Department of Medicine, Medical University of South Carolina, Charleston (M.R.G.).
Institute of Cardiovascular Science, University College of London, Barts Heart Centre and University College, London, United Kingdom (P.D.L.).
Circulation. 2021 Jan 5;143(1):7-17. doi: 10.1161/CIRCULATIONAHA.120.048728. Epub 2020 Oct 19.
The subcutaneous (S) implantable cardioverter-defibrillator (ICD) is safe and effective for sudden cardiac death prevention. However, patients in previous S-ICD studies had fewer comorbidities, had less left ventricular dysfunction, and received more inappropriate shocks (IAS) than in typical transvenous ICD trials. The UNTOUCHED trial (Understanding Outcomes With the S-ICD in Primary Prevention Patients With Low Ejection Fraction) was designed to evaluate the IAS rate in a more typical, contemporary ICD patient population implanted with the S-ICD using standardized programming and enhanced discrimination algorithms.
Primary prevention patients with left ventricular ejection fraction ≤35% and no pacing indications were included. Generation 2 or 3 S-ICD devices were implanted and programmed with rate-based therapy delivery for rates ≥250 beats per minute and morphology discrimination for rates ≥200 and <250 beats per minute. Patients were followed for 18 months. The primary end point was the IAS-free rate compared with a 91.6% performance goal, derived from the results for the ICD-only patients in the MADIT-RIT study (Multicenter Automatic Defibrillator Implantation Trial-Reduce Inappropriate Therapy). Kaplan-Meier analyses were performed to evaluate event-free rates for IAS, all-cause shock, and complications. Multivariable proportional hazard analysis was performed to determine predictors of end points.
S-ICD implant was attempted in 1116 patients, and 1111 patients were included in postimplant follow-up analysis. The cohort had a mean age of 55.8±12.4 years, 25.6% were women, 23.4% were Black, 53.5% had ischemic heart disease, 87.7% had symptomatic heart failure, and the mean left ventricular ejection fraction was 26.4±5.8%. Eighteen-month freedom from IAS was 95.9% (lower confidence limit, 94.8%). Predictors of reduced incidence of IAS were implanting the most recent generation of device, using the 3-incision technique, no history of atrial fibrillation, and ischemic cause. The 18-month all-cause shock-free rate was 90.6% (lower confidence limit, 89.0%), meeting the prespecified performance goal of 85.8%. Conversion success rate for appropriate, discrete episodes was 98.4%. Complication-free rate at 18 months was 92.7%.
This study demonstrates high efficacy and safety with contemporary S-ICD devices and programming despite the relatively high incidence of comorbidities in comparison with earlier S-ICD trials. The inappropriate shock rate (3.1% at 1 year) is the lowest reported for the S-ICD and lower than many transvenous ICD studies using contemporary programming to reduce IAS. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT02433379.
皮下（S）植入式心脏复律除颤器（ICD）可安全有效地预防心源性猝死。然而，与典型的经静脉 ICD 试验相比，先前 S-ICD 研究中的患者合并症较少，左心室功能障碍较少，且接受了更多的不适当电击（IAS）。UNTOUCHED 试验（了解 S-ICD 在射血分数较低的一级预防患者中的应用结果）旨在评估使用标准化编程和增强的鉴别算法植入 S-ICD 的更典型的当代 ICD 患者人群中的 IAS 发生率。
纳入左心室射血分数≤35%且无起搏指征的一级预防患者。植入第二代或第三代 S-ICD 装置，并进行基于速率的治疗输送编程（≥250 次/分钟）和基于形态的鉴别编程（≥200 次/分钟且<250 次/分钟）。对患者进行 18 个月的随访。主要终点是与 91.6%性能目标（源自 MADIT-RIT 研究（多中心自动除颤器植入试验-减少不适当治疗）中 ICD 仅患者的结果）相比的 IAS 无电击率。采用 Kaplan-Meier 分析评估 IAS、全因电击和并发症的无事件率。采用多变量比例风险分析确定终点的预测因素。
尝试对 1116 例患者进行 S-ICD 植入，1111 例患者纳入植入后随访分析。该队列的平均年龄为 55.8±12.4 岁，25.6%为女性，23.4%为黑人，53.5%患有缺血性心脏病，87.7%患有有症状的心力衰竭，平均左心室射血分数为 26.4±5.8%。18 个月时 IAS 无电击率为 95.9%（置信下限较低，94.8%）。IAS 发生率降低的预测因素包括植入最新一代设备、使用三切口技术、无房颤史和缺血性病因。18 个月时全因电击无事件率为 90.6%（置信下限较低，89.0%），达到了预设的 85.8%的性能目标。适当、离散发作的转复成功率为 98.4%。18 个月时无并发症率为 92.7%。
尽管与早期 S-ICD 试验相比，该研究中的患者合并症发生率相对较高，但与当前 S-ICD 设备和编程相比，该研究显示出了较高的疗效和安全性。IAS 发生率（1 年时为 3.1%）为报告的最低水平，低于许多使用当代编程降低 IAS 的经静脉 ICD 研究。
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