Efficacy and Complications of Subcutaneous versus Conventional Cardioverter Defibrillators: A Systematic Review and Meta-Analysis

Background/Objectives: Implantable cardioverter defibrillators are used to prevent sudden cardiac death. The subcutaneous implantable cardioverter defibrillator was newly developed to overcome the limitations of the conventional implantable cardioverter defibrillator-transvenous device. The subcutaneous implantable cardioverter defibrillator is indicated for young patients with heart disease, congenital heart defects, and poor venous access, who have an indication for implantable cardioverter defibrillator without the need for anti-bradycardic stimulation. We aimed to compare the efficacy and complications of subcutaneous with transvenous implantable cardioverter defibrillator devices. Methodology: A systematic review was conducted using different databases. The inclusion criteria were observational and clinical randomized trials with no language limits and no publication date limit that compared subcutaneous with transvenous implantable cardioverter defibrillators. The selected patients were aged > 18 years with complex ventricular arrhythmia. Results : Five studies involving 2111 patients who underwent implantable cardioverter defibrillator implantation were included. The most frequent complication in the subcutaneous device group was infection, followed by hematoma formation and electrode migration. For the transvenous device, the most frequent complications were electrode migration and infection. Regarding efficacy, the total rates of appropriate shocks were 9.04% and 20.47% in the subcutaneous and transvenous device groups, respectively, whereas inappropriate shocks to the subcutaneous and transvenous device groups were 11,3% and 10,7%, respectively. Conclusion: When compared to the transvenous device, the subcutaneous device had lower complication rates owing to lead migration and less inappropriate shocks due to supraventricular tachycardia; nevertheless, infection rates and improper shocks due to T wave oversensing were comparable for both devices

537 Oversensing due to micro-air bubbles leading to inappropriate shocks in patient with subcutaneous implantable cardioverter defibrillator

Aims Subcutaneous air has been reported as uncommon cause of early device malfunction after implantation of subcutaneous implantable cardioverter defibrillator (S-ICD). Methods and results A 43-year-old man was admitted to our hospital due to syncopal episodes. During a brain computed tomography (CT), he was resuscitated from cardiac arrest due to ventricular fibrillation. Further investigations excluded ischaemic heart disease and cardiac magnetic resonance showed signs of prior myocarditis. After successful screening, an S-ICD was inserted for secondary prevention using the standard technique. The chest X-ray excluded acute post-procedural complications. Three days after implantation, he experienced two inappropriate shocks while conscious. Device interrogation revealed frequent high-amplitude signals followed by two shocks (Figure 1A and B) that could be interpreted as oversensing. During provocative maneuvers on the generator case, minimal and intermittent noise only on the secondary sensing vector was observed. Lateral and antero-posterior chest X-ray excluded subcutaneous air. However, the general agreement based on previous reports was that oversensing as observed in Figures 1A and B was typical for noise due to micro-air bubbles in the connection between the lead and the generator case. As a consequence, the sensing vector was successfully changed and no other inappropriate shocks were observed during follow-up. Conclusions Entrapped micro-air bubbles in the connection between the leads and the generator case can cause inappropriate shocks in the early period after S-ICD implantation. Timely recognition of this complication is important to prevent inappropriate shocks. It can occur shortly after the procedure even if the intra-procedural parameters were normal and chest X-ray excluded acute complications. As demonstrated in our case, the device can be reprogrammed using another sensing vector to solve these oversensing problems.

Abstract 9764: Prevalence of Inappropriate Defibrillation Attempts During Pediatric In-Hospital Cardiac Arrest

Introduction: Shockable rhythms (ventricular fibrillation [VF] and ventricular tachycardia [VT]) occur in <25% of pediatric in-hospital cardiac arrest (IHCA) events, yet the prevalence of inappropriate defibrillation attempts for non-VF/VT rhythms is unknown. We aim to describe the prevalence of inappropriate shocks across a large, multi-national pediatric cardiac arrest network. Methods: We included children <18y reported to the pedi atric RES uscitation- Q uality (pediRES-Q) network from 2015-2019 with complete defibrillator files who received defibrillation attempts during IHCA (ZOLL R-Series, MA). Two pediatric cardiologists independently classified rhythms immediately prior to shock as: 1) appropriate (VF or wide complex ≥ 150/min), 2) indeterminate (narrow complex ≥150/min or wide complex 100-149/min), or 3) inappropriate (asystole, sinus, narrow complex <150/min, or wide complex <100/min). Rhythms that were undecipherable due to artifact were excluded from analysis (n=22). Disagreements were resolved by arbitration and consensus. Results: Of 896 IHCA events, 124 (14%) had defibrillation attempts. A total of 303 shocks were delivered: 87 (29%) in age <1y, 84 (28%) in 1-8y, and 132 (44%) in 9-17y. Of shocks delivered, 206 (68%) were appropriate, 12 (4%) indeterminate, and 85 (28%) inappropriate. There was no difference in inappropriate shock delivery by age category: <1y (24/87, 28%), 1-8y (26/84, 31%), 9-17y (35/132, 27%) ( p =0.4). Conclusions: Across a multi-national pediatric cardiac arrest network, a large proportion (28%) of defibrillation attempts were inappropriate, suggesting significant opportunity for improvement in rhythm identification in pediatric cardiac arrest. There was no difference in inappropriate shock delivery across age groups. Figure 1. Representation of rhythm classification and appropriateness of defibrillation attempts with exemplar rhythms.

Inappropriate shocks from a transvenous implantable defibrillator caused by atrial fibrillation and a missed atrial septal defect in a patient with a modified Bentall procedure

Background Inappropriate shocks have been reported in approximately 1/3 of patients with implantable cardiac defibrillators (ICDs). We report an unusual case of inappropriate ICD shocks due to atrial fibrillation (AF) caused by a missed atrial septal defect (ASD) in a patient with a modified Bentall procedure. Case summary A 67-year-old Caucasian male, with an ICD and a history of a modified Bentall procedure 24 years ago, reported to our outpatient clinic with recurrent inappropriate ICD shocks due to episodes of fast AF. The transthoracic echocardiographic exam revealed 2 large aneurysms at the ostia of the coronary arteries. We performed further evaluation with transesophageal echocardiogram (TOE) and computed tomography (CT) angiography. The aneurysms measured on CT were 3.14*2.29 cm on the right ostium and 1.9*0.99 cm on the left. A large secundum-type atrial septal defect (ASD) of 1.5 cm was revealed that was missed in all previous echocardiographic studies. The therapeutic options of surgical closure of the ASD and repair of the aneurysms or a more conservative approach with percutaneous closure of the ASD and closer follow-up were discussed with the patient. The patient declined the surgical option due to high complication risk, and closure of the ASD with an Amplatzer device was performed 3 months later. A 3 -year Follow-up was uneventful. Conclusion It is of major importance to comprehensively and thoroughly assess patients before and after a surgical intervention to not miss other treatable conditions preoperatively and complications in the postoperative period.

Incidence and Clinical Management of Atrial Arrhythmias in Patients with Catecholaminergic Polymorphic Ventricular Tachycardia

Background: Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a genetic arrhythmia syndrome characterized by adrenergically-triggered ventricular arrhythmias, syncope, and sudden cardiac death. Several small studies suggest that atrial arrhythmias (AAs) are common in patients with CPVT. Objective: To determine the incidence and type of AAs observed within a large, single-center cohort of CPVT cases as well as the efficacy and durability of AA-directed management. Methods: In this retrospective study, the electronic medical record of 129 patients (52% female; average age at diagnosis 20.8  15.3 years) with CPVT (95% with a putative CPVT1-causative RYR2 variant) between 01/2000 and 09/2019 were reviewed for electrocardiographic evidence of AAs. Clinical features and efficacy of pharmacologic and ablation therapy were assessed. Results: Overall, 10/129 (7.8%) CPVT patients, all RYR2 variant-positive, had evidence of an AA (atrial fibrillation/flutter in 6, atrial tachycardia in 3, and supraventricular tachycardia in 1). The median age at AA diagnosis was 23 (14.2-35.5) years. 8/10 of patients experienced symptoms attributed to their AA, including inappropriate shocks. All patients were trialed on anti-arrhythmics, including -blockers, and/or flecainide. Owing to drug failure (1/10), drug intolerance (1/10), or patient preference (2/10); 4/10 patients received an ablation. Over a median follow-up of 23.5 (4.5-63) months, no AA recurrences were observed. Conclusion: Compared to prior studies, the incidence of AAs in this large, single-center referral cohort of CPVT patients was substantially lower (7.8% vs. 26%-35%). Although larger multi-center studies are needed to confirm, this study suggests that ablation is efficacious and durable in CPVT-associated AAs.

High Incidence of Inappropriate Alarms in Patients with Wearable Cardioverter-Defibrillators: Findings from the Swiss WCD Registry

Background: The wearable cardioverter defibrillator (WCD) uses surface electrodes to detect arrhythmia before initiating a treatment sequence. However, it is also prone to inappropriate detection due to artefacts. Objective: The aim of this study is to assess the alarm burden in patients and its impact on clinical outcomes. Methods: Patients from the nationwide Swiss WCD Registry were included. Clinical characteristics and data were obtained from the WCDs. Arrhythmia recordings ≥30 s in length were analysed and categorized as VT/VF, atrial fibrillation (AF), supraventricular tachycardia (SVT) or artefact. Results: A total of 10653 device alarms were documented in 324 of 456 patients (71.1%) over a mean WCD wear-time of 2.0 ± 1.6 months. Episode duration was 30 s or more in 2996 alarms (28.2%). One hundred and eleven (3.7%) were VT/VF episodes. The remaining recordings were inappropriate detections (2736 (91%) due to artefacts; 117 (3.7%) AF; 48 (1.6%) SVT). Two-hundred and seven patients (45%) had three or more alarms per month. Obesity was significantly associated with three or more alarms per month (p = 0.01, 27.7% vs. 15.9%). High alarm burden was not associated with a lower average daily wear time (20.8 h vs. 20.7 h, p = 0.785) or a decreased implantable cardioverter defibrillator implantation rate after stopping WCD use (48% vs. 47.3%, p = 0.156). Conclusions: In patients using WCDs, alarms emitted by the device and impending inappropriate shocks were frequent and most commonly caused by artefacts. A high alarm burden was associated with obesity but did not lead to a decreased adherence.