增加缝隙连接耦联对兔长QT综合征心律失常的影响

目的:观察增加缝隙连接耦联对兔长QT综合征(LQTS)模型室性心律失常的影响。方法:应用心肌细胞快速延迟整流钾通道(IKr)阻滞剂E-4031(0.5μmol/L)在兔左室楔型心肌块建立LQT2模型,随机分为正常组、LQT2组、100 nmol/L缝隙连接激动剂(AAP-10)干预组(AAP-100组)、500 nmol/L AAP-10干预组(AAP-500组),每组10只。采用浮置玻璃微电极法同步记录心内膜、心外膜心肌细胞跨膜动作电位及跨室壁心电图。结果:LQT2组QT间期,跨室壁复极离散度(TDR)、早期后除极(EAD)、R-on-T期前收缩和尖端扭转性室性心动过速(TdP)发生率均显著高于正常组(P<0.05)。在LQT2模拟状态下,500 nmol/L AAP显著缩短了QT间期和TDR(P<0.05),降低了EAD、R-on-T期前收缩和TdP的发生率(P<0.05)。结论:增加缝隙连接耦联能减少兔LQT2模型TDR和室性心律失常发生率。     

伊布利特致尖端扭转性室性心动过速机制的研究

目的:探讨特效转复心房颤动药物伊布利特致尖端扭转性室性心动过速(Tdp)的机制。方法:利用兔左室楔形心肌块灌流伊布利特或溶有伊布利特的低钾低镁台氏液。30只新西兰大白兔随机分为正常组、伊布利特组和低钾低镁组,每组10只。正常组灌流台氏液,伊布利特组灌流2 mg/L伊布利特40 min,低钾低镁组灌流同浓度但溶于低钾低镁台氏液的伊布利特。同步记录各组内、外膜下心肌动作电位和容积心电图,观察灌流过程中早后除极(EAD)和Tdp的发生情况,对QT间期以及跨室壁复极离散度(TDR)的影响。结果:伊布利特组QT间期较正常组显著延长[(337±46)ms∶(548±73)ms],TDR也显著增加[(49±15)ms∶(132±36)ms],EAD的发生率为4/10,与正常组比较,均P<0.05;Tdp的发生率为0。低钾低镁组QT间期近一步延长至(652±184)ms、TDR增至(157±59)ms,EAD发生率为5/10,与正常组比较,均P<0.05,与伊布利特组比较,均P>0.05;Tdp的发生率增加为7/10,与正常组、伊布利特组比较,均P<0.05。结论:在伊布利特合并低钾低镁的情况下才易诱发Tdp,电解质正常时不...     

缝隙连接对心肌肥厚兔室性心律失常的影响

目的研究兔慢性压力超负荷模型中缝隙连接(G J)对室性心律失常的影响。方法30只兔随机分为假手术组(Sham组)、心肌肥厚组(LVH组)和抗心律失常肽组(AAP10组)。LVH组和AAP10组通过缩窄腹主动脉制备兔左室压力超负荷心肌肥厚模型,Sham组仅游离腹主动脉未进行缩窄。动物饲养3个月后制备兔左室楔形心肌块的灌注模型,Sham组和LVH组灌流台氏液,AAP10组灌流含AAP10的台氏液,记录不同起搏周长下容积心电图、跨室壁离散度(TDR)及刺激反应间期(SR I),并观察早期后除极(EAD)及室性心律失常的发生率。结果在不同频率起搏下,LVH组SR I和TDR与Sham组比较均明显增加(P<0.05)。而AAP10组的SR I和TDR与LVH组比较明显减小(P<0.05)。Sham组无1例诱发EAD和室性心律失常;在5 000 m s起搏时LVH组和AAP10组EAD的发生率分别为10/10、3/10,室性心律失常发生率分别为4/10,1/10,两组比较差异有显著性(P<0.05)。结论G J激动剂AAP10减轻了心肌肥厚时SR I的延长和TDR增加,相应的减少了EAD和室性心律失常的发生率。     

克拉霉素致室性心律失常的观察及部分机制探讨

目的探讨克拉霉素致室性心律失常的机制。方法 30只健康新西兰长耳兔随机分为对照组、常规剂量组(克拉霉素1倍血药浓度)和大剂量组(克拉霉素10倍血药浓度)组,每组各10只制作兔左室楔形心肌块模型。采用浮置玻璃微电极法同步记录各组内、外膜下心肌动作电位和容积心电图,观察在基础周长为2 000 ms电刺激情况下,灌流过程中QT间期、跨室壁离散度(TDR)和T波顶点到终点距离(T_(p-e))及致心律失常危险度。结果相比对照组,常规剂量组的QT间期、TDR、T_(p-e)和致心律失常危险度未见差异(P0.05);相比其他两组,大剂量组QT间期、TDR和T_(p-e)明显延长(P0.05),致心律失常危险度明显增大(5±3.27vs 0,0vs 0,P0.05)。结论慢心率下,正常血药浓度克拉霉素致室性心律失常可能性较低,过高血药浓度克拉霉素易诱发尖端扭转性室性心律失常。     

缝隙连接在长QT综合征2型电活动不稳定中的作用

目的探讨缝隙连接(GJ)的功能改变在长QT综合征2型(LQT2)模型中电活动不稳定中的作用。方法纽西兰大白兔30只,随机分为正常对照组、LQT2组和抗心律失常肽(AAP10)组。应用0.5μmol/L的E-4031对兔左室楔形心肌组织块进行灌流制备LQT2模型。采用浮置玻璃微电极法同步记录心内膜、心外膜心肌细胞跨膜动作电位及跨室壁心电图。观察各组QT间期和跨室壁复极离散度(TDR)的变化,通过免疫印迹和免疫荧光的方法观察GJ的分布和磷酸化状态的改变。结果①LQT2组QT间期较正常对照组显著延长(P<0.05),TDR较正常对照组显著增大(P<0.05)以及缝隙连接去磷酸化水平较正常对照组显著增高(P<0.01);②AAP10组QT间期较LQT2组显著缩短(P<0.05),TDR较LQT2组显著减小(P<0.05或0.01)以及缝隙连接去磷酸化水平较LQT2组显著降低(P<0.05或0.01);③三组的Cx43总量无明显差异(P>0.05)。结论 GJ的功能改变是LQT2模型中电活动不稳定的重要因素。     

抗心律失常肽对兔长QT综合征模型室性心律失常的影响

目的:观察缝隙连接激动剂抗心律失常肽(AAP10)对兔长QT综合征(LQTS)模型室性心律失常的影响并探讨其作用机制.方法:应用心肌细胞钠通道开放剂海葵毒素(ATX-Ⅱ,20 nmol/L)在兔左室楔型心肌块建立LQTS模型,随机分为正常组、LQTS组、AAP-100组和AAP-500组,采用浮置玻璃微电极法同步记录心内膜、心外膜心肌细胞跨膜动作电位及跨室壁心电图.通过免疫印迹法(Western blot)反映心肌细胞缝隙连接蛋白43(Cx43)去磷酸化水平的变化.结果:LQTS组QT间期和跨室壁复极离散度(TDR)与正常组相比较显著增大,早期后除极(EAD),R-on-T期前收缩和尖端扭转性室性心动过速(TdP)发生率也显著高于正常组,并伴有Cx43去磷酸化水平增高(均P＜0.01).在LQTS模拟状态下,AAP-500组QT间期和TDR显著缩短(均P＜0.01),EAD、R-on-T和TdP发生率显著小于LQTS组(P＜0.01、P＜0.01、P＜0.05),并伴随Cx43去磷酸化水平降低(P＜0.01).结论:缝隙连接激动剂AAP10能通过防止Cx43去磷酸化来减少兔LQTS模型TDR和室性心律失常发生率,说明缝隙连接可能参与了兔LQTS模型TDR的形成.     

犬短QT综合征发生心室颤动的电生理机制研究

目的：研究犬短QT综合征模型易发致命性心室颤动的电生理机制.方法：应用吡那地尔建立比格犬短QT综合征模型,利用篮状电极标测左室心内膜心肌电位.比较静脉推注吡那地尔（负荷剂量0.5 mg/kg,维持剂量每小时0.5 mg/kg）前后,QT间期、T波峰末间期（Tp-Te）、心肌细胞复极90％的动作电位（APD90）及激动恢复时间（ARI）、心室颤动周长（VF-CL）等参数的变化. 结果：与基础状态相比,吡那地尔显著缩短窦性心律和300 ms起搏时的QT间期,分别为（264±17） ms对（240±15） ms,P＜0.01;（247±7）ms对（229±10） ms,P＜0.01.应用吡那地尔后,APD90、ARI和VF-CL均较基础值显著降低,分别为（175±11） ms对（164±11） ms,P＜0.01;（156±11） ms对（147±10） ms,P＜0.01;（104±9） ms对（95±7）ms,P＜0.01.同时,Tp-Te间距较基础状态延长19％,即（35.8±3.4） ms对（44.1±1.4） ms,P＜0.01. 结论：不应期缩短和不应期心室跨壁离散度增加可能是吡那地尔诱导短QT综合征并发致命性室性心律失常的电生理基础.     

抗心律失常肽对陈旧性心肌梗死兔室性心律失常的影响

目的观察缝隙连接激动剂抗心律失常肽(AAP10)对陈旧性心肌梗死(OMI)兔室性心律失常的影响,并探讨其作用机制。方法将30只雄性日本大耳白兔随机分为假手术组(Sham)、OMI 组和 AAP10组,每组各10只。Sham 组开胸但不结扎冠状动脉,OMI 组和 AAP10组开胸并结扎冠状动脉左室支制备心肌梗死模型,普通饲料喂养3个月后制备兔左心室楔形心肌块的灌注模型。Sham 组和 OMI 组灌流正常台氏液,AAP10组灌流正常台氏液+AAP10(80 nmol/L)。灌流全程同时采用浮置玻璃微电极法同步记录内膜下心肌、外膜下心肌跨膜动作电位和跨壁心电图,并观察心外膜下心肌的刺激反应间期(stimulus-response-interval,SRI)和室性心动过速(室速)的诱发率。结束试验后测量梗死周边区心室壁的厚度、左室重、全心重。结果 OMI 组和 AAP10组兔均存在显著的心肌重构,并且 OMI 组兔有较高的室速诱发率(80%)。OMI 组与 AAP10组相比,AAP10显著缩短 SRI[SRI-1为(28.71±0.55)ms 与(20.59±0.79)ms;SRI-2为(38.67±0.49)ms 与(30.42±0.74)ms,P<0.01],而且 AAP10明显降低室速的诱发率(20%),但对动作电位形态和时程均无影响。结论AAP10可以在不影响动作电位形态和时程的前提下提高缝隙连接的传导速度,并可降低 OMI 兔室性心律失常的发生率。     

抗心律失常肽与溶血磷脂酸对兔室性心律失常影响的研究

目的 探讨抗心律失常肽(antiarrhythmic petide 10,AAP10)和溶血磷脂酸(lysophosphatidic acid,LPA)对兔室性心律失常的影响及其作用机制.方法 24只新西兰大白兔随机分为正常对照组、LPA组和AAP10干预组,建立兔左心室楔形心肌块模型,同步记录楔形心肌块内、外膜心肌细胞动作电位和跨室壁心电图,程序电刺激起搏,记录室性心律失常发生率.通过免疫印迹技术(Western blot)检测三组心肌去磷酸化缝隙连接蛋白43(non-phosphorylated connexin 43,NPCx43)的变化,采用免疫荧光技术观察NP-Cx43的分布.结果 LPA组QT间期、动作电位复极90%时程(90%of duration of action potential,APD90)、跨室壁复极离散度(transmural repolarization dispersion,TDR)与对照组相比均明显增加(P＜0.01),同时多形性室性心动过速的诱发率也明显增加(62.5%比0,P＜0.01),并伴随NP-Cx43含量明显增加(P＜0.01);AAP10干预组与LPA组相比,QT间期、内膜APD90、TDR均明显缩小(P＜0.01),多形性室性心动过速的诱发率也明显降低(P＜0.05),NP-Cx43含量也明显下降(P＜0.01).三组之间总Cx43含量差异无统计学意义.结论LPA有明显致心律失常作用,其机制可能与引起NP-Gx43含量增加、抑制缝隙连接通道功能有关,而AAP10可以拮抗LPA引起的NP-Cx43含量增加,同时降低LPA所致室性心律失常的发生率,具有抗心律失常的保护作用.

Abstract：

Objective To investigate the effect and potential mechanism of lysophosphatidic acid (LPA) and antiarrhythmic peptide (AAP10) on rabbit ventricular arrhythmia. Methods Twenty-four rabbits were randomly divided into three groups (n =8 each): control group, LPA group and AAP10 + LPA group. Using arterially perfused rabbit ventricular wedge preparations, transmural ECG and action potentials from both endocardium and epicardium were simultaneously recorded in the whole process of all experiments with two separate floating microeletrodes. The incidence of ventricular arrhythmia post S1S2 stimulation was recorded. Protein levels of nonphosphorylated Cx43 and total Cx43 were evaluated by Western blot. The distribution of nonphosphorylated Cx43 was observed by confocal immunofluorescence microscopy. Results Compared with the control group, the QT interval, endocardial action potential duration, transmural repolarization dispersion (TDR) and incidence of ventricular arrhythmia were significantly increased and nonphosphorylated Cx43 expression was significantly upregulated in the LPA group. Compared with the LPA group, cotreatment with AAP10 can reduce the QT interval, endocardial action potential duration, TDR and incidence of ventricular arrhythmia (25.0% vs 62. 5%, P ＜ 0. 01 ) and downregulate nonphosphorylated Cx43. Conclusions LPA could promote the arrhythmia possibly by upregulating nonphosphorylated Cx43 and subsequent gap junction transmission inhibition. Gap junction enhancer AAP10 could attenuate the proarrhythmic effect of LPA probably by downregulating myocardial nonphosphorylated Cx43 expression.     

抗心律失常肽对低钾低镁条件下伊布利特致尖端扭转性室性心动过速的影响

目的探讨缝隙连接开放剂抗心律失常肽(AAP10)对低钾、低镁条件下伊布利特致尖端扭转性室性心动过速(TdP)及心肌电不稳定性的影响。方法 54只日本长耳大白兔随机制备成左室楔形心肌块模型,随机分为对照组、低钾低镁组、伊布利特组、低钾低镁伊布利特组和AAP10干预组。对照组灌流正常台氏液,低钾低镁组灌流低钾低镁台氏液,伊布利特组灌流浓度2mg/l的伊布利特,低钾低镁伊布利特组灌流溶有同浓度伊布利特的低钾低镁台氏液,AAP10组给予AAP10干预的条件后灌流溶有伊布利特的低钾低镁台氏液。比较各组早期后除极(EAD)、R on T室性早搏和TdP的发生情况,以及QT间期、T波顶点到终点距离(Tp-e)和Tp-e/QT的变化。结果与对照组比较,低钾低镁伊布利特组QT间期、Tp-e和Tp-e/QT延长,EAD、R on T室性早搏、TdP的发生率明显增多。AAP10干预组,TdP、QT间期、Tp-e和Tp-e/QT比低钾、低镁伊布利特组显著减少。结论 AAP10可能通过开放缝隙连接减少跨壁复极离散度,从而起到预防伊布利特在低钾、低镁条件下的致TdP的作用。     

短QT间期发生室性心律失常的电生理机制探讨

目的了解短QT间期发生室性心律失常的电生理机制。方法应用吡那地尔在家兔左室楔形灌注组织建立短QT模型,利用标准玻璃微电极技术记录心外膜下、心内膜下及中层心肌细胞动作电位,并观测三层心肌细胞复极达90%的动作电位(APD90)及跨壁复极离散度(TDR)在吡那地尔、吡那地尔+异丙肾上腺素、奎尼丁、glybenclamide作用下的变化。采用S1S2程序刺激,观测在各种条件下心律失常的诱发状况。结果吡那地尔明显缩短APD90且伴有TDR增大(58.84±13.42ms vs35.26±13.30ms),并可诱发出异常心肌搏动。异丙肾上腺素可增大吡那地尔的该作用(64.60±21.46ms vs58.84±13.42ms),而奎尼丁和glybenclamide则可逆转吡那地尔的此作用,并减少异常搏动的发生。结论TDR增大可能是短QT综合征易于发生致命性心律失常的基础,而奎尼丁通过减小室壁心肌细胞的不均一性而对短QT综合征起到治疗作用。     

Antiarrhythmic peptide AAPl0 prevents ventricular arrhythmia in rabbit LQT2 model

Background and Objective Increased transmural dispersion of repolarization (TDR) has been shown to contribute toinitiation and maintenance of ventricular arrhythmia in long QT syndromes(LQTS).Intercellular uncoupling through gap junctions isan important mechanism for maintaining TDR in both intact and diseased heart.The present study was to test the hypothesis thatimproving gap junction communication reduces TDR and prevents ventricular arrhythmia in rabbit LQT2 model.Methods Anarterially perfused rabbit left ventricular preparation and E-403 (0.5μmol/L)were used to establish a model of LQT2.Preparationswere randomly assigned to control(n=10),AAP-100nmol/L(n=10),AAP-500nM(n=10)groups.Transmural ECG as well as actionpotentials from both endocardium and epieardium was simultaneously recorded. Resuits In LQT2 model.presence of 500nmol/LAAP10 reduced endocardial action potential and TDR and prevented ventricular arrhythmia comparing with the control and AAP 100nmol/Lgroups(P＜0.05).Conclusions The presence of 500 nmol/LAAP10 reduces TDR and prevents ventricular arrhythmia in rabbitventricular model of LOT2.This study suggests a possible role of GJs in TDR in rabbit LQT2 model and indicates a new clinicalapproach to the management of LQTS.     

Amplification of spatial dispersion of repolarization underlies sudden cardiac death associated with catecholaminergic polymorphic VT, long QT, short QT and Brugada syndromes

This review examines the hypothesis that amplification of spatial dispersion of repolarization in the form of transmural dispersion of repolarization (TDR) underlies the development of life-threatening ventricular arrhythmias associated with inherited ion channelopathies including the long QT, short QT and Brugada syndromes as well as catecholaminergic polymorphic ventricular tachycardia. In the long QT syndrome, amplification of TDR is often secondary to preferential prolongation of the action potential duration (APD) of M cells, whereas in the Brugada syndrome, it is thought to be because of selective abbreviation of the APD of right ventricular epicardium. Preferential abbreviation of APD of either endocardium or epicardium appears to be responsible for amplification of TDR in the short QT syndrome. In catecholaminergic polymorphic VT, the reversal of the direction of activation of the ventricular wall is responsible for the increase in TDR. In conclusion, the long QT, short QT, Brugada and catecholaminergic VT syndromes are pathologies with very different phenotypes and aetiologies, but which share a common final pathway in causing sudden death.     

丹参酮ⅡA在兔离体心脏2型长QT综合征模型中的电生理作用研究

目的研究丹参酮ⅡA在家兔离体心脏2型长QT综合征(LQT2)模型中的电生理作用。方法选用8只新西兰兔(2.5~3.5 kg),采用Langendorff系统经主动脉进行灌流离体心脏,稳定后持续灌流80 nmol/L的E-403115 min制备LQT2模型。继以梯度浓度丹参酮ⅡA(1、3、10、30、60μmol/L)灌流,观察其对室性心律失常诱发率、QT间期,有效不应期(ERP)和左室内、外膜[从动作电位0相至复极完成90%的单相动作电位时程(MAPD90)]的影响。结果80 nmol/L E-4031能使家兔离体心脏的QT间期、左心室内膜MAPD90、ERP延长(与对照相比,P<0.01),室性心动过速诱发率为37.5%(3/8)。联合丹参酮ⅡA使用后,离体心脏的QT间期、左心室内外膜的MAPD90、ERP以浓度依赖的方式缩短,当灌流浓度≥10μmol/L,QT间期明显缩短(与单独使用E-4031相比,P<0.05),浓度≥30μmol/L,左心室内、外膜的MAPD90、ERP缩短有统计学意义(P<0.05);1、3、10、30、60μmol/L丹参酮ⅡA灌流后的室性心动过速诱发率为2/8、0/8、0/8、0/8、0/8,差异无统计学意义(P>0.05)。结论丹参酮ⅡA可显著缩短LQT2的QT间期、左心室内、外膜的MAPD90和ERP;室性心动过速诱发率呈下降趋势。     

Increasing gap junction coupling reduces transmural dispersion of repolarization and prevents torsade de pointes in rabbit LQT3 model

Introduction: Increased transmural dispersion of repolarization (TDR) contributes importantly to the development of torsades de pointes (TdP) in long QT syndrome (LQTS). Intercellular electrical coupling via gap junctions plays an important role in maintaining TDR in both normal and diseased hearts. This study examined the effects of antiarrhythmic peptide AAP10, a gap junction enhancer, on TDR and induction of TdP in a rabbit LQT3 model.
Methods and Results: An arterially perfused rabbit left ventricular preparation and sea anemone toxin II (ATX-II, 20 nM) were used to establish a LQT3 model. Transmural ECG as well as action potentials from both endocardium and epicardium were simultaneously recorded. Changes in nonphosphorylated connexin43 (Cx43) were measured by immunoblotting. Compared with the control group, the QT interval, TDR, early afterdepolariztion (EAD), R-on-T extrasystole, and TdP increased sharply with augmented nonphosphorylated Cx43 in the LQT3 group (P < 0.001 for both). Interestingly, compared with the LQT3 group, 500 nM AAP10 reduced QT interval, TDR (P < 0.001 for both), and prevented EAD, R-on-T extrasystole, and TdP (P = 0.003, P = 0.001, P = 0.02) with a parallel decrease in nonphosphorylated Cx43 in the presence of ATX-II (P < 0.001).
Conclusion: Gap junction enhancer AAP10 is capable of abbreviating the QT interval, reducing TDR, and suppressing TdP in a rabbit LQT3 model probably via its effect by preventing dephosphorylation of Cx43. These data suggest that increasing intercellular coupling may reduce TDR and, therefore, prevent TdP in LQTS.     

不同部位左心室内膜与外膜起搏对心力衰竭心脏的电生理作用差异

目的 评估左心室不同部位心内膜与外膜起搏对心力衰竭（心衰）犬心脏的电激动同步性以及复极离散度的影响及其差异.方法 12只比格犬,体重（12.5±1.7）kg.使用随机数字法平均分为2组（正常组和心衰组）.利用右心室心尖部快速起搏制作慢性心衰模型.左心室放置64极篮状电极导线进行电生理标测.通过左心室不同部位起搏（心底部心内膜与心外膜,心尖部心内膜与心外膜）记录并测量体表12导联心电图的QT间期、T波峰点与T波下降支最大斜率处切线与等电位线交点（Tp-e）间期,同时测定左心室心内膜整体激动时间以及各篮状电极记录的激动恢复间期及其复极离散度.结果 基础状态下,与正常心脏相比,心衰组QT间期、T波顶点与T波终点之间的时限Tp-e间期以及激动恢复间期均延长（P＜0.05）.心衰组中,与左心室心内膜起搏相比,相同部位的心外膜起搏时的QT和Tp-e间期均显著延长[QT：心底部（270±13）ms对（255±15）ms,（P＜0.01）;心尖部（275±12）ms对（257±11）ms,（P＜0.01）;Tp-e：心底部（50.2±8.3） ms对（42.7±4.5） ms,（P＜0.01）;心尖部,（52.9±10.1）ms对（45.6±9.3）ms,（P＜0.01）].心室激动恢复间期离散度无论在左心室心内膜还是在心外膜,近心底部起搏时较近心尖部起搏时显著减小.[心内膜起搏（4.1±0.5） ms对（5.8±0.7）ms,（P＜0.05）;心外膜起搏（4.7±0.6） ms对（6.2±0.9） ms,（P＜0.05）].在心衰心脏,左心室心外膜起搏时,左心室整体心内膜平均激动时间较心内膜起搏时明显延长（42.9±5.9）ms对（26.1±4.0）ms,（P＜0.001）].结论 左心室心内膜起搏较心外膜起搏有更好的心脏激动电同步性.心衰后,左心室心外膜起搏较心内膜起搏可致更长的复极时间以及更大的复极离散度.本研究结果提示左心室心内膜起搏较心外膜起搏可产生更好的电生理效应,有可能降低心衰心脏再