实验性心房颤动血栓形成时内皮型一氧化氮合酶和纤溶酶原激活剂抑制物-1的变化

目的研究心房颤动(房颤)犬心房心内膜一氧化氮(NO)浓度、内皮型一氧化氮合酶(eNOS)和纤溶酶原激活剂抑制物-1(PAl-1)蛋白表达的变化,探讨房颤左房血栓形成的可能机制。方法应用埋藏式高频心脏起搏器快速起搏心房(400次／min)6周,建立房颤犬动物模型。采用ISO-NOP3005N0敏感电极测定心内膜NO含量,Western blot和免疫组化检测eNOS、PAl-1蛋白表达,酶联免疫吸附双抗体夹心法检测血浆PAl-1含量。结果房颤组左房心内膜NO含量明显低于窦性心律组,eNOS蛋白表达下调,PAl-1蛋白表达上调,右房无明显变化。房颤组血浆PAl-1含量亦明显高于窦性心律组。结论房颤引起的左房心内膜NO含量降低、eNOS蛋白表达下调、PAl-1蛋白表达上调可能是左房血栓形成的重要原因。     

高位胸段硬膜外阻滞对心房颤动自主神经重构的影响

目的:观察高位胸段硬膜外阻滞(HTEB)对长期右心耳快速起搏诱发心房颤动(房颤)犬心房自主神经重构的影响,并探讨心房肌神经生长因子(NGF)在心房自主神经重构中的作用。方法:18只犬随机分为假手术组、对照组和HTEB组。对照组和HTEB组犬给予持续快速心房起搏建立房颤模型,HTEB组给予硬膜外腔注射0.5%利多卡因行高位胸段硬膜外阻滞。通过Masson染色检测犬心房肌胶原容积分数(CVF)改变,免疫组化法测定犬心房肌神经生长相关蛋白43(GAP43)及酪氨酸羟化酶(TH)表达,蛋白免疫印迹法检测犬心房肌NGF、GAP43及TH蛋白表达情况。结果:与对照组相比,右心耳快速起搏6周后,HTEB组犬心房肌CVF值显著降低;GAP43及TH神经萌出量显著减少(P0.05);NGF、GAP43及TH蛋白表达量显著减少(P0.05~0.01)。与假手术组比较,HTEB组犬心房肌CVF值显著增加;GAP43及TH神经萌出量显著增加(P0.05~0.01);NGF、GAP43及TH蛋白表达量显著增加(P0.05)。结论:长期右心耳快速起搏诱发犬房颤致心房肌神经不均一萌出,诱发自主神经重构,而NGF在其中发挥重要作用。HTEB可有效阻止房颤犬心房肌NGF表达上调,减轻自主神经重构。     

犬急性心房颤动电重构现象的实验研究

目的 观察短阵心房颤动(房颤)的电重构现象及其恢复过程，探讨电重构与房颤再发及维持的关系。方法 15只健康成年犬于左、右心房外膜7个部位缝合双极记录电极，自心耳给予600次／min起搏诱发2h房颤，其中5只犬每间隔10min测量左、右心耳的心房有效不应期(AERP)，观察其恢复过程；另10只犬在房颤前后分别测量在起搏周长350ms、250ms、200ms时7个部位的AERP并记录电生理检查时房颤的诱发率及其持续时间。结果 2h房颤后心房各点AERP显著缩短，对心率适应不良，AERP离散度增高，继发性房颤诱发率增高、持续时间延长。AERP缩短可持续30min，60-80min后恢复。左心耳AERP恢复过程慢于右心耳。可诱发房颤的部位AERP更短，与继发性房颤的平均持续时间呈显著性负相关。可诱发房颤的心房其AERP离散度明显增高，但与继发性房颤的持续时间无关。AERP心率适应不良部位继发性房颤的诱发率高于生理性AERP心率适应性部位。低位右心房及左心耳部位的期前兴奋易于诱发房颤。结论 2h诱发的房颤足以使健康心房发生类似持续性房颤的电重构，电重构使房颤易于再发。AERP离散度与房颤的诱发有关，AERP缩短与房颤的持续性有关，房性早搏的发生部位与房颤的易患性有关。     

快速右心房起搏致犬心房迷走神经重构的研究

目的 通过对快速心房起搏犬的神经相关因子的研究,观察右心房快速起搏48 h是否引起神经重构及其在心房颤动(房颤)中的作用.方法 健康杂种犬12只,随机分为房颤组(6只)和对照组(6只).右心房起搏600次/min、持续48 h.通过一种在发芽轴突生长丘中表达的蛋白质(GAP-43)和乙酰胆碱转移酶(CHAT)来了解心脏神经萌发和迷走神经的重构.结果 在房颤犬的左心房、左心耳、右心房和右心耳,GAP-43和CHAT的神经密度同对照组相比明显增高,差异均有统计学意义(P<0.05).此外,房颤犬的右心房GAP-43和CHAT的神经密度与左心房有明显差异(P<0.05),显微镜下显示每个样点心脏神经不均匀分布.结论 48 h持续起搏犬右心房形成阵发性房颤,可见明显的神经萌发和迷走神经重构且不均一分布.     

犬急性心房颤动时心房尿激酶型纤溶酶原激活物表达的变化

目的：研究犬急性心房颤动（房颤）时心房内皮细胞尿激酶型纤溶酶原激活物（u-PA）蛋白表达的变化,探讨房颤时心房附壁血栓形成的可能机制。方法：取12只健康成年杂种犬,随机分为两组：快速心房起搏（RAP）组（6只）：建立犬急性房颤动物模型;正常对照组（6只）：仅给予开胸,不进行起搏。分别取两组犬的左心耳、右心耳部位心肌组织,应用免疫组织化学技术检测心耳内皮细胞u-PA蛋白表达的改变。结果：（1）RAP组所有犬均可诱发出阵发性房颤;（2）RAP组犬心耳内皮细胞均未见u-PA蛋白表达,正常对照组u-PA蛋白表达阳性率为75.0%,RAP组u-PA蛋白阳性率显著低于正常对照组的（P〈0.001）。结论：急性房颤时心耳内皮细胞尿激酶型纤溶酶原激活物水平下降,提示在房颤早期内皮细胞纤溶储备功能降低,这可能与房颤时附壁血栓形成有关。     

β3肾上腺素能受体对心房颤动心房肌细胞凋亡和溶解作用的实验研究

目的 观察β3肾上腺素能受体(β3AR)对长期心房快速起搏诱发心房颤动(房颤)犬心房肌细胞凋亡和溶解的影响.方法 21只犬分为假手术组、对照组和β3AR抑制剂组.无菌条件下行开胸手术,植入高频起搏器(600次/min)行心房快速起搏3周,建立房颤犬模型.β3AR抑制剂组于术后1周经皮下给予β3AR抑制剂(L748337)2 μg·kg-1·h-1,直至起搏3周结束.分别于起搏前、起搏3周后测量各组犬左心房最大容积(LAVmax)、左心房最小容积(LAVmin)和左心房射血分数(LAEF),左心耳最大容积(LAAVmax)、左心耳最小容积(LAAVmin)和左心耳射血分数(LAAEF),并检测各组犬房颤诱发率.采用HE染色和TUNEL染色观察各组犬心房肌病理组织改变和凋亡指数.采用实时定量逆转录聚合酶链式反应(RT-PCR)和免疫印迹(western-blot)方法测定各组犬心房肌β3AR基因和蛋白表达,采用免疫组化法检测各组犬心房肌细胞外信号调节激酶(ERK) 1/2、c-jun蛋白表达.结果 心房快速起搏3周后,对照组犬LAVmax、LAVmin、LAAVmax和LAAVmin明显增大,LAEF、LAAEF显著减小(P＜0.01),心脏功能明显降低,房颤诱发率显著增加;β3AR抑制剂组犬心脏功能明显改善,房颤诱发率显著降低.与假手术组相比,对照组犬心房肌凋亡指数和肌溶解心率显著增加;与对照组相比,β3AR抑制剂组凋亡指数和肌溶解比率显著降低(P＜0.01).与假手术组比较,对照组犬心房肌β3AR、ERK1/2、c-jun表达显著上调(P＜0.01);与对照组相比,β3AR抑制剂组β3AR、ERK1/2、c-jun表达显著降低(P＜0.01).结论 长期心房快速起搏诱发房颤犬心房肌β3AR表达显著增加,并能通过上调ERK1/2、c-jun蛋白表达促进心房肌细胞凋亡和肌溶解.β3AR抑制剂够通过抑制房颤犬心房肌ERK1/2、c-jun蛋白表达,进而抑制房颤犬心房结构重构,改善心房功能,有效控制房颤发生.     

HSP70表达上调对兔快速心房起搏致房颤心肌K_(Ca)3.1表达的影响

目的:观察热应激诱导心肌热休克蛋白(HSP)70表达上调,对兔快速心房起搏致房颤心肌钙激活钾通道(K_(Ca))3.1表达的影响。方法:将24只新西兰大白兔随机分为假手术组(n=8,仅植入电极而不起博)、起搏组(n=8,以600次/min快速起搏右心房6h)和热应激起搏组(热应激组,n=8,先行热应激预处理,再行与起搏组一样的快速起搏)。结果:与假手术组和起搏组比较,热应激组心脏各部位HSP70mRNA和蛋白表达显著上调[HSP70蛋白,左房:(39.00±3.21)比(39.75±2.82)比(69.75±3.45),右房:(38.38±2.92)比(39.50±3.89)比(69.00±2.93),左心耳:(37.75±3.28)比(39.00±3.89)比(68.63±3.23),右心耳:(37.00±3.85)比(38.38±3.74)比(68.75±2.82)],P均0.01,而起搏组和假手术组间无显著性差异(P0.05);与起搏组K_(Ca)3.1mRNA和蛋白表达量显著下调比较,热应激组心脏各部位K_(Ca)3.1 mRNA和蛋白表达量显著上调[K_(Ca)3.1蛋白,左房:(21.25±1.67)比(24.00±2.62),右房:(21.13±1.96)比(23.75±1.83),左心耳:(21.00±2.07)比(23.75±1.67),右心耳:(20.88±2.03)比(23.50±2.45)],P均0.05,且热应激组与假手术组间无显著差异(P0.05)。结论:热应激可诱导心房起搏心肌热休克蛋白(HSP)70表达上调,抑制K_(Ca)3.1mRNA和蛋白表达量显著下降。     

西拉普利和缬沙坦与心房颤动犬心房肌钙激活蛋白酶表达及心房结构重构关系的实验研究

目的 观察西拉普利和缬沙坦对心房颤动(房颤)犬心房肌钙激活蛋白酶(calpairIs)mR-NA和蛋白表达及心房结构重构的影响.方法 27只犬随机分为假手术组、对照组、西拉普利组和缬沙坦组.对照组、西拉普利组和缬沙坦组犬以400次/min心房快速起搏6周,建立房颤犬模型.假手术组犬埋植起搏器后不起搏.测量左心房容积及收缩功能变化,记录房颤诱发及维持情况,检测心房肌calpains mRNA和蛋白表达,观察心房肌病理组织学和超微结构改变.结果 西拉普利组和缬沙坦组犬心房肌calpain I mRNA和蛋白表达较假手术组增多(P＜0.05),但较对照组显著减少(P＜0.01).各组犬心房肌calpain I蛋白表达与肌溶解高度相关(r=0.89,P＜0.01).各组犬心房肌calpainⅡmRNA和蛋白表达差异无统计学意义.与对照组相比,西拉普利组和缬沙坦组犬心房肌病理组织学和超微结构改变显著减轻,左心房及左心耳容积明显减小,左心房收缩功能显著增强,房颤诱发率和持续时间明显降低.结论 房颤犬心房肌calpain I mRNA和蛋白表达显著上调.西拉普利和缬沙坦能明显抑制房颤犬心房肌ealpain I表达,防治心房结构重构,减少房颤发生.     

氧化应激对心房颤动心房间质纤维化影响的实验研究

目的 观察氧化应激对慢性心房快速起搏诱发心房颤动(房颤)犬心房肌间质纤维化的影响.方法 20只犬分为假手术组、对照组和普罗布考组.无菌条件下开胸手术,植入高频起搏器(400次/min)心房快速起搏6周,建立房颤犬模型.普罗布考组于起搏前1周服用普罗布考(100 mg/kg),至起搏6周结束.采用Masson染色观察各组犬心房肌胶原容积分数(CVF);采用Western印迹法检测各组犬心房肌MMP-9、TMP-1表达;分别于起搏前、起搏6周后测量各组犬左心房最大容积(LAVmax)、最小容积(LAVmin)和射血分数(LAEF);测定左心耳最大容积(LAAVmax)、最小容积(LAAVmin)和射血分数(LAAEF);记录左心耳最大正向血流速度(V-LAA+)和负向血流速度(V-LAA-);比色法检测各组犬心房肌氧化应激相关指标.结果 与假手术组相比,对照组犬心房肌CVF值显著增加,普罗布考能够显著降低房颤犬心房肌CVF值.与假手术组比较,对照组犬心房肌MMP-9表达显著上调(P＜0.01),TMP-1表达显著下调(P＜0.01);与对照组犬比较,普罗布考组犬心房肌MMP-9表达显著降低(P＜0.01),TMP-1表达显著升高(P＜0.01).心房快速起搏6周后,对照组犬LAVmax、LAVmin、LAAVmax和LAAVmin明显增大,LAEF、LAAEF、V-LAA+和V-LAA-显著减小.与假手术组犬比较,对照组犬心房肌MDA-水平显著增加(P＜0.01),与对照组犬比较,普罗布考组犬心房肌MDA水平显著降低(P＜0.01),心房肌氧化应激指标(MDA)与CVF值呈正相关(r=0.976,P＜0.001).结论 长期心房快速起搏诱发房颤犬心房肌存在氧化应激,心房肌MMP-9表达显著上调,TIM-1表达显著下调,心房肌纤维化程度显著增加.普罗布考能够通过抑制氧化应激,抑制房颤犬心房肌MMP-9表达上调,促进TIM-1表达上调,防止房颤犬心房结构重构,改善心房功能,对房颤防治有益.     

犬急性心房颤动时心房内皮超微结构的变化（英文）

目的:研究犬急性心房颤动时心房内皮细胞超微结构的变化,探讨房颤左房血栓形成的可能机制。方法:取16只健康成年杂种犬,随机均分为空白对照组(仅接受开胸手术而不起博)和快速心房起搏(RAP)组(建立急性房颤模型)。分别取两组犬的左心耳、右心耳部位心肌组织,进行苏木素伊红(HE)染色,在普通光镜下观察心肌细胞形态学改变;在电镜下观察心耳内皮细胞形态学改变。结果:(1)RAP组所有犬均成功诱发出阵发性房颤;(2)普通光镜下两组的心耳、心内膜组织在形态学上无显著差异;(3)透射电镜下,RAP组心耳组织内皮细胞呈现不同程度的不完整,部分脱落,而空白对照组内皮细胞层完整,未见坏死、脱落,与空白对照组比较,RAP组内皮细胞不完整性(12.5%比75.0%)显著增加(P=0.041)。结论:急性房颤时内皮细胞的超微结构已经发生改变,这可能与房颤时附壁血栓形成有关。     

迷走神经刺激和乙酰胆碱灌注对心房肌电生理特性的影响

研究在体情况下迷走神经刺激(VNS)和乙酰胆碱(Ach)灌注对心房肌不同部位的电生理影响,并探讨其诱发心房颤动(AF)的机制。10只杂种犬自身随机对照,运用单相动作电位(MAP)记录技术,同步记录10只开胸犬的右心耳(RAA)、高位右房(HRA)、低位右房(LRA)、左心耳(LAA)、高位左房(HLA)、低位左房(LLA)的MAP,分别给予切断迷走神经、VNS、Ach灌注(分别做为对照组、VNS刺激组、Ach灌注组)后,观察诱发AF的情况和动作电位时程APD50、APD90和APD离散(dAPD)的变化。结果:10只犬在VNS刺激和Ach灌注同时,右心耳单一刺激分别有7只和6只犬诱发AF;VNS明显缩短APD50、APD90,其中RAA缩短最明显(APD50从72±5ms到19±4ms,APD90从136±7ms到43±5ms,P<0.001);Ach灌注也明显缩短APD50和APD90,与VNS相比,LLA的APD90缩短更明显(47±6msvs62±8ms,P<0.01);VNS明显升高心房肌APD50和APD90的离散(17±5msvs7±3ms,25±7msvs8±5ms,P<0.01)。结论:VNS和Ach灌注可引起APD缩短和离散升高,但影响的部位和程度稍有差异,都易诱发AF。     

持续性心房颤动山羊模型的心房单极电极标测

在持续性心房颤动 (简称房颤 )山羊模型上 ,研究心房不同部位房颤周长 (AFCL)及单极心外膜电图的差异 ,并利用激动标测图分析房颤时的蝉联现象。将 83个电极分别缝合于 7只山羊的左心房游离壁、左心耳、Bachmann束 (BB)、右心耳游离壁的心外膜。利用自动房颤刺激器维持房颤 ,待房颤持续 4周后 ,取 16s的心外膜电图作分析。利用单极电图标记局部激动时间 ,并根据单极电图的形态特点将其标记为正常电位 (单电位和短的双电位 )及异常电位 (长的双电位、三电位及碎裂电位 )。根据左心房局部激动时间重建等电位激动标测图 ,如超过 7次连续心房搏动经过相同路径 ,则定义为蝉联片段。在左心房、左心耳、BB、右心耳及右心房的AFCL分别为 94 .9± 4 .6 ,95 .7±4 .4 ,10 5 .7± 6 .5 (与其他部位比较 ,P <0 .0 5 ) ,99.2± 8.0及 98.5± 6 .3ms ;异常电位的百分比分别为 2 0 .9%± 6 .3% ,2 7.8%± 11.8% ,5 7.4 %± 7.8% (与其他部位比较 ,P <0 .0 1) ,18.6 %± 9.7%和 19.4 %± 3.9%。在所记录的 16s房颤过程中 ,左心房共有 70 5次心搏 ,其中 6 8次 (9.6 % )属于蝉联片段。结论 :在山羊持续房颤模型 ,BB的AFCL最长 ,异常电位的发生率最高 ,提示BB在房颤的维持上起重要作用。蝉联现象的存在表明房颤时心房激动并     

Differential densities of muscarinic acetylcholine receptor and I(K,ACh) in canine supraventricular tissues and the effect of amiodarone on cholinergic atrial fibrillation and I(K,ACh)

BACKGROUND: Vagal nerve plays an important role in the induction and maintenance of atrial fibrillation (AF). This study investigated the differential densities of M2 receptor and acetylcholine-induced inward rectifier K+ current (I(K,ACh)) in atrial appendage, atrium, pulmonary vein (PV) and super vena cava (SVC) to discuss the role of atrial appendage and PV in cholinergic AF. METHODS AND RESULTS: In 10 dogs, action potential duration was determined at 24 sites during bilateral cervical vagal stimulation and amiodarone administration. AF could be induced at first in right atrial appendage (RAA) and right atrium (RA) without left atrial appendage (LAA) and left atrium (LA). Amiodarone decreased the initiation of AF in vivo. Western blot and patch clamp were used to determine M2 receptor and I(K,ACh) in RAA, LAA, RA, LA, PV and SVC. The densities of M2 receptor and I(K,ACh) in LAA, RAA and LA were higher than that in RA, PV and SVC (21.34 +/- 0.92 vs. 8.24 +/- 0.45 pA/pF, p < 0.05). Furthermore, the densities of the M2 receptor and I(K,ACh) in LAA and RAA were higher than that in LA (21.34 +/- 0.92 vs. 14.17 +/- 0.65 pA/pF, p < 0.05). After amiodarone administration, densities of I(K,ACh) in LA and RA were not different, but densities of I(K,ACh )were also less in atrium than in atrial appendage. CONCLUSIONS: Densities of the M2 receptor and I(K,ACh) are higher in atrial appendage than other sites. Atrial appendage perhaps plays an important role in initiation of cholinergic AF. However, PV and SVC less often play an important role in vagotonic paroxysmal AF. Reduced dispersion of I(K,ACh) is the mechanism for amiodarone to therapy AF.     

犬Marshall韧带的电生理特征实验研究

目的 评估不同电生理刺激方案对犬Marshall电位的影响.方法 成年杂种犬15只暴露Marshall韧带,Lasso电极导管置于韧带上方记录Marshall电位.分别于左心耳、右心耳处予以电生理刺激.记录Marshall电位及心房-Marshall电位间期(AM间期).随机选择10只犬组织学检查明确Marshall韧带肌束(Marshall束)与心房间解剖连接(组1为无连接,组2为有连接).余5只犬酒精消融Marshall韧带(组3).结果 组1共6只犬,1只犬窦性心律下未记录到Marshall电位,但在左心耳刺激时Marshall电位从左心房电位中分离出来.5只犬窦性心律下记录到Marshall电位,左心耳刺激时AM间期延长(＞20 ms)[(125±9)ms vs(80 ±6)ms,P=0.043,左心耳刺激=350 ms;(126±9)ms vs(80±6)ms,P=0.044,左心耳刺激=450 ms].组2共4只犬,2只犬窦性心律下未记录到Marshall电位,左心耳刺激时可见Marshall电位从左心房电位中分离出来.2只犬窦性心律下记录到Marshall电位,左心耳刺激时AM间期可延长,但亦可缩短.组3犬窦性心律或左心耳刺激下记录到Marshall电位,酒精消融Marshall韧带后,Marshall电位消失.结论 与窦性心律比较,左心耳刺激时,Marshall电位呈现多种形式,包括AM间期延长.后者对Marshall韧带消融有益.     

快速右心房起搏对实验犬心房胶原纤维分布的影响

目的 实验探讨切除上腔静脉中部和主动脉根部脂肪垫(简称脂肪垫)对快速右心房(RA)起搏实验犬的心房胶原容积分数(CVF)的空间分布变化意义.方法 24只成年健康杂种犬雌雄不限,随机分为切除脂肪垫组、保留脂肪垫组和假手术组,每组8只.RA心外膜起搏6周,按左心房(LA)、RA、左心耳(LAA)、右心耳(RAA)、房间隔(AS)5个部位取材,Masson染色测算CVF,荧光定量聚合酶链反应技术检测缝隙连接蛋白(Cx)40和Cx43mRNA表达.结果 (1)假手术组和切除脂肪垫组CVF在部位分布上差异无统计学意义;保留脂肪垫组胶原增生明显,见于LAA和AS,P＜0.01.(2)假手术组Cx40mRNA含量分布在LA、RA、RAA、AS间差异无统计学意义;Cx40mRNA表达在切除脂肪垫组与保留脂肪垫组以LA、LAA增多且组间差异有统计学意义(P＜0.01).(3)假手术组Cx43mRNA含量优势表达于RA、RAA,P＜0.01;而在切除脂肪垫组LA、RA、RAA、AS其含量增多,在保留脂肪垫组的相应部位,其含量减少,P＜0.01.结论 快速RA起搏所致心房间质纤维增生具有空间各异向性,去迷走神经能抑制此效应.迷走神经效应影响起搏后Cx40mRNA与Cx43mRNA在心房与心耳间含量的表达.     

Differential densities of cholinergic nerves in canine supraventricular regions of hearts

PurposeCholinergic nerve plays an important role in the induction and maintenance of atrial fibrillation (AF). Cholinergic innervation at supraventricular tissues is considered to be the histological basis and intervention-associated target site for the arrhythmia; however, the distribution of cholinergic nerve in supraventricular tissues has not been clearly studied. In this study, we investigated the cholinergic nerve innervation in canine supraventricular regions of hearts.MethodsWe performed histological and immunohistochemical staining on canine tissues of left atrial appendage (LAA), right atrial appendage (RAA), left atrium (LA), right atrium (RA), atrial septum (AS), crista terminalis (CT), pulmonary vein (PV), and super vena cava (SVC) using hematoxylin and eosin (H&E) and antibodies to choline acetyltransferase.ResultsNormal canine cardiovascular histological structures were shown from H&E staining. Cholinergic nerve densities at LAA and RAA were significantly higher than LA, which was higher than RA, but no significant difference was observed between LAA and RAA. Furthermore, RA was significantly higher than AS, CT, PV, and SVC and there were no significant differences among the latter four.ConclusionThe heterogeneity of different densities of cholinergic nerve innervation of canine supraventricular regions establishes the histological basis of cholinergic nerve-mediated pathological conditions.     

慢性快速肺静脉起搏建立犬持续性心房颤动模型

目的探讨利用慢性快速刺激肺静脉的方法,建立犬持续性心房颤动(简称房颤)模型。方法在15只犬的左上肺静脉放置自制的环状起搏电极,并在左房游离壁缝合一片状标测电极。将肺静脉起搏电极在体外连接自制的脉冲发生器,持续快速起搏(1200次/分)肺静脉。每隔三天进行心房程序电刺激和burst刺激,分析电生理指标,直至房颤维持超过24h。超声心动图测量基础状态和起搏结束后左右房面积等指标。结果11只犬完成研究。在28.2±3.0天内诱发出持续超过24h的房颤,4只不需刺激诱发即发生自发性房颤,5只经程序刺激可发生房颤,2只经burst刺激可发生房颤,持续时间大于24h。超声心动图测量显示起搏结束后心房面积明显扩大(左房:6.9±1.1cm2vs11.7±1.6cm2;右房:4.3±0.8cm2vs7.0±1.2cm2,P均<0.001)。结论慢性快速刺激犬肺静脉建立持续性房颤模型的方法临床模拟性好,可靠易行。     

Effects of Cilazapril on atrial electrical, structural and functional remodeling in atrial fibrillation dogs

Background and purpose

The effects of angiotensin-converting enzyme inhibitor on long-term atrial electrophysiologic and structural remodeling are still unclear. The purpose of this study is to investigate the effects of Cilazapril on atrial electrical, structural, and functional remodeling in atrial fibrillation (AF) dogs induced by chronic rapid atrial pacing.

Methods

Twenty dogs were randomly divided into sham-operated group (n = 6), control group (n = 7), and Cilazapril group (n = 7). One thin silicon plaque containing 4 pairs of electrodes was sutured to each atrium. A pacemaker was implanted in a subcutaneous pocket and attached to a screw-in epicardial lead in the right atrial appendage. The dogs in control group and Cilazapril group were paced at 400 beats per minute for 6 weeks. The dogs in Cilazapril group received Cilazapril (0.5 mg•kg⁻¹•d⁻¹) 1 week before rapid atrial pacing until pacing stop. Before and after 6-week rapid atrial pacing, atrial effective refractory period (AERP) at 8 sites, AERP dispersion, intraatrium conduction time, inducibility, and duration of AF were measured. Transthoracic and transesophageal echocardiographic examinations included left atrium (LA) maximal volume, LA minimal volume, LA ejection fraction, left atrial appendage (LAA) maximal volume, LAA minimal volume, LAA ejection fraction, LAA maximal forward flow velocity, and LAA minimal backward flow velocity were performed. Atrial collagen volume fraction was analyzed by Masson staining.

Results

After 6-week rapid atrial pacing, although there was no significant difference in AERP shortening and AERP rate adaptation reduction between the control group and the Cilazapril group, the inducibility and duration of AF were found to be dramatically lower in the Cilazapril group than those in the control group (AF inducibility, 65.7% vs 95.7%, P < .05; AF duration, 531.5 ± 301.2 vs 1432.2 ± 526.5 s, P < .01).The post-tachycardia intraatrium conduction times after 6 weeks with Cilazapril were significantly shorter than those in the control group. Cliazapril could partially prevent AERP dispersion increase induced by chronic rapid atrial pacing. Compared with the control group, the LA and LAA volumes were significantly smaller; LA ejection fraction, LAA ejection fraction, LAA maximal forward flow velocity, and LAA minimal backward flow velocity were dramatically higher in the Cilazapril group. The Cilazapril group had a significantly lower percentage of interstitial fibrosis than the control group.

Conclusions

Cilazapril can suppress structural and functional remodeling and prevent the induction and promotion of AF in chronic rapid atrial pacing dogs.     

Inhomogeneity in the appearance of electrical remodeling during chronic rapid atrial pacing: evaluation of the dispersion of atrial effective refractoriness

In the present study, the long-term process of progression of electrical remodeling at various atrial sites, which is not well understood, was compared while monitoring continuously the electrophysiologic parameters at multirecording sites in canine atria during continuous atrial burst pacing. A rapid pacing device was implanted in 5 dogs, and continuous atrial burst pacing (400 beats/min) was delivered at the right atrial appendage (RAA). Four pairs of epicardial wire electrodes were sutured on (1) the RAA, (2) Bachmann's bundle (BB), (3) the right atrium close to the inferior vena cava (IVC), and (4) the left atrium (LA). The distal ends of those wires were exteriorized posteriorly and used for pacing and recording. The atrial effective refractory period (AERP), AERP dispersion (AERPd), atrial conduction time (CT) and inducibility of atrial fibrillation (AF) were evaluated during burst pacing for 14 days and during the subsequent 7 days' recovery. The AERP at the LA pacing site was shorter than that at the other sites on day 0. The AERP shortening was greater in the RAA and LA sites than in the BB and IVC sites. The AERPd increased during pacing and reached the maximum level on day 3, and then decreased during the recovery phase. Prolongation of CT tended to be longer between the RAAand IVC sites than that between the other sites. The incidence of AF induction became higher in accordance with the time course of the rapid pacing phase. There was another peak of AF induction on days 7-10. In a canine chronic rapid atrial stimulation model, the progression of electrical remodeling (ie, the shortening of the AERP and the prolongation of the CT) was not homogeneous in both atria, the AERPd showed a temporal increase between days 3 and 7 and matched the increase in AF inducibility at the LA pacing site, the increase in the AERPd was mainly caused by more rapid AERP shortening at the RAA or LA sites, and the LA site always showed a shorter AERP than the other atrial sites in the control state and during the rapid pacing phase, whereas AF inducibility was higher at the LA site than the other sites.