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.

Perioperative Safety and Early Patient and Device Outcomes Among Subcutaneous Versus Transvenous Implantable Cardioverter Defibrillator Implantations : A Randomized, Multicenter Trial

BACKGROUND

Implantable cardioverter defibrillators (ICDs) improve survival in patients at risk for cardiac arrest, but are associated with intravascular lead-related complications. The subcutaneous ICD (S-ICD), with no intravascular components, was developed to minimize lead-related complications.

OBJECTIVE

To assess key ICD performance measures related to delivery of ICD therapy, including inappropriate ICD shocks (delivered in absence of life-threatening arrhythmia) and failed ICD shocks (which did not terminate ventricular arrhythmia).

DESIGN

Randomized, multicenter trial. (ClinicalTrials.gov: NCT02881255).

SETTING

The ATLAS trial.

PATIENTS

544 eligible patients (141 female) with a primary or secondary prevention indication for an ICD who were younger than age 60 years, had a cardiogenetic phenotype, or had prespecified risk factors for lead complications were electrocardiographically screened and 503 randomly assigned to S-ICD (251 patients) or transvenous ICD (TV-ICD) (252 patients). Mean follow-up was 2.5 years (SD, 1.1). Mean age was 49.0 years (SD, 11.5).

MEASUREMENTS

The primary outcome was perioperative major lead-related complications.

RESULTS

There was a statistically significant reduction in perioperative, lead-related complications, which occurred in 1 patient (0.4%) with an S-ICD and in 12 patients (4.8%) with TV-ICD (-4.4%; 95% CI, -6.9 to -1.9; P = 0.001). There was a trend for more inappropriate shocks with the S-ICD (hazard ratio [HR], 2.37; 95% CI, 0.98 to 5.77), but no increase in failed appropriate ICD shocks (HR, 0.61 (0.15 to 2.57). Patients in the S-ICD group had more ICD site pain, measured on a 10-point numeric rating scale, on the day of implant (4.2 ± 2.8 vs. 2.9 ± 2.2; P < 0.001) and 1 month later (1.3 ± 1.8 vs. 0.9 ± 1.5; P = 0.035).

LIMITATION

At present, the ATLAS trial is underpowered to detect differences in clinical shock outcomes; however, extended follow-up is ongoing.

CONCLUSION

The S-ICD reduces perioperative, lead-related complications without significantly compromising the effectiveness of ICD shocks, but with more early postoperative pain and a trend for more inappropriate shocks.

PRIMARY FUNDING SOURCE

Boston Scientific.

Clinical impact of ECG change on oversensing of subcutaneous implantable cardioverter-defibrillators

BACKGROUND

Inappropriate shocks delivered from subcutaneous implantable cardioverter-defibrillators (S-ICD) are most frequently caused by cardiac oversensing. However, the predictors for oversensing of S-ICD remain unclear.

OBJECTIVE

We aimed to investigate the predictors for oversensing of S-ICD, especially clinical impact of ECG change.

METHODS

We retrospectively enrolled 99 consecutive patients who underwent S-ICD implantation between 2013 and 2021. Oversensing events were defined as inappropriate charge of the capacitors induced by cardiac or noncardiac signals other than tachycardia.

RESULTS

During a median 34 month (IQR 20-50 months) of the follow-up period, 11 of the 99 patients experienced 34 oversensing events and 4 patients received inappropriate shocks during their events. Six patients exhibited ECG changes (bundle branch block, 3; ventricular pacing, 1; inverted T wave, 1; poor R progression, 1) during follow-up period. Oversensing events were observed in four of the six patients with ECG changes (67%), and three patients underwent S-ICD removal because of inevitable shock. Contrastingly, among the remaining patients without ECG change, all 7 patients who experienced oversensing events could continue using S-ICD with reprogramming sensing vector and/or restriction of excessive exercise. Logistic regression analysis showed lower voltage of Sokolow-Lyon ECG (V₁S+V₅R) was the predictor of oversensing event among the patients without ECG change. When the cut off value was 2.1mV, the sensitivity, specificity, positive predictive value, and negative predictive value were 85.7%, 62.7%, 15.7%, and 98.1%, respectively.

CONCLUSION

Unavoidable oversensing resulting in S-ICD removal is caused by ECG changes. Oversensing in patients without ECG change can be managed.

Air entrapment as a potential cause of early subcutaneous implantable cardioverter defibrillator malfunction: a systematic review of the literature

AIMS

Air entrapment (AE) has been reported as a potential cause of early inappropriate shocks (ISs) following subcutaneous implantable cardioverter defibrillator (S-ICD) implantation, but a cause-effect relationship is not always evident. This systematic review aims to analyse this phenomenon concerning implantation techniques, electrogram (EGM) features, radiologic findings, and patient management.

METHODS AND RESULTS

A systematic search was conducted using PubMed, Embase, and Google Scholar databases following the PRISMA guidelines to obtain all available literature data since 2010 on S-ICD malfunctions possibly due to AE. The final analysis included 54 patients with AE as a potential cause of S-ICD malfunction. Overall, the aggregate incidence of this condition was 1.2%. Of ICD malfunctions possibly due to AE, 93% were ISs, and 95% were recorded within the first week following implantation. Radiologic diagnosis of AE was confirmed in 28% of the entire study cohort and in 68% of patients in whom this diagnostic examination was reported. At the time of device malfunction, EGMs showed artefacts, baseline drift, and QRS voltage reduction in 95, 76, and 67% of episodes, respectively. Management included ICD reprogramming or testing, no action (observation), and invasive implant revision in 57, 33, and 10% of patients, respectively. No recurrences occurred during follow-up, irrespective of management performed.

CONCLUSIONS

Device malfunction possibly due to AE may occur in ∼1% of S-ICD recipients. Diagnosis is strongly suggested by early occurrence, characteristic EGM features, and radiologic findings. Non-invasive management, principally device reprogramming, appears to be effective in most patients.

A real‐world experience of subcutaneous and transvenous implantable cardiac defibrillators—comparison with the PRAETORIAN study

Background

Methods

Results

Conclusion

Predicting inappropriate S-ICD® episodes by simple 12-lead surface ECG parameters

AIMS

The present study aims at analyzing the role of a preimplantation 12-lead electrocardiogram (ECG) on the prediction of inappropriate S-ICD® episodes.

METHODS

N=116 screened patients (pts) with an S-ICD® and a follow-up of at least 6 months were included. A preimplantation 12-lead ECG (50 mm/s, 10 mm/mV) was analyzed with regard to QRS and T-wave amplitude, T wave concordance or discordance and QRS/T wave ratio in all 12 leads. To ensure an exact determination of parameters Datinf® Measure software was used. Results were correlated to the occurrence of oversensing of cardiac signals during follow-up.

RESULTS

N = 116 pts. (63,8% male, mean age 40,9 ± 15,5 years) were included (primary prevention in 47.4% of pts). The most frequent cardiac diseases were hypertrophic cardiomyopathy (HCM) in n = 25 (21,6%), electrical heart disease in n = 20 (17,2%), and dilated cardiomyopathy in n = 17 (14,7%). Mean follow-up was 740 ± 549 days. During follow- up n = 17 (14.7%) pts. experienced n = 27 inappropriate episodes due to T-wave oversensing. Besides HCM (OR 6.16, CI 1.79-21.15, p = 0.004) a discordance of QRS to T-wave in lead I (OR 6.5, CI 1.86-22.67, p = 0.003) was found to be a strong predictor for inappropriate shocks. In multivariate analysis the pts. with a combination of both had an 8.4-fold higher risk of misclassification of intracardiac signals (p = 0.003) with consecutive inappropriate therapy.

CONCLUSION

A discordance of QRS to T-wave in lead I turned out to be a strong predictor for future inappropriate shocks in a typical S-ICD® cohort with special impact on HCM pts.

Pitfalls of the S-ICD therapy: experiences from a large tertiary centre

Aim

The subcutaneous ICD (S-ICD) has evolved to a potential first option for many patients who have to be protected from sudden cardiac death. Many trials have underlined a similar performance regarding its effectiveness in relation to transvenous ICDs and have shown the expected benefits concerning infective endocarditis and lead failure. However, there have also been problems due to the peculiarities of the device, such as oversensing and myopotentials. In this study, we present patients from a large tertiary centre suffering from complications with an S-ICD and propose possible solutions.

Methods and results

All S-ICD patients who experienced complications related to the device (n = 40) of our large-scale single-centre S-ICD registry (n = 351 patients) were included in this study. Baseline characteristics, complications occurring and solutions to these problems were documented over a mean follow-up of 50 months. In most cases (n = 23), patients suffered from oversensing (18 cases with T wave or P wave oversensing, 5 due to myopotentials). Re-programming successfully prevented further oversensing episode in 13/23 patients. In 9 patients, generator or lead-related complications, mostly due to infectious reasons (5/9), occurred. Further problems consisted of ineffective shocks in one patient and need for antibradycardia stimulation in 2 patients and indication for CRT in 2 other patients. In total, the S-ICD had to be extracted in 10 patients. 7 of them received a tv-ICD subsequently, 3 patients refused re-implantation of any ICD. One other patient kept the ICD but had antitachycardic therapy deactivated due to inappropriate shocks for myopotential oversensing.

Conclusion

The S-ICD is a valuable option for many patients for the prevention of sudden cardiac death. Nonetheless, certain problems are immanent to the S-ICD (limited re-programming options, size of the generator) and should be addressed in future generations of the S-ICD.

Graphic abstract

Over- and undersensing-pitfalls of arrhythmia detection with implantable devices and wearables

Cardiac implantable electronic devices (CIEDs) are a cornerstone of arrhythmia and heart failure detection as well as management. In recent years new kinds of devices have emerged which can be used subcutaneously or worn on the skin. In particular for large-scale arrhythmia monitoring, small, unobtrusive gadgets seem positioned to upend paradigms and care delivery. However, the performance of CIEDs and wearables is only as good as their sensing and detection capacities. Whether for pacing, defibrillation or diagnostic monitoring, the device must be able to process and filter the sensed signal to reduce noise and to exclude irrelevant physiological signals. The demands on sensing and detection quality will differ depending on how the information is applied. With a pacemaker or implantable cardioverter/defibrillator, withheld or erroneous therapy can have severe consequences and accurate and reliable detection of cardiac function is crucial. Monitoring devices are usually used in risk assessment and management, with greater tolerance for isolated artefacts or lower quality of readings. This review discusses sensing and detection and the performance to date by CIEDs as well as subcutaneous and wearable devices.