普通电极导线行右房左室或双心室起搏的初步临床观察

探讨普通电极导线置入心脏静脉起搏左室的可行性。选择 9例患者为研究对象 ,其中扩张型心肌病 3例、缺血性心脏病 3例、其他 3例 ,均伴不同程度的心力衰竭 ,心功能Ⅱ～Ⅳ级。所有患者都安置DDD起搏器。窦性心律伴房室阻滞 (AVB)或完全性左束支阻滞 (CLBBB)患者 ,行右房左室顺序起搏 ;房颤患者行双心室起搏。左心室起搏是将普通右心室导线 (MedtronicCapSureSP 4 0 2 3)通过冠状窦送入心脏静脉施行的。结果 :7例成功 ,2例失败。导线定位在左室后静脉 1例、后侧静脉 3例、侧静脉 3例。术中测左室起搏阈电压、阻抗和R波振幅分别是 0 .7± 0 .2V、6 2 3± 6 6Ω、10 .1± 6 .0mV。术后 2～ 18个月阈电压、阻抗分别是 0 .5± 0V、5 2 1± 5 1Ω。术后 1～ 2周平均心功能从2 .9级改善到 1.9级 ,平均心胸比值从 0 .6 1缩小到 0 .5 7,平均左室射血分数从 0 .39升至 0 .4 4。随访期未发现左室导线脱位 ,膈肌起搏等并发症。结论 :普通电极导线置入心脏静脉长期起搏左心室是可行的、牢靠的。     

双心室起搏埋藏式心脏转复除颤器的安置

评价一次性置入双心室起搏埋藏式心律转复除颤器 (双腔ICD)的安全性和有效性。5例冠心病冠状动脉搭桥术后的患者 ,伴有严重的慢性充血性心力衰竭和恶性室性心律失常 ,置入双腔ICD。结果 :5例左室电极导管和双腔ICD均一次成功置入 ,左室电极放入冠状静脉的侧后枝 ,急性起搏阈值 0 .8± 0 .6V ,电阻 72 2± 12 8Ω ,R波振幅18.6± 5 .3mV ,电流 1.6± 0 .5mA ,而双心室起搏时其起搏电极参数均优于左室电极 ,除颤阈值≤ 14J。结论 :对伴严重慢性充血性心力衰竭和恶性室性心律失常的患者 ,置入双腔ICD是安全、易行的。     

双房单室三腔起搏器治疗病窦综合征并快速房性心律失常

观察双心房、单心室三腔起搏器治疗病窦综合征合并阵发性房性快速心律失常患者的疗效。三根电极导线分别置入冠状静脉窦内、右心耳和右室心尖部行三腔起搏。冠状窦电极导线与右心房电极导线通过一个Y型转接器构成心房部分。结果 :10例患者 ,9例经左锁骨下静脉径路置入导线 ,1例因存在残存左上腔静脉 ,从右锁骨下静脉置入。 10例中 9例冠状窦电极导线置于冠状静脉窦中部、1例置于冠状静脉窦远端。冠状窦起搏阈值为 1.0 6±0 .2 0V、起搏阻抗 6 11± 115 .8Ω、P波振幅为 4.0 7± 0 .88mV ;右室电极起搏阈值为 0 .5 3± 0 .12V、起搏阻抗 6 70 .3±191.7Ω、R波振幅为 9.6 6± 1.87mV。随访 5～ 2 4个月有 9例起搏器呈DDD工作方式 ,1例呈AAT工作方式。起搏和感知功能良好。 10例中 8例快速性房性心律失常完全控制 ,2例发作次数减少 ,持续时间明显缩短。无一例出现并发症。结论 :三腔起搏器技术安全、可靠。适合于缓慢型心律失常合并阵发性房性快速性心律失常     

Kappa 700型双腔起搏器的临床随访

观察具有自动夺获功能的双腔起搏器 (Kappa 70 0 )置入后参数的变化和安全性情况。随访 1 3例置入Kappa70 0型起搏器患者 ,观察术中、术后 1周及术后 1 ,3,6个月心室起搏阈值、输出电压、输出脉宽、电极阻抗、R波振幅的变化 ,了解起搏器的工作情况。术后测得的起搏阈值较术中明显升高 ( 0 .71± 0 .2 3Vvs 0 .39± 0 .0 6V ,P <0 .0 5 ) ,术后不同时间测得的起搏阈值无明显差异。R波振幅术中、术后无明显差异。术后阻抗较术中明显降低 ( 62 5 .7± 1 2 3.0Ωvs 894.3± 1 90 .3Ω ,P <0 .0 5 ) ,术后 1个月后的阻抗基本稳定。起搏器自动夺获功能打开后 ,平均输出电压为 0 .96～ 1 .1 6V ,平均输出脉宽 0 .32～ 0 .34ms,平均心房感知灵敏度 0 .71～ 0 .83mV ,心室感知灵敏度 3.82～3.91mV。随访期间起搏、感知功能正常 ,无误感知现象。具有自动夺获功能的双腔起搏器输出电压低 ,安全可靠。     

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?     

经静脉埋藏式三腔起搏心脏转复除颤器的临床应用

探讨经静脉埋藏式三腔起搏心脏转复除颤器 (BVP ICD)的临床应用。病例入选标准 :①缺血性心脏病、扩张性心肌病合并充血性心力衰竭。②左室射血分数 <0 .35。③QRS波时限 >130ms。④ 2 4h动态心电图、临床心电监护、腔内电生理检查中 ,任一项记录到明确室性心动过速 (VT)或心室颤动 (VF)。采用经锁骨下静脉和头静脉 ,分别置入右室电极导管到右室 ,右房电极导管到右心耳 ,左室电极经冠状静脉窦到冠状静脉后侧支 ,其中 1例为经静脉埋藏三腔双室起搏器 (BVP)升级为BVP ICD。结果 :双室起搏阈值 1.7± 0 .7V ,R波幅度 10 .3± 4mV ,双室电极阻抗 896 .2± 82Ω。4例先后 2次采用电击T波诱发出VT或VF ,并除颤成功。 3例因心功能差仅诱发 1次并除颤成功。最低有效除颤能量 2例 11J ,5例 2 0～ 2 1J ,手术时间 12 9.2 8± 4 7.3min。 7例随访 3～ 12个月 ,心功能改善 1～ 2级。 2例分别各有 1例除颤事件记录 ,7例全部存活。结论 :BVP ICD临床疗效较好 ,但设定首次电击能量时不宜太小 ,力争尽快转复心律 ,以策安全。慎用快速心室起搏 (Ramp)终止VT。     

右室双部位起搏治疗心力衰竭的临床观察

评价 15例患者经右室双部位起搏治疗慢性心力衰竭 (简称心衰 )的疗效。其中原发性扩张型心肌病心衰 13例、缺血性心肌病心衰 2例 ;心功能Ⅲ级 9例、Ⅳ级 6例。结果 :15例患者安置时右室心尖部起搏阈值 0 .5± 0 .3(0 .3～ 1.0 )V、R波振幅 15± 5 .98(6～ 2 4.6 )mV ,阻抗 6 13± 172 (32 0～ 90 0 )Ω。右室流出道起搏阈值 0 .7± 0 .2 6 (0 .3～1.3)V、R波振幅 13± 5 .5 5 (6 .5～ 2 3.6 )mV、阻抗 5 6 3± 194(30 0～ 90 0 )Ω ;双部位起搏阈值 1.45± 0 .45 (0 .9～ 1.7)V。双部位起搏心电图QRS波群时限比右室心尖部及右室流出道单部位起搏缩短了 40～ 90ms。超声心动图检查提示双部位起搏后二尖瓣返流面积平均减少 5 .6cm2 ,射血分数值提高 5 .2 %。经 6 .0± 1.5个月的随访 ,15例中除 2例因突发恶性室性心律失常猝死外 ,其余患者的心功能分别从Ⅲ、Ⅳ级改善到Ⅱ和Ⅲ级。右室双部位慢性起搏阈值1.85± 0 .5 6 (1.5～ 2 .5 )V。随访期间QRS波群时限平均下降 5 0ms。结论 :右室双部位起搏能有效的治疗心肌病患者的心衰。     

埋藏式心脏转复除颤器安置的临床经验

总结非开胸经锁骨下静脉穿刺安置埋藏式心脏转复除颤器 (ICD)的手术方法、除颤阈值 (DFT)测定及ICD工作参数设置等临床经验。 10例患者 ,6例有反复晕厥病史。 2例晕厥时心电图证实为心室颤动 (简称室颤 ) ,体外电除颤成功 ,另 8例心内电生理均诱发出持续性室性心动过速或室颤。其中冠心病 8例 (1例合并Brugada综合征 ) ,扩张性心肌病 1例 ,原发性室颤 1例。 5例术前口服胺碘酮治疗。结果 :全部经锁骨下静脉置入ICD ,术中所有患者成功诱发室颤 ,并一次电击成功。手术时间 92± 2 7min。DFT≤ 2 0J,电击阻抗 4 1.2± 15 .3Ω ,R波高度 16 .3± 6 .6mV ,无手术并发症。结论 :经锁骨下静脉置入ICD方法简单 ,安全可靠 ;术前口服适量胺碘酮对术中诱发室颤无影响。     

Champion 7302起搏系统临床应用体会

评价Ｃｈａｍｐｉｏｎ 730 2心脏起搏系统的临床疗效及应用价值。 9例患者 ,男 6例 ,女 3例 ,年龄 6 7.0± 10 .9(4 3～ 81)岁 ,其中病窦综合征 5例 ,Ⅲ度房室阻滞 4例 ,术前均伴有晕厥、乏力、气短等心动过缓症状。植入时的起搏阈值 0 .5 6± 0 .15Ｖ(脉宽 0 .5ｍｓ)、阻抗5 0 0 .0± 10 0 .8Ω(5Ｖ起搏时 )、Ｒ波振幅 12 .2± 3.6ｍＶ。本组病例术后晕厥、气短、乏力等心动过缓症状消失 ,无头晕、胸痛等特殊不适 ,无囊袋血肿及破溃发生 ,亦无胸大肌跳动、膈肌刺激症状出现。 1例于置入第 4天出现竞争心律 ,Ｘ线证实电极由右室流入道脱位至…     

VVI型起搏器更换时心室电极直接参数的变化及临床意义

研究长期起搏器治疗后起搏阈值、电极阻抗的变化及电极使用的寿命。 32例病人 ,在起搏器置入术及更换术时 ,用起搏器分析仪直接测量心室电极参数。心室电极在体内埋置时间为 10 4 .2 2± 30 .10 (49～ 16 8)个月。置入时起搏阈值为 0 .72± 0 .33(0 .2～ 1.5 )V ,更换脉冲发生器时为 1.85± 0 .75 (1.0～ 3.5 )V ,P <0 .0 0 0 1。更换脉冲发生器时起搏阈值是置入时的 2 .5 7倍 ,增加幅度为 2 0 1.2 %± 16 2 .9% (10 %～ 70 0 % ) ,增加绝对值为 1.13± 0 .71(0 .1～2 .5 )V。置入时电极阻抗为 6 4 2 .83± 185 .39(333～ 980 )Ω ,更换脉冲发生器时为 70 2 .79± 73.0 0 (40 2～ 12 4 0 )Ω ,P >0 .0 5。更换起搏器后 ,对继续使用原心室电极的 2 8例随访 5 4 .91± 5 1.2 1(1～ 16 8)个月。 3例在更换术后 1～ 2 4个月分别出现起搏及感知障碍 ,再次手术时发现导管不全断裂、绝缘包鞘破损及微脱位。结论 :置入性右心室心内膜电极在使用 8年以上 ,大部分的直接参数在正常范围 ,可考虑继续使用 ,但早年生产的电极 ,更换术时参数即使正常 ,亦不排除电极可能短期内发生故障 ,须随访及定期复查。     

Comparison of defibrillation efficacy using implantable cardioverter-defibrillator with single- or dual-coil defibrillation leads and active can

INTRODUCTION: The reduction of defibrillation threshold (DFT) in patients treated with an implantable cardioverter-defibrillator increases patients' safety and prolongs ICD battery life. AIM: To evaluate the possibility of reducing the defibrillation threshold in ICDs with an active can and an additional atrial defibrillation coil instead of the typical intracardiac single-coil lead. METHOD: This study involved 138 patients (36 F and 102 M, mean age 54+/-15 years) including 62 subjects with dual-coil defibrillation lead (group A) and 76 ones with single-coil defibrillation lead (group B). No statistically significant differences with respect to age, left ventricular function, main disease or exacerbation of heart failure according to the NYHA functional class were observed between groups. The defibrillation threshold was measured using the DFT+ protocol. RESULTS: No significant differences between groups were identified with respect to pacing and sensing parameters. The comparison of DFT values between the two studied groups revealed significant improvement (by 14% mean) of defibrillation efficacy in group A. In group A, the mean DFT was 9.8+/-4.6 J (3-20 J) and mean defibrillation resistance - 45+/-7 W (32-73 W), whereas in group B: 11.45+/-5.25 J (3-28 J) and 72+/-12.8 W (38-106 W), respectively. In 93% of patients from group A, DFT was below 15 J, in comparison to 81% of patients from group B (p=0.046). The odds ratio of a higher defibrillation threshold (?15 J) in group A vs. group B was 0.3 (95% confidence interval: 0.09-0.98). The DFT reduction associated with modified ICD system use was independent of following clinical parameters: patient age, gender, main disease, end-diastolic left ventricular diameter, left ventricular ejection fraction, NYHA functional class and concomitant treatment with antiarrhythmic agents. CONCLUSIONS: Modification of the electric field during defibrillation, achieved with the use of active-can ICDs with dual-coil defibrillation leads, allows a reduction of DFT by 14%. At the same time, it reduces the risk of a higher (> or =15 J) DFT by three times compared to patients with a standard single-coil defibrillation lead.     

Defibrillation efficacy comparing a subcutaneous array electrode versus an "active can" implantable cardioverter defibrillator and a subcutaneous array electrode in addition to an "active can" implantable cardioverter defibrillator: results from active can versus array trials I and II

INTRODUCTION: Placement of implantable cardioverter defibrillators (ICDs) has been simplified by using the shell of a pectorally implanted ICD as a defibrillation electrode in combination with an endocardial right ventricular defibrillation lead. However, a sufficiently low defibrillation threshold (DFT) cannot be obtained in a few patients. Therefore, alternative approaches were systematically tested in the Active Can versus Array Trial (ACAT). METHODS AND RESULTS: In the first of two prospective randomized studies, the DFT of a subcutaneous left dorsolateral array anode introduced from a pectoral incision was compared to that of a standard active can anode in 68 patients. Intraoperatively, the DFT was determined twice in each patient using either the active can or, in patients with a subcutaneous array lead, once with all three fingers and once omitting the middle finger of the array. The second prospective randomized study included 40 patients. DFT also was determined twice in each patient using an active can in a left pectoral position as anode alone and combined with a left dorsolateral array electrode with two fingers. In ACAT I, stored energy at DFT decreased from 13.1+/-7.7 J (active can) to 9.6+/-6.1 J (three-finger array lead) (P = 0.04), impedance decreased from 53+/-8 ohms to 40+/-6 ohms (P < 0.0001). Omitting the middle finger of the array lead, stored energy at DFT increased by 0.9 J (P = 0.47) and impedance by 2 ohm (P < 0.0001). In ACAT II, DFT and impedance using an active can device were significantly lower when a two-finger array lead was added that decreased stored energy at DFT from 10.1+/-5.2 J to 6.9+/-3.9 J (P = 0.001) and impedance from 56+/-5 1 to 42+/-5 l (P < 0.0001). CONCLUSION: In combination with a right ventricular defibrillation electrode, a left pectoral subcutaneous array lead improves defibrillation efficacy if used instead of, or in addition to, a left pectoral active can ICD device. Implantation of the array lead can be simplified by using two instead of three fingers, without a significant loss of defibrillation efficacy.     

Effects of shock polarity reversal on defibrillation threshold in an implantable cardioverter-defibrillator

BACKGROUND: An increased defibrillation threshold (DFT) may limit the efficacy of an implantable cardioverter-defibrillator (ICD) in termination of life-threatening ventricular arrhythmias. A search for methods of decreasing DFT has been ongoing since the introduction of ICD into clinical practice. AIM: To assess the effects of various shock polarities on DFT. METHODS: The study group consisted of 19 patients (8 females and 11 males, mean age 52+/-17 years) who received devices (Biotronik, Germany) with a single-coil defibrillation lead. In all patients the value of DFT was assessed using a normal shock polarity as well as using a reversed polarity shock, starting from the energy lower than that measured during normal DFT testing. The impedance of the defibrillation system using two different polarities was also measured. The effects of demographic and clinical parameters on defibrillation parameters were also examined. RESULTS: When using normal shock polarity, the mean DFT value was 12+/-5 J (range 3.1-20 J) and impedance was 64+/-12 Omega. When shock polarity was reversed, the mean DFT value was 9.2+/-5.0 J (range 2-20 J) and impedance was 67+/-11 Omega. In 11 (58%) patients the polarity change caused a marked (by 37%) decrease in the mean DFT value - from 11.5+/-5.1 J to 7.2+/-3.8 J. In 5 patients DFT reduction was > or = 5 J. There was no relationship between demographic or clinical parameters and defibrillation efficacy using the two tested shock polarities. CONCLUSIONS: The reversal of shock polarity reduces DFT in more than half of patients. In patients with a high DFT the use of reversed polarity of defibrillating impulse may reduce DFT, which widens the safety margin and makes implantation of additional leads unnecessary. Because clinical parameters have no value in predicting the effects of polarity changes on DFT, the efficacy of reversed polarity shock has to be assessed individually in each patient.     

Fractally coated defibrillation electrodes: is an improvement in defibrillation threshold possible?

AIMS: In patients with implantable cardioverter-defibrillators (ICD), the goals of lowering the defibrillation threshold (DFT) can be achieved by means of higher defibrillation safety margins, more rapid charging of capacitors, improved battery longevity, implying smaller devices. Whether an increase in the electrically active surface of ICD leads by fractal coating results in decreased DFTs is unknown. METHODS AND RESULTS: In this prospective randomized cross-over study the defibrillation efficacy of a novel right ventricular endocardial defibrillation electrode fractally coated with iridium was compared with an uncoated but otherwise identical electrode in 30 patients undergoing ICD implantation. In each patient, DFT testing was performed twice according to a binary search protocol introducing the two different electrodes in a random order. The mean DFT was 8.4 +/- 4.1 J with the fractally coated lead and 9.6 +/- 3.6 J using the uncoated lead. The improvement of 1.2 J was statistically not significant (P = 0.11). No differences were observed between the patients with an improved DFT (n =12) and those with an unchanged or worsened DFT (n = 18) concerning age, underlying cardiac disease, NYHA class, or left ventricular ejection fraction, respectively. CONCLUSION: Increasing the electrical surface of defibrillation leads by fractal coating does not lead to a substantial clinically relevant reduction in defibrillation thresholds. Defibrillation impedance is not influenced by the increased electrical surface of the defibrillation lead.     

A randomized comparison of defibrillation thresholds in the right ventricular outflow tract versus right ventricular apex

OBJECTIVE: To determine whether the placement of an implantable cardioverter-defibrillator (ICD) lead in the right ventricular outflow tract (RVOT) has the same defibrillation threshold (DFT) as the right ventricular apex (RVA). BACKGROUND: Right ventricular ICD leads have usually been placed in the RVA. Development of active fixation technology has allowed the placement of these leads in alternate locations such as the RVOT. METHODS: At time of device implantation, 26 patients with either ischemic or dilated cardiomyopathy underwent DFT testing in both the RVA and RVOT using a binary search algorithm. RESULTS: Placement of the lead in the RVA had a mean DFT of 7.6 +/- 2.8 J while the placement of the lead in the RVOT had a mean DFT of 10.3 +/- 3.0 J. The median (25th and 75th percentiles) DFTs in the RVA and RVOT were 7.5 J (6 and 11 J) and 11 J (9 and 14 J), respectively (p = 0.0002). CONCLUSIONS: Placement of the right ventricular lead in the RVA has a significantly lower DFT than placement of the lead in the RVOT.     

Clinical predictors of atrial defibrillation thresholds with a dual-coil, active pectoral lead system.

OBJECTIVES: The purpose of this study was to identify clinical predictors of atrial defibrillation thresholds (DFTs) with standard implantable cardioverter-defibrillator (ICD) leads. BACKGROUND: Atrial defibrillation can be achieved with active pectoral, dual-coil transvenous ICD lead systems. If clinical predictors of atrial defibrillation efficacy with these lead systems were identified, they could be used to predict which patients may require more complex lead systems for atrial defibrillation, such as a coronary sinus electrode. METHODS: This was a prospective study of 135 consecutive patients undergoing initial ICD implant for standard indications. The lead system evaluated was a transvenous defibrillation lead with coils in the superior vena cava (SVC) and right ventricular apex (RV), and a left pectoral pulse generator emulator (CAN). The shocking pathway was RV-->SVC+CAN. Atrial DFT was measured using a step-up protocol. Clinical and echocardiographic parameters were evaluated as predictors of atrial DFT and multiple linear regression was performed. RESULTS: Mean atrial DFT was 4.6 +/- 3.8 J. Atrial DFT was < or =3 J in 70 patients (52%) and < or = 10 J in 97% of patients. The highest atrial DFT was 20 J (one patient). Left atrial size (r = 0.21, P = .01) and left ventricular end-diastolic diameter (r = 0.19, P = .02) were independent predictors of atrial DFT. However, these two predictors accounted for only 6% of the variability in atrial DFT. CONCLUSIONS: Clinical parameters are of limited use in predicting atrial DFT with a dual-coil, active pectoral ICD lead system. Because the RV--> SVC + CAN shocking pathway provides reliable atrial and ventricular defibrillation, this configuration should be preferred for combined atrial and ventricular ICDs.     

置入型心律转复除颤器52例术中除颤阈值的测定及术后随访

目的 探讨置入型心律转复除颤器(ICD)置入术中除颤阈值(DFT)的测定方法并观察术后随访结果.方法 52例置入ICD患者,其中单腔ICD 25例(48.08%),双腔ICD 23例(44.23%),三腔ICD 4例(7.69%).置入术中用测定除颤安全范围(DSM)方法进行DFT测定,并对患者进行定期随访.结果 52例ICD置入术中,测得DFT为(13.27±2.95)J,DSM为(17.40±2.89)J,手术中无严重并发症发生.52例中,38例出现恶性室性心律失常,其中469次为非持续性(可自行终止)室性心动过速(VT),持续性VT发作265次;经抗心动过速起搏治疗1阵转复成功245次(92.45%),2阵转复成功13次(4.91%),抗心动过速起搏治疗转复未成功经电转复7次(2.64%),均经低能量电转复成功.心室颤动(VF)发作141次均成功识别,其中14次在释放治疗前VF自行终止.127次VF经电除颤治疗,经电除颤治疗1次成功116次(91.34%),除颤能量为(12.84±3.18)J,2次成功11次(8.66%),除颤能量为(16.36±2.34)J.结论 应用DSM测定进行ICD置入术中DFT测定安全可行.     

Optimization of atrial defibrillation with a dual-coil, active pectoral lead system

INTRODUCTION: Atrial defibrillation can be achieved with standard implantable cardioverter defibrillator (ICD) leads, but the optimal shocking configuration is unknown. The objective of this prospective study was to compare atrial defibrillation thresholds (DFTs) with three shocking configurations that are available with standard ICD leads. METHODS AND RESULTS: This study was a prospective, randomized, paired comparison of shocking configurations on atrial DFTs in 58 patients. The lead system evaluated was a transvenous defibrillation lead with coils in the superior vena cava (SVC) and right ventricular apex (RV) and a left pectoral pulse generator emulator (Can). In the first 33 patients, atrial DFT was measured with the ventricular triad (RV --> SVC + Can) and unipolar (RV --> Can) shocking pathways. In the next 25 patients, atrial DFT was measured with the ventricular triad and the proximal triad (SVC --> RV + Can) configurations. Delivered energy at DFT was significantly lower with the ventricular triad compared to the unipolar configuration (4.7 +/- 3.7 J vs 10.1 +/- 9.5 J, P < 0.001). Peak voltage and shock impedance also were significantly reduced (P < 0.001). There was no significant difference in DFT energy when the ventricular triad and proximal triad shocking configurations were compared (3.6 +/- 3.0 J vs 3.4 +/- 2.9 J for ventricular and proximal triad, respectively, P = NS). Although shock impedance was reduced by 13% with the proximal triad (P < 0.001), this effect was offset by an increased current requirement (10%). CONCLUSION: The ventricular triad is equivalent or superior to other possible shocking pathways for atrial defibrillation afforded by a dual-coil, active pectoral lead system. Because the ventricular triad is also the most efficacious shocking pathway for ventricular defibrillation, this pathway should be preferred for combined atrial and ventricular defibrillators.     

Effect of an active abdominal pulse generator on defibrillation thresholds with a dual-coil, transvenous ICD lead system

INTRODUCTION: Many patients with implantable cardioverter defibrillators (ICDs) have older lead systems, which are usually not replaced at the time of pulse generator replacement unless a malfunction is noted. Therefore, optimization of defibrillation with these lead systems is clinically important. The objective of this prospective study was to determine if an active abdominal pulse generator (Can) affects chronic defibrillation thresholds (DFTs) with a dual-coil, transvenous ICD lead system. METHODS AND RESULTS: The study population consisted of 39 patients who presented for routine abdominal pulse generator replacement. Each patient underwent two assessments of DFT using a step-down protocol, with the order of testing randomized. The distal right ventricular (RV) coil was the anode for the first phase of the biphasic shocks. The proximal superior vena cava (SVC) coil was the cathode for the Lead Alone configuration (RV --> SVC). For the Active Can configuration, the SVC coil and Can were connected electrically as the cathode (RV --> SVC + Can). The Active Can configuration was associated with a significant decrease in shock impedance (39.5 +/- 5.8 Omega vs. 50.0 +/- 7.6 Omega, P < 0.01) and a significant increase in peak current (8.3 +/- 2.6 A vs. 7.2 +/- 2.4 A, P < 0.01). There was no significant difference in DFT energy (9.0 +/- 4.6 J vs. 9.8 +/- 5.2 J) or leading edge voltage (319 +/- 86 V vs. 315 +/- 83 V). An adequate safety margin for defibrillation (> or =10 J) was present in all patients with both shocking configurations. CONCLUSION: DFTs are similar with the Active Can and Lead Alone configurations when a dual-coil, transvenous lead is used with a left abdominal pulse generator. Since most commercially available ICDs are only available with an active can, our data support the use of an active can device with this lead system for patients who present for routine pulse generator replacement.