用实验性心力衰竭制作持续性心房颤动模型

为探讨实验性心力衰竭（简称心衰）形成持续性心房颤动（简称房颤）的可行性，用２００～２５０ｐｐｍ的频率以ＶＯＯ方式起搏犬心室３～７周形成实验性心衰，在犬清醒状态下观察心衰前、后刺激诱发的房性快速心律失常。快速起搏右室３～７周，８条犬均发生充血性心衰，３周时体重由心衰前的２８±６ｋｇ降至２４±４ｋｇ（Ｐ＜０．０５）；左室射血分数由０．６４±０．０６降至０．２３±０．０９（Ｐ＜０．０１），右房直径由２５±３ｍｍ增至３６±６ｍｍ（Ｐ＜０．０１），心房不应期由１１６±５ｍｓ增至１３７±１２ｍｓ（Ｐ＝０．０１），不应期离散度无显著性改变（１６±１２ｍｓｖｓ２０±９ｍｓ，Ｐ＝０．２０），心房平均传导时间亦无显著性变化（６１±１９ｍｓｖｓ６６±２４ｍｓ，Ｐ＝０．２０）。１条犬于起搏后第６周夜间突然死亡。心衰前，８条犬均未诱发心房扑动，４条犬诱发短暂房颤；心衰后，８条犬均可反复诱发心房扑动和持续性房颤（持续时间超过１５ｍｉｎ，平均周长９５±５ｍｓ），最长者持续２４ｈ以上。结果表明起搏心室导致犬心衰可形成非瓣膜病性慢性房颤的实验模型。     

不同起搏方式对病窦综合征患者远期效果的影响

为了解不同起搏方式对病窦综合征特别是慢－快综合征患者心功能及房性心律失常的影响，利用超声心动图、体表心电图及Ｈｏｌｔｅｒ检查，对２１１例病窦综合征患者采用自身对照方法进行回顾性分析。结果发现：生理性起搏（ＡＡＩ／ＤＤＤ）组术后左室射血分数（ＬＶＥＦ）、心输出量（ＣＯ）明显增加（ＡＡＩ：５３．５±６．１％ｖｓ４７．２±７．８％，４．９５±０．５７Ｌ／ｍｉｎｖｓ４．２０±０．６２Ｌ／ｍｉｎ；ＤＤＤ：５２．５±６．８％ｖｓ４４．３±０．１％，５．１２±０．７１Ｌ／ｍｉｎｖｓ４．４１±０．３８Ｌ／ｍｉｎ；Ｐ均＜０．０１），左房内径（ＬＡＤ）无明显变化；ＤＤＤ组Ｅ／Ａ比值明显增加（０．９８±０．０９ｖｓ０．８７±０．１５，Ｐ＜０．０１），ＡＡＩ组Ｅ／Ａ比值呈增加趋势（Ｐ＝０．０５７）。房性心律失常发生率明显减少（１５．９％ｖｓ５０％，Ｐ＜０．０１）。非生理性起搏（ＶＶＩ）组术后ＬＶＥＦ、ＣＯ明显下降（４４．１±４．７％ｖｓ４８．３±４．３％，３．７７±０．４２Ｌ／ｍｉｎｖｓ４．１７±０．８５Ｌ／ｍｉｎ，Ｐ均＜０．０１），ＬＡＤ明显增大（３９．２６±２．３７ｍｍｖｓ３６．８１±２．３５ｍｍ，Ｐ＜０．０１），Ｅ／Ａ比值呈?     

VDD起搏对缓慢性心律失常心力衰竭的血液动力学影响

为了评估ＶＤＤ起搏对缓慢性心律失常心力衰竭的血液动力学影响，对２１例心功能Ⅲ～Ⅳ级的缓慢性心律失常病人安置ＶＤＤ起搏器，并用Ｓｗａｎ－Ｇａｎｚ导管监测起搏前和起搏后３０ｍｉｎ、２４ｈ、４８ｈ、７２ｈ的心输出量（ＣＯ）、心脏指数（ＣＩ）、右房压（ＲＡＰ）、平均肺动脉压（ＭＰＡＰ）和肺毛细血管楔嵌压（ＰＣＷＰ），并记录各时期的心房率（ＡＲ）和心室率（ＶＲ）。结果：ＶＲ在术后即时及各时期显著升高（Ｐ均＜０．０５），ＣＯ、ＣＩ在起搏后３０ｍｉｎ即显著升高〔分别为４．１８±０．８１Ｌ／ｍｉｎｖｓ２．８１±０．９３Ｌ／ｍｉｎ、２．３６±０．６６Ｌ／（ｍｉｎｍ２）ｖｓ１．１８±０．６３Ｌ／（ｍｉｎｍ２），Ｐ均＜０．０５〕，起搏４８ｈ达高峰；ＲＡＰ、ＭＰＡＰ、ＰＣＷＰ在起搏后３０ｍｉｎ无显著改变（Ｐ＞０．０５），但２４ｈ开始显著性下降（分别为１．２８±０．４１ｋＰａｖｓ１．４１±０．３４ｋＰａ、２．６０±０．５１ｋＰａｖｓ３．４０±０．５６ｋＰａ、３．１０±０．５６ｋＰａｖｓ３．５４±０．６８ｋＰａ，Ｐ均＜０．０５），７２ｈ后进一步降低。结果提示ＶＤＤ起搏治疗能显著改善缓慢性心律失常心力衰竭的血液动力学，可作为治疗缓慢性心?     

电极组合方式与经食管心房起搏阈值的关系

对１０７例病人每例用六极起博导管组成１０种起搏电极组合，以相同脉宽和导管位置作食管心房起搏。发现负极接第３极，正极接第２、４、５极的四极组合法起搏阈值仅１８．８±３．０Ｖ，仅２例（１．９％）有明显不适感，与其它组合方法比较差异非常显著（Ｐ＜０．０１），该法起搏脉冲振幅适中，与Ｖ１导联的ＱＲＳ波方向相反。便于进行观察，测量和分析。因此，有助于食管心房调搏术的推广应用。     

心房起搏阈值的随访分析

对３３例植入心房电极者进行起搏阈值的随访，结果表明：起搏阈值峰值为１．４４±０．７４Ｖ／０．５ｍｓ，出现在植入后两周内；慢性期起搏阈值为１．２２±０．４０Ｖ／０．５ｍｓ；伴器质性心脏病患者慢性期起搏阈值（１．７０士０．３７Ｖ／０．５ｍｓ）明显高于不伴器质性心脏病者（１．１６±０．３７Ｖ／０．５ｍｓ），Ｐ＜０．０１；激素电极的起搏阈值峰值（１．１２±０．２９Ｖ／０．５ｍｓ）和慢性期起搏阈值（０．７７±０．１７Ｖ／０．５ｍｓ）均显著低于非激素电极（１．８０±０．６８Ｖ／０．５ｍｓ和１．４０±０．３３Ｖ／０．５ｍｓ），Ｐ＜０．０５及０．００１。提出在非特殊情况下，将出厂时的电能由５．０Ｖ／０．５ｍｓ降至２．５Ｖ／０．５ｍｓ既可保证有效起搏，又可节省电能，从而延长起搏器的使用寿命。     

心肌缺血对心室颤动的诱发和除颤效率的影响

近来埋藏式心律转复除颤器（ＩＣＤ）已成为抗心律失常药物治疗无效的高危病人的优先选择。由于大多数需要ＩＣＤ治疗的病人常伴有缺血性心脏病,因此急性心肌缺血对ＩＣＤ病人的除颤失败和心脏猝死可能起一定作用。本文在离体灌流兔心脏标本上测定了急性心肌缺血对单相动作电位（ＭＡＰ）各参数以及心室颤动（ＶＦ）诱发和除颤的影响。结果表明,心肌缺血１５ｍｉｎ缩短ＭＡＰ时程（复极达９０％,ＡＰＤ９０）（１５４±８ｍｓｖｓ１０２±１８ｍｓ,Ｐ＜０．００１）和复极时间（ＲＴ９０）（１８５±６ｍｓｖｓ１３８±１３ｍｓ,Ｐ＜０．００１）;使激活时间（ＡＴ）增加（３１±５ｍｓｖｓ３６±８ｍｓ,Ｐ＜０．０１）;同时使ＲＴ９０弥散明显增加（３７±１６ｍｓｖｓ６９±２９ｍｓ,Ｐ＜０．０１）。心肌缺血对易损性上限（ＵＬＶ）和除颤阈值（ＤＦＴ）稍有影响,但无统计学意义（ＵＬＶ：２７４±５３Ｖｖｓ２９４±４４Ｖ,Ｐ＝ＮＳ;ＤＦＴ２６８±４２Ｖｖｓ２７１±３３Ｖ,Ｐ＝ＮＳ）;却使易损窗（ＶＷ）的宽度增加三倍（对照２５±２２ｍｓ,缺血１５ｍｉｎ时７５±２６ｍｓ,Ｐ＜０．００１）。复极时间与ＶＷ边界的相关分析表明,ＶＷ左边界和１０个ＭＡＰ中最短的ＲＴ９０高度?     

体动感知频率应答型起搏器的频率应答及运动耐量观察

采用动态心电图连续监测１０例安装体动式ＶＶＩＲ起搏器者休息、登梯、散步、快走、拖地板、二级梯试验、扩胸运动、按压起搏器时的频率应答情况。结果显示体动式ＶＶＩＲ起搏器频率应答的上升或下降速度较符合生理；频率应答与活动幅度、走动速度有关（ｒ＝０．６７．Ｐ＜０．０１），与用力程度、耗能大小的相关性较差。应用Ｍａｓｔｅｒ二级梯试验按照随机、双盲、交叉对照原则比较了ＶＶＩ、ＶＶＩＲ二种起搏方式运动耐量的差别，结果６例起搏器依赖者的运动时间ＶＶＩＲ比ＶＶＩ明显延长（８．６±１．２ｍｉｎＶＳ５．８±１．６ｍｉｎ，Ｐ＜０．０５）．本结果提示：体动式频率应答型起搏器频率反应速度快，较符合生理情况，并可提高运动耐量。     

心室频率适应式起搏对老年患者的应用价值

为探讨心室频率适应式起搏（ＶＶＩＲ）对老年人的应用价值，对１８例安置ＶＶＩＲ的老年患者按单盲交叉法随机程控为ＶＶＩＲ及ＶＶＩ两种起搏方式各四周，起搏期间作有关症状的定量评分、生活质量量表评价，并对患者进行自行选择起搏方式的调查。１６例完成上述研究者显示ＶＶＩＲ方式起搏时乏力与气急症状评分值较ＶＶＩ方式起搏时增加（３．８±１．３ｖｓ３．５±１．４，４．５±０．８ｖｓ４．３±１．０，Ｐ均＜０．０５），即症状好转；而心悸、头晕、胸闷、胸痛症状评分及每日硝酸甘油用量比较，差异无显著性（Ｐ均＞０．０５）。ＶＶＩＲ方式起搏时总体生活质量、精神状态及认知能力、社会参与性评分值较ＶＶＩ方式起搏时明显提高（１３２．６±１２．１ｖｓ１２５．０±１７．２，４０．４±４．４ｖｓ３８．４±５．７，１７．１±２．７ｖｓ１５．８±２．１，Ｐ均＜０．０５）。选择ＶＶＩＲ方式起搏者多于选择ＶＶＩ者（６２，Ｐ＜０．０５）。结果提示：ＶＶＩＲ起搏较ＶＶＩ起搏更能改善老年患者的自觉症状、提高其生活质量     

右室流出道特发性室速的射频消融治疗体会

目的 总结不同起源部位特发性右室流出道室性心动过速（ＩＲＶＯＴ）经导管射频消融（ＲＦＣＡ）治疗的方法和结果。方法 对３５例ＩＲＶＯＴ进行ＲＦＣＡ治疗,男性１８例、女性１７例,平均年龄（３９．１±１８．３）岁（８～７２岁）。其中１５例用常规方法消融,２０例用非常规方法消融,非常规方法加用８Ｆ ＳＢ０ Ｓｗａｒｔｚ鞘并在右室流出道放置参考电极。两者均采用起搏与激动标测来确定消融靶点。结果ＲＦＣＡ治疗ＩＲＶＯＴ的总成功率为８８．６％（３３／３５）,常规方法组成功率为８６．７％,复发率为１５．３％,非常规方法组分别为９０．１％和５．６％;常规方法组的导管操作时间为（７１±１２）ｍｉｎ,Ｘ线曝光时间平均为（３２±８）ｍｉｎ,非常规组分别为（４０± ９）ｍｉｎ和（１６ ±５）ｍｉｎ。ＩＲＶＯＴ起自右室流出道近间隔部１３例、游离壁１０ 例及介于两者之间 １２例。成功消融部位激动标测 Ｖ波提前 ＱＲＳ波 １８～３８ｍｓ,起搏标测与心动过速时１２导联心电图（ＥＣＧ）之ＱＲＳ波形态完全相同。结论ＩＲＶＯＴ非常规方法消融可以明显缩短导管操作时间、减少Ｘ线曝光时间及降低复发率;ＩＲＶＯＴ采用ＲＦＣＡ治疗具有较高的成功率和较低的复发率及并发症。     

MS-551对麻醉犬心肌的电生理作用及血液动力学影响

为研究１，３二甲基－６［２－（Ｎ－２羟乙基－３－４硝苯丙氨基）乙氨基］－２，４（１Ｈ，３Ｈ）－盐酸嘧啶二酮即ＭＳ－５５１（简称ＭＳ）对麻醉犬心肌的电生理作用和血液动力学影响，采用自身前后对照的方法测定用药（５ｍｉｎ内每公斤体重静脉注射ＭＳ０．５ｍｇ，继以每公斤体重静脉滴注０．５ｍｇ持续３０ｍｉｎ）前后麻醉犬（ｎ＝８）有关电生理参数及心输出量、肺毛细血管楔嵌压等变化。结果表明ＭＳ：①使心房有效不应期和心室有效不应期显著延长，分别为２７．１±６．８，２０．７±５．２ｍｓ，Ｐ均＜０．０１。②使自发性窦性周期、窦房结恢复时间和校正的窦房结恢复时间均显著延长，分别为４１．４±８．０，５０．０±９．８，８．６±３．４ｍｓ，前两者Ｐ＜０．０１，后者Ｐ＜０．０５。但对窦房传导时间无明显影响（３．６±１．８ｍｓ，Ｐ＞０．０５）。③对ＡＨ、ＨＶ、ＰＱ间期及ＱＲＳ波群时限无明显影响，显著延长ＱＴ间期，明显降低文氏点（调搏周长延长）。④轻度减低心输出量，但无统计学意义（变化值：－０．５６±０．２３Ｌ／ｍｉｎ，Ｐ＝０．０６１），对肺毛细血管楔嵌压无显著性影响。结论：ＭＳ延长心肌不应期，对心内传导影响不明显，有良好的血液动力学特性，可?     

Role of a catheter lead system for transvenous countershock and pacing during electrophysiologic tests: an assessment of the usefulness of catheter shocks for terminating ventricular tachyarrhythmias

The practicality and safety of using a single catheter system for transvenous countershock, programmed stimulation and ventricular pacing during electrophysiologic tests were evaluated in 13 patients with inducible sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). The efficacy and patient toleration of transvenous countershock were compared with other methods of arrhythmia termination. The same lead was used for programmed stimulation at the right ventricular apex and for VT termination by pacing methods during serial testing (20 ± 15 days [mean ± standard deviation]). Synchronized countershock using energies that patients found tolerable (0.01 to 5 J) terminated 31 of 50 episodes (62%) of induced VT. Episodes of VT cardioverted with these low energies were distinguished from other episodes by a longer cycle length (352 ± 62 ms versus 297 ± 50 ms, p < 0.004). Among paired episodes of VT matched for patient, date of induction, morphologic characteristics, cycle length and drugs administered, pacing methods (single extrastimuli and bursts of rapid pacing) were just as effective as low-energy countershock for VT termination (25 of 25 versus 21 of 25, difference not significant). Transvenous countershock was uniformly effective for termination of ventricular flutter and VF when sufficient energy was used (range 5 to 30 J, mean 20.4 ± 7.7). This required interfacing leads to a defibrillation unit. VT acceleration occurred during 7 of 50 synchronized low-energy cardioversion attempts (14%). There was no evidence of myocardial injury as a result of shocks as high as 30 J, but patients required increasing sedation when energy exceeded 0.5 J.Thus, a single catheter system can be used for programmed stimulation, ventricular pacing and countershock during electrophysiologic tests. Low-energy countershock (0.01 to 5 J) is no more effective than pacing methods for VT termination and is tolerated less well. The most practical use of this catheter system, including any implantable unit, may be for slightly higher energy (5 to 30 J) countershock termination of repeated episodes of very rapid VT or VF, in which pacing techniques are ineffective. This method may be safer and less traumatic than conventional transthoracic countershock.     

DDDR起搏器程控功能的临床应用价值

对埋植ＤＤＤＲ起搏器的２１例患者随访２６（６～５４）个月，未见电极移位。２０条激素电极慢性能量阈值为０．４４±０．５１μＪ，有意义地低于１５条螺旋电极的１．８９±１．９８μＪ。通常程控到慢性能量阈值的３倍以获得适当的安全范围，其中６５％的激素电极程控到１．６Ｖ，０．３ｍｓ仍具３．９４倍能量阈值的安全范围。提示具有较大范围可程控电压和脉宽输出的ＤＤＤＲ起搏器配用低阈值激素电极可延长起搏器寿命，这也将是今后起搏系统设计的方向。     

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。     

Ventricular capture management in pediatric pacing: efficacy and safety.

BACKGROUND: The Ventricular Capture Management (VCM) of Medtronic Kappa 700 series pacemakers (PM) performs automatic threshold detection and optimization of pacing output that may enhance generator longevity. We evaluated efficacy and safety of this algorithm in children. METHODS: The study was prospective, non-randomized, involving 50 consecutive patients (mean age 5.6 +/- 6.6 years, median 4 years), enrolled at first PM implant. VCM was active from the implant, with nominal values of safety margin, minimum adapted pulse amplitude and width. Leads were endocardial and epicardial, all unipolar. Thresholds and pacing outputs were registered with telemetric PM interrogation. Endocardial and epicardial thresholds and outputs were also compared. Follow-up duration was 27 +/- 13 months (range 6-49 months). RESULTS: A significant reduction in pulse amplitude was evident since the sixth month. Thresholds and outputs were lower in endocardial than in epicardial pacing. A false negative capture detection occurred during the "acute phase" in 3 patients (6.0%), with incorrect automatic output increase to 5 V/1 ms. After this phase, the problem was still detected in 2 patients (4.0%). VCM correctly identified threshold increases in 2 patients (1%). No pacing defect was documented. VCM was not performed in 4 infants (8.0%) for pacing rate > or = 100 b/min. CONCLUSIONS: VCM function is safe and effective in reducing pacing output in pediatric patients; this may increase PM longevity. Epicardial pacing shows higher thresholds and outputs than endocardial pacing.     

117例低能量起搏患者的长期随访观察

对１１７例安装不同品牌、型号起搏器的患者进行长期随访观察，探讨低能量起搏的安全性及程控计算方法。在安装起搏器２个月～１２年后测定起搏阈值，结果为２．４３±０．７５Ｖ、０．１４±０．１０ｍｓ，同时将脉宽设置为阈值的２倍、３倍或更多。１５例经１．１～４．３年的随访，再次重复测定阈值（８例增加、４例下降、３例不变），并调整相应参数。１１７例患者的随访时间为１～６年，此间均未发现起搏失效。由此认为起搏阈值设置为能量阈值的３～４倍是安全的。     

Effect of pacing rate on the human atrial strength-duration curve

The effect of rapid pacing on the atrial constant voltage stimulation threshold in humans has not been defined at rates applicable to those of antitachycardia pacing. The effect of pacing rate on the atrial strength-duration relation was determined in 10 patients at pacing rates between 125 and 300 beats/min to explore excitability over the range of rates used for permanent antitachycardia pacing systems. Two points that define the strength-duration curve were measured at each pacing rate: rheobase voltage--the lowest stimulus voltage that results in capture at a pulse duration of 2 ms; and chronaxie pulse duration--the threshold pulse duration at twice rheobase voltage. A permanent, tined, J-shaped pacing lead with a high current density and low polarization electrode was positioned in the right atrial appendage for cathodal stimulation. A constant voltage output, incorporating a fast recharge pulse designed to minimize electrode polarization, was used for stimulation. There was a significant increase in rheobase voltage (p = 0.009), chronaxie pulse duration (p = 0.001) and minimal threshold stimulus energy (p = 0.05) at pacing rates greater than 225 beats/min. A rheobase voltage greater than 5 V occurred in three patients at pacing rates greater than or equal to 275 beats/min. At a pacing rate of 300 beats/min, rheobase voltage had increased in 8 of 10 patients.(ABSTRACT TRUNCATED AT 250 WORDS)     

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。     

Postcountershock pulseless rhythms: response to CPR, artificial cardiac pacing, and adrenergic agonists

Clinically, countershock of ventricular fibrillation (VF) may result in asystole or a pulseless rhythm in more than 50% of attempts. We conducted a study to assess the effects of immediate artificial pacing, CPR, and adrenergic drug therapy in the management of postcountershock pulseless rhythms. Thirty-four episodes of VF followed by countershock were studied in eight anesthetized dogs. Transducer-tipped catheters were positioned in the ascending aorta (Ao) and right atrium (RA). A bipolar pacing catheter was advanced to the apex of the right ventricle and a catheter for measurement of coronary sinus blood flow (CSQ) (continuous thermodilution technique) was positioned in the coronary sinus. VF was induced electrically and a countershock at 400 J was given two minutes later; CPR was not performed during VF episodes. Countershock was followed by asystole or a pulseless rhythm in all animals. Immediate endocardial pacing (0.1 to 5 mA) of bradyarrhythmias produced electrical capture but did not result in arterial pressure pulses in any animal. After pacing, CPR was performed for two minutes or until restoration of spontaneous circulation (ROSC). During CPR, the diastolic coronary perfusion gradient (Ao-RA) was 20 +/- 7 mm Hg (mean +/- SD) and CSQ was 14 +/- 7 mL/min/100 g (53% +/- 43% of control). ROSC followed CPR of less than two minutes duration in 24% of VF study episodes. If ROSC did not follow two minutes of CPR, 1 mg epinephrine, or 50 micrograms or 100 micrograms isoproterenol was given IV.(ABSTRACT TRUNCATED AT 250 WORDS)     

Changes in pacing threshold and R wave amplitude after transvenous catheter countershock

Transvenous electrode catheter countershock in patients with recurrent ventricular tachyarrhythmias may be followed by transient bradycardia and require temporary pacing with a catheter. The serial changes in R wave amplitude and stimulation threshold after catheter countershock in 11 halothane-anesthetized open chest dogs ranging in weight from 11.8 to 24 kg were studied. Ventricular fibrillation was electrically induced and followed by catheter defibrillation using nonsynchronized trapezoidal waveform (65% tilt) current discharge in incremental doses (5 to 50 J). Significant decreases in bipolar R wave amplitude (8.3 +/- 1 versus 2 +/- 0.2 mV, p less than 0.001) and increases in stimulation threshold (1 +/- 0.1 versus 2.3 +/- 0.4 V, p less than 0.001) were observed using the countershock catheter 15 seconds after countershock; these changes persisted for up to 10 minutes. To determine whether these changes were localized to the defibrillating catheter and whether they were species-specific, a second electrode catheter was positioned in the right ventricle distant from the countershock catheter in five pigs. Increases in stimulation threshold were observed only at the countershock catheter, suggesting that changes were secondary to local changes at the catheter-myocardium interface. No significant change in R wave amplitude or stimulation threshold was observed at the countershock catheter in three pigs given transthoracic shocks (60 to 250 J). It is concluded that current discharge through the countershock catheter results in a significant temporary reduction in R wave amplitude and an increase in pacing threshold. This may make pacing through the countershock catheter unreliable after shock delivery.     

右室双部位起搏与双室同步起搏的急性血液动力学对比研究

比较右室双部位 (RV Bi)起搏和双室 (BiV)同步起搏对血液动力学的影响 ,并与右室心尖部 (RVA)、右室流出道 (RVOT)、左室基底部 (LVB)起搏相比较 ,明确双部位起搏是否优于单部位起搏。 15例患者中病窦综合征 8例、Ⅲ度房室阻滞 7例。分别行RVA、RVOT、LVB、RV Bi、BiV起搏 (VVI,6 0～ 90次 /分 ) ,测定心输出量 (CO)和心脏指数(CI)、肺毛细血管嵌顿压 (PCWP)和QRS波时限 (QRSd)。结果 :①与RVA起搏相比 ,RVOT、LVB、RV Bi、BiV起搏CI分别增加了 7.5 %、11.3%、15 .5 %和 17.2 % ,PCWP分别降低了 14.9%、10 .3%、2 1.7%和 2 0 .0 % (P均 <0 .0 1)。②RV Bi、BiV起搏较RVOT、LVB起搏的CO、CI增高而PCWP降低 (P均 <0 .0 5 )。③RV Bi与BiV起搏、RVOT与LVB起搏之间CO、CI和PCWP无显著差异。④RVOT、RV Bi、BiV起搏的QRSd(分别为 12 8± 11,111± 16 ,10 3± 13ms)较RVA起搏 (146± 18ms)时显著缩短 (P≤ 0 .0 0 1) ,而LVB起搏 (142± 15ms)与RVOT、RVA起搏时无显著差异。结论 :RV Bi起搏和BiV同步起搏的急性血液动力学效果无明显差异 ,但双部位起搏的效果明显优于单部位起搏 ;双部位起搏的QRSd也比单部位起搏明显缩短