The learning curve associated with the introduction of the subcutaneous implantable defibrillator

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 "inappropriately appropriate" shock in a subcutaneous implantable cardioverter-defibrillator: The importance of the SMART pass algorithm

We report on a case of a 78-years-old patient with a subcutaneous implantable cardioverter defibrillator (S-ICD) and an episode of a sustained ventricular tachycardia (VT) at a rate slower than the programmed shock zone. Because of T-wave oversensing the device interpreted it as fast VT that triggered the delivery of an "inappropriately appropriate shock" that terminated it. The patient had again more VT episodes but after programming the SMART pass algorithm (previously programmed "OFF") the device showed no longer frequent T-wave oversensing and no additional inappropriate shocks occurred.

Comparison of complications and shocks in paediatric and young transvenous and subcutaneous implantable cardioverter-defibrillator patients

BACKGROUND

Young implantable cardioverter-defibrillator (ICD) patients are prone to complications and inappropriate shocks (IAS). The subcutaneous ICD (S-ICD) may avoid lead-related complications. This study aims to describe the incidence and nature of device-related complications in young transvenous ICD (TV-ICD) and S‑ICD patients.

METHODS

Single-chamber TV-ICD and S‑ICD patients up to and including the age of 25 years implanted between 2002 and 2015 were retrospectively analysed. Complications were defined as device-related complications requiring surgical intervention. IAS were defined as shocks for anything other than ventricular tachycardia or ventricular fibrillation. Follow-up data were collected 5 years post-implantation. Kaplan-Meier estimates for complications at 5‑year follow-up were calculated with a corresponding 95% confidence interval.

RESULTS

Eighty-one patients (46 TV-ICD, 35 S-ICD) were included (median age 19.0 (IQR 16.0-23.0) and 16.5 (IQR 13.0-20.2) years respectively). Median follow-up was 60 and 40 months respectively. All-cause complication rate was 34% in the TV-ICD group and 25% in the S‑ICD group (p = 0.64). TV-ICD patients had more lead complications: 23% (10-36%) versus 0% (p = 0.02). The rate of infections did not differ between TV-ICD and S‑ICD: 2% (0-6%) versus 10% (0-21%) (p = 0.15). No systemic infections occurred in the S‑ICD patients. The rates of IAS were similar, TV-ICD 22% (9-35%) versus S‑ICD 14% (0-30%) (p = 0.40), as were those for appropriate shocks: 25% (11-39%) versus 27% (6-48%) (p = 0.92).

CONCLUSION

The rates of all-cause complications in this cohort were equal, though the nature of the complications differed. S‑ICD patients did not suffer lead failures or systemic infections. An era effect is present between the two groups.

Leadless pacing

Leadless self-contained intracardiac pacemakers were developed with the aim of abolishing the short- and long-term risk of lead- and pocket-related complications associated with transvenous devices. Leadless pacemakers promise minimally invasive procedures, long battery lives, and small amounts of foreign materials in the body. Experiences with the pioneering single-chamber devices have provided reasons for optimism about the future of the leadless concept. In the future, as more patients receive and live longer with implantable devices, the total risk of procedure- and lead-related complications is expected to increase, adding a sense of urgency to the need for leadless alternatives to transvenous pacemakers. This review surveys the performance of currently available leadless pacemakers as well as emerging new innovative adaptations and applications of the leadless concept.

Trends and In-Hospital Outcomes Associated With Adoption of the Subcutaneous Implantable Cardioverter Defibrillator in the United States

Importance

Trends and in-hospital outcomes associated with early adoption of the subcutaneous implantable cardioverter defibrillator (S-ICD) in the United States have not been described.

Objectives

To describe early use of the S-ICD in the United States and to compare in-hospital outcomes among patients undergoing S-ICD vs transvenous (TV)-ICD implantation.

Design, Setting, and Participants

A retrospective analysis of 393 734 ICD implants reported to the National Cardiovascular Data Registry ICD Registry, a nationally representative US ICD registry, between September 28, 2012 (US Food and Drug Administration S-ICD approval date), and March 31, 2015, was conducted. A 1:1:1 propensity-matched analysis of 5760 patients was performed to compare in-hospital outcomes among patients with S-ICD with those of patients with single-chamber (SC)-ICD and dual-chamber (DC)-ICD.

Main Outcomes and Measures

Analysis of trends in S-ICD adoption as a function of total ICD implants and comparison of in-hospital outcomes (death, complications, and defibrillation threshold [DFT] testing) among S-ICD and TV-ICD recipients.

Results

Of the 393 734 ICD implants evaluated during the study period, 3717 were S-ICDs (0.9%). A total of 109 445 (27.8%) of the patients were female; the mean (SD) age was 67.03 (13.10) years. Use of ICDs increased from 0.2% during the fourth quarter of 2012 to 1.9% during the first quarter of 2015. Compared with SC-ICD and DC-ICD recipients, those with S-ICDs were more often younger, female, black, undergoing dialysis, and had experienced prior cardiac arrest. Among 2791 patients with S-ICD who underwent DFT testing, 2588 (92.7%), 2629 (94.2%), 2635 (94.4%), and 2784 (99.7%) were successfully defibrillated (≤65, ≤70, ≤75, and ≤80 J, respectively). In the propensity-matched analysis of 5760 patients, in-hospital complication rates associated with S-ICDs (0.9%) were comparable to those of SC-ICDs (0.6%) (P = .27) and DC-ICD rates (1.5%) (P = .11). Mean (SD) length of stay after S-ICD implantation was comparable to that after SC-ICD implantation (1.1 [1.5] vs 1.0 [1.2] days; P = .77) and less than after DC-ICD implantation (1.1 [1.5] vs 1.2 [1.5] days; P < .001).

Conclusions and Relevance

The use of S-ICDs is rapidly increasing in the United States. Early adoption has been associated with low complication rates and high rates of successful DFT testing despite frequent use in patients with a high number of comorbidities.

The learning curve associated with the implantation of the Nanostim leadless pacemaker

Purpose

Use of novel medical technologies, such as leadless pacemaker (LP) therapy, may be subjected to a learning curve effect. The objective of the current study was to assess the impact of operators’ experience on the occurrence of serious adverse device effects (SADE) and procedural efficiency.

Methods

Patients implanted with a Nanostim LP (Abbott, USA) within two prospective studies (i.e., LEADLESS ll IDE and Leadless Observational Study) were assessed. Patients were categorized into quartiles based on operator experience. Learning curve analysis included the comparison of SADE rates at 30 days post-implant per quartile and between patients in quartile 4 (> 10 implants) and patients in quartiles 1 through 3 (1–10 implants). Procedural efficiency was assessed based on procedure duration and repositioning attempts.

Results

Nanostim LP implant was performed in 1439 patients by 171 implanters at 60 centers in 10 countries. A total of 91 (6.4%) patients experienced a SADE in the first 30 days. SADE rates dropped from 7.4 to 4.5% (p = 0.038) after more than 10 implants per operator. Total procedure duration decreased from 30.9 ± 19.1 min in quartile 1 to 21.6 ± 13.2 min (p < 0.001) in quartile 4. The need for multiple repositionings during the LP procedure reduced in quartile 4 (14.8%), compared to quartiles 1 (26.8%; p < 0.001), 2 (26.6%; p < 0.001), and 3 (20.4%; p = 0.03).

Conclusions

Learning curves exist for Nanostim LP implantation. Procedure efficiency improved with increased operator experience, according to a decrease in the incidence of SADE, procedure duration, and repositioning attempts.

Electronic supplementary material

The online version of this article (10.1007/s10840-018-0438-8) contains supplementary material, which is available to authorized users.

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

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

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

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

The Subcutaneous Defibrillator

The transvenous implantable cardioverter-defibrillator (ICD) has been shown in multiple studies to be effective in the prevention of sudden cardiac death in select populations. The Achilles heel of traditional ICD technology has been the transvenous lead. The subcutaneous ICD provides effective sudden death protection while avoiding lead-related complications of traditional transvenous systems. The subcutaneous ICD is a reasonable option for patients with an ICD indication who do not need bradycardia pacing or cardiac resynchronization therapy.

Implantation of subcutaneous implantable cardioverter defibrillators in Europe: results of the European Heart Rhythm Association survey

AIMS

The purpose of this European Heart Rhythm Association (EHRA) survey is to provide an overview of the current use of subcutaneous cardioverter defibrillators (S-ICDs) across a broad range of European centres.

METHODS AND RESULTS

A questionnaire was sent via the internet to centres participating in the EHRA electrophysiology research network. Questions included standards of care and policies used for patient management, indications, and techniques of implantation of the S-ICDs. In total, 52 centres replied to the questionnaire. More than one-fourth of the responding centres does not implant the S-ICD (n = 14, 27%). The majority reported to have implanted <10 (50%) or 10-29 (23%) S-ICDs during the last 12 months. Lack of reimbursement (25%), non-availability (19%), and cost of the device (25%) seem to limit the use of the S-ICD. The most commonly reported indications for S-ICD implantation are a difficult vascular access (82%), a history of previous complicated transvenous ICD (8O%), young age (69%), or an anticipated higher risk of infection (63%). Inappropriate therapies were the most frequently reported major problems (38%), but the majority of respondents (51%) never encountered any issue after an S-ICD implantation. Most of the respondents (83%) anticipate significant increase of S-ICD use within the next 2 years.

CONCLUSION

This survey provides a contemporary insight into S-ICD implantation and management in the European electrophysiology centres, showing different approaches, depending on local policies. Cost issues or lack of reimbursement strongly influence the dissemination of the device. However, most respondents retain that S-ICD use will significantly increase in a very short time.

Entirely subcutaneous defibrillator and complex congenital heart disease: Data on long-term clinical follow-up

AIM

To describe the long-term follow-up of patients with complex congenital heart disease who underwent subcutaneous implantable cardiac defibrillator (S-ICD), focusing on local complications, appropriate and inappropriate shocks.

METHODS

Patients with complex congenital heart disease underwent S-ICD implant in two centers with the conventional technique. Data at follow-up were retrieved from clinical notes and institutional database.

RESULTS

Eight patients were implanted in two centres between 2010 and 2016. Median age at implant was 37.5 years (range 13-57). All patients who were deemed suitable for S-ICD implant passed the pre-procedural screening. Three patients were previously implanted with a anti-bradycardia device, one of whom with CRT. In one patient the device was explanted due to local infection. During the total median follow-up of 874 d, one patient had an appropriate and one inappropriate shock triggered by fast atrial tachycardia. None of the patients had inappropriate shocks secondary to T wave oversensing or electrical interference with anti- bradycardia devices.

CONCLUSION

S-ICD appears to be effective and safe in patients with complex congenital heart disease.

Impact of operator experience and training strategy on procedural outcomes with leadless pacing: Insights from the Micra Transcatheter Pacing Study

BACKGROUND

Leadless pacemaker systems have been designed to avoid the need for a pocket and transvenous lead. However, delivery of this therapy requires a new catheter-based procedure. This study evaluates the role of operator experience and different training strategies on procedural outcomes.

METHODS

A total of 726 patients underwent implant attempt with the Micra transcatheter pacing system (TPS; Medtronic, Minneapolis, MN, USA) by 94 operators trained in a teaching laboratory using a simulator, cadaver, and large animal models (lab training) or locally at the hospital with simulator/demo model and proctorship (hospital training). Procedure success, procedure duration, fluoroscopy time, and safety outcomes were compared between training methods and experience (implant case number).

RESULTS

The Micra TPS procedure was successful in 99.2% of attempts and did not differ between the 55 operators trained in the lab setting and the 39 operators trained locally at the hospital (P = 0.189). Implant case number was also not a determinant of procedural success (P = 0.456). Each operator performed between one and 55 procedures. Procedure time and fluoroscopy duration decreased by 2.0% (P = 0.002) and 3.2% (P < 0.001) compared to the previous case. Major complication rate and pericardial effusion rate were not associated with case number (P = 0.755 and P = 0.620, respectively). There were no differences in the safety outcomes by training method.

CONCLUSIONS

Among a large group of operators, implantation success was high regardless of experience. While procedure duration and fluoroscopy times decreased with implant number, complications were low and not associated with case number. Procedure and safety outcomes were similar between distinct training methodologies.

Implantation of the Subcutaneous Implantable Cardioverter-Defibrillator

Background—

Alternative techniques to the traditional 3-incision subcutaneous implantation of the subcutaneous implantable cardioverter-defibrillator may offer procedural and cosmetic advantages. We evaluate 4 different implant techniques of the subcutaneous implantable cardioverter-defibrillator.

Methods and Results—

Patients implanted with subcutaneous implantable cardioverter-defibrillators from 2 hospitals between 2009 and 2016 were included. Four implantation techniques were used depending on physician preference and patient characteristics. The 2- and 3-incision techniques both place the pulse generator subcutaneously, but the 2-incision technique omits the superior parasternal incision for lead positioning. Submuscular implantation places the pulse generator underneath the serratus anterior muscle and subfascial implantation underneath the fascial layer on the anterior side of the serratus anterior muscle. Reported outcomes include perioperative parameters, defibrillation testing, and clinical follow-up. A total of 246 patients were included with a median age of 47 years and 37% female. Fifty-four patients were implanted with the 3-incision technique, 118 with the 2-incision technique, 38 with submuscular, and 37 with subfascial. Defibrillation test efficacy and shock lead impedance during testing did not differ among the groups; respectively, P =0.46 and P =0.18. The 2-incision technique resulted in the shortest procedure duration and time-to-hospital discharge compared with the other techniques ( P <0.001). A total of 18 complications occurred, but there were no significant differences between the groups ( P =0.21). All infections occurred in subcutaneous implants (3-incision, n=3; 2-incision, n=4). In the 2-incision group, there were no lead displacements.

Conclusions—

The presented implantation techniques are feasible alternatives to the standard 3-incision subcutaneous implantation, and the 2-incision technique resulted in shortest procedure duration.

[Optimisation of subcutaneous defibrillator programming after inappropriate shocks due to new onset of right bundle branch block]

The subcutaneous implantable defibrillator (S-ICD) has become an established tool for the prevention of sudden cardiac death. Based on its detection properties, the S‑ICD is essentially dependent on correct morphology discrimination of the QRS complex and avoidance of potential T‑wave sensing. We report on a patient who experienced multiple inappropriate S‑ICD shocks due to T‑wave oversensing in the setting of new onset of right bundle branch block. Strategies for the optimisation of the device programming are discussed.