Sensitivity and specificity of the subcutaneous implantable cardioverter defibrillator pre-implant screening tool

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.

Changes in eligibility for a subcutaneous cardioverter-defibrillator after implantation of a left ventricular assist device-A prospective analysis

BACKGROUND

The number of left ventricular assist devices (LVADs) implanted in patients with end-stage heart failure is increasing. In this patient cohort, subcutaneous implantable cardioverter defibrillators (S-ICDs) could be a promising alternative to transvenous ICDs due to lower infection rates and avoidance of venous access. However, eligibility for the S-ICD depends on ECG features that may be influenced by an LVAD. The aim of the present study was a prospective evaluation of S-ICD eligibility before and after LVAD implantation.

METHODS

The study recruited all patients presenting at Hannover Medical School for LVAD implantation between 2016 and 2020. S-ICD eligibility was evaluated using the ECG-based and the device-based S-ICD screening test before and after LVAD implantation.

RESULTS

Twenty-two patients (57.3 ± 8.7 years of age, 95.5% male) were included in the analysis. The most common underlying diseases were dilated cardiomyopathy (n = 16, 72.7%) and ischemic cardiomyopathy (n = 5, 22.7%). Before LVAD implantation 16 patients were found eligible for the S-ICD according to both screening tests (72.7%), but only 7 patients were eligible after LVAD, 31.8%; p = 0.05). Oversensing due to electromagnetic interference was observed in 6 patients (66.6%) found ineligible for S-ICD after LVAD implantation. A lower S wave amplitude in leads I (p = 0.009), II (p = 0.006) and aVF (p = 0.006) before LVAD implantation was associated with higher rate of S-ICD ineligibility after LVAD implantation.

CONCLUSION

LVAD implantation can impair S-ICD eligibility. Patients with lower S wave amplitude in leads I, II and aVF were more likely to be ineligible for S-ICD implantation after LVAD implantation. Thus, S-ICD therapy should be carefully considered in patients who are candidates for LVAD therapy.

Impact of SMART Pass filter in patients with ajmaline-induced Brugada syndrome and subcutaneous implantable cardioverter-defibrillator eligibility failure: results from a prospective multicentre study

AIMS

Ajmaline challenge can unmask subcutaneous implantable cardioverter-defibrillator (S-ICD) screening failure in patients with Brugada syndrome (BrS) and non-diagnostic baseline electrocardiogram (ECG). The efficacy of the SMART Pass (SP) filter, a high-pass filter designed to reduce cardiac oversensing (while maintaining an appropriate sensing margin), has not yet been assessed in patients with BrS. The aim of this prospective multicentre study was to investigate the effect of the SP filter on dynamic Brugada ECG changes evoked by ajmaline and to assess its value in reducing S-ICD screening failure in patients with drug-induced Brugada ECGs.

METHODS AND RESULTS

The S-ICD screening with conventional automated screening tool (AST) was performed during ajmaline challenge in subjects with suspected BrS. The S-ICD recordings were obtained before, during and after ajmaline administration and evaluated by the means of a simulation model that emulates the AST behaviour with and without SP filter. A patient was considered suitable for S-ICD if at least one sensing vector was acceptable in all tested postures. A sensing vector was considered acceptable in the presence of QRS amplitude >0.5 mV, QRS/T-wave ratio >3.5, and sense vector score >100. Of the 126 subjects (mean age: 42 ± 14 years, males: 61%, sensing vectors: 6786), 46 (36%) presented with an ajmaline-induced Brugada type 1 ECG. Up to 30% of subjects and 40% of vectors failed the screening during the appearance of Brugada type 1 ECG evoked by ajmaline. The S-ICD screening failure rate was not significantly reduced in patients with Brugada ECGs when SP filter was enabled (30% vs. 24%). Similarly, there was only a trend in reduction of vector-failure rate attributable to the SP filter (from 40% to 36%). The most frequent reason for screening failure was low QRS amplitude or low QRS/T-wave ratio. None of these patients was implanted with an S-ICD.

CONCLUSION

Patients who pass the sensing screening during ajmaline can be considered good candidates for S-ICD implantation, while those who fail might be susceptible to sensing issues. Although there was a trend towards reduction of vector sensing failure rate when SP filter was enabled, the reduction in S-ICD screening failure in patients with Brugada ECGs did not reach statistical significance.

CLINICAL TRIAL REGISTRATION

https://clinicaltrials.gov Unique Identifier NCT04504591.

Association Between Subcutaneous Implantable Cardioverter Defibrillator Preimplantation Screening and the Response to Cardiac Resynchronization Therapy

Background and Objectives

Preimplantation QRS-T morphology screening (TMS) is a composite tool for selecting subcutaneous implantable cardioverter defibrillator (S-ICD) candidates. However, its role in predicting the patient's response to cardiac resynchronization therapy (CRT) is uncertain.

Methods

A total of 55 consecutive de novo CRT candidates were enrolled between January 2016 and March 2017. Electrocardiogram (ECG) and TMS were performed before and soon after implantation. The ECG parameters were recorded, including QRS duration and morphology (such as ΔQRS_Index, QTc during biventricular pacing mode [BiV pacing QTc], and QRS/T ratio during biventricular pacing mode [BiV pacing QRS/T ratio]). TMS monitored three sensory vectors of the S-ICD. Six months after implantation, the responses to CRT were evaluated.

Results

Thirty-nine patients (70.9%) passed the TMS during biventricular pacing mode. At the six-month follow-up, the number of responders and super-responders was significantly higher in the passing group than in the non-passing group (responders: 31/39 [79.5%] vs. 5/16 [31.3%], p<0.001; super-responders: 9/39 [23.1%] vs. 1/16 [6.3%], p=0.020). The super-response rate was higher among patients who passed all three vectors than among those who passed 1 or 2 vectors (3 vs. 2 vectors, p=0.018; 3 vs. 1 vector, p=0.003). A smaller left atrial diameter, vectors that passed TMS during biventricular pacing mode, and larger ΔQRS_Index values were independently associated with good CRT response.

Conclusions

Our study demonstrated that patients on CRT who pass the TMS during biventricular pacing mode are more likely to respond and super-respond to CRT.

A novel screening tool to unmask potential interference between S-ICD and left ventricular assist device

INTRODUCTION

In patients with a left ventricular assist device (LVAD), the subcutaneous implantable cardioverter-defibrillator (S-ICD) can be an alternative to transvenous ICD systems due to reduced risk of systemic infection, which could lead to extraction of the ICD as well as the LVAD. S-ICD eligibility is lower in patients with LVAD than in patients with end-stage heart failure without LVAD. Several reports have shown inappropriate S-ICD therapy in the coexistence of LVAD and S-ICD. The aim of the present study was to evaluate S-ICD eligibility in patients with LVAD using the established electrocardiogram (ECG)-based screening test as well as a novel device-based screening test to identify potentially inappropriate S-ICD sensing in this specific patient cohort.

METHODS AND RESULTS

The present study included 115 patients implanted with an LVAD. The standard ECG-based screening test and a novel device-based screening test were performed in all patients. Eighty patients (70%) were eligible for S-ICD therapy with the standard ECG-based screening test. Performance of the novel device-based screening test identified device-device interference in 14 of these 80 patients (12%).

CONCLUSION

Using a novel extended device-based S-ICD screening method, a small number of patients with LVAD deemed eligible for S-ICD with the standard ECG-based screening test exhibit device-device interference. Careful S-ICD screening should be performed in patients with LVAD, who are candidates for S-ICD therapy, to prevent inappropriate sensing or ICD therapy.

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).

Evaluation of a novel automatic screening tool for determining eligibility for a subcutaneous implantable cardioverter-defibrillator

BACKGROUND

The manufacturer has developed a new ECG screening tool to determine eligibility for the subcutaneous ICD (S-ICD), the "automatic screening tool" (AST), which may render manual ECG-screening unnecessary. The aim of the study was to determine the eligibility for the S-ICD using two methods (manual ECG-screening versus AST) in different patient categories including patients with cardiomyopathy, congenital heart disease and inherited primary arrhythmia syndrome.

METHODS

We prospectively evaluated the ECG suitability for an S-ICD in consecutive patients at our outpatient clinic between February and June 2017. The primary endpoint of the study was ECG eligibility defined as at least 1 successful vector in both supine and sitting postures.

RESULTS

A total of 254 patients (167 men; mean age 45 ± 16 years) were screened using both methods. Overall, there was a high ECG eligibility using either method (93% versus 92%, P = 0.45). Overall agreement between both methods was 94%. Patients with hypertrophic cardiomyopathy (HCM) more often had a failed screening test using either test in comparison to the patients without HCM (manual: odds ratio [OR] 3.3, 95% confidence interval [CI] 1.2-9.3, P = 0.02; AST: OR 3.0, 95% CI 1.2-7.6, P = 0.02).

CONCLUSION

AST showed a high agreement with manual ECG-screening for S-ICD. Overall there was a high ECG eligibility for S-ICD, although patients with HCM had a lower passing rate irrespective of the screening method.

Subcutaneous ICD screening with the Boston Scientific ZOOM programmer versus a 12-lead ECG machine

BACKGROUND

The subcutaneous implantable cardioverter-defibrillator (S-ICD) requires preimplant screening to ensure appropriate sensing and reduce risk of inappropriate shocks. Screening can be performed using either an ICD programmer or a 12-lead electrocardiogram (ECG) machine. It is unclear whether differences in signal filtering and digital sampling change the screening success rate.

METHODS

Subjects were recruited if they had a transvenous single-lead ICD without pacing requirements or were candidates for a new ICD. Screening was performed using both a Boston Scientific ZOOM programmer (Marlborough, MA, USA) and General Electric MAC 5000 ECG machine (Fairfield, CT, USA). A pass was defined as having at least one lead that fit within the screening template in both supine and sitting positions.

RESULTS

A total of 69 subjects were included and 27 sets of ECG leads had differing screening results between the two machines (7%). Of these sets, 22 (81%) passed using the ECG machine but failed using the programmer and five (19%) passed using the ECG machine but failed using the programmer (P < 0.001). Four subjects (6%) passed screening using the ECG machine but failed using the programmer. No subject passed screening with the programmer but failed with the ECG machine.

CONCLUSION

There can be occasional disagreement in S-ICD patient screening between an ICD programmer and ECG machine, all of whom passed with the ECG machine but failed using the programmer. On a per lead basis, the ECG machine passes more subjects. It is unknown what the inappropriate shock rate would be if an S-ICD was implanted. Clinical judgment should be used in borderline cases.

Analysis of Screening Electrocardiogram for the Subcutaneous Defibrillator in Adults with Congenital Heart Disease

Candidates for the subcutaneous implantable cardioverter-defibrillator (S-ICD) are screened using an electrocardiogram (S-ECG) tool to measure appropriate detection. We sought to define the S-ICD candidacy of congenital heart disease patients using the S-ECG tool. We also analyzed the reliability of the (S-ECG) tool between measurers in this population. Patients above the age of 12 and with a diagnosis associated with either a higher incidence of cardiac arrest or vascular access challenges were asked to undergo screening. S-ECGs were then analyzed by a pediatric electrophysiologist, an S-ICD device engineer, and an S-ICD clinical representative for candidacy. Results were compared for interobserver variability and S-ECGs were analyzed by t test to determine variables that differ among passing and failing leads. Thirty-one patients underwent screening. Two of the 31 (6.5%) patients failed S-ICD screening. Analysis of the screening leads demonstrated the highest passing rates using lead III at a 5 mm/mV amplitude setting with 71 and 62% pass rate in the supine and standing positions, respectively. Interobserver analysis correlated well among the three measurers. There was a higher amplitude difference between QRS and T waves among passing versus failing S-ECG. Congenital heart disease patients have acceptable passage rates utilizing the S-ECG algorithm. Interobserver measurements were well correlated and these data suggest that the proximal coil to device (lead III) vector would be best utilized in this patient population. A larger difference between QRS and T wave amplitudes was associated with a higher S-ECG passing rate.

Successful intermuscular implantation of subcutaneous implantable cardioverter defibrillator in a Japanese patient with pectus excavatum

The entirely subcutaneous implantable cardioverter-defibrillator (ICD) system was developed to provide a life-saving defibrillation therapy that does not affect the heart and vasculature. The subcutaneous ICD is preferred over the transvenous ICD for patients with a history of recurrent infection presenting major life-threatening rhythms. In this case report, we describe the first successful intermuscular implantation of a completely subcutaneous ICD in a Japanese patient with pectus excavatum. There were no associated complications with the device implantation or lead positioning. Further, the defibrillation threshold testing did not pose any problem with the abnormal anatomy of the patient.

Subcutaneous implantable cardioverter defibrillators in children, young adults and patients with congenital heart disease

The demonstration of severe complications in patients implanted with a transvenous implantable cardioverter defibrillator (ICD) has led to the development of devices equipped with a subcutaneous lead. This new technique offers numerous advantages but also certain disadvantages. Various studies or anecdotal clinical cases have specifically been conducted with this subcutaneous defibrillation system in children and/or patients with congenital heart disease. Results of these studies suggest: 1) a high feasibility despite being limited by a selection process that excludes patients requiring permanent pacing and patients declared ineligible during pre-screening; 2) good efficacy of electrical shocks in reducing induced or spontaneous ventricular arrhythmias; 3) in this specific subset of patients, 2 types of complications have been particularly described: a risk of device exteriorization and infection, and a large number of inappropriate therapies primarily related to T-wave oversensing. The subcutaneous ICD could therefore constitute the gold standard for patients with complex congenital heart disease with no venous access to the heart or with a persistent shunt increasing the risk of systemic emboli as well as in young patients with channelopathy or hypertrophic cardiomyopathy not requiring long-term pacing. Technological change (reduction in device size, better differentiation between R- and T-waves, possibility of pacing if device coupled with a leadless pacemaker) could reduce the limitations and complications and thereby increase the indications in this sub-group of patients.