Postapproval Study of a Subcutaneous Implantable Cardioverter-Defibrillator System

Subcutaneous versus Transvenous Implantable Cardioverter Defibrillator in Patients with End-Stage Renal Disease Requiring Dialysis: Extended Long-Term Retrospective Multicenter Follow-Up

BACKGROUND

Implantable cardioverter defibrillators (ICD) prevent sudden cardiac death (SCD). Patients with end-stage renal disease (ESRD) requiring dialysis are at a very high risk of infection from cardiac implantable electronic device (CIED) implantation as well as mortality. In the present study, we compared the long-term complications and outcomes between subcutaneous ICD (S-ICD) and transvenous ICD (TV-ICD) recipients.

METHODS

In this retrospective analysis, we analyzed a total of 43 patients with ESRD requiring dialysis who received either a prophylactic S-ICD (26 patients) or a single right ventricular lead TV-ICD (17 patients) at seven experienced centers in Germany. Follow-up was performed bi-annually, at the end of which the data concerning comorbidities and, if applicable, reason for death were checked and confirmed with patients' general practitioner, nephrologist and cardiologist.

RESULTS

The median follow up duration was 95.6 months (range 42.8-126.3 months). Baseline characteristics were without noteworthy significant differences between groups. During follow-up (FU), there were significantly more device-associated infections (HR 8.72, 95% confidence interval (CI), 1.18 to 12.85, p < 0.05) and device-associated hospitalizations (HR 10.20, 95% CI 1.22 to 84.61, p < 0.001), as well as a higher cardiovascular mortality (HR 9.17, 95% CI 1.12 to 8.33, p < 0.05), in the TV-ICD group. The number of patients requiring hospitalization for any reason was significantly higher in the TV-ICD group (HR 2.59, 95% CI 1.12 to 6.41, p < 0.05). There was no significant difference in overall mortality (HR 1.92, 95% CI 0.96 to 6.15, p = 0.274).

CONCLUSIONS

Our data suggest that, in this extended follow-up in seriously compromised renal patients on dialysis, the S-ICD patients have statistically fewer device infections and hospitalizations as well as lower cardiac mortality compared with the TV-ICD cohort.

Candidacy and long-term outcomes of subcutaneous implantable cardioverter-defibrillators in current practice in patients with hypertrophic cardiomyopathy

BACKGROUND

In patients with Hypertrophic Cardiomyopathy (HCM) S-ICD is usually the preferred option as pacing is generally not indicated. However, limited data are available on its current practice adoption and long-term follow-up.

METHODS

Consecutive HCM patients with S-ICD implanted between 2013 and 2021 in 3 international centers were enrolled in this observational study. Baseline, procedural and follow-up data were regularly collected. Efficacy and safety were compared with a cohort of HCM patients implanted with a tv-ICD.

RESULTS

Seventy patients (64% males) were implanted with S-ICD at 41 ± 15 years, whereas 168 patients with tv-ICD at 49 ± 16 years. For S-ICD patients, mean ESC SCD risk score was 4,5 ± 1.9%: 25 (40%) at low-risk, 17 (27%) at intermediate and 20 (33%) at high-risk. Patients were followed-up for 5.1 ± 2.3 years. Two patients (0.6 per 100-person-years, vs 0.4 per 100 person-years with tv-ICD, p = 0.45) received an appropriate shock on VF, 17 (24%) were diagnosed with de-novo AF. Inappropriate shocks occurred in 4 patients (1.2 per 100-person-years, vs 0.9 per 100 person-years with tv-ICD, p = 0.74), all before Smart-Pass algorithm implementation. Four patients experienced device-related adverse events (1.2 per 100-person-years, vs 1 per 100 person-years with tv-ICD, p = 0.35%).

CONCLUSIONS

S-ICDs were often implanted in patients with an overall low-intermediate ESC SCD risk, reflecting both the inclusion of additional risk markers and a lower decision threshold. S-ICDs in HCM patients followed for over 5 years showed to be effective in conversion of VF and safe. Greater scrutiny may be required to avoid overtreatment in patients with milder risk profiles.

Device programing and SMART pass algorithm activation in subcutaneous implantable defibrillator patients: Data from a remote monitoring database

BACKGROUND

The programing of subcutaneous implantable cardioverter-defibrillators (S-ICD) in clinical practice has been little studied, as the activation status of the SMART Pass filter, which was implemented to reduce inappropriate shocks.

PURPOSE

We assessed device programing during follow-up and the rate of detected arrhythmias in consecutive S-ICD recipients.

METHODS

We analyzed data from 670 S-ICD patients followed on the remote network at 17 Italian centers for a median of 31 months (25th-75th percentile: 16-51). The enhanced SMART Pass version, introduced in October 2022, was expected to reduce the unintentional deactivation rate.

RESULTS

At the latest remote data transmission, the median conditional zone cut-off was set to 210 bpm (25th-75th percentile: 200-220), the shock zone cutoff was 250 bpm (25th-75th percentile: 240-250), and the SMART Pass was enabled in 586 (87%) patients. During follow-up, 194 automatic deactivation events were reported in 118 (18%) patients. Shocks were delivered in 129 (19%) patients, and untreated arrhythmias were recorded in 136 (20%) patients. The rate of shocks was lower when SMART Pass was enabled -0.12/patient-year (95% CI: 0.10-0.14) versus 0.20 (95% CI: 0.15-0.26) (p = .002), as it was the rate of untreated arrhythmias -0.12/patient-year (95% CI: 0.11-0.14) versus 0.23 (95% CI: 0.18-0.30) (p = .001). The enhanced SMART Pass version was associated with a lower rate of deactivations -0.04/patient-year (95% CI: 0.02-0.05) versus 0.14 (95% CI: 0.12-0.16) (p < .001), and with a reduction in treated and untreated arrhythmias (Incidence rate ratios: 0.40 (95% CI: 0.28-0.53) and 0.40 (95% CI: 0.30-0.55), respectively (p < .001)).

CONCLUSIONS

Centers tend to program devices to detect high ventricular rates for arrhythmia detection, to minimize inappropriate shock occurrences. SMART Pass activation is associated with lower rates of detected and treated arrhythmias. The enhanced SMART Pass version seems associated with a lower deactivation rate and with a further decrease in treated arrhythmias.

Occurrence of premature battery depletion in a large multicentre registry of subcutaneous cardioverter-defibrillator patients

AIMS

Subcutaneous implantable cardioverter-defibrillators (S-ICDs) have become established in preventing sudden cardiac death, with some advantages over transvenous defibrillator systems, including a lower incidence of lead failures. Despite technological advancements, S-ICD carriers may suffer from significant complications, such as premature battery depletion (PBD), that led to an advisory for nearly 40 000 patients. This multicentre study evaluated the incidence of PBD in a large set of S-ICD patients.

METHODS AND RESULTS

Data from patients implanted with S-ICD models A209 and A219 between October 2012 and July 2023 across nine centres in Europe and the USA were reviewed. Incidence and implications of PBD, defined as clinically observed sudden drop in battery longevity, were analysed and compared to PBD with the definition of battery depletion within 60 months. Prospectively collected clinical data were obtained retrospectively from medical records, device telemetry, and manufacturer reports. This registry is listed on ClinicalTrials.gov (NCT05713708). Of the 1112 S-ICD devices analysed, 547 (49.2%) were equipped with a potentially affected capacitor linked to PBD occurrence, currently under Food and Drug Administration advisory. The median follow-up time for all patients was 46 [inter-quartile range (IQR) 24-63] months. Clinically suspected PBD was observed in 159 (29.1%) of cases, with a median time to generator removal or replacement of 65 (IQR 55-72) months, indicative of significant deviations from expected battery lifespan. Manufacturer confirmation of PBD was made in 91.7% of devices returned for analysis. No cases of PBD were observed in devices that were not under advisory.

CONCLUSION

This manufacturer-independent analysis highlights a notable incidence of PBD in patients equipped with S-ICD models under advisory, and the rate of PBD in this study corresponds to the rate currently estimated by the manufacturer. To the best of our knowledge, this provides the largest contemporary peer-reviewed study cohort investigating the actual incidence of PBD in S-ICD patients. These findings emphasize the importance of post-market registries in collaboration between clinicians and the manufacturer to optimize safety and efficacy in S-ICD treatment.

Fifteen years of subcutaneous implantable cardioverter-defibrillator therapy: Where do we stand, and what will the future hold?

The subcutaneous implantable cardioverter-defibrillator (S-ICD) has emerged as a feasible alternative to the transvenous ICD in the treatment of ventricular tachyarrhythmias in patients without indications for pacing or cardiac resynchronization therapy. Since its introduction, numerous innovations have been made and clinical experience has been gained, leading to its adoption in current practice and preference in certain populations. Moreover, emerging technologies like the extravascular ICD and the combination of the S-ICD with the leadless pacemaker offer new possibilities for the future. These advancements underscore the evolving role of the S-ICD in management of ventricular tachyarrhythmias. This review outlines implantation considerations, patient selection, and troubleshooting advancements in the last 15 years and provides insights into future perspectives.

Incidence, implications, and management of sense-B-noise failure in subcutaneous cardioverter-defibrillator patients: insights from a large multicentre registry

AIMS

Subcutaneous implantable cardioverter-defibrillators (S-ICDs) offer potentially distinct advantages over transvenous defibrillator systems. Recent randomized trials showed significantly lower lead failure rates than transvenous ICD. Still, S-ICDs remain associated with the risk of inappropriate shocks (IAS). While previous studies have reported varying causes of IAS, this study explores a rare cause of IAS, referred to as 'sense-B-noise.' It was recently described in case series, but its incidence has not been studied in a large cohort of S-ICD patients.

METHODS AND RESULTS

We retrospectively reviewed data from patients implanted with S-ICD models 1010, A209, and A219 between October 2009 and July 2023 across nine centres in Europe and the USA. The analysis concentrated on determining the incidence and understanding the implications of sense-B-noise events. Sense-B-noise represents a rare manifestation of distinct electrogram abnormalities within the primary and alternate sensing vectors. Data were collected from medical records, device telemetry, and manufacturer reports for investigation. This registry is registered on clinicaltrials.gov (NCT05713708). Subcutaneous implantable cardioverter-defibrillator devices of the 1158 patients were analysed. The median follow-up time for all patients was 46 (IQR 23-64) months. In 107 patients (9.2%) ≥1 IAS was observed during follow-up. Sense-B-noise failure was diagnosed in six (0.5 and 5.6% of all IAS) patients, in all patients, the diagnosis was made after an IAS episode. Median lead dwell time in the affected patients was 23 (2-70) months. To resolve the sense-B-noise defect, in three patients reprogramming to the secondary vector was undertaken, and two patients underwent system removal with subsequent S-ICD reimplantation due to low amplitude in the secondary vector. In one patient, the secondary vector was initially programmed, and subsequently, an S-ICD system exchange was performed due to T-wave-oversensing IAS episodes.

CONCLUSION

This multicentre analysis' findings shed light on a rare but clinically highly significant adverse event in S-ICD therapy. To our knowledge, we provide the first systematic multicentre analysis investigating the incidence of sense-B-noise. Due to being difficult to diagnose and limited options for resolution, management of sense-B-noise is challenging. Complete system exchange may be the only option for some patients. Educating healthcare providers involved in S-ICD patient care is crucial for ensuring accurate diagnosis and effective management of sense-B-noise issues.

[Treatment with cardiac electronic implantable devices]

Cardiac device therapy provides not only treatment options for bradyarrhythmia but also advanced treatment for heart failure and preventive measures against sudden cardiac death. In heart failure treatment it enables synergistic reverse remodelling and reduces pharmacological side effects. Cardiac resynchronization therapy (CRT) has revolutionized the treatment of reduced left ventricular ejection fraction (LVEF) and left bundle branch block by decreasing the mortality and morbidity with improvement of the quality of life and resilience. Conduction system pacing (CSP) as an alternative method of physiological stimulation can improve heart function and reduce the risk of pacemaker-induced cardiomyopathy. Leadless pacers and subcutaneous/extravascular defibrillators offer less invasive options with lower complication rates. The prevention of infections through preoperative and postoperative strategies enhances the safety of these therapies.

Sex differences among subcutaneous implantable cardioverter-defibrillator recipients: a propensity-matched, multicentre, international analysis from the i-SUSI project

AIMS

Women have been historically underrepresented in implantable cardioverter-defibrillator (ICD) trials. No data on sex differences regarding subcutaneous ICDs (S-ICD) carriers have been described. Aim of our study was to investigate sex-related differences among unselected S-ICD recipients.

METHODS AND RESULTS

Consecutive patients enrolled in the multicentre, international i-SUSI registry were analysed. Comparisons between sexes were performed using a 1:1 propensity matching adjusted analysis for age, body mass index (BMI), left ventricular function, and substrate. The primary outcome was the rate of appropriate shocks during follow-up. Inappropriate shocks and other device-related complications were deemed secondary outcomes. A total of 1698 patients were extracted from the i-SUSI registry; 399 (23.5%) were females. After propensity matching, two cohorts of 374 patients presenting similar baseline characteristics were analysed. Despite similar periprocedural characteristics and a matched BMI, women resulted at lower risk of conversion failure as per PRAETORIAN score (73.4% vs. 81.3%, P = 0.049). Over a median follow-up time of 26.5 [12.7-42.5] months, appropriate shocks were more common in the male cohort (rate/year 3.4% vs. 1.7%; log-rank P = 0.049), while no significant differences in device-related complications (rate/year: 6.3% vs. 5.8%; log-rank P = 0.595) and inappropriate shocks (rate/year: 4.3% vs. 3.1%; log-rank P = 0.375) were observed. After controlling for confounders, sex remained significantly associated with the primary outcome (aHR 1.648; CI 0.999-2.655, P = 0.048), while not resulting predictor of inappropriate shocks and device-related complications.

CONCLUSION

In a propensity-matched cohort of S-ICD recipients, women are less likely to experience appropriate ICD therapy, while not showing higher risk of device-related complications.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT0473876.

Editor-in-Chief's Top Picks From 2023

Each week, I record audio summaries for every paper in JACC, as well as an issue summary. This process has become a true labor of love due to the time they require, but I am motivated by the sheer number of listeners (16M+), and it has allowed me to familiarize myself with every paper that we publish. Thus, I have selected the top 100 papers (Original Investigations, Review Articles, Society Documents, and the Global Burden of Diseases) from distinct specialties each year. In addition to my personal choices, I have included papers that have been the most accessed or downloaded on our websites, as well as those selected by the JACC Editorial Board members. In order to present the full breadth of this important research in a consumable fashion, we will present these abstracts in this issue of JACC, as well as their Central Illustrations∗ and podcasts. The highlights comprise the following sections: Aorta; Basic and Translational Science; Cardiac Failure, Myocarditis, and Pericarditis; Cardiomyopathies and Genetics; Congenital Heart Disease; Coronary, Peripheral, and Structural Interventions; Coronavirus; Health Promotion and Preventive Cardiology; Imaging; Metabolic and Lipid Disorders; Neurovascular Disease and Dementia; Rhythm Disorders and Thromboembolism; and Valvular Heart Disease.1-104 ∗ To view the full manuscript, including the full-sized Central Illustration, please refer to the original publication in JACC.

Ten years of subcutaneous defibrillator therapy: Consolidated clinical evidence and future perspectives

The subcutaneous implantable cardioverter defibrillator (S-ICD) was developed as an alternative to the traditional transvenous implantable cardioverter defibrillator (TV-ICD), aiming to provide easier implantation, simplified detection algorithm of malignant ventricular arrhythmias and prevention from placing components in the cardiovascular system. The S-ICD is implanted subcutaneously or intramuscularly with the generator placed in the left midaxillary line and the lead tunneled subcutaneously in the left para-sternal region. Preimplant electrocardiogram screening is recommended to prevent implantation in patients at high risk of T wave over-sensing. Currently, the S-ICD is unsuitable for patients requiring pacing or cardiac resynchronization. Since the beginning, the S-ICD underwent extensive preclinical investigation until the first prospective multicentre trial demonstrating high efficacy and safety led to market release. While earlier studies focused on younger patients with higher ejection fraction, more recent studies showed favorable outcomes even in patients with comorbidities similar to those typically observed in patients receiving TV-ICD. The development of second and third generation devices has contributed to reduce inappropriate shocks and overcome previous limitations. The aim of this paper is to review the evidence in the literature over the past decade supporting S-ICD as a valid alternative to TV-ICD in terms of safety and efficacy, highlighting the improvements in technology, as well as outcomes.