Safety and Efficacy of a Totally Subcutaneous Implantable-Cardioverter Defibrillator

Abstract

F irst introduced to clinical practice in 1980,1 the implantable cardioverter-defibrillator (ICD) improves survival in patients at high risk for sudden cardiac death. [2][3][4][5] Randomized, multicenter studies have shown a relative risk reduction in total mortality of up to 54% and an arrhythmic mortality reduction of 50% to 70%. Offsetting this mortality benefit, however, are significant acute and chronic morbidities associated with the use of transvenous leads.6-9 Procedure-related transvenous lead complications include major events such as lead dislodgement, pneumothorax, cardiac perforation, pericardial effusion, and cardiac tamponade. Chronic transvenous lead complications include systemic infections as well as insulation breaches and conductor coil breaks, which can cause inappropriate shocks and physical trauma to the heart and may render ICD therapy unavailable. The lead is the most common failure mechanism for a transvenous ICD system, and patients often outlive the useful life of the lead. 9-11 Editorial see p 938 Clinical Perspective on p 953The long-term complications associated with the transvenous ICD leads have been a rationale to develop a totally subcutaneous ICD (S-ICD). The S-ICD System (Cameron Health/Boston Scientific) senses, detects, and treats malignant ventricular tachycardia (VT)/ventricular fibrillation (VF) but leaves the heart and vasculature untouched. The subcutaneous pulse generator and electrode are placed extrathoracically, and no part of the system is exposed to most of the risks associated Background-The most frequent complications associated with implantable cardioverter-defibrillators (ICDs) involve the transvenous leads. A subcutaneous implantable cardioverter-defibrillator (S-ICD) has been developed as an alternative system. This study evaluated the safety and effectiveness of the S-ICD System (Cameron Health/Boston Scientific) for the treatment of life-threatening ventricular arrhythmias (ventricular tachycardia/ventricular fibrillation). Methods and Results-This prospective, nonrandomized, multicenter trial included adult patients with a standard indication for an ICD, who neither required pacing nor had documented pace-terminable ventricular tachycardia. The primary safety end point was the 180-day S-ICD System complication-free rate compared with a prespecified performance goal of 79%. The primary effectiveness end point was the induced ventricular fibrillation conversion rate compared with a prespecified performance goal of 88%, with success defined as 2 consecutive ventricular fibrillation conversions of 4 attempts. Detection and conversion of spontaneous episodes were also evaluated. Device implantation was attempted in 321 of 330 enrolled patients, and 314 patients underwent successful implantation. The cohort was followed for a mean duration of 11 months. The study population was 74% male with a mean age of 52±16 years and mean left ventricular ejection fraction of 36±16%. A previous transvenous ICD had been implanted in 13%. Both primary end points were met: Th...

2015 HRS/EHRA/APHRS/SOLAECE expert consensus statement on optimal implantable cardioverter-defibrillator programming and testing

“…The minimum CL for SVT-VT discrimination should be set to prevent clinically significant delays in the detection of hemodynamically unstable VT. PREPARE, EMPIRIC, and MADIT-RIT all support the safety of empirical programming at 200 bpm [96,101,134]. In MADIT-II, approximately 50% of SVT episodes were faster than 170 bpm, and a few were as fast as 250 bpm [82] In INTRINSIC RV, SVT comprised 19% of episodes, with rates between 200 and 250 bpm [135].…”

“…In the single-zone configuration, shocks are delivered for detected heart rates above the programmed rate threshold: the "shock zone" [134]. In the dual-zone configuration, arrhythmia discrimination algorithms are active from the lower rate: the "conditional shock zone."…”

Subcutaneous Implantable Cardioverter Defibrillator in Patients With Hypertrophic Cardiomyopathy: An Initial Experience

“…In contrast to the development of transvenous ICDs 20 to 30 years ago, step‐down defibrillation threshold (DFT) testing was rarely performed. In the largest S‐ICD registry to date, only 10 of 450 patients had any testing done at <65 J 6, 7…”

Low Prevalence of Inappropriate Shocks in Patients With Inherited Arrhythmia Syndromes With the Subcutaneous Implantable Defibrillator Single Center Experience and Long‐Term Follow‐Up

“…Of the 321 subjects of the IDE trial who underwent attempted S‐ICD implantation, 7 (2.2%) did not receive the device as a result of incomplete or unsuccessful acute VF conversion testing 5. In contrast, we did not observe screening failures before implantation, despite varying ECG morphologies of the included patients (eg, ST‐segment elevation in Brugada patients, QRS splitting and T‐wave inversions in hypertrophic cardiomyopathy patients).…”