埋藏式心脏转复除颤器除颤阈值测试的争议

在埋藏式心脏复律除颤器(ICD)应用初期,由于相关技术的不成熟,ICD除颤失败时有发生。为了确保ICD能可靠地检测到心室颤动发生并能成功除颤,医生往往需要在植入ICD时诱发心室颤动。但随着ICD除颤性能提高,临床上除颤失败事件已鲜有发生,更重要的是除颤阈值(DFT)测试可给患者带来一定的危险。目前支持或不支持DFT测试的各有自己的证据和观点支持。因此其争议还将持续。     

埋藏式心脏复律除颤器：回顾

心脏猝死(SCD)在美国是危害健康的主要问题之一,其定义为心脏症状发作后1小时内发生的死亡,绝大多数由室颤(VF)或持续性室速(VT)恶化为VF所致。在美国每年约40～50万人患此种心律失常,其中仅20～30%经急救存活。尽管药物治疗、外科手术及急救医学取得进展,SCD率仍居高不下。在120万接受抗心律失常药物治疗的患者中,30%并不能防止SCD发生。埋藏式心脏复律除颤器(ICD)为有SCD潜在危险的患者带来希望,自1985年美国食品及药物管理(FDA)批准ICD临床应用以来,埋植ICD已     

埋藏式心脏复律除颤器1例分析

本文通过我院所做的1例埋藏式心脏复律除颤器（ICD）植入术,对其进行分析,以期更好地使患者受益.     

埋藏式心脏转复除颤器除颤阈值测试没有必要的理由

自从埋藏式心脏转复除颤器(ICD)在上世纪80年代进入临床使用以来,是否需要评估除颤阈值(DFT)测试逐渐成为一个令人困惑的问题。鉴于诱发性心室颤动(简称室颤)与自发性室颤不同;是否测试DFT并不影响远期死亡率;ICD大多数针对的治疗为室性心动过速而不是室颤;DFT存在脑梗死,心肌酶升高,心功能恶化,甚至直接死亡等风险;器械的改善(单相变双相)已经降低了DFT;首次放电失败的患者,二次放电均成功除颤;诱发室颤除颤成功率不能预测临床室颤除颤成功率;废除DFT测试最大的诱惑是更多的患者有机会接受这种挽救生命的治疗等诸多原因,我们认为ICD植入术中应放弃进行DFT测试。     

埋藏式心脏复律除颤器的临床试验

预防和减少心脏猝死依然是临床的重要课题[1] 。埋藏式心脏复律除颤器 (ＩＣＤ)治疗作为一种有效的治疗方法已为众多的临床试验所证明。关于这些临床试验丰富的亚组分析结果、以及最大获益的病例选择等问题国内文献均缺乏详细报道 ,本文介绍这方面的成果。1　ＩＣＤ的一级预防临床试验一系列随机的临床试验开始于 90年代。早期人们认为ＩＣＤ可能只是短期延长严重冠心病患者的生命。 1996年及1999年分别发表了下列两个一级预防试验 ,结果证明 :ＩＣＤ治疗显著地改善了冠心病非持续性室性心动过速 (简称室速 )病人的生存率[1] 。1.1　多中心…     

双腔埋藏式心脏复律除颤器

双腔埋藏式心脏复律除颤器 (ICD)可提供起搏及抗室性和房性心律失常的治疗。报道 11例双腔ICD应用的临床体会。男 8例、女 3例 ,年龄 6 0 .5 5± 10 .0 7岁。缺血性心脏病 9例、Brugada综合征 1例、缺血性心脏病合并肥厚型梗阻性心脏病 1例。双腔ICD安置指征有 :室上性快速心律失常伴室性快速心律失常 6例 ,室性快速性心律失常伴房室阻滞 1例、伴左室功能不全 4例 ;临床上明确记录到室性心动过速 (简称室速 )、心室颤动 (简称室颤 )和室上性快速心律失常者分别为 8,2和 5例。 8例病人术前进行电生理检查 ,诱发出持续性室速 6例、室颤 2例 ;3例行电生理检查 ,其中 2例太虚弱、1例为反复发作持续性室速。 5例安置具有心室转复除颤伴心房、心室起搏的ICD ,5例安置具有心房、心室起搏转复及除颤的ICD ,1例安置具有双心室起搏及心室转复、除颤的ICD。所有病人在置入ICD时都进行除颤阈值的测定。总共有 2 3次室颤被诱发 ,除颤阈值为 12 .0 9± 5 .2 4J,除颤电极阻抗为 44 .0 0±11.0 5Ω ,P波和R波电压幅度分别为 3.5 3± 1.32mV ,13.42± 4.73mV ,心房、心室起搏阈值分别为 1.39± 0 .71和 0 .91± 0 .38V。随访 8.82± 5 .0 0 (2～ 19)个月 ,5例共有 12 0次持续性室速发生 ,其中 118次经抗心动过速起搏成功?     

15例埋藏式心脏复律除颤器植入的诊治体会

埋藏式心脏复律除颤器（ICD）的应用为恶性室性心律失常的治疗开辟了一个新领域。最初,ICD植入的适应症范围较窄,只作为心脏性猝死的二级预防,目前ICD植入的适应症已经扩展到心脏性猝死的一级预防。在我国,ICD植入尚不广泛。我们2008年7月-2010年7月间共收治15例ICD植入病例,现将其临床资料分析如下。     

埋藏式自动复律除颤器植入术的护理

心脏性猝死临床上并非少见 ,其主要原因是恶性室性心律失常。因此 ,预防和治疗恶性室性心律失常是预防心脏性猝死的关键。埋藏式心脏自动复律除颤器(AICD)降低心律失常病人死亡率的效果明显优于使用抗心律失常药。目前已将 AICD作为治疗恶性室性心律失常 ,预防心脏性猝死首选方法 [1 ]。但因价格昂贵 ,限制了AICD在临床上的应用。我院于 2 0 0 1年 2月至 4月成功地为 2位女性患者行 AICD植入术。现将有关护理过程报告如下 :1　一般资料本组共 2例 ,均为女性。其中 1例 77岁 ,患“冠心病”,有 2支血管病变 ,已行 PTCA十支架术 ,EKG…     

加强埋藏式心脏复律除颤器的应用意识和术后随访

心脏性猝死一直是心血管内科临床的重要课题。我国虽然缺少准确的流行病学统计资料 ,但大家都明显地意识到 :近年来心脏性猝死的发生呈上升趋势。心脏性猝死的主要原因是心律失常 ,其中又以恶性室性心律失常为主。因此 ,预防和治疗恶性室性心律失常是预防心脏性猝死的关键。多个大规模临床试验 (ＡＶＩＤ、ＣＩＤＳ、ＣＡＳＨ)业已证明埋藏式心脏复律除颤器 (ｉｍｐｌａｎｔａｂｌｅｃａｒｄｉｏｖｅｒｔｅｒ ｄｅｆｉｂｒｉｌｌａｔｏｒ,ＩＣＤ)降低心律失常病人死亡率的效果明显优于抗心律失常药。目前已将ＩＣＤ作为治疗恶性室性心律失常…     

埋藏式心脏复律除颤器(ICD):目前认识和建议

致命性室性心律失常 (室性心动过速 /心室颤动 ,ＶＴ/ＶＦ)是心脏性猝死 (ＳＣＤ)的主要原因 ,美国每年约 40万人死于此症。一系列多中心临床试验证明埋藏式心脏复律除颤器 (ＩＣＤ)是优于药物的有效治疗方法 ,明显降低ＳＣＤ发生率。美国每年上万人安装ＩＣＤ ,其数量呈直线上升趋势。我国由于经济条件和认识水平普及的限制 ,采用ＩＣＤ治疗的患者甚少 ,但近年来逐渐增多 ,一年约 1 0 0例患者安装ＩＣＤ。为提高医生和病人对应用ＩＣＤ的认识及使用规范化 ,两个学会的ＩＣＤ专家组于 2 0 0 1年 1 1月在北京召开研讨会 ,就ＩＣＤ适应证、多…     

Role of Defibrillation Threshold Testing in the Contemporary Defibrillator Patient Population

Role of Defibrillation Threshold Testing. Introduction: Defibrillation threshold (DFT) testing has been performed to prove functionality of the implantable cardioverter defibrillator (ICD). Over the past years it has become increasingly controversial because of possible morbidity and mortality. The goal of this study was to determine unsuccessful shock testing and report strategies used to overcome these problems. Methods and Results: A total of 314 patients with a de novo implantation of an ICD and 127 patients receiving a generator exchange were identified retrospectively. All patients underwent defibrillation threshold testing after induction of VF using a low‐energy T‐wave shock during the intervention, 2 shock tests after de novo implantations, 1 after generator change. A safety margin of 10 J or more was requested. Seven (2.3%) patients in the de novo group and 2 patients (1.4%) in the generator exchange group could not be defibrillated using the standard approach. All of those patients had either chronic amiodarone therapy, secondary prevention or a cardiac resynchronization therapy device (CRT). In univariate analysis, amiodarone therapy, dilated cardiomyopathy, and lower ejection fraction were predictors of failure. Conclusion: Our study's results as well as a review of the current literature favor shock testing, especially in patients with specific risk factors as mentioned above. (J Cardiovasc Electrophysiol, Vol. 24, pp. 437‐441, April 2013)     

Upper Limit of Vulnerability Predicts Chronic Defibrillation Threshold for Transvenous Implantable Defibrillators

ULV Predicts Chronic DFT. Introduction: The upper limit of vulnerability (ULV) is the shock strength at or above which ventricular fibrillation cannot be induced when delivered in the vulnerable period. It correlates acutely with the acute defibrillation threshold (DFT) and can be determined with a single episode of fibrillation. The goal of this prospective study was to determine the relationship between the ULV and the chronic DFT.
Methods and Results: We studied 40 patients at, and 3 months after, implantation of transvenous cardioverter defibrillators. The ULV was defined as the weakest biphasic shock that failed to induce fibrillation when delivered 0,20, and 40 msec before the peak of the T wave. Patients were classified as clinically stable or unstable based on prospectively defined criteria. There were no significant differences between the group means for the acute and chronic determinations of ULV (13.5 ± 5.3 J vs 12.4 ± 6.8 J, P = 0.25) and DFT (10.1 ± 5.0 J vs 9.9 ± 5.7 J, P = 0.74). Five patients (15%) were classified as unstable. The strength of the correlation between acute ULV and acute DFT (r = 0.74, P < 0.001) was similar to that between the chronic ULV and chronic DFT (r = 0.82, P < 0.001). There was a correlation between the change in ULV from acute to chronic and the corresponding change in DFT (r = 0.67, P < 0.001). The chronic DFT was less than the acute ULV + 3 J in all 35 stable patients, but it was greater in 2 of 5 unstable patients (P = 0.04).
Conclusions: The strength of the correlation between the chronic ULV and the chronic DFT is comparable to that between the acute ULV and the acute DFT. Temporal changes in the ULV predict temporal changes in the DFT. In clinically stable patients, a defibrillation safety margin of 3 J above the acute ULV proved an adequate chronic safety margin.     

Elevated Defibrillation Threshold When Right-Sided Venous Access is Used for Nonthoracotomy Implantable Defibrillator Lead Implantation

Right/Left-Sided ICD Implantation. Introduction: Although myriad factors influence the defibrillation threshold, the relation between the site of transvenous lead entry into the vascular system and the defibrillation threshold has not been reported. This study examines the influence that venous entry site has on defibrillation success for a transvenous implantable cardioverter defibrillator lead with two defibrillating coils. Methods and Results: The study population comprised 345 patients. Their mean age was 61 ± 13 years and, left ventricular ejection fraction was 0.33 ± 0.13. A left-sided approach was used in 324 (93.9%) of the patients, and a right-sided approach was used in the remaining 21 (6.1%) patients. There was no difference in the gender, age, left ventricular ejection fraction, or underlying cardiac disease in the two groups. For all patients, with a transvenous lead used either alone or with a submuscular or subcutaneous patch, the biphasic defibrillation threshold was 9.9 ± 4.8 J when a left-sided approach was used, and 14.0 ± 7.3 J when a right-sided approach was used (P = 0.02). When a transvenous lead was used with a submuscular or subcutaneous patch (115 patients), the biphasic defibrillation threshold was 9.5 ± 4.3 J when a left-sided approach was used, and 12.0 ± 10.0 J when a right-sided approach was used (P = 0.98). When a transvenous lead was used without a submuscular or subcutaneous patch (230 patients), the biphasic defibrillation threshold was 10.1 ± 5.0 J when a left-sided approach was used, and 14.6 ± 6.6 J when a right-sided approach was used (P < 0.01). For the entire group of patients and for each specific lead arrangement, there was no significant difference in the defibrillating lead system impedance when right-sided versus left-sided approaches were compared. Conclusion: Left-sided approaches to implant transvenous leads with two coils for defibrillation result in lower biphasic defibrillation thresholds than when right-sided approaches are used.     

Long-Term Evaluation of the Ventricular Defibrillation Energy Requirement

Defibrillation Energy Requirements. Introduction : Defibrillation energy requirements in patients with nonthoracotomy defibrillators may increase within several months after implantation. However, the stability of the defibrillation energy requirement beyond 1 year has not been reported. The purpose of this study was to characterize the defibrillation energy requirement during 2 years of clinical follow-up.
Methods and Results : Thirty-one consecutive patients with a biphasic nonthoracotomy defibrillation system underwent defibrillation energy requirement testing using a step-down technique (20, 15, 12, 10, 8, 6, 5, 4, 3, 2, and 1 J) during defibrillator implantation, and then 24 hours, 2 months, 1 year, and 2 years after implantation. The mean defibrillation energy requirement during these evaluations was 10.9 ± 5.5 J, 12.3 ± 7.3 J, 11.7 ± 5.6 J, 10.2 ± 4.0 J, and 11.7 ± 7.4 J, respectively ( P = 0.4). The defibrillation energy requirement was noted to have increased by 10 J or more after 2 years of follow-up in five patients. In one of these patients, the defibrillation energy requirement was no longer associated with an adequate safety margin, necessitating revision of the defibrillation system. There were no identifiable clinical characteristics that distinguished patients who did and did not develop a 10-J or more increase in the defibrillation energy requirement.
Conclusion : The mean defibrillation energy requirement does not change significantly after 2 years of biphasic nonthoracotomy defibrillator system implantation. However, approximately 15% of patients develop a 10-J or greater elevation in the defibrillation energy requirement, and 3% may require a defibrillation system revision. Therefore, a yearly evaluation of the defibrillation energy requirement may he appropriate.     

Defibrillation thresholds in hypertrophic cardiomyopathy

Defibrillation Thresholds in Hypertrophic Cardiomyopathy . Background: Defibrillation threshold (DFT) testing is performed in part to ensure an adequate safety margin for the termination of spontaneous ventricular arrhythmias. Left ventricular mass is a predictor of high DFTs, so patients with hypertrophic cardiomyopathy (HCM) are often considered to be at risk for increased defibrillation energy requirements. However, there are little prospective data addressing this issue. Objective: To assess DFTs in patients with HCM and evaluate the clinical predictors of elevated DFTs. Methods: Eighty‐nine consecutive patients with HCM and 600 control patients with ischemic or nonischemic cardiomyopathy underwent a uniform modified step‐down DFT testing protocol. DFT was compared between the control and HCM populations. Predictors of elevated DFT were evaluated in the HCM group. Results: There was no difference in DFT between HCM and control groups (10.4 ± 5.8 J vs 11.2 ± 5.6 J, respectively). Among patients with HCM, clinical parameters such as left ventricular ejection fraction, interventricular septal thickness, left ventricular mass, and QRS duration were not predictive of an elevated DFT. Only 3 patients (3.4%) with HCM had a DFT >20 J. Conclusion: Patients with HCM do not have elevated DFTs as compared to more typical populations undergoing implantable cardioverter‐defibrillator implant; high‐energy devices or complex lead systems are not needed routinely in this population. (J Cardiovasc Electrophysiol, Vol. 22, pp. 569‐572 May 2011)     

Single Capacitive Discharge Utilizing an Auxiliary Shock in the Coronary Venous System Reduces the Defibrillation Threshold

Auxiliary shocks (AS) from electrodes sutured to the left ventricle (LV) prior to primary biphasic shocks (PS) have been shown to reduce defibrillation thresholds (DFT). Two capacitors are required to generate these waveforms. We investigate delivery of AS from one capacitor using a novel waveform. The epicardial surface of the LV is accessed transvenously via the middle cardiac vein (MCV) avoiding a thoracotomy. Methods: A defibrillation electrode was placed in the right ventricle (RV) and superior vena cava (SVC) in 12 pigs (37±2kg). A 50×1.8mm electrode was inserted in the MCV through a guide catheter. A can was placed in the left pectoral region. A monophasic AS (100F, 1.5J) was delivered along one pathway before switching to deliver a biphasic waveform (40% tilt, 2ms phase 2) along another. DFTs (PS+AS) were assessed using a binary search. Two configurations not incorporating AS acted as controls. DFTs were compared using repeated measures analysis of variance. Results: DFTs of the four novel configurations (AS/PS) were: RVCan/MCVCan=14.9±3.7J, MCVCan/RVCan=17.2±5.7J, RVSVC+Can/MCVSVC+Can=13.4±4.6J, MCVSVC+Can/RVSVC+Can=17.1±5.9J. Delivering AS in the RV followed by PS in the MCV reduced the DFT (RVCan (19.9±7.3 J, P<0.01) and RVSVC+Can (19.2±6.0 J, P<0.05)). Conclusions: Delivering AS prior to PS in the MCV reduces the DFT by up to a third compared to conventional configurations of RVCan and RVSVC+Can. This is possible using only a single capacitor and an entirely transvenous approach to the LV.     

Trans venous-Subcutaneous Defibrillation Leads:

Effect of Transvenous Electrode Polarity on DFT. Introduction: The defibrillation threshold (DFT) of a transvenous-subcutaneous electrode configuration is sometimes unacceptably high. To obtain a DFT with a sufficient safety margin, the defibrillation field can be modified by repositioning the electrodes or more easily by a change of electrode polarity. In a prospective randomized cross-over study, the effect of transvenous electrode polarity on DFT was evaluated.
Methods and Results: In 21 patients receiving transvenous-subcutaneous defibrillation leads, the DFT was determined intraoperatively for two electrode configurations. Two monophasic defibrillation pulses were delivered in sequential mode between either the right ventricular (RV) electrode as common cathode and the superior vena cava (SVC) and subcutaneous electrodes as anodes (configuration I) or the SVC electrode as common cathode and the RV and subcutaneous electrodes as anodes (configuration II). In each patient, both electrode configurations were used alternately with declining energies (25, 15, 10, 5, 2 J) until failure of defibrillation occurred. The DFT did not differ between both configurations (18.3 ± 8.2 J vs 18.9 ± 8.9 J; P = 0.72). Eleven patients had the same DFT with both electrode configurations, 5 patients a lower DFT with the RV electrode as cathode, and 5 patients a lower DFT with the SVC as cathode. Four patients had a sufficiently low DFT (≤ 25 J) with only 1 of the 2 configurations.
Conclusion: A change of electrode polarity of transvenous-subcutaneous defibrillation electrodes may result in effective defibrillation if the first electrode polarity tested fails to defibrillate. In general, neither the RV electrode nor the SVC electrode is superior if used as a common cathode in combination with a subcutaneous anodal chest patch.     

Effect of Shock Waveform on Relationship Between Upper Limit of Vulnerability and Defibrillation Threshold

ULV-DFT Waveform. Introduction: The upper limit of vulnerability (ULV) correlates with the defibrillation threshold (DFT). The ULV can he determined with a single episode of ventricular fibrillation and is more reproducible than the single-point DFT. The critical-point hypothesis of defibrillation predicts that the relation between the ULV and the DFT is independent of shock waveform. The principal goal of this study was to test this prediction. Methods and Results: We studied 45 patients at implants of pectoral cardioverter defibrillators. In the monophasic-biphasic group (n = 15), DFT and ULV were determined for monophasic and biphasic pulses from a 120-μF capacitor. In the 60- to 110-μF group (n = 30), DFT and ULV were compared for a clinically used 110-μF waveform and a novel 60-μF waveform with 70% phase 1 tilt and 7-msec phase 2 duration. In the monophasic-biphasic group, all measures of ULV and DFT were greater for monophasic than biphasic waveforms (P < 0.0001). In the 60- to 110-/tF group, the current and voltage at the ULV and DFT were higher for the 60-μF waveform (P < 0.0001), hut stored energy was lower (ULV 17%, P < 0.0001; DFT 19%, P = 0.03). There was a close correlation between ULV and DFT for both the monophasic-biphasic group (monophasic r²= 0.75, P < 0.001; hiphasic r²= 0.82, P < 0.001) and the 60- to 110-μF group (60 μF r²= 0.81 P < 0.001; 110 μF r²= 0.75, P < 0.001). The ratio of ULV to DFT was not significantly different for monophasic versus biphasic pulses (1.17 ± 0.12 vs 1.14 ± 0.19, P = 0.19) or 60-μF versus 110-μF pulses (1.15 ± 0.16 vs 1.11 ± 0.14, P = 0.82). The slopes of the ULV versus DFT regression lines also were not significantly different (monophasic vs biphasic pulses, P = 0.46; 60-μF vs UO-μF pulses, P = 0.99). The sample sizes required to detect the observed differences between experimental conditions (P < 0.05) were 4 for ULV versus 6 for DFT in the monophasic-biphasic group (95% power) and 11 for ULV versus 31 for DFT in the 60- to 110-μF group (75% power). Conclusion: The relation between ULV and DFT is independent of shock waveform. Fewer patients are required to detect a moderate difference in efficacy of defibrillation waveforms by ULV than by DFT. A small-capacitor biphasic waveform with a long second phase defibrillates with lower stored energy than a clinically used waveform.     

Thoracotomy Elevates the Defibrillation Threshold and Modifies the Defibrillation Dose-Response Curve

Thoracotomy Elevates the Defibrillation Threshold. Introduction : Despite innovations in nonthoracotomy defibrillation systems, thoracotomies are still required in some clinical settings and are utilized in many animal-based research protocols. The effect of a thoracotomy on defibrillation energy, however, has not been well characterized.
Methods and Results : Ten dogs in the immediate testing; group underwent defibrillation testing immediately following a thoracotomy: another ten dogs in the delayed testing group were given 48 to 72 hours of recovery before defibrillation testing. A right ventricular endocardial coil to cutaneous thoracic patch biphasic system was used. At the time of defibrillation testing, the immediate testing group had a faster mean heart rate (144.7 ± 30.2 vs 105.8 ± 17.5 beats/min, P < 0.01), higher mean pulmonary artery pressures (systolic: 18.14 ± 9.48 vs 11.28 ± 6.46 mmHg. P = 0.1; diastolic: 6.59 ± 2.88 vs 3.89 ± 1.75 mmHg, P <0.051, and higher mean defibrillation shock impedance (89.0 ± 11.6 vs 70.9 ± 7.3 ω, P < 0.002) than the delayed group. The mean ED₅₀ (energy with a 50% success rate) was significantly higher in the immediate group than in the delayed group (26.9 ± 14.9 vs 14.2 ± 6.9 J, P < 0.05), and the slopes of the dose-response curves were significantly different (P = 0.03).
Conclusion : In a right ventricular endocardial to cutaneous patch system, thoracotomy significantly and transiently increased the defibrillation threshold and modified the defibrillation dose-response curve.