Electrocardiographic Eligibility for Subcutaneous Implantable Cardioverter Defibrillator: Evaluation during Bicycle Exercise

Subcutaneous Implantable Cardioverter Defibrillators in Pediatrics and Congenital Heart Disease

Subcutaneous implantable cardioverter defibrillators (S-ICDs) are being used with increased frequency in children and patients with congenital heart disease. Vascular access complexities, intracardiac shunts, and specific anatomies make these devices particularly appealing for some of these patients. Alternative screening, implantation, and programming techniques should be considered based on patient size, body habitus, anatomy, procedural history, and preference. Appropriate and inappropriate shock rates are generally comparable to those seen with transvenous devices. Complications such as infection can occur, although their severity is likely to be less than that seen with transvenous devices. Technical advances are likely to further broaden S-ICD applicability.

Subcutaneous Implantable Cardioverter Defibrillator: A Contemporary Overview

The difference between subcutaneous implantable cardioverter defibrillators (S-ICDs) and transvenous ICDs (TV-ICDs) concerns a whole extra thoracic implantation, including a defibrillator coil and pulse generator, without endovascular components. The improved safety profile has allowed the S-ICD to be rapidly taken up, especially among younger patients. Reports of its role in different cardiac diseases at high risk of SCD such as hypertrophic and arrhythmic cardiomyopathies, as well as channelopathies, is increasing. S-ICDs show comparable efficacy, reliability, and safety outcomes compared to TV-ICD. However, some technical issues (i.e., the inability to perform anti-bradycardia pacing) strongly limit the employment of S-ICDs. Therefore, it still remains only an alternative to the traditional ICD thus far. This review aims to provide a contemporary overview of the role of S-ICDs compared to TV-ICDs in clinical practice, including technical aspects regarding device manufacture and implantation techniques. Newer outlooks and future perspectives of S-ICDs are also brought up to date.

Use of an exercise test to enhance sensing vector assessment and prevent inadequate subcutaneous implantable cardioverter-defibrillator discharges

Subcutaneous implantable cardioverter-defibrillators are a modern alternative to classic cardioverter-defibrillators. Prior to implantation of the device, qualification based on assessment of the heart's specific rhythm shape during a resting electrocardiogram examination must be performed. In the presented case, a patient with a subcutaneous implantable cardioverter-defibrillator experienced numerous discharges during exercise. An exercise test was performed, which revealed a bundle branch block that appeared during exercise. The wide QRS complex was double- or triple-counted by the device, resulting in an inaccurate heart rate estimation and multiple discharges. Optimising the sensing vectors during exercise solved this problem.

Predictors of inappropriate shock in Brugada syndrome patients with a subcutaneous implantable cardiac defibrillator

BACKGROUND

Subcutaneous implantable cardioverter defibrillators (S-ICDs) avoid complications secondary to transvenous leads, but inappropriate shocks (ISs) are frequent. Furthermore, IS data from patients with Brugada syndrome (BrS) with an S-ICD are scarce.

OBJECTIVE

We aimed to establish the frequency and predictors of IS in this population.

METHODS

We analyzed the clinical and electrocardiographic characteristics, automated screening test data, device programming, and IS occurrence in adult patients with BrS with an S-ICD.

RESULTS

Thirty-nine patients were enrolled (69% male, mean age at diagnosis 46 ± 13 years, mean age at implantation 48 ± 13 years). During a mean follow-up of 26 ± 21 months, 18% patients experienced IS. Patients with IS were younger at the time of diagnosis (36 ± 8 vs. 48 ± 13 years, p = .018) and S-ICD implantation (38 ± 9 vs. 50 ± 23 years, p = .019) and presented with spontaneous type 1 Brugada electrocardiogram pattern more frequently at diagnosis or during follow-up (71% vs. 25%, p = .018). During automated screening tests, patients with IS showed lower QRS voltage in the primary vector in the supine position (0.58 ± 0.26 vs. 1.10 ± 0.35 mV, p = .011) and lower defibrillator automated screening score in the primary vector in the supine (123 ± 165 vs. 554 ± 390 mV, p = .005) and standing (162 ± 179 vs. 486 ± 388 mV, p = .038) positions. Age at diagnosis was the only independent predictor of IS (hazard ratio = 0.873, 95% confidence interval: 0.767-0.992, p = .037).

CONCLUSION

IS was a frequent complication in patients with BrS with an S-ICD. Younger age was independently associated with IS. A more thorough screening process might help prevent IS in this population.

A Historical Perspective of Cardiac Implantable Electronic Device Infection: How a Menace Can Drive Technological and Clinical Improvement

In recent decades there has been a relevant increase in the implantation rate of cardiac implantable electronic devices (CIEDs), albeit with relevant geographical inhomogeneities. Despite the positive impact on clinical outcomes, the possibility of major complications is not negligible, particularly with respect to CIED infections. CIED infections significantly affect morbidity and mortality, especially in instances of delayed diagnosis and appropriate treatment. In the present review, we will start to depict the factors underlying the development of CIED infection as well as the difficulties related to its diagnosis and treatment. We will explain the reasons underlying the need to focus on prophylaxis rather than treatment, in view of the poor outcomes despite improvements in lead extraction procedures. This will lead to the consideration of management of this complication in a hub-spoke manner, and to our analysis of the several technological and procedural improvements developed to minimize this complication. These include prolongation of CIED longevity, the development of leadless devices, and integrated prophylactic approaches. We will conclude with a discussion regarding new devices and strategies under development. This complete excursus will provide the reader with a new perspective on how a major complication can drive technological improvements.

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.

Shoulder Function After Cardioverter-Defibrillator Implantation: 5-Year Follow-up

BACKGROUND

Implantable cardioverter-defibrillator (ICD) represents the main tool for prevention of sudden cardiac death. Different kinds of postimplant complications have been described; however, little is known about shoulder functional impairment and its impact on quality of life.

METHODS

Patients with standard indications for elective prepectoral subcutaneous ICD insertion were enrolled during a 1-year period. The impact of ICD implantation on shoulder motility, pain, general disability, and quality of life was evaluated prospectively at baseline, and after 2 weeks, 3 months, 1 year, and 5 years using the Constant score, the Numeric Pain Rating Scale, the Disabilities of the Arm, Shoulder, and Hand scale, and the Short Form-36 Health Survey questionnaire.

RESULTS

A total of 50 patients underwent insertion of single, dual chamber, or biventricular ICDs. Two weeks after implantation, functional impairment and mild pain were observed in ipsilateral shoulder movements, with a reduction in the Short Form-36 Health Survey score. Shoulder functional impairment improved at the third-month evaluations, with almost normalization at 1-year and 5-year assessments, as well as pain and quality of life.

CONCLUSIONS

Prepectoral subcutaneous ICD implantation may be associated with ipsilateral shoulder functional impairment that regresses partially after 3 months and completely at 1-year and 5-year assessments. The less invasive implantation technique and the relatively small size of modern ICDs, independently from types and volumes, may be relevant to the degree of postimplantation shoulder functional impairment and recovery time. Shoulder function should be assessed at routine checks, especially soon after ICD implantation because of potential functional impairment and subsequent impact on quality of life.

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.