Characteristics of ventricular tachyarrhythmias and their susceptibility to antitachycardia pacing termination in patients with ischemic and nonischemic cardiomyopathy: A patient-level meta-analysis of three large clinical trials

A Modular Communicative Leadless Pacing-Defibrillator System

BACKGROUND

The subcutaneous implantable cardioverter-defibrillator (ICD) is associated with fewer lead-related complications than a transvenous ICD; however, the subcutaneous ICD cannot provide bradycardia and antitachycardia pacing. Whether a modular pacing-defibrillator system comprising a leadless pacemaker in wireless communication with a subcutaneous ICD to provide antitachycardia and bradycardia pacing is safe remains unknown.

METHODS

We conducted a multinational, single-group study that enrolled patients at risk for sudden death from ventricular arrhythmias and followed them for 6 months after implantation of a modular pacemaker-defibrillator system. The safety end point was freedom from leadless pacemaker-related major complications, evaluated against a performance goal of 86%. The two primary performance end points were successful communication between the pacemaker and the ICD (performance goal, 88%) and a pacing threshold of up to 2.0 V at a 0.4-msec pulse width (performance goal, 80%).

RESULTS

We enrolled 293 patients, 162 of whom were in the 6-month end-point cohort and 151 of whom completed the 6-month follow-up period. The mean age of the patients was 60 years, 16.7% were women, and the mean (±SD) left ventricular ejection fraction was 33.1±12.6%. The percentage of patients who were free from leadless pacemaker-related major complications was 97.5%, which exceeded the prespecified performance goal. Wireless-device communication was successful in 98.8% of communication tests, which exceeded the prespecified goal. Of 151 patients, 147 (97.4%) had pacing thresholds of 2.0 V or less, which exceeded the prespecified goal. The percentage of episodes of arrhythmia that were successfully terminated by antitachycardia pacing was 61.3%, and there were no episodes for which antitachycardia pacing was not delivered owing to communication failure. Of 162 patients, 8 died (4.9%); none of the deaths were deemed to be related to arrhythmias or the implantation procedure.

CONCLUSIONS

The leadless pacemaker in wireless communication with a subcutaneous ICD exceeded performance goals for freedom from major complications related to the leadless pacemaker, for communication between the leadless pacemaker and subcutaneous ICD, and for the percentage of patients with a pacing threshold up to 2.0 V at a 0.4-msec pulse width at 6 months. (Funded by Boston Scientific; MODULAR ATP ClinicalTrials.gov NCT04798768.).

Decision-making regarding subcutaneous implantable cardioverter defibrillator as primary prevention in patients with low ejection fraction

BACKGROUND

Conventional transvenous implantable cardioverter-defibrillator (TV-ICD) is the standard device used for primary prevention of sudden cardiac death (SCD) in patients with reduced left ventricular ejection fraction (LVEF). Nonetheless its use is associated with lead-related complications including infection and malfunction. A subcutaneous implantable cardioverter-defibrillator (S-ICD) offers an alternative option without the need for a transvenous lead but has limitations. The decision to implant a TV-ICD or S-ICD in patients with impaired LVEF for primary prevention of SCD is controversial. Several randomised controlled trials and large observational studies have confirmed similar safety and efficacy of S-ICDs and TV-ICDs in such population.

METHODS

A literature review was conducted to compare the outcomes of subcutaneous (S-ICD) versus transvenous (TV-ICD) implantable cardioverter-defibrillators. Databases including PubMed, MEDLINE, and Cochrane were searched for relevant peer-reviewed articles. Studies were selected based on relevance and quality. Key outcomes like complication rates, efficacy, and patient survival were summarized in a comparative table.

RESULTS

Different factors that influence the choice between an TV-ICD and S-ICD for primary prevention of SCD in patients with LVEF are highlighted to guide selection of the appropriate device in different patient populations. Moreover, future perspective on the combination of SICD with leadless pacemaker, and the latest development of the extravascular implantable cardioverter defibrillator are also discussed.

CONCLUSIONS

S-ICD offers a safe and efficacious option to primary prevention in reduced ejection fraction. Future development including incorporation of leadless pacemaker will add to the arsenal of choice to protect patients from sudden cardiac death.

Multidisciplinary Critical Care Management of Electrical Storm: JACC State-of-the-Art Review

Electrical storm (ES) reflects life-threatening cardiac electrical instability with 3 or more ventricular arrhythmia episodes within 24 hours. Identification of underlying arrhythmogenic cardiac substrate and reversible triggers is essential, as is interrogation and programming of an implantable cardioverter-defibrillator, if present. Medical management includes antiarrhythmic drugs, beta-adrenergic blockade, sedation, and hemodynamic support. The initial intensity of these interventions should be matched to the severity of ES using a stepped-care algorithm involving escalating treatments for higher-risk presentations or recurrent ventricular arrhythmias. Many patients with ES are considered for catheter ablation, which may require the use of temporary mechanical circulatory support. Outcomes after ES are poor, including frequent ES recurrences and deaths caused by progressive heart failure and other cardiac causes. A multidisciplinary collaborative approach to the management of ES is crucial, and evaluation for heart transplantation or palliative care is often appropriate, even for patients who survive the initial episode.

Opportunities and drawbacks of the subcutaneous defibrillator across different clinical settings

INTRODUCTION

The subcutaneous implantable cardioverter-defibrillator (S-ICD) is an established therapy for the prevention of sudden cardiac death (SCD) and an alternative to a transvenous implantable cardioverter-defibrillator system in selected patients. Beyond randomized clinical trials, many observational studies have described the clinical performance of S-ICD across different subgroups of patients.

AREAS COVERED

Our review aimed to describe the opportunities and drawbacks of the S-ICD, focusing on their use in special populations and across different clinical settings.

EXPERT OPINION

The choice to implant S-ICD should be based on the patient's tailored approach, which takes into account the adequate S-ICD screening at rest or during stress, the infective risk, the ventricular arrhythmia susceptibility, the progressive nature of the underlying disease, the work or sports activity, and the risk of lead-related complications.

Device-Related Complications and Inappropriate Therapies Among Subcutaneous vs. Transvenous Implantable Defibrillator Recipients: Insight Monaldi Rhythm Registry

Introduction

In the context of randomized clinical trials, subcutaneous implantable cardiac defibrillators (S-ICDs) are non-inferior to transvenous ICDs (T-ICDs) concerning device-related complications or inappropriate shocks in patients with an indication for defibrillator therapy and not in need of pacing. We aimed at describing the clinical features of patients who underwent S-ICD implantation in our clinical practice, as well as the ICD-related complications and the inappropriate therapies among S-ICD vs. T-ICD recipients during a long-term follow-up.

Materials and Methods

All patients undergoing ICD, both S-ICD and TV-ICD, at Monaldi Hospital from January 1, 2015 to January 1, 2019 and followed up at our institution were included in the present analysis. The clinical variables associated with S-ICD implantation were evaluated by logistic regression analyses. We collected the ICD inappropriate therapies, ICD-related complications (including both pulse generator and lead-related complications), ICD-related infections, appropriate ICD therapies, and overall mortality. Kaplan-Meier (KM) analyses were performed to assess the risk of clinical outcome events between the two subgroups. A time-dependent Cox regression analysis was performed to adjust the results.

Results

Total 607 consecutive patients (mean age 53.8 ± 16.8, male 77.8%) with both TV-ICD (n: 290, 47.8%) and S-ICD (n: 317, 52.2%), implanted and followed at our center for a mean follow-up of 1614 ± 1018 days, were included in the study. At multivariate logistic regression analysis, an independent association between S-ICD implantation and ionic channel disease [OR: 6.01 (2.26–15.87); p < 0.0001] and ischemic cardiomyopathy [OR: 0.20 (0.12–0.35); p < 0.0001] was shown. The KM analysis did not show a significantly different risk of the inappropriate ICD therapies (log rank p = 0.64) between the two subgroups; conversely, a significant increase in the risk of ICD-related complications (log rank p = 0.02) and infections (log rank p = 0.02) in TV-ICD group was shown. The adjusted risk for ICD-related infections [OR: 0.07 (0.009–0.55), p = 0.01] and complications [0.31 (0.12–0.81), p = 0.01] was significantly lower among patients with S-ICD.

Conclusions

The choice to implant S-ICD was mainly driven by younger age and the presence of ionic channel disease; conversely ischemic cardiomyopathy reduces the probability to use this technology. No significant differences in inappropriate ICD therapies were shown among S-ICD vs. TV-ICD group; moreover, S-ICD is characterized by a lower rate of infectious and non-infectious complications leading to surgical revision or extraction.

Cycle length of nonsustanied ventricular tachycardias among ICD patients: implications on subsequent appropriate therapies

Background

ICD patients with episodes of nonsustained ventricular tachycardias (NSVT) are at risk of appropriate therapies. However, the relationship between the cycle length (CL) of such NSVTs and the subsequent incidence of appropriate interventions is unknown.

Methods

416 ICD patients with LVEF < 45% were studied. ICD programming was standardized. NSVT was defined as any VT of 5 or more beats at ≥ 150 bpm occurred in the first 6 months after implantation that terminated spontaneously and was not preceded by any appropriate therapy. The mean follow-up was 41 ± 27 months.

Results

We analyzed 2201 NSVTs (mean CL = 323 ms) that occurred in 250 patients; 111 of such episodes were fast (CL ≤ 300 ms). Secondary prevention (HR = 1.7; p < 0.001), number of NSVT episodes (HR = 1.05; 95% CI 1.04–1.07; p < 0.001) and beta-blocker treatment (HR = 0.7; p = 0.04) were independent predictors of appropriate interventions; however, the mean CL of NSVTs was not (p = 0.6). There was a correlation between the mean CL of NSVTs and the CL of the first monomorphic VT: r = 0.88; p < 0.001. This correlation was especially robust in individuals with > 5 NSVTs (r = 0.97; p < 0.001), with an agreement between both values greater than 95%. Patients with any fast NSVT experienced a higher incidence of VF episodes (26%) compared to those without NVSTs (3%) or with only slow NSVTs (7%); p < 0.001.

Conclusions

Unlike the burden, the CL of NSVTs is not a predictor of subsequent appropriate interventions. However, there is a close relationship between the CL of NSVTs and that of arrhythmias that will later lead to appropriate therapies.