阈下条件刺激对心室不应期及心室起搏节律的作用

通过右心电极导管法观察14例病人阈下条件单个刺激(S_s)和串刺激(S_t)对心室不应期和心室起搏节律的作用,初步结果表明,在S_1-S_2间期中加发S_t,可使心室相对不应期和有效不应期延长;且随S_t强度的增加,不应期延长量增加:在S_1-S_2间期中加发S_s,仅3.9例心室相对及有效不应期延长。另外,S_t和S_s可抑制心室起搏节律。     

阈下刺激对家兔心室不应期影响测定方法的建立

在心室不应期中施予阈下刺激不能使心室产生新的兴奋,但能使受刺激局部的心肌不应期延长或缩短。临床上,已利用这一特性成功地终止了室上性和室性心动过速。以往阈下刺激作用的基础电生理研究主要在人体进行,但观察方法有创且繁琐。本文根据在体兔心室电生理特点,建立了适合于兔的阈下条件刺激对心室不应期影响观察的新方法,为进一步深入研究打下基础。     

电刺激犬心室神经节丛对自主神经介导房颤的影响

目的 本研究探讨低频电刺激心室主动脉根部神经节丛（ganglionated plexi,GP）对肺静脉源性房颤(AF)诱发率的影响。方法 20只犬分别测量基础状态下,高频和低频电刺激主动脉根部GP时的心房有效不应期和肺静脉有效不应期。分别在基础状态下,高频和低频电刺激主动脉根部GP时,自肺静脉远端以程序刺激诱发AF和AF诱发率的变化。结果 高频电刺激主动脉根部GP 明显缩短心房的肺静脉的有效不应期,增加AF的诱发率。而低频电刺激使心房及肺静脉有效不应期呈延长趋势,并降低AF诱发率。结论 低频电刺激主动脉根部GP降低自主神经介导的AF诱发率。     

依那普利对心房急性电重构影响的临床研究

目的　探讨依那普利对快速心房起搏诱发心房急性电重构的干预作用。方法　 2 7例阵发性室上性心动过速行射频消融术患者随机分为对照组 ( 16例 )和依那普利组 ( 11例 )。阻断自主神经后 ,以最快 1:1心房起搏 [( 349± 37) /min]诱发急性心房颤动 (房颤 ) ,观察各组患者心房快速刺激前后心房有效不应期 (AERP)、AERP频率自适应性、不应期离散度 (AERPd)的变化及房颤诱发情况。结果　①心房快速起搏后 ,对照组AERP明显缩短 ,依那普利组AERP无显著变化。两组患者心房快速起搏前后AERPd差异无显著性 ;②心房快速起搏前后 ,对照组右心耳 (RAA)处AERP与相应程控刺激基础周长拟合直线的斜率分别为 0 0 6 2和 0 0 18;依那普利组分别为 0 0 5 9和 0 0 5 3;③心房快速起搏后 ,对照组房颤诱发例数、次数显著增加 ,平均房颤持续时间明显延长 ;依那普利组心房快速起搏前后房颤诱发情况无显著差异。结论　依那普利能够防止心房快速激动引起的心房急性电重构 ,降低房颤诱发率     

植物神经对实验性心肌梗塞心脏电生理性质的影响

本文观察了植物神经对缺血心肌电生理性质的影响。结果表明在切除迷走神经的条件下,刺激交感神经可降低心室起搏阈值、室颤阈值,缩短心室相对不应期和有效不应期,并使强度间期曲线向左明显移位。上述变化可促进室性心律失常的发生。     

食管心房调搏对预激综合征潜在危险性的评价

为探讨评价预激综合征潜在危险性的方法,采用食管心房调搏检查32例显性预激综合征患者。结果显示程控刺激的起搏周长由≥600ms缩短至≤400ms时,旁道顺向有效不应期均值由287.19±31.85缩短至264.06±36.27ms,≤270ms的短旁道顺向有效不应期检出率由21.88％增至53.13％,旁道1:1下传最大心室率与起搏周长≥600ms及≤400ms的旁道顺向有效不应期均呈负相关(r分别为-0.68及-0.79);心房颤动时经旁道下传最短R-R间期与旁道1:1下传最大心室率呈负相关(r=-0.96),与起搏周长≥600ms及≤400ms的旁道顺向有效不应期呈正相关(r分别为0.79及0.93)。与早期心内电生理研究结果基本一致。认为食管心房调搏在很大程度上可替代心内电生理测定旁道顺向有效不应期(程控刺激的起搏周长至少包括≥600ms及≤400ms)、旁道1:1下传的最大心室率及心房颤动时心室反应来评价预激综合征潜在危险性。     

经食管心房调搏对阵发性房颤患者心房电生理特性的研究

用食管心房调搏技术，对２０例阵发性房颤患者及２０例健康成年人的心房电生理特性进行对照研究。结果显示：阵发性房颤患者的心房有效不应期缩短，相对不应期延长，早搏刺激的房间传导延缓显著增加。这些异常可能是房颤患者基本的电生理学改变。认为在心房电生理的研究方面，食管心房调搏可望部分代替心内电生理检查。     

心房电重构与房颤关系的基础研究

目的检查观测心房电生理改变与房颤（AF）发生和持续的关系,探讨心房电重构与房颤的内在联系。方法健康成年杂种犬14只（雌雄不拘,体重10．0～12．5kg）,随机分为2组：对照组（A组）和起搏组（B组）。右侧开胸将电极置于右心房,以400次／min的频率快速起搏右心房（A组只手术不起搏）,分别于实验开始及起搏6h后对每只犬进行电生理检查,测定心房有效不应期（AERP）。起搏开始及起搏后测定burst刺激诱发房颤的频率和持续时间。结果A组在整个时间内AERP无变化,B组心房快速起搏后,AERP明显缩短。A、B两组起搏前房颤的频率和持续时间差异无统计学意义。A组起搏前、后房颤的频率和持续时间无变化,B组心房快速起搏后房颤的频率增多,持续时间延长。结论快速心房起搏可以引起心房有效不应期缩短,即心房电重构。心房电重构造成的心房有效不应期等电生理变化促进了房颤的发生和维持,是心房电重构与房颤关系的基础。     

室房逆传对窦房结功能及心房肌电活动影响及其意义的实验研究

目的:探讨室房逆传(VAC)对兔窦房结功能低下动物模型窦房结功能及心房肌电活动的影响.方法:选用40只健康新西兰大耳白家兔,其中32只成功制作窦房结功能低下动物模型,以200次/分的起搏频率起搏右心室,将家兔分为1:1VAC组(22只)、非1:1VAC组(10只).观察心室起搏1 h,2 h,4 h,7 d后窦房结功能低下家兔模型右心房压、心房有效不应期、心房激动时间、心肌波长指数、校正窦房结恢复时间的变化,并比较两组上述指标的差别.结果:①1:1VAC组心室起搏1 h后右心房压明显升高(P＜0.01),心房有效不应期、心房激动时间、心肌波长指数、校正窦房结恢复时间无明显变化(P＞0.05);2 h后右心房压继续升高(P＜0.01),校正窦房结恢复时间、心房激动时间延长(P＜0.01),心房有效不应期缩短(P＜0.01),心肌波长指数减小(P＜0.01);4 h后上述指标变化更明显(P＜0.01);7 d后右心房压恢复至原来水平(P＞0.05),心房有效不应期、心房激动时间、心肌波长指数、校正窦房结恢复时间变化更明显(P＜0.01).②非1:1VAC组心室起搏1 h后右心房压明显升高(P＜0.01),校正窦房结恢复时间、心房有效不应期、心房激动时间、心肌波长指数无明显变化(P＞0.05);2 h、4 h后右心房压进一步升高(P＜0.01),校正窦房结恢复时间、心房有效不应期、心房激动时间、心肌波长指数无明显变化(P＞0.05);7 d后右心房压恢复至原来水平(P＞0.05),心房有效不应期、心房激动时间缩小(P＜0.05),校正窦房结恢复时间、心肌波长指数无明显变化(P＞0.05).③1:1VAC组与非1:1VAC组比较:1 h时两组间右心房压、校正窦房结恢复时间、心房有效不应期无明显变化(P＞0.05),但1:1VAC组心房激动时间延长(P＜0.05)、心肌波长指数减小(P＜0.05);2 h时右心房压、心房有效不应期无明显变化(P＞0.05),1:1VAC组校正窦房结恢复时间、心房激动时间明显延长(P＜0.01),心肌波长指数明显减少(P＜0.01);心室起搏4 h,7 d后右心房压无明显变化(P＞0.05),但1:1VAC组心房有效不应期、校正窦房结恢复时间、心房激动时间、心肌波长指数变化更明显(P＜0.01).结论:VAC对窦房结功能及心房肌电活动能产生不良影响.病态窦房结综合征患者应尽量避免使用VVI起搏器,最好安装生理性起搏器.     

阈下电刺激对心律及异位节律点影响的实验研究

采用持续（２～８ｓ）阈下电刺激的方法，对９只家兔进行了研究，以探讨其安全性和对室性异位节律点传播的抑制效果。结果提示：（１）用不同频率，以起搏阈值的７０％为阈下刺激持续刺激心房或心室，对心律无影响。未发现心房颤动、心室颤动等心律失常。Ｐ─Ｅ、ＱＲＳ、Ｑ─Ｔ间期无变化（Ｐ＞０．０５）．（２）这种阈下刺激可有效地阻滞模拟室性心动过速的传播（８／９），其作用有空间限制性。作者认为简化的阈下电刺激方法更便于临床应用。     

人工心房调搏S_1-S_2/(S_1-S_1)~1/2的临床意义

心室肌相对不应期可用人工心房调搏法产生Ashman现象时的S_1-S_2间期来表示,但产生Ashman现象时的S_1-S_2时程受其前的S_1-S_2长短影响。笔者用S_1-S_2/(S_1-S_1)~(1/2)作为心室肌相对不应期校正公式,对A(病人)组72例及B(正常对照)组100例的心房调搏,结果进行对照分析两组S_1-S_2(x±s)分别为536±76ms及530±62ms(P>0.05),而用S_1-S_2/(S_1-S_2)~(1/2)计算结果S_1-S_2(x±s)分别为685±65ms;518±66ms(P<0.01)。提示:S_1-S_2/(S_1-S_2)~(1/2)可作为心室肌相对不应期校正公式,而且当其大于或等于640ms时提示心肌相对不应期延长。     

Trans-esophageal stimulation of the heart: electrophysiological properties of the heart of healthy subjects IV

The aim of the study to compare left atrial and ventricular electrophysiological properties determined by transesophageal stimulation with those of right atrium and ventricle measured by other authors using transvenous cardiac stimulation. 45 healthy persons (13 females and 32 males) with average age 37 years underwent the study. Transesophageal pacemaker SP-5 made by TEMED and an universal diagnostic electrode for atrial as well as ventricular stimulation were used to obtain ++noise-free recordings. ECG was recorded by 6-channel Mingograph 61 (Simens-Elema) with a paper speed - 100 mm/s. Left atrial effective refractory period (ERP LA), left ventricular effective refractory period (ERP LV), ERP of a-v conduction system measured from atrium and ventricle (ERP AVCS A, ERP AVCS R) were determined basing on generally acceptable criteria. Parameters were measured during sinus rhythm as well as atrial and ventricular stimulation with a pacing cycle length of 700 and 500 ms. There were also determined maximal antero- and retrograde 1:1 conduction via a-v node and a-v conduction time in both directions during atrial and ventricular pacing with a cycle length of 600 ms. No retrograde a-v conduction was stated in 33% of patients. Shortening of left atrial and ventricular effective refractory periods was respective to shortening of pacing cycle length from 700 to 500 ms: ERPLA-256-245-235 ms, for ERPLV-278-248-241 ms for ERP AVCS A-301, 405, 360 ms and for ERP AVCS R during sinus rhythm-312 ms. Maximal anterograde 1:1 a-v conduction was 162/min and retrograde one 156/min.(ABSTRACT TRUNCATED AT 250 WORDS)     

Initiation of ventricular tachycardia by interpolated ventricular premature depolarizations

Programmed electrical stimulation of the heart was performed in a 47 year old man with prior myocardial infarction and recurrent sustained ventricular tachycardia that was refractory to standard medical therapy. The tachycardia could be provoked by regular atrial pacing at a rate of 100/min, regular ventricular pacing at the same rate and regular atrial pacing at a rate of 200/min in the presence of 2:1 atrioventricular block. All three techniques resulted in an interval of approximately 600 ms between successive ventricular depolarizations. Single interpolated ventricular premature depolarizations delivered during sinus rhythm were followed by a postextrasystolic conducted sinus beat that initiated ventricular tachycardia. However, when the same interpolated ventricular premature depolarization was followed by a ventricular fusion beat no tachycardia ensued. This study therefore emphasizes the importance of heart rate and the pattern of ventricular activation in determining whether ventricular tachycardia can be provoked by programmed electrical stimulation of the heart.     

慢性充血性心力衰竭时K_(ATP)通道与心室肌电生理特性变化的关系

探讨慢性充血性心力衰竭 (CHF)时三磷酸腺苷敏感性钾通道 (KATP通道 )在心室肌电生理特性改变和室性心律失常发生中的意义。采用阿霉素制作CHF兔模型。 2 9只兔分为健康对照组 (HC组 )和CHF实验组 ,后者包括CHF对照组 (CHFC组 )、CHF +KATP通道开放剂组 (P组 )、CHF +KATP通道阻断剂组 (G组 )、CHF +KATP通道开放剂和阻断剂组 (P +G组 )四个亚组。每组均予心房快速起搏 30min ,分别测定起搏前后 90 %单相动作电位时程(MAPD90 )、心室有效不应期 (VERP)及其离散度和兴奋时间 (AT)离散度 ,测定毕程序刺激诱发室性心动过速或心室颤动。结果 :快速起搏使MAPD90 、VERP延长 ,在CHFC组较HC组显著 (11.82± 10 .2 0vs 8.18± 6 .97ms,P <0 .0 5和14 .95± 12 .82vs 9.0 7± 8.79ms,P <0 .0 1) ,而G组和P +G组的MAPD90 、VERP延长更明显。各组快速起搏均未引起MAPD90 、VERP离散度变化 ,但CHFC组和P组都有AT离散度显著增大 (2 8.5 3± 8.6 3vs 36 .80± 6 .97ms ,P <0 .0 1和 2 6 .33± 5 .82vs 33.80± 9.5 0ms,P <0 .0 5 ) ,阻断剂可对抗AT离散度的增大。结论 :快速心房起搏可开放CHF心室肌KATP通道 ,一方面阻止MAPD90 、VERP的延长 ,另一方面又加大AT的非同步性 ,使室性心动过速易于诱发。     

Determinants of the ventricular rate during atrial fibrillation

Determinants of the ventricular cycle length during atrial fibrillation were examined in 52 patients. Thirty-three patients had structural heart disease and none had an accessory atrioventricular (AV) connection. The AV node effective and functional refractory periods, the shortest atrial pacing cycle length associated with 1:1 conduction, the AV node conduction time and indexes of concealed conduction in the AV node were measured in the baseline state (36 patients) and after modification of sympathetic tone by infusion of isoproterenol or propranolol (8 patients each). Atrial fibrillation was then induced with rapid atrial pacing, and the mean, shortest and longest ventricular cycle lengths were measured. Variables that correlated most strongly with the mean RR interval during atrial fibrillation were the AV node effective refractory period (r = 0.93; p less than 0.001), AV node functional refractory period (r = 0.87; p less than 0.001) and shortest atrial pacing cycle length associated with 1:1 conduction (r = 0.91; p less than 0.001). The AH interval during sinus rhythm (r = 0.74; p less than 0.001) and during atrial pacing at the shortest cycle length with 1:1 conduction (r = 0.52; p less than 0.001) had weaker correlations. Measures of concealed conduction did not improve the prediction of the mean or longest ventricular cycle length during atrial fibrillation. In conclusion, the refractory periods and conductivity of the AV node are the best indicators of the potential of the node to transmit atrial impulses to the ventricles during atrial fibrillation. The degree of concealed conduction in the AV node is a less important determinant of the mean ventricular rate during atrial fibrillation.     

大鼠左心房肌单相动作电位的增龄性变化

目的　研究年龄对大鼠左心房肌单相动作电位(monophasicactionpotential,MAP)的影响。方法　选取实验用Wistar大鼠4 0只,按出生年龄分为青年组、成年组、中年组及老年组,每组10只。体外Langendorff灌流心脏,右心室刺激。分别记录各组左心房肌在4 0 0ms刺激周长下动作电位复极到90 %、5 0 %及2 0 %时的单相动作电位时程(MAPD90 )、MAPD50 、MAPD2 0 和心房有效不应期,以及在不同刺激周长下的MAPD90 、MAPD50 、MAPD2 0 。结果　MAPD各时相和有效不应期都随着年龄的增加而出现延长(P <0 .0 1) ;但老年组缩短。在同一年龄组中,刺激频率增加使动作电位时程都相应缩短,以MAPD90 明显;中年组MAPD改变明显。结论　年龄是影响心脏电活动重要的独立因素之一。     

丹参酮ⅡA磺酸钠对家兔快速心房起搏时心房动作电位及有效不应期的影响

研究丹参酮ⅡA磺酸钠(TSN)对家兔短期快速心房起搏时在体心房单相动作电位(AMAP)及心房有效不应期(AERP)的影响,探讨其防治心房颤动的可能机制。家兔24只,随机分为对照组与TSN组各12只。将电极经颈内静脉置入右房记录AMAP,观察基础状态下、给药后0.5h及以600次/分心房快速起搏后0.5,8hAMAP及其频率适应性的变化。结果:与起搏前相比对照组在S1S1200ms刺激时测量的AERP(AERP200)在起搏后0.5h缩短21.2ms,起搏后8h缩短21.6ms(P<0.05),且心房肌的频率适应性丧失。TSN在基础状态下对AMAPA、AMAPD无明显影响,但使AERP200由105.9±3.8ms延长至114.7±7.2ms(P<0.05)。起搏后TSN组维持原有的心房肌频率适应性。结论:快速心房起搏使心房肌的频率适应性丧失而致电重构,TSN能减轻短期快速心房起搏所致电重构。     

Atrial gradient as a potential predictor of atrial fibrillation

OBJECTIVES: We tested the utility and comparability of the atrial gradient and atrial ERP as early markers of electrical remodeling and a propensity to atrial fibrillation (AF). BACKGROUND: Pacing at physiologic rates from the left atrium alters the atrial gradient and is associated with atrial tachyarrhythmias. At these physiologic rates, there is no change in the atrial effective refractory period (ERP). METHODS: Sixty-one chronically instrumented mongrel dogs in complete heart block were paced from the left or right atrium at 400 to 900 bpm for 46 +/- 3 days. Dogs were monitored weekly and electrophysiologic studies conducted to determine changes in the atrial gradient, ERP, and rhythm. RESULTS: Rapid atrial pacing was associated with concordant decreases in atrial gradient, ERP, and occurrence of AF. Incidence of AF increased with increasing pacing rate. Although there ultimately was an equal incidence of AF with left atrial and right atrial pacing, the onset of AF occurred earlier with left atrial pacing. As expected, ERP decreased in both atria. Animals with long control ERP did not fibrillate. CONCLUSIONS: Rapid pacing induces changes in atrial gradient, which can be used as a noninvasive marker of electrical remodeling. AF is accompanied by decreases in atrial gradient and ERP, and the incidence is highest in dogs with short control ERP.     

Pacing studies after cardiac surgery

The diagnostical use of pacemaker after cardiac surgery is presented. Temporary pacemaker electrodes have been inserted during surgery into the wall of atrial and ventricular myocardium. With the aid of these electrodes, an analysator wire of 6 volts, and a Medtronic 5840 type pacemaker electrophysiological studies have been performed. The diastolic and supernormal stimulation threshold, the duration of atrial and ventricular relative refractory period were measured, the clinical significance of latency was analysed. It has been found that decrease of stimulation threshold, shortening of relative refractory period, and appearance of latency phenomenon promote arrhythmias. By investigating the conduction capacity of atrioventricular conduction system, latent conduction disturbances could be revealed, and a significant difference could be demonstrated between the atrioventricular conduction of WPW syndrome and that of other kinds of PR interval shortening. In addition the optimal heart rate requirement (optimal pacing rate) following heart surgery was defined. These parameters present more precise information on the electrophysiological condition of the heart than does the generally used ECG monitoring. When these parameters are repeatedly determined, the significance of patient's arrhythmias can be evaluated more safely and accurately; in a number of cases, even in the absence of any rhythm disturbances, impending arrhythmias can be predicted. "Pacemaker monitoring" of the postoperative heart patients, therefore, affords greater possibility for preventing the development of major cardiac arrhythmias.