【作者】 张树龙；

【导师】 杨延宗；

【作者基本信息】 大连医科大学 ， 生理学， 2008， 博士

【摘要】 第一部分迷走神经活动对心房电重构的影响目的:心房电重构在心房颤动(房颤)的发生和维持中起着重要作用。迷走神经与房颤密切相关。然而,关于迷走神经与心房电重构关系的研究尚少。本实验目的在于研究迷走神经干预对心房电重构的影响。方法:24只杂种犬随机分为3组,为排除交感神经对心房电重构的影响,3组犬均应用美托洛尔阻断交感神经效应。A组10只犬心房电重构过程中无迷走神经干预,B组8只犬应用阿托品阻断迷走神经效应,C组6只犬在心房电重构过程中同时进行迷走神经刺激。在右心房(RA)、冠状静脉窦(CS)和右心室(RV)放置多极电极导管。通过RA电极导管进行600次/分心房起搏30分钟构建急性心房电重构模型。在右心房快速起搏前后测量基础状态(无迷走神经刺激)和迷走神经刺激下的心房有效不应期(ERP)和房颤易感窗口(VW)。结果:A组犬右心房快速起搏后基础状态下及迷走神经刺激时的ERP较起搏前明显缩短(P均<0.05)。B组犬右心房快速起搏后基础状态下及迷走神经刺激时的ERP较起搏前无明显变化(P均> 0.05)。C组犬右心房快速起搏后基础状态下及迷走神经刺激时的ERP较起搏前明显缩短(P均<0.05)。A组及C组右心房快速起搏后ERP缩短值明显大于B组(P <0.05),但A组及C组ERP缩短值没有明显差异(P >0.05)。基础状态下,三组实验犬在右心房快速起搏前后均不能诱发房颤(VW接近0)。迷走神经刺激下,B组实验犬在右心房快速起搏前后也不能诱发房颤(VW接近0),但A组及C组实验犬右心房快速起搏后较起搏前容易诱发房颤(P均<0.05)。结论:短期的右心房快速起搏能够缩短心房的有效不应期,导致心房电重构。快速心房刺激所致的心房电重构过程中伴随着迷走神经兴奋性增强。迷走神经兴奋性增强及迷走神经刺激加重心房电重构,导致房颤易感性增加。迷走神经阻滞能减轻心房电重构,降低房颤易感性。第二部分上腔静脉隔离对心房电重构的影响目的:上腔静脉隔离(SVCI)主要通过阻断触发病灶治疗阵发性房颤,对于持续性房颤患者,SVCI是否通过改变心房基质而具有治疗效应目前尚不明确。心房电重构在房颤的发生和维持中起着重要作用,而迷走神经对心房电重构有重要影响。上腔静脉与迷走神经脂肪垫毗邻,因而,本研究假设SVCI能够导致犬的心房去迷走神经效应,减轻心房电重构,从而改变房颤的基质。方法:成年杂种犬18只,随机分为A和B组各9只。全身麻醉后分离双侧颈部交感迷走神经干。静脉应用美托洛尔阻断交感神经的影响。A组直接通过右心房600次/分起搏30分钟构建急性心房电重构模型。B组在完成SVCI后再构建急性心房电重构模型。分别于心房电重构前后在右心耳(RAA)、冠状静脉窦近端(CSp)和冠状静脉窦远端(CSd)测量基础状态下(无颈部交感迷走神经干刺激)及迷走神经刺激下的心房有效不应期(ERP)、房颤易感窗口(VW)和窦性周长(SCL)。对消融部位的心肌进行组织病理学检查。结果:(1)A组迷走神经刺激后心房率明显减慢(心房电重构前:基础状态及迷走神经刺激下的心率分别为171±19次/分和44±39次/分,P <0.05);心房电重构后:基础状态及迷走神经刺激下的心率分别为162±15次/分和30±15次/分, P <0.05)。B组行SVCI后迷走神经刺激后心房率减慢程度明显降低(心房电重构前:135±19次/分VS 114±31次/分,P=0.109;电重构后:基础状态及迷走神经刺激时的心率分别为137±26次/分VS136±30次/分,P=0.984)。(2)A组基础状态下的ERP在心房电重构后明显缩短(CSd的ERP分别为97.78±16.41 vs 85.56±15.90 ms,P=0.005;RAA的ERP分别为100±20.62 vs 82.22±19.86 ms,P =0.021)。迷走神经刺激下的ERP在心房电重构后也明显缩短( CSd的ERP分别为48.89±32.96 vs 28.89±16.16 ms,P =0.034;RAA的ERP分别为48.89±29.34 vs 25.56±8.82 ms,P =0.053)。B组基础状态下心房电重构后较重构前测得ERP变化无统计学意义(CSd的ERP分别为95.56±22.97 vs 96.67±18.03 ms, P =0.729 ; RAA的ERP分别为94.44±12.36 vs 94.44±16.67ms, P =1)。迷走神经刺激时心房电重构后测得的ERP较重构前亦无明显变化(CSd的ERP分别为85.56±16.67 vs 88.89±15.37 ms, P =0.471;RAA的ERP分别为90±12.5 vs 94.44±16.67, P =0.426)。A组基础状态下电重构所致的ERP缩短值较B组明显增加(CSd:12.22±9.72 vs 2.22±8.33 ms, P =0.032; RAA:22.22±18.56 vs–3.33±7.07 ms, P =0.001)。A组迷走神经刺激时电重构所致的ERP缩短值较B组亦明显增加(CSd:20±23.45 vs 1.11±13.64 ms, P =0.053; RAA:23.33±30.82 vs 0±13.23 ms, P =0.053)。(3)A组基础状态下心房电重构前后均不能诱发房颤(VW接近0)。迷走神经刺激时,房颤易感窗口在心房电重构后明显增大(冠状静脉窦远端的VW分别为24.44±23.51 vs 52.22±23.80 ms,P =0.009;高位右心房的VW分别为23.33±19.36 vs 38.89±13.97 ms,P =0.0007)。B组心房电重构前后基础及迷走神经刺激下均不能诱发房颤(VW接近0)。(4)心肌病理检查表明SVCI导致了消融位点的心外膜脂肪垫内神经节损伤结论: SVCI导致了心房局部去迷走神经效应,减轻了心房电重构,抑制了迷走神经介导性房颤。第三部分针对碎裂电位消融对心房电重构的影响目的:在心房颤动(房颤)过程中,在心房某些部位可以记录到高频低幅的碎裂电图(complex fractionated atrial electrogram,CFAE),针对CFAE消融是目前治疗房颤的重要手段之一。但是,针对CFAE消融治疗房颤的机制目前尚不清楚。心房电重构是房颤的发生和维持的电生理基础。因而,本研究假设针对CFAE消融能够减轻心房电重构,从而改变房颤的基质。方法:17只杂种犬分为二组。A组10只犬房间隔穿刺后诱发房颤并标测CFAE分布,之后直接以600次/分起搏右心房30分钟构建急性心房电重构模型,与B组针对CFAE消融后心房电重构前后数据进行比较,观察针对CFAE消融对心房电重构的影响。B组7只犬先通过双侧颈部交感-迷走神经干刺激诱发房颤,在房颤过程中标测并记录CFAE的分布部位,并针对CFAE消融。针对CFAE消融后构建急性心房电重构模型,观察针对CFAE消融对心房电重构的影响。分别于心房电重构前后在右心耳(RAA)、冠状静脉窦近端(CSp)和冠状静脉窦远端(CSd)测量基础状态下(无颈部交感迷走神经干刺激)及迷走神经刺激下的心房有效不应期(ERP)、房颤易感窗口(VW)和窦性周长(SCL)。对消融部位的心肌进行组织病理学检查。结果:(1)A组迷走神经刺激后心房率明显减慢(心房电重构前:基础状态及迷走神经刺激下的心率分别为167±15次/分和47±21次/分,P <0.05);心房电重构后:基础状态及迷走神经刺激下的心率分别为163±17次/分和38±12次/分, P <0.05)。B组针对CFAE消融后迷走神经刺激后心房率减慢程度明显降低(心房电重构前:159±13次/分VS 148±27次/分,P>0.05;电重构后:基础状态及迷走神经刺激时的心率分别为161±23次/分VS 157±28次/分,P>0.05)。(2)A组基础状态下的ERP在心房电重构后明显缩短(LAA的ERP分别为100±16.99 vs 86±15.06 ms,P=0.003;RAA的ERP分别为104±23.19 vs 84±19.56 ms,P =0.008)。迷走神经刺激下的ERP在心房电重构后也明显缩短(LAA的ERP分别为50±31.27 vs 31±16.63 ms,P =0.02;RAA的ERP分别为49±27.67 vs 28±11.35 ms,P =0.05)。B组基础状态下心房电重构后较重构前测得ERP变化无统计学意义(LAA的ERP分别为98.57±8.99 vs 105.71±11.34 ms, P > 0.05 ; RAA的ERP分别为105.71±27.61 vs 105.71±25.07ms, P>0.05)。迷走神经刺激时心房电重构后测得的ERP较重构前亦无明显变化(LAA的ERP分别为90±19.15 vs 94.29±25.73 ms, P>0.05;RAA的ERP分别为84.29±41.17 vs92.86±30.39, P>0.05)。A组基础状态下电重构所致的ERP缩短值较B组明显增加(LAA:14±10.75 vs -7.14±9.51 ms, P <0.001; RAA:20±18.86 vs 0±8.16 ms, P =0.02)。A组迷走神经刺激时电重构所致的ERP缩短值较B组亦明显增加(LAA:19±22.33 vs -4.29±9.76 ms, P =0.02; RAA:19±27.67 vs -8.57±19.52 ms, P =0.04)。(3)A组基础状态下心房电重构前后均不能诱发房颤(VW接近0)。迷走神经刺激时,房颤易感窗口在心房电重构后明显增大(LAA的VW分别为51±24.69 vs 26±22.71 ms,P =0.01;RAA的VW分别为40±16.33 vs 27±21.63ms,P =0.006)。B组心房电重构前后基础及迷走神经刺激下均不能诱发房颤(VW接近0)。(4)心肌病理检查表明针对CFAE消融导致了消融位点的心外膜脂肪垫内神经节损伤结论:针对CFAE消融导致了心房局部去迷走神经效应,减轻了心房电重构,抑制了迷走神经介导性房颤。更多还原

【Abstract】 Impact of Vagal Activity on Atria Electrical Remodeling in DogsObjective: Atrial fibrillation (AF) is the most common arrhythmia and its prevalence increases with the aging of the population. Atrial electrical remodeling (AER) including the shortening of action potential duration and atrial effective refractory period (ERP), the decrease of rate adaptation and wavelength index, and so on, plays an important role in the pathogenesis and maintenance of AF. Many studies have demonstrated that atrial vagal denervation could result in the decrease of vulnerability to AF. Furthermore, recent data have proved that mapping and ablation of fatty pats thereby vagal innervation to the heart was very effective in AF interventional treatment. However, little is known regarding the mechanisms of vagal denervation for treatment of AF: eradication of triggering foci or modification of substrates. The study is aimed to elucidate the effects of vagal intervention on AER in order to explore the mechanisms of the vagal denervation for the AF treatment.Methods: Twenty four adult mongrel dogs of either sex weighing 10 to 15 kg were anesthetized with sodium pentobarbital (150mg/kg IV) ,additional amounts of 250 to 500 mg per 60 minutes to 120 minutes were given as necessary to maintain anesthesia during the study. They were ventilated with room air by a cuffed endotracheal tube, and a constant oximetry was monitored throughout the experiment. Metoprolol was administered (0.2 mg/kg initial bolus with a maintenance dose of 0.2 mg/kg per hour) in order to exclude the influence of sympathetic activity. Multipolar catheters were placed into high right atria (RA), coronary sinus (CS) and right ventricle (RV). Bilateral cervical sympathovagal trunks were decentralized. AER was established by rapid pacing right atrium at the rate of 600 beats per minute for 30 minutes. ERP and vulnerability window (VW) were measured to evaluate the effects of the AER on the atrial electrophysiology and vulnerability of AF. Atrioventricular node ablation and temporary pacemaker were applied in case of the bradycardia induced by vagal stimulation and tachycardia due to induction of AF. Twenty four dogs were randomized into 3 groups. Sympathetic activity was blocked by administration of metoprolol in 3 groups. The changes of vagal modulation to atria after AER were observed in 10 dogs without vagal interruption in group A. The effects of vagal intervention on AER were investigated in 8 dogs with administration of atropine in group B. The impact of aggressively vagal activity on AER was studied in 6 dogs with bilateral cervical sympathovagal trunks stimulation during AER in group C. ERP and VW were measured before and after remodeling with and without vagal stimulation in all groups.Results: (1) Effect of vagal modulation on AERP.In group A, ERP decreased significantly after AER compared with that before AER both at baseline (84±19.55ms vs 104±23.19ms at RA,P =0.008; 87±17.03ms vs 100±16.99ms at CS , P=0.0007) and during the vagal stimulation (26±8.43ms vs 51±28.46ms at RA,P =0.03; 30±15.63ms vs 49±31.07ms at CS,P=0.02) . In group B, ERP remained unchanged before and after AER both at baseline (112.5±21.21ms vs 115±14.14ms at RA , P>0.05 ;117.5±11.65ms vs 115±19.27ms at CS , P>0.05 ) and during vagal stimulation(111.25±18.08ms vs 116.25±11.88ms at RA,P>0.05;110±9.26ms vs 110±18.52ms at CS,P >0.05). In group C, ERP decreased significantly after AER compared with that before AER both at baseline (95±22.58ms vs 106.67±24.22ms at RA,P =0.0009; 85±22.58ms vs 13.33±20.66ms at CS,P =0.04) and during vagal stimulation (31.67±14.72ms vs 56.67±33.27ms at RA, P=0.04; 38.33±29.27ms vs 61.67±29.94ms at CS, P =0.02). ERP shortening after AER in group A and C inecreased significantly than that in group B at baseline(20±18.86ms in group A, 2.5±14.88ms in group B and 11.67±4.08ms in group C at RA;13±8.23ms in group A, -5±16.9ms in group B and 16.67±15.06ms in group C at CS) and vagal stimulation(25±29.53ms in group A, 5±11.95ms in group B and 25±22.58ms in group C at RA; 19±22.34ms in group A, 0±16.9ms in group B and 23.33±16.33ms in group C at CS) (all P<0.05), while there is no significant difference between group A and C (all P >0.05).(2) Effect of vagal modulation on VW. Atrial fibrillation was rarely induced at baseline (VW close to 0) before and after AER in all groups. VW increased signifycantly during vagal stimulation after AER in group A (40±16.33ms vs 27±21.63ms at RA, P =0.006; 51±24.69ms vs 26±22.71ms at CS,P =0.01) and group C (76.67±38.82ms vs 26.67±28.75ms at RA,P =0.04; 53.33±39.33ms vs 21.67±23.17ms at CS,P =0.02), while VW remained unchanged in group B (VW close to 0).Conclusions: Short-term AER results in the decrease of ERP. AER is accompanied by the increases of atrial vagal modulation. The increased vagal activity and vagal stimulation promote AER, thereby increase the susceptibility to atrial fibrillation. The interrupted vagal activity attenuates AER, thereby suppresses the atrial fibrillation mediated by vagal stimulation.Impact of Superior Vena Cava Isolation on Atrial Electrical RemodelingObjective: Atrial fibrillation (AF) is the most common sustain arrhythmia. Numerous studies have shown that superior vena cava (SVC) isolation is effective method in suppressing AF by blocking the triggering or driving foci in some patients with paraxysmal AF. However, little has been known about the role of SVC isolation in suppression of sustained AF eventhough SVC isolation has been regarded as an ablative strategy . Atrial electrical remodeling(AER) plays an important role in the pathogenesis and maintainenance of AF. This study aimed to investigate effects of SVC isolation on AER in order to explore the neceesserity of SVC isolation for persisteny AF ablation. Methods: 18 adult mongrel dogs under general anesthesia were randomized into A group and B group. Bilateral cervical sympathovagal trunks were decentralized. Metoprolol was given to block sympathetic effects. AER was performed by 600bpm pacing through right atrial catheter for 30 minutes in A group in 9 dogs. AER was performed after SVC isolation guided by Lasso catheter on the junction of right atrium and SVC in B group in 9 dogs. Atrial effective refractory period(ERP), vulnerability window(VW) of AF ,and sinus cycle length(SCL) were measured at baseline(without vagal stimulation) and vagal stimulation at right atrial appendage (RAA), distal coronary sinus (CSd) and paroximal coronary sinus (CSp) before and after AER. The underlying tissue was excised from ablative sites and the same sites without ablation as control specimens and fixed in buffered neutral formalin. Serial sections were stained with haematoxylin and eosin for microscopic examination.Results: (1) SCL shortened significantly during vagal stimulation before and after AER in A group (all P value <0.05), while SCL remained unchanged during vagal stimulation before and after AER (all P value >0.05) . It suggests that SVC isolation eliminate vagal regulation on sinus node.In Group A, ERP shortened significantly at baseline (97.78±16.41 vs 85.56±15.90 ms at CSd, P= 0.005, 100±20.62 vs 82.22±19.86 ms at HRA, P=0.021) after AER. ERP decreased also significantly during vagal stimulation (48.89±32.96 vs 28.89±16.16 ms at CSd, P = 0.034, 48.89±29.34 vs 25.56±8.82 ms at HRA, P= 0.053) after AER. It suggests that rapid atrial pacing result in not only AER but also change of atrial electrophysicological properties due to vagal modulation. In group B, ERP remained unchanged before and after rapid atrial pacing both at baseline (95.56±22.97 vs 96.67±18.03 ms at CSd, P = 0.729, 94.44±12.36vs 94.44±16.67 ms at HRA), P=1 and during vagal stimulation (85.56±16.67 vs 88.89±15.37 ms at CSd, P = 0.471, 90±12.35 vs 94.44±16.67 ms at HRA, P=0.426). ERP shortening mediated by AER in Group A increased significantly than that in group B at baseline (12.22±9.72 vs 2.22±8.33 ms at CSd, P=0.032; 22.22±18.56 vs -3.33±7.07 ms at HRA, P= 0.001) and during vagal stimulation (20±23.45 vs 1.11±13.64 ms at CSd, P = 0.053; 23.33±30.82 vs 0±13.23 ms at HRA, P= 0.053). It suggests that SVC isolation relieve AER due to partly vagal dennervation.In Group A, AF could not be induced at baseline (VW close to 0) before and after AER. VW increased significantly during vagal stimulation after AER(24.44±23.51ms VS 52.22±23.80ms at CSd,P=0.009; 23.33±19.36ms VS 38.89±13.97ms at HRA,P=0.0007) . In group B, AF could not be induced at baseline and during vagal stimulation (VW close to 0) before and after AER. It suggests that SVC isolation may contribute to the suppression of AF mediated by vagal activity and the AER. (2) Histological sections showed numerrious nerves distribution alone SVC septum. In control specimens, the ganglia contained numerous nerve cells and was surrounded by fibrous and fatty tissue. After ablation, the ganglia were damaged. Some parts of the fibrous capsule of ganglia were thinned or broken. Neurons distributed sparsely in the ganglia, while among these neurons neuroglia increased in number. And concentration of nucleus appeared in some neurons of ganglia.Conclusions: AER can decrease ERP and enhance the vagal modulation to atria, thereby increase the susceptibility to atrial fibrillation triggered by vagus. SVC isolation can release AER, which maybe contribute to the attenuated vagal modulation to atria.Impact of ablation focused on the complex fractionated atrial electrogram on atrial electrical remodeling in dogsObjective: Ablation targeting complex fractionated atrial electrogram (CFAE) has been demonstrated to be effective for atrial fibrillation. Some promising observation have shown that the distribution of CAFE has a relationship with the efferent vagal innervation to atria. However, mechanisms of CFAE ablation for atrial fibrillation remained controversy. This study aimed to observe the impact of CAFP ablation on atrial electrical remodeling (AER) in order to investigate mechanisms of CFAE ablation in treatment of atrial fibrillation because AER plays an important role in the pathogenesis and maintainenance of atrial fibrillation. Methods: 17 adult mongrel dogs under general anesthesia were random- ized into A group and B group. Bilateral cervical sympathovagal trunks were decentralized. Metoprolol was given to block sympathetic effects. AER was performed by 600bpm pacing through right atrial catheter for 30 minutes in A group in 10 dogs. AER was performed after CAFE abaltion guided by multipolar catheters or Ensite mapping system in B group in 7 dogs. Multipolar catheters were placed into the right and left atrium and coronary sinus. CAFP was recorded by multipolar catheters or Ensite mapping system during atrial fibrillation induced by S1S2 stimul- ation during sympathovagal trunks stimulation. Atrial effective refractory period (ERP), vulnerability window (VW) of atrial fibrillation, and sinus rhythm cycle length (SCL) were measured at right atrial appendage (RAA), left atrial appendage (LAA), distal coronary sinus(CSd) and proximal coronary sinus(CSp) at baseline (without vagal stimulation) and during vagal stimulation before and after ablation. The underlying tissue were excised from ablative sites and the same sites without ablation as control specimens. Serial sections were taken and stained with hematoxylin and eosin for microscopic examination.Results: (1) SCL shortened significantly during vagal stimulation before and after AER in A group (all P value <0.05), while SCL remained unchanged during vagal stimulation before and after AER (all P value >0.05) . It suggests that CAFE abaltion eliminate vagal regulation on sinus node. (2) In Group A, ERP shortened significantly at baseline (100±16.99 vs 86±15.06 ms at LAA, P= 0.003, 104±23.19 vs 84±19.56 ms, P=0.008 at RAA) after AER. ERP decreased also significantly during vagal stimulation (50±31.27 vs 31±16.63 ms at LAA, P = 0.02, 49±27.67 vs 28±11.35 ms, P= 0.05 at RAA) after AER. It suggests that rapid atrial pacing result in not only AER but also change of atrial electrophys- icological properties due to vagal modulation. In group B, ERP remained unchanged before and after rapid atrial pacing both at baseline (98.57±8.99 vs 105.71±11.34 ms at LAA, P>0.05, 105.71±27.61vs 105.71±11.34 ms at HRA,P>0.05) and during vagal stimulation (90±19.15 vs 94.29±25.73 ms at LAA, P>0.05, 84.29±41.17 vs 92.86±30.39 ms at RAA,P>0.05). ERP shortening mediated by AER in Group A increased significantly than that in group B at baseline (14±10.75 vs -7.14±9.51 ms at LAA, P=0.001; 20±18.86 vs 0±8.16 ms at RAA, P= 0.02) and during vagal stimulation (19±22.33 vs -4.29±9.76 ms at RAA, P = 0.02; 19±27.67 vs -8.57±19.52 ms at RAA, P= 0.04). It suggests that CAFE abaltion relieve AER due to partly vagal dennervation.(3)In Group A, AF could not be induced at baseline (VW close to 0) before and after AER. VW increased significantly during vagal stimulation after AER(51±24.69 ms VS 26±22.71ms at LAA, P=0.01; 40±16.33ms VS 27±21.63ms at HRA,P=0.006) . In group B, AF could not be induced at baseline and during vagal stimulation (VW close to 0) before and after AER. It suggests that CAFE abaltion may contribute to the suppression of AF mediated by vagal activity and the AER. (4) Histological sections showed numerrious nerves distrib- ution in CAFE area. In control specimens, the ganglia contained numerous nerve cells and was surrounded by fibrous and fatty tissue. After ablation, the ganglia were damaged. Some parts of the fibrous capsule of ganglia were thinned or broken. Neurons distributed sparsely in the ganglia, while among these neurons neuroglia increased in number. And concentration of nucleus appeared in some neurons of ganglia.Conclusions: AER can decrease ERP and enhance the vagal modulation to atria, thereby increase the susceptibility to atrial fibrillation triggered by vagus. CAFE abaltion can release AER, which maybe contri- bute to the attenuated vagal modulation to atria.更多还原