Pre-implant predictors of inappropriate shocks with the third-generation subcutaneous implantable cardioverter defibrillator

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.

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.

Intra-Abdominal Hemorrhage Triggering Inappropriate Therapy From a Subcutaneous Defibrillator

The SMART Pass filter (Boston Scientific) aims to reduce inappropriate shocks (IASs) from subcutaneous implantable cardioverter-defibrillators by filtering out low-frequency signals such as T waves. However, this filter is deactivated in the presence of diminished R-wave sensing. We describe a case of IAS in the setting of extensive intra-abdominal hemorrhage.

Comparison of Preoperative ECG Screening and Device-Based Vector Analysis in Patients Receiving a Subcutaneous Implantable Cardioverter-Defibrillator

Background and Objectives: Subcutaneous implantable cardioverter-defibrillators (S-ICDs) provide protection against sudden cardiac death from outside the cardiovascular system. ECG screening is a prerequisite for implantation, but the reproducibility of its results post-operatively in the device is only partial. We aimed to compare the results of ECG screening with device-based sensing vector analysis. Materials and Methods: We screened the hospital records of all S-ICD recipients in our clinic. All of them had pre-operative ECG screening performed (primary, secondary, and alternate vectors). The results were compared with device-based vector analysis to determine the relation of the pre- and post-operative vector availability. Results: Complete ECG screening and device-based vector analysis were obtained for 103 patients. At least two acceptable vectors were found in 97.1% of the patients pre-operatively and in 96.1% post-operatively. When comparing vectors in terms of agreement (OK or FAIL) pre- and post-operatively, in 89.3% of the patients, the result for the primary vector was the same in both situations; for the secondary, it was in 84.5%, and for the alternate, it was in 74.8% of patients, respectively. In 55.3% of patients, all three vectors were labeled the same (OK or FAIL); in 37.9%, two vectors had the same result, and in 6.8%, only one vector had the same result pre- and post-operatively. The number of available vectors was the same pre- and post-operatively in 62.1% of patients, while in 15.5%, it was lower, and in 22.3% of patients, it was higher than observed during screening. Conclusions: Routine clinical pre-operative screening allowed for a good selection of candidates for S-ICD implantation. All patients had at least one vector available post-operatively. The final number of vectors available in the device-based analysis in most patients was at least the same (or higher) than during screening. The repeatability of the positive result for a single vector was high.

Inappropriate Subcutaneous Implantable Cardioverter-defibrillator Shocks-A Rare Case of Triple Counting

Sudden cardiac death (SCD) caused by ventricular tachyarrhythmias is a significant contributor to cardiovascular deaths worldwide. Implantable cardioverter-defibrillators (ICDs) have shown efficacy in preventing and reducing mortality from SCD, but traditional transvenous ICDs have inherent challenges and drawbacks, such as lead fractures, lead-associated endocarditis, and lead failure. To address these issues, subcutaneous ICDs (S-ICDs) have been developed. S-ICDs lack pacing capacity but are a valid alternative for patients at high risk for infection or with difficult venous access. Pre-implantation screening can help prevent inappropriate device shocks. We present a case in which a patient received inappropriate S-ICD therapy, which was attributed to the triple counting of P-, R-, and T-waves in a patient with sinus rhythm. This is an unusual occurrence, and, to the best of our knowledge, there are only a limited number of case reports documenting inappropriate shocks due to the oversensing of P-waves and T-waves.

Modern subcutaneous implantable defibrillator therapy in patients with cardiomyopathies and channelopathies: data from a large multicentre registry

AIMS

Patients with cardiomyopathies and channelopathies are usually younger and have a predominantly arrhythmia-related prognosis; they have nearly normal life expectancy thanks to the protection against sudden cardiac death provided by the implantable cardioverter defibrillator (ICD). The subcutaneous ICD (S-ICD) is an effective alternative to the transvenous ICD and has evolved over the years. This study aimed to evaluate the rate of inappropriate shocks (IS), appropriate therapies, and device-related complications in patients with cardiomyopathies and channelopathies who underwent modern S-ICD implantation.

METHODS AND RESULTS

We enrolled consecutive patients with cardiomyopathies and channelopathies who had undergone implantation of a modern S-ICD from January 2016 to December 2020 and who were followed up until December 2022. A total of 1338 S-ICD implantations were performed within the observation period. Of these patients, 628 had cardiomyopathies or channelopathies. The rate of IS at 12 months was 4.6% [95% confidence interval (CI): 2.8-6.9] in patients with cardiomyopathies and 1.1% (95% CI: 0.1-3.8) in patients with channelopathies (P = 0.032). No significant differences were noted over a median follow-up of 43 months [hazard ratio (HR): 0.76; 95% CI: 0.45-1.31; P = 0.351]. The rate of appropriate shocks at 12 months was 2.3% (95% CI: 1.1-4.1) in patients with cardiomyopathies and 2.1% (95% CI: 0.6-5.3) in patients with channelopathies (P = 1.0). The rate of device-related complications was 0.9% (95% CI: 0.3-2.3) and 3.2% (95% CI: 1.2-6.8), respectively (P = 0.074). No significant differences were noted over the entire follow-up. The need for pacing was low, occurring in 0.8% of patients.

CONCLUSION

Modern S-ICDs may be a valuable alternative to transvenous ICDs in patients with cardiomyopathies and channelopathies. Our findings suggest that modern S-ICD therapy carries a low rate of IS.

CLINICAL TRIAL REGISTRATION

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