention of Sudden Cardiac Death: A Narrative Review

An implantable cardioverter-defibrillator (ICD) is one of those devices that is a big boom for the prevention of sudden deaths due to heart failure. This particular device has been in use for just a couple of years, but its impact in the domain has brought about a considerable change in the way a specific issue of the cardiovascular system is tackled. Although subcutaneous or hypodermic implantable cardioverter-defibrillator (S-ICD) is considered to be a better alternative as far as transvenous implantable cardioverter-defibrillator (TV-ICD) is concerned, the former, being a newer introduction in the market, needs to be assessed in depth to clearly understand its effects and complications. Various types of research have been conducted on the efficacy of this device, and in most of the studies, the supremacy of this device is clearly evident when compared with other devices that are used for the same purpose. Better innovations in subcutaneous or hypodermic implantable cardioverter-defibrillators would enable them to be manufactured in a more efficient and cost-effective way so that a huge lot of people are benefited from this device. This review article is a whole peep into the various studies done in this domain, thereby providing adequate scientific insights about subcutaneous or hypodermic implantable cardioverter-defibrillators in a very simple and comprehensive manner.

Subcutaneous implantable cardioverter defibrillator after transvenous lead extraction: safety, efficacy and outcome

BACKGROUND

Subcutaneous implantable cardioverter defibrillator (S-ICD) is a suitable alternative for transvenous ICD (TV-ICD) patients who have undergone transvenous lead extraction (TLE). Limited data are available on the outcome of S-ICD patients implanted after TLE. We assessed the safety, efficacy, and outcome of S-ICD implantation after TLE of TV-ICD.

METHODS

The study population consisted of 36 consecutive patients with a median age of 52 (44-66) years who underwent S-ICD implantation after TLE of TV-ICD.

RESULTS

Indications for TLE were infection (63.9%) and lead malfunction (36.1%). During a median follow-up of 31 months, 3 patients (8.3%) experienced appropriate therapy and 7 patients (19.4%) experienced complications including inappropriate therapy (n = 4; 11.1%), isolated pocket erosion (n = 2; 5.5%), and ineffective therapy (n = 1; 2.8%). No lead/hardware dysfunction was reported. Premature device explantation occurred in 4 patients (11%). Eight patients (22.2%) died during follow-up, six of them (75%) because of refractory heart failure (HF). There were no S-ICD-related deaths. Predictors of mortality included NYHA class ≥ 2 (HR 5.05; 95% CI 1.00-26.38; p = 0.04), hypertension (HR 22.72; 95% CI 1.05-26.31; p = 0.02), diabetes (HR 10.64; 95% CI 2.05-55.60; p = 0.001) and ischemic heart disease (HR 5.92; 95% CI 1.17-30.30; p = 0.01).

CONCLUSION

Our study provides evidences on the use of S-ICD as an alternative after TV-ICD explantation for both infection and lead failure. Mortality of S-ICD patients who underwent TV-ICD explantation does not appear to be correlated with the presence of a prior infection, S-ICD therapy (appropriate or inappropriate), or S-ICD complications but rather to worsening of HF or other comorbidities.

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.

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%.

The potential impact of acute coronary syndromes on automatic sensing system in Subcutaneous-ICDs

BACKGROUND

The Subcutaneous-ICD (S-ICD) is emerging as a suitable option for most ICD candidates, however some open issues regarding the sensing algorithm still remain.

OBJECTIVES

We aimed to examine the performance of the S-ICD sensing algorithm in patients hospitalized for ST elevation myocardial infarction (STEMI), non ST elevation acute coronary syndrome (NSTE-ACS) or chronic coronary syndrome (CCS), before and after revascularization.

METHODS

We performed a S-ICD automated screening on 75 patients, 21 hospitalized for STEMI, 23 for NSTE-ACS and 31 for CCS, before and after percutaneous revascularization, regardless their eligibility to ICD implantation.

RESULTS

Patients did not differ in clinical, electrocardiographic and echocardiographic parameters. Rates of screening pass were significantly lower in STEMI patients compared to NSTE-ACS and CCS (5% vs 56.7% vs 81% respectively, p < .0001). The viability of the primary vector was lower in STEMI patients compared to NSTE-ACS and CCS (33% vs 56% vs 71%, p .027 respectively). After revascularization, there were no more significant differences between groups. Pairing subjects at baseline and after revascularization, STEMI subjects percentages of screening success were respectively 5% and 81% (p < .001) and the rates of primary vector viability were 33% and 81% (p .002). STEMI was the only independent predictor of screening failure at multivariate logistic regression analysis (odds ratio 10.68 confidence interval 2.77-41.38, p = .001).

CONCLUSION

The performance of the S-ICD and possible malfunction detections in the context of an acute ischemic event deserve further evaluation. Adequate patient selection and the development of dynamic device programming are warranted.

Subcutaneous implantable cardioverter-defibrillator electrode fracture: Follow-up, troubleshooting, and evaluation

The subcutaneous-implantable cardioverter-defibrillator (S-ICD) and its electrode were developed to avoid long-term complications of transvenous leads in the vasculature. We report a case of unexpected, inappropriate S-ICD shocks due to oversensing of high-amplitude, nonphysiologic, electrical noise artifacts that were not preceded by high-impedance alerts or sensing electrogram noise detections. Following explant, high-magnification X-ray imaging of the S-ICD electrode demonstrated partial fracture of the distal sensing conductor located near a short radius bend in the electrode at the electrode-header interface. Clinicians should be aware of a potential for fatigue failure fracture of the S-ICD electrode. Recommendations for systematic S-ICD follow-up and troubleshooting are discussed.

Performance and outcome of the subcutaneous implantable cardioverter-defibrillator after transvenous lead extraction

AIMS

The subcutaneous cardioverter-defibrillator (S-ICD) may be a valuable option in patients after successful transvenous lead extraction (TLE) without indication for pacemaker therapy and persistent risk of sudden cardiac death. The aim of this study was to evaluate device performance, postoperative outcome, and safety in patients who received a S-ICD after TLE compared to patients who underwent de-novo S-ICD implantation.

METHODS

A retrospective analysis of all patients included into our institution's S-ICD database between September 2010 and May 2019 was conducted.The patients were divided in two groups, depending on whether they had received their S-ICD after TLE (n = 31) or de-novo (n = 113).

RESULTS

The TLE group was significantly older with a mean age of 54.3 ± 15.7 versus 46.7 ± 14.4 years; p = .007. Leading S-ICD indication in the TLE group was previous infection (50%), whereas in the de-novo group the S-ICD was primarily chosen due to young patient age (74.6%). Median duration of follow-up was 527.0 versus 472.5 days, respectively; p = .576. Most common complication during follow-up was inappropriate ICD therapy (12.9% vs. 13.3%); p = 1.000. Pocket erosion/infection occurred in 3.2% versus 3.5% with no reported cases of systemic (re-)infection in either group; p = 1.000. All-cause mortality was low (6.2% vs. 2.7%) and entirely unrelated to S-ICD implantation or the device itself; p = .293.

CONCLUSION

The S-ICD is a safe and effective alternative for patients after TLE with very similar results regarding device performance and postoperative outcome, when compared to patients who underwent de-novo S-ICD implantation.

Brugada syndrome: Eligibility for subcutaneous implantable cardioverter-defibrillator after exercise stress test

INTRODUCTION

Brugada syndrome (BrS) is a channelopathy associated with ventricular arrhythmias and sudden cardiac death. In patients at high risk of sudden death, an implantable cardioverter-defibrillator is indicated. Subcutaneous implantable cardioverter-defibrillators (S-ICDs) are an alternative to transvenous systems, with reduced risk of infection and complications associated with system extraction or explantation.

OBJECTIVE

To test electrocardiographic eligibility for S-ICD placement after exercise stress testing (EST) in patients with BrS.

METHODS

The sample included 35 consecutive patients with BrS. Electrocardiographic eligibility was assessed using the Boston Scientific model 2889 EMBLEM™ S-ICD automated screening tool, in four phases: decubitus and orthostatism, and before and after EST. Those who had at least one acceptable vector in the four measurements were considered eligible.

RESULTS

In this study, 71.4% of patients were male and mean age was 53.86±12 years. In screening prior to EST, 14.3% of patients (n=5) were not eligible for an S-ICD. There was a statistically significant association between ineligibility and presence of complete right bundle branch block and history of syncope. After EST, 16.7% of initially eligible patients no longer had eligible vectors (n=5).

CONCLUSION

In this study, 16.7% of patients previously eligible for an S-ICD were no longer eligible after EST. This result demonstrates the importance of screening after EST in all patients with BrS and with indication for an S-ICD, and may influence decisions concerning which ICD to implant or whether to institute pharmacological measures that avoid inappropriate therapies.

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.

1-Year Prospective Evaluation of Clinical Outcomes and Shocks: The Subcutaneous ICD Post Approval Study

OBJECTIVES

This study evaluated spontaneous arrhythmias and clinical outcomes in the S-ICD System PAS (Subcutaneous Implantable Cardioverter-Defibrillator Post Approval Study) cohort.

BACKGROUND

The U.S. S-ICD PAS trial patient population more closely resembles transvenous ICD cohorts than earlier studies, which included many patients with little structural heart disease and few comorbidities. Early outcomes and low peri-operative complication rates were demonstrated in the S-ICD PAS cohort, but there are no data detailing spontaneous arrhythmias and clinical outcomes.

METHODS

The S-ICD PAS prospective registry included 1,637 de novo patients from 86 U.S. centers. Descriptive statistics, Kaplan-Meier time to event, and multivariate logistic regression were performed using data out to 365 days.

RESULTS

Patients (68.5% men; mean ejection fraction of 32.0%; 42.9% ischemic; 13.4% on dialysis) underwent implantation for primary (76.6%) or secondary prevention indication. The complication-free rate was 92.5%. The appropriate shock (AS) rate was 5.3%. A total of 395 ventricular tachycardia (VT) or fibrillation (VF) episodes were appropriately sensed, with 131 (33.2%) self-terminating. First and final shock efficacy (up to 5 shocks) for the 127 discrete AS episodes were 91.3% and 100.0%, respectively. Discrete AS episodes included 67 monomorphic VT (MVT) and 60 polymorphic VT (PVT)/VF, with first shock efficacy of 95.2% and 86.7%, respectively. There were 19 storm events in 18 subjects, with 84.2% conversion success. Storm episodes were more likely PVT/VF (98 of 137).

CONCLUSIONS

In the first year after implantation, a predominantly primary prevention population with low ejection fraction demonstrated a high complication-free rate and spontaneous event shock efficacy for MVT and PVT/VF arrhythmias at rapid ventricular rates. (Subcutaneous Implantable Cardioverter-Defibrillator System Post Approval Study [S-ICD PAS; NCT01736618).

Subcutaneous or Transvenous Defibrillator Therapy

BACKGROUND

The subcutaneous implantable cardioverter-defibrillator (ICD) was designed to avoid complications related to the transvenous ICD lead by using an entirely extrathoracic placement. Evidence comparing these systems has been based primarily on observational studies.

METHODS

We conducted a noninferiority trial in which patients with an indication for an ICD but no indication for pacing were assigned to receive a subcutaneous ICD or transvenous ICD. The primary end point was the composite of device-related complications and inappropriate shocks; the noninferiority margin for the upper boundary of the 95% confidence interval for the hazard ratio (subcutaneous ICD vs. transvenous ICD) was 1.45. A superiority analysis was prespecified if noninferiority was established. Secondary end points included death and appropriate shocks.

RESULTS

A total of 849 patients (426 in the subcutaneous ICD group and 423 in the transvenous ICD group) were included in the analyses. At a median follow-up of 49.1 months, a primary end-point event occurred in 68 patients in the subcutaneous ICD group and in 68 patients in the transvenous ICD group (48-month Kaplan-Meier estimated cumulative incidence, 15.1% and 15.7%, respectively; hazard ratio, 0.99; 95% confidence interval [CI], 0.71 to 1.39; P = 0.01 for noninferiority; P = 0.95 for superiority). Device-related complications occurred in 31 patients in the subcutaneous ICD group and in 44 in the transvenous ICD group (hazard ratio, 0.69; 95% CI, 0.44 to 1.09); inappropriate shocks occurred in 41 and 29 patients, respectively (hazard ratio, 1.43; 95% CI, 0.89 to 2.30). Death occurred in 83 patients in the subcutaneous ICD group and in 68 in the transvenous ICD group (hazard ratio, 1.23; 95% CI, 0.89 to 1.70); appropriate shocks occurred in 83 and 57 patients, respectively (hazard ratio, 1.52; 95% CI, 1.08 to 2.12).

CONCLUSIONS

In patients with an indication for an ICD but no indication for pacing, the subcutaneous ICD was noninferior to the transvenous ICD with respect to device-related complications and inappropriate shocks. (Funded by Boston Scientific; PRAETORIAN ClinicalTrials.gov number, NCT01296022.).

Diagnosis and management of subcutaneous implantable cardioverter-defibrillator infections based on process mapping

BACKGROUND

Infection is a well-recognized complication of cardiovascular implantable electronic device (CIED) implantation, including the more recently available subcutaneous implantable cardioverter-defibrillator (S-ICD). Although the AHA/ACC/HRS guidelines include recommendations for S-ICD use, currently there are no clinical trial data that address the diagnosis and management of S-ICD infections. Therefore, an expert panel was convened to develop consensus on these topics.

METHODS

A process mapping methodology was used to achieve a primary goal - the development of consensus on the diagnosis and management of S-ICD infections. Two face-to-face meetings of panel experts were conducted to recommend useful information to clinicians in individual patient management of S-ICD infections.

RESULTS

Panel consensus of a stepwise approach in the diagnosis and management was developed to provide guidance in individual patient management.

CONCLUSION

Achieving expert panel consensus by process mapping methodology in S-ICD infection diagnosis and management was attainable, and the results should be helpful in individual patient management.

A novel screening test for inappropriate shocks due to myopotentials from the subcutaneous implantable cardioverter–defibrillator

Background

The subcutaneous implantable cardioverter-defibrillator (S-ICD) is effective in preventing sudden cardiac death. Compared with transvenous ICDs, S-ICDs have a lower rate of inappropriate shocks (IASs) for supraventricular arrhythmias, but such shocks for T-wave oversensing (TWO) and extracardiac myopotentials are more common. No screening tests to identify patients at risk for IAS due to myopotential interference (MPI) currently are available.

Objective

The purpose of this study was to assess the efficacy of a tube exercise test (TET) developed to detect MPI post S-ICD implantation.

Methods

TET includes 3 different maneuvers using an exercise tube. S-ICD electrograms were recorded to assess MPI while patients performed each of the maneuvers.

Results

TET was performed in 43 patients, and MPI was observed in 12 patients (28%). In 10 of the 12 TET-positive patients, the positive vector corresponded with a vector that did not show TWO on standard S-ICD preoperative screening. During median follow-up of 672 days (interquartile range 465–805 days), 3 patients (7%) experienced IAS due to MPI. Importantly, the vector at the time of IAS in all 3 patients passed standard preoperative screening for TWO but was positive with TET. Sensitivity and specificity of TET were 100% and 78%, respectively, and positive and negative predictive values were 25% and 100%, respectively.

Conclusion

Postimplant screening for MPI identified patients at increased risk for IAS. TET may be helpful for guiding optimal programming to prevent IAS.

Outcome differences and device performance of the subcutaneous ICD in patients with and without structural heart disease

BACKGROUND

The performance of the subcutaneous ICD (S-ICD™) has been described in different kinds of heart disease and has been proven to be an important advance in prevention of sudden cardiac death (SCD). While positive experiences with the S-ICD™ initially came from collectives of patients without structural heart diseases, positive results have also been collected from cohorts with structural heart disease.

MATERIALS AND METHODS

All S-ICD™ patients with either ischemic cardiomyopathy (ICM), dilated cardiomyopathy (DCM) or hypertrophic cardiomyopathy (HCM) as the main indication for ICD implantation (n = 144 patients) or electrical heart disease/idiopathic ventricular fibrillation (n = 83 patients) in our large-scaled single-center S-ICD™ registry were included in this study. Baseline characteristics, appropriate and inappropriate shocks, and complications were documented in a mean follow-up of 18 ± 15 months.

RESULTS

Baseline characteristics were significantly different between the two groups in most categories. In contrast, there was no difference concerning neither appropriate nor inappropriate shock delivery between the two groups. Also other outcome parameters such as need for surgical revisions and all-cause mortality did not differ. There was a significant difference between the first- and second-generation S-ICDs™ in inadequate shocks mainly driven by patients with HCM.

CONCLUSION

In our study, S-ICD™ performance was similar in patients with and without structural heart disease. Decision pro- or contra-S-ICD™ should be made rather on the basis of expected shock rate and probability of the need for future anti-tachycardia or anti-bradycardia pacing than in dependence of the underlying heart disease.

Incidence of myopotential induction in subcutaneous implantable cardioverter-defibrillator patients: Is the oversensing issue really solved?

BACKGROUND

The subcutaneous implantable cardioverter-defibrillator (S-ICD) has established its role in the prevention of sudden cardiac death in a defined population. Inappropriate shocks and device malfunction in S-ICD therapy may be caused by myopotential (MP) oversensing.

OBJECTIVE

The purpose of this study was to systematically evaluate a cohort of consecutive S-ICD patients for MP inducibility.

METHODS

After S-ICD implantation, all vectors (primary [PrimV], secondary [SecV], alternative [AltV]) were analyzed during isometric chest press (ICP), lifting and holding a 20-kg weight, and side plank exercise (SPE), supporting the body weight on the left arm. When MPs were induced, signal classification was assessed: adequate noise detection, induced undersensing (R waves classified as noise), and oversensing (noise annotated as R waves). In case of noise induction in the current vector, device reprogramming to a noise-free vector was done.

RESULTS

We systematically assessed 41 patients. In nearly all patients (90.2%), MPs were inducible. ICP was the most potent inductor of MPs. Whereas SecV (70.7%) and AltV (75.6%) were most vulnerable during ICP, PrimV was most affected during SPE (51.2%). In only a few cases did the S-ICD software distinguish correctly between MPs and QRS. MPs predominantly led to undersensing (up to 65.9%), but in up to 22% of patients MP-induced oversensing occurred but did not lead to tachycardia detection. No relation was seen between S-ICD lead and generator position and MP inducibility.

CONCLUSION

Induction of MPs during physical exercise was observed frequently. Although in most cases MP noise led to undersensing, oversensing events were commonly observed.

Efficacy, safety, and in-hospital outcomes of subcutaneous versus transvenous implantable defibrillator therapy: A meta-analysis and systematic review

BACKGROUND

Lead-related complication is an important drawback of trans-venous implantable cardioverter-defibrillators (TV-ICD). The subcutaneous ICD (S-ICD) was developed to overcome ICD lead associated complications; however, whether the S-ICD confers enhanced clinical benefits compared with TV-ICD remains unclear. The present systematic review and meta-analysis aimed to assess TV-ICD and S-ICD for safety, efficacy, and in-hospital outcomes in the prevention of sudden cardiac death (SCD) in patients not requiring pacing.

METHODS

The Medline, PubMed, EmBase, and Cochrane Library databases were searched for studies comparing TV-ICD and S-ICD.

RESULTS

A total of 9 eligible studies, including 5 propensity-matched case-control, 3 retrospective, and 1 cross-sectional studies were identified, assessing 7361 patients in all. Pool analyses demonstrated that SICD were associated with lower lead-related complication rates [odds ratio (OR) = 0.13; 95% confidence interval [CI] 0.05-0.33; I = 0%], and S-ICD was more beneficial in terms of reducing ICD shocks [OR = 0.48; 95% CI 0.32-0.72, I = 4%]. In addition, the patients administered S-ICD tend to have shorter length of hospital stay after implantation (SMD = -0.06; 95% CI -0.11 to 0.00, I = 0%) and reduce total complication rates (OR = 0.72; 95% CI 0.50-1.03; I = 18%), non-decreased quality of life (QoL). Moreover, both devices appeared to perform equally well with respect to infection rate and death.

CONCLUSIONS

Available overall data suggested that S-ICD is associated with reducing lead-related complications, ICD shocks. In addition, S-ICD has tendency to shorten hospitalization and reduce total complications, although the difference is no significant. Equivalent death rate, infection, and QoL were found between 2 groups. Therefore, S-ICD could be considered an alternative approach to TV-ICD in appropriate patients for SCD prevention.

Feasibility of entirely subcutaneous ICD™ systems in patients with coronary artery disease

BACKGROUND

The subcutaneous ICD (S-ICD™) is an important advance in device therapy for the prevention of sudden cardiac death (SCD). Although current guidelines recommend S-ICD™ use, long-term data are still limited, especially in subgroups. Among several cardiac diseases that prone to SCD, coronary artery disease (CAD) carries several peculiarities that may hamper S-ICD™ therapy in this cohort. CAD can lead to an ischemic cardiomyopathy (ICM) with a reduced left-ventricular ejection fraction (LVEF) and bundle branch blocks, which can be difficult for ICD sensing and discrimination of arrhythmia. CAD is mainly driven by risk factors such as diabetes mellitus, which put these patients at an elevated risk for infectious complications of cardiac devices. Furthermore, in ICM myocardial scars are frequent and are a potential substrate for ventricular tachycardia, which may be accessible for antitachycardia pacing. At the moment, it remains unclear if there is a value of S-ICD™ therapy in this subgroup. Therefore, this study analysed patients with CAD.

MATERIALS AND METHODS

All S-ICD™ patients with CAD as the main indication for ICD implantation (n = 45 patients) in our large-scaled single-center S-ICD™ registry (n = 249 patients) were included in this study. Baseline characteristics, appropriate and inappropriate shocks, and complications were documented in a mean follow-up of 22.5 ± 8.3 months.

RESULTS

Primary prevention of SCD was the indication for implantation of an S-ICD™ in 28 patients (62%). Of all 45 patients with an overall mean age of 58.1 ± 11.4 years, 40 were male (88%). The mean LVEF was 37.7 ± 12.6%. Three episodes of ventricular arrhythmia (one monomorphic, one polymorphic, one ventricular fibrillation) were adequately terminated in three patients (7%). In only one patient, oversensing resulting in an inappropriate shock was observed, which could be managed by changing the sensing vector. 15 of the examined 45 patients previously had a transvenous ICD, which was explanted due to system-related infections. In only two patients, S-ICD™ was changed to transvenous ICD because of the need of antibradycardia stimulation. There were no S-ICD™ system-related infections.

CONCLUSION

The S-ICD™ seems to be a valuable option for the prevention of SCD in CAD patients. Patients with systemic infections of a transvenous ICD and, therefore, a need for an alternative might benefit from the absence of intracardiac leads as the S-ICD™ is safe and works flawlessly in these patients. Inadequate shock delivery was very rare, while every episode of ventricular arrhythmia was terminated by the first shock.

Spotlight on S-ICD™ therapy: 10 years of clinical experience and innovation

Subcutaneous ICD (S-ICD™) therapy has been established in initial clinical trials and current international guideline recommendations for patients without demand for pacing, cardiac resynchronization, or antitachycardia pacing. The promising experience in ‘ideal’ S-ICD™ candidates increasingly encourages physicians to provide the benefits of S-ICD™ therapy to patients in clinical constellations beyond ‘classical’ indications of S-ICD™ therapy, which has led to a broadening of S-ICD™ indications in many centres. However, the decision for S-ICD™ implantation is still not covered by controlled randomized trials but rather relies on patient series or observational studies. Thus, this review intends to give a contemporary update on available empirical evidence data and technical advancements of S-ICD™ technology and sheds a spotlight on S-ICD™ therapy in recently discovered fields of indication beyond ideal preconditions. We discuss the eligibility for S-ICD™ therapy in Brugada syndrome as an example for an adverse and dynamic electrocardiographic pattern that challenges the S-ICD™ sensing and detection algorithms. Besides, the S-ICD™ performance and defibrillation efficacy in conditions of adverse structural remodelling as exemplified for hypertrophic cardiomyopathy is discussed. In addition, we review recent data on potential device interactions between S-ICD™ systems and other implantable cardio-active systems (e.g. pacemakers) including specific recommendations, how these could be prevented. Finally, we evaluate limitations of S-ICD™ therapy in adverse patient constitutions, like distinct obesity, and present contemporary strategies to assure proper S-ICD™ performance in these patients. Overall, the S-ICD™ performance is promising even for many patients, who may not be ‘classical’ candidates for this technology.

Rationale and design of the randomized prospective ATLAS study: Avoid Transvenous Leads in Appropriate Subjects

BACKGROUND

The defibrillator lead is the weakest part of the transvenous (TV) implantable cardioverter defibrillation (ICD) system and a frequent cause of morbidity. Lead dislodgement, cardiac perforation, insertion-related trauma including pneumothorax and vascular injury, are common early complications of TV-ICD implantation. Venous occlusion, tricuspid valve dysfunction, lead fracture and lead insulation failure are additional, later complications. The introduction of a totally sub-cutaneous ICD (S-ICD) may reduce these lead-related issues, patient morbidity, hospitalizations and costs. However, such benefits compared to the TV-ICD have not been demonstrated in a randomized trial.

DESIGN

ATLAS (Avoid Transvenous Leads in Appropriate Subjects) is a multi-centered, randomized, open-label, parallel group trial. Patients younger than 60 years are eligible. If older than 60 years, patients are eligible if they have an inherited heart rhythm disease, or risk factors for ICD-related complication, such as hemodialysis, a history of ICD or pacemaker infection, heart valve replacement, or severe pulmonary disease. This study will determine if using an S-ICD compared to a TV-ICD reduces a primary composite outcome of perioperative complications including pulmonary or pericardial perforation, lead dislodgement or dysfunction, tricuspid regurgitation and ipsilateral venous thrombosis. Five hundred patients will be enrolled from 14 Canadian hospitals, and data collected to both early- (at 6 months) and mid-term complications (at 24 months) as well as mortality and ICD shock efficacy.

SUMMARY

The ATLAS randomized trial is comparing early- and mid-term vascular and lead-related complications among S-ICD versus TV-ICD recipients who are younger or at higher risk of ICD-related complications.

An Overview of Clinical Outcomes in Transvenous and Subcutaneous ICD Patients

PURPOSE OF REVIEW

Clear guidelines on when to select a subcutaneous ICD (S-ICD) over a transvenous ICD (TV-ICD) are lacking. This review will provide an overview of the most recent clinical data on S-ICD and TV-ICD therapy by pooling comparison studies in order to aid clinical decision making.

RECENT FINDINGS

Pooling of observational-matched studies demonstrated an incidence rate ratio (IRR) for device-related complication of 0.90 (95% CI 0.58-1.42) and IRR for lead-related complications of 0.15 (95% CI 0.06-0.39) in favor of S-ICD. The IRR for device infections was 2.00 (95% CI 0.95-4.22) in favor of TV-ICD. Both appropriate shocks (IRR 0.67 (95% CI 0.42-1.06)) and inappropriate shocks (IRR 1.17 (95% CI 0.77-1.79)) did not differ significantly between both groups. With randomized data underway, the observational data demonstrate that the S-ICD is associated with reduced lead complications, but this has not yet resulted in a significant reduction in total number of complications compared to TV-ICDs. New technologies are expected to make the S-ICD a more attractive alternative.