川芎嗪对心室快速起搏心力衰竭实验犬心房颤动及心房纤维化的影响

目的:观察川芎嗪(tetra methyl pyrazine,TMP)对心室快速起搏致充血性心力衰竭(congestive heart failure,CHF)实验犬心房颤动及心房纤维化的影响。方法:选择健康成年杂种犬21只,随机分为正常对照组、CHF模型组和TMP治疗组。采用右心室快速起搏建立实验犬CHF模型。Burst刺激诱发心房颤动(atrial fibrillation,AF)。超声心动图仪检测实验犬左心室射血分数(left ventricular ejection fraction,LVEF)。Mallory’s三色法染色检测心房组织纤维化程度。采用放射免疫法测定血浆血管紧张素Ⅱ和醛固酮的浓度,测定血清Ⅲ型前胶原氨基末端肽(amino-terminal peptide of typeⅢ procollagen,PⅢNP)、层粘连蛋白(laminin,LN)和透明质酸(hyaluronic acid,HA)的水平。结果:CHF模型组LVEF较正常对照组明显下降(P<0.01);AF发生率、持续性AF发生率及AF持续时间较正常对照组均明显增加(P<0.01);左右心房纤维化程度较正常对照组亦有明显增加(P<0.01);AF持续时间与左心房纤维化程度呈密切正相关(r=0.84,P=0.018);血浆血管紧张素Ⅱ、醛固酮以及血清PⅢNP、HA水平较正常对照组均有明显升高(P<0.05,P<0.01);LN比较则无统计学差异;血浆血管紧张素Ⅱ水平与醛固酮水平呈密切正相关(r=0.759,P=0.048)。TMP治疗组LVEF较CHF模型组有明显改善(P<0.05);持续性AF发生率较CHF模型组有明显降低(P<0.05);左右心房纤维化程度较CHF模型组有明显减轻(P<0.01)。结论:TMP可减轻CHF时心房纤维化的程度,这可能是其减少CHF时AF发生率及持续时间的机制之一。     

犬阵发性房颤转复窦律后时间依赖性心房电逆重构的研究

目的 探讨犬阵发性房颤转复期间时间依赖性心房电逆重构情况.方法 健康成年杂种犬18只,随机分为快速起搏组(n=10,ATP组)和假手术组(n=8,Sham组).分别于快速右心房起搏48 h及转复24 h期间,在0、48(起搏停止)、52、56、60、64,68、72 h电生理检测高右房(HRA)的有效不应期(ERP)、传导速度(CV)、折返波长(WL)、频率自适应性、房颤诱发率等反映心房电生理特性的指标.结果 起博48 h后,ATP组ERP、CV、WL较Sham组减少,ATP组频率自适应性较Sham组降低(P<0.05),房颤诱发率明显增加.停止起搏24 h后ERP、FA、房颤诱发率与Sham组及起搏前相比差异无统计学意义(P>0.05);CV与Sham组及起搏前相比差异有统计学意义(P<0.05).结论 犬48 h快速心房起搏所致左、右心房电重构在转复24 h后,ERP、FA、房颤诱发率发生逆转,但CV、WL仍不能逆转.     

羊持续心房颤动心房有效不应期变化的时间进程及其逆转观察

目的：探讨持续心房颤动（AF）心房有效不应期（ERP）变化的时间进程及其逆转过程.方法：采用起搏方法建立AF模型,在起搏前和起搏后的第1 d,3 d,5 d,7 d对左、右心耳的有效不应期（ERP）进行测定.采用S1S2程序刺激,基础起搏周长（PCL）分别为400 ms,350 ms,300 ms,250 ms,200 ms,S2为200 ms,以5 ms的步长递减.程序刺激结合Burst刺激对上述心房结构进行AF的诱发,记录AF的发生频率.上述相同方法对起搏停止后0 h,3h,5 h,24 h左、右心耳的ERP进行测定.结果：各个基础起搏周长下左、右心耳的ERP在AF后1 d,3 d,5 d,7 d逐渐缩短,且较AF前明显缩短（P＜0.05）;AF终止后左、右心耳的ERP逐渐延长,但AF终止0 h,3 h,5 h ERP与AF前相比仍有明显缩短（P＜0.05）;AF终止后24 h ERP基本恢复到AF前水平,两者相比差异无统计学意义（P＞0.05）;随着AF持续时间的延长,左、右心耳AF的诱发率逐渐增高,与AF前相比,AF后1 d、3 d、5 d、7 d AF的诱发率明显增高（P＜0.05）.结论：随着AF持续,心房的ERP逐渐缩短,AF的诱发率逐渐增高,AF终止后缩短的ERP逐渐延长致AF前水平.     

白藜芦醇干预对慢性心房纤颤猪心房组织中去乙酰化酶1表达的影响

目的探讨白藜芦醇（resveratrol,RES）干预对快速右房起搏诱发的慢性心房纤颤（atrial fibrillation,AF）猪心房组织中去乙酰化酶（SIRT）1表达的影响。方法18头小家猪（雌雄不拘）随机分为3组（n=6）：起搏组（ATP组）、假手术组（sham组）和白藜芦醇干预组（RES组）。采用Seldinger血管穿刺技术穿刺右或左侧颈内静脉送入双极电极至右心房并连接至实验用起搏器（AOO）,快速起搏心房（500次/min）2周（假手术组猪不起搏）制备慢性AF实验模型。RES组猪于起搏前1周开始服用RES（2.5 mg.kg-1.d-1）。RT-PCR分析SIRT1mRNA表达情况,Western blot法检测SIRT1蛋白表达水平的变化。结果RES组SIRT1 mRNA和蛋白的表达较ATP组和sham组均明显增加（P〈0.05）,ATP组稍高于sham组但差异无统计学意义（P〉0.05）。结论RES干预可以明显增强快速起搏右房诱发的慢性AF猪心房组织中SIRT1的表达。     

环孢素A对心房颤动大鼠心房有效不应期及血清中MMP-2、TIMP-2水平的影响

目的：探讨环孢素A（cyclosporineA,CsA）对心房颤动（AF）大鼠心房有效不应期（ERP）、血清中基质金属蛋白酶-2（MMP-2）及金属蛋白酶组织抑制剂-2（TIMP-2）水平的影响。方法：将SD大鼠随机分为对照组、AF组、AFCsA处理组。除对照组外,采用乙酰胆碱-氯化钙药物经尾静脉注射法构建AF大鼠模型;对照组静脉注射等体积的0．9％氯化钠注射液。AFCsA处理组饮食加5mg·kg^-1·d^-1CsA;对照组和AF组每天胃内注入等体积的0．9％氯化钠注射液。心电图检测AF持续时间;测定心房ERP;采用ELISA法检测大鼠血清中MMP-2及TIMP-2水平。结果：与对照组比较,AF组心房ERP明显缩短（P〈0．01）,血清中MMP-2水平明显增高,TIMP-2水平明显下降（P〈0．01）;与AF组比较,AFCsA处理组AF持续时间明显缩短,心房ERP明显延长（P〈0．01）,血清中MMP-2水平明显降低,TIMP-2水平明显升高（P〈0．01）。结论：CsA具有抗AF作用,其可能的机制是延长心房ERP从而改善大鼠心房电重构。以及调控MMP-2及TIMP-2表达而改善大鼠心房结构重构。     

血管紧张素-（1-7）对快速心房起搏犬心房重构及p38MAPK蛋白表达的影响

目的:观察快速心房起搏后犬心房重构与p38MAPK蛋白激活的关系,以及血管紧张素（Ang）-(1-7)的干预作用。方法:普通杂种犬15只随机分为3组,假手术组（Sham,S组）、心房起搏组（Pacing,P组）和心房起搏+Ang-(1-7)组（A组）,每组5只,所有犬均安置心房起搏器,除假手术组外,其余两组均给予500次/min持续右心房起搏,A组以6 μg/（kg·h）连续给予Ang-（1-7）,起搏2周后分别测定各组犬的心脏结构变化、心房有效不应期、房颤诱发率及持续时间,HE染色及Masson染色观察心房肌细胞结构变化,Western blot技术测定左心房组织p38MAPK、磷酸化p38MAPK的蛋白表达情况。结果:与假手术组比较,心房起搏组左室射血分数降低,心房有效不应期缩短,房颤诱发率及持续时间升高,心肌细胞排列紊乱,细胞间纤维组织增多,磷酸化p38MAPK水平明显升高（P＜0.05),Ang-(1-7)组较心房起搏组左室射血分数、心房有效不应期、房颤诱发率及持续时间均明显改善,磷酸化p38MAPK蛋白降低（P＜0.05）,但p38MAPK在3组间的差异未达到统计学意义。结论:快速心房起搏导致的心房重构与p38MAPK磷酸化激活有关,Ang-（1-7）可通过降低p38MAPK激活而保护心房重构。     

慢性心房重构犬心房肌细胞内游离钙离子浓度的变化

目的 观察慢性心房重构犬心房肌细胞内游离钙变化，探讨慢性心房重构分子机制。方法 实验犬随机分为两组：对照组，起搏组。起搏组利用快速心房起搏（ATP）建立慢性心房重构模型，用激光共聚焦显微镜技术，以Flou-3／AM作为钙指示剂，测定两组犬心房肌细胞内游离钙浓度。结果 起搏组犬心房肌细胞内游离钙离子浓度较对照组明显增加（P〈0．01）。结论 慢性心房重构犬心房肌细胞存在钙超载，提示钙超负荷是慢性心房重构分子机制。     

房颤电重构的离子通道及结构重构的分子生物基础

心房颤动(AF)是心律失常领域的研究热点,房颤电重构、结构重构是心房颤动细胞电生理的主要表现。近年来的研究发现,AF及快速心房起搏能引起心房电生理功能的改变,促使AF的发生和维持,这种现象称为心房电重构。电重构表现为心房动作电位时程(APD)及有效不应期(ERP)缩短,心房不应     

快速左心耳起搏对犬心房构型、心功能及病理组织学特点改变的时间进程研究

目的 探讨慢性心房颤动(Atrial Fibrillation,AF)犬随时间进程心房构型、心功能、病理组织学及超微结构的变化特点.方法 14只比格犬随机分为起搏组(n=7)和对照组(n=7),于左心耳缝植起搏电极,连接实验用VOO型起搏器(频率为400次/min),快速持续起搏8周,建立犬慢性AF模型.分别于0、1、2、4、6、8周时应用超声心动图测量左房横径及心室射血分数,实验结束后取心房肌组织用光镜和电镜观察心房肌的超微结构.结果 (1)心脏超声结果显示8周的左房内径与起搏前比较明显增加,差异有统计学意义(P<0.01),在起搏1周时左房内径已经明显增加,随后2、4、6、8周的左房内径出现逐渐增加趋势.同时,起搏8周心室射血分数与起搏前相比显著降低,差异有统计学意义(P<0.01),心室射血分数1周时已经明显降低,与起搏前比较,差异有统计学意义(P<0.01),随后2、4、6、8周心室射血分数出现逐渐降低趋势.而对照组起搏电极植入前后均未发生明显变化.(2)起搏犬心房肌细胞明显肥大,变性,心肌纤维排列紊乱,线粒体增多、体积变大,细胞间存在不同程度的纤维化及间质胶原增生和糖原沉积.结论 高频起搏左心耳8周建立的慢性AF模型,心肌超微结构、心房构型和心功能发生明显改变,引起心房结构重构和收缩功能重构,这是发生心房颤动的重要原因之一.     

星状神经节电刺激建立交感神经介导的急性房颤犬模型

目的：建立交感神经张力异常介导的急性房颤动物模型的方法学。方法：将16只家犬分为三组：对照组（n=4）,右侧星状神经节（RSG）组（n=6）和左侧星状神经节（LSG）组（n=6）,测定心房和肺静脉不同部位的房颤诱发率、房颤持续时间。结果： RSG刺激显著增加右心房（RA）的房颤诱发率和持续时间（P＜0.05）,LSG刺激显著增加左房（LA）、左上肺静脉（LSPV）、左下肺静脉（LIPV）的房颤诱发率和持续时间（P＜0.05）;与刺激时相比,RSG切除显著降低RA的房颤诱发率和持续时间（P＜0.05）;LSG切除显著降低LA、LSPV、LIPV的房颤诱发率和持续时间（P＜0.05）;结论：星状神经节电刺激同时快速心房起搏6h可成功建立交感神经介导的急性房颤犬模型,星状神经节电刺激使心房和肺静脉部位的房颤诱发率显著升高,房颤持续时间显著延长,去星状神经节支配可减少房颤的发生和维持。     

Effects of spironolactone on electrical and structural remodeling of atrium in congestive heart failure dogs

Background Renin-angiotensin-aldosterone system has been demonstrated to be associated with both congestive heart failure （CHF） and atrial fibrillation （AF）. This study investigated the effects of spironolactone, a kind of aldosterone antagonist, on atrial electrical remodeling and fibrosis in CHF dogs induced by chronic rapid ventricular pacing. Methods Twenty one dogs were randomly divided into sham-operated group, control group, and spironolactone group. In control group and spironolactone group, dogs were ventricular paced at 220 beats per minute for 6 weeks. Additionally, spironolactone at 15 mg.kgl.d1 was given to dogs 1 week before rapid ventricular pacing until pacing stopped. Transthoracic and transoesophageal echocardiographic examinations were performed to detect structural and functional changes of the atrium. Swan2 Ganz floating catheters were used to measure hemadynamics variances. Atrial effective refractory period （AERP）, AERP dispersion （AERPd） conduction velocity （CV） were determined. The inducib atrial fibrosis was quantified with Masson staining. intra- and inter-atrium conduction time （CT） and intra-atrium ity and duration of AF were also measured in all groups. Finally, Results AERP did not change significantly after dogs were ventricular paced for 6 weeks. However, AERPd, intra- and inter-atrium CT increased significantly, and CV decreased apparently, which was negatively correlated to the atrial fibrosis （r=-0.74, P〈0.05）. Simultaneously, left atriums were enlarged and cardiac hemadynamics worsened in pacing dogs. Although spironolactone could not affect cardiac hemadynamics effectively, it can obviously improve left atrial ejection fraction （P〈0.05）. Spironolactone treatment did not alter AERP duration, but this medicine dramatically decreased AERPd （P〈0.05）, shortened intra- and inter-atrium conduction time （P〈0.05）, and increased atrium CV. Moreover, spironolactone decreased the inducibility and duration of AF （P〈0.05）, as well as at     

Probucol attenuates atrial autonomic remodeling in a canine model of atrial fibrillation produced by prolonged atrial pacing

Background We hypothesize that increased atrial oxidative stress and inflammation may play an important role in atrial nerve sprouting and heterogeneous sympathetic hyperinnervation during atrial fibrillation （AF）. To test the hypothesis, we examined whether the antioxidant and anti-inflammatory treatment with probucol attenuates atrial autonomic remodeling in a canine model of AF produced by prolonged rapid right atrial pacing.
Methods Twenty-one dogs were divided into a sham-operated group, a control group and a probucol group. Dogs in the control group and probucol group underwent right atrial pacing at 400 beats per minute for 6 weeks, and those in the probucol group received probucol 1 week before rapid atrial pacing until pacing stopped. After 6-week rapid atrial pacing, general properties including left atrial structure and function, atrial hemodynamics and the inducibility and duration of AF were measured in all the groups. Atrial oxidative stress markers and serum C-reactive protein （CRP） concentration were estimated. The degree of nerve sprouting and sympathetic innervation at the right atrial anterior wall （RAAW） and the left atrial anterior wall （LAAW） were quantified by immunohistochemistry, atrial norepinephrine contents were also detected. Atrial beta-nerve growth factor （beta-NGF） mRNA and protein expression at the RAAW and LAAW were assessed by real-time quantitative RT-PCR and Western blotting respectively.
Results Atrial tachypacing induced significant nerve sprouting and heterogeneous sympathetic hyperinnervation, and the magnitude of nerve sprouting and hyperinnervation was higher in the RAAW than in the LAAW. Atrial beta-NGF mRNA and protein levels were significantly increased at the RAAW and LAAW, and the upregulation of beta-NGF expression was greater at the RAAW than at the LAAW in the control group. The beta-NGF protein level was positively correlated with the density of sympathetic nerves in all groups. Probucol decreased the increase of CRP concentration and attenuated atrial oxidative stress caused by atrial tachypacing. In addition, probucol could effectively inhibit atrial beta-NGF upregulation, significantly attenuate atrial nerve sprouting and heterogeneous sympathetic hyperinnervation, and dramatically reduce the inducibility and duration of AF.
Conclusions The atrial over-expression of beta-NGF possibly caused by increased oxidative stress and inflammation may be the main mechanism underlying atrial autonomic remodeling during AF. Probucol attenuates atrial autonomic remodeling possibly by its antioxidant and anti-inflammatory actions.     

心房颤动电生理重构的实验研究

目的 :研究心房颤动 (atrialfibrillation ,AF)时心房肌的电生理重构。方法 :快速持续起搏犬右心房 8～ 10周 ,制备持续性AF模型。比较对照犬 ( 8只 )与起搏犬 ( 10只 )的有效不应期 (effectiverefractoryperiod ,ERP)和心房颤动波周长 (atrialfibrillationcyclelength ,AFCL)的变化来分析心房肌的电生理重构。结果 :起搏组P波时间和PA间期比起搏前明显延长 (P波时间 90 5± 10 5对 5 3 6± 8 3ms ;PA间期 5 9 6± 8 8对 3 8 6± 11 4ms ,P <0 0 5 )。经程序刺激ERP较对照组明显缩短 (S1S13 0 0ms 115± 2 3对 15 0± 2 1;S1S14 0 0ms 10 5± 2 7对 15 4± 2 4ms ,P <0 0 5 )。同一心房不同部位的ERP和AFCL也存在差异。结论 :心房率的长期变化可引起ERP和AFCL的变化 ,即心房肌发生电生理重构 ,而且不同部位心房肌电生理重构是不同的。     

Calpain I inhibition prevents atrial structural remodeling in a canine model with atrial fibrillation

Background Atrial fibrillation （AF） is accompanied by atrial structural remodeling. Calpain activity is induced during AE To test a causal relationship between calpain activation and atrial structural changes, N-acetyI-Leu-Leu-Met （ALLM）, a calpain inhibitor, was utilized in a canine AF model. Methods Fifteen dogs were randomly divided into 3 groups： sham-operated group, control group and calpain inhibitor group; each with 5 dogs. Sustained AF was induced by rapid right atrium pacing at 600 beats per minute for 3 weeks. ALLM was administered at a dosage of 1.0 mg-kg-l-d1 in the calpain inhibitor group. Three weeks later, the proteolysis, protein expression of TnT and myosin, calpain I localization and expression and structural changes were examined in left atrial free walls, right atrial free walls and the interatrial septum respectively. Atrial size and contractile function were also measured by echocardiography. Results Long-term rapid atrial pacing induced marked structural changes such as enlarged atrial volume, myolysis, degradation of TnT and myosin, accumulation of glycogen and changes in mitochondrial shape and size, which were paralleled by an increase in calpain activity. The positive correlation between calpain activity and the degree of myolysis （rs=0.90 961, P〈0.0001） was demonstrated. In addition to structural abnormalities, pacing-induced atrial contractile dysfunction was observed in this study. The pacing-induced atrial structural alterations and loss of contractility were partially prevented by the calpain inhibitor ALLM. Conclusions Activation of calpain represents key features in the progression towards overt structural remodeling. Calpain inhibitor, ALLM, suppressed the increased calpain activity and reversed structural remodeling caused by sustained atrial fibrillation in the present model. Calpain inhibition may therefore provide a possibility for therapeutic intervention in AE     

Effect of nifekalant on acute electrical remodelling in rapid atrial pacing canine model

Atpresent, treatment of atrial fibrillation (AF) with antiarrhythmic drugs is problematic, a better understanding of the mechanisms determining antiarrhythmic drug efficacy would help in improving therapy.1 Recent evidence indicates that disease or arrhythmic induced alterations in cardiac electrophysiology (electrical remodelling) are central in arrhythmic genesis, Aparticularly for AF, which alters cardiac electrophysiology to promote its own maintenance.2,3 Pharmacological therapy to prev…     

Changes in microRNAs expression are involved in age-related atrial structural remodeling and atrial fibrillation

Background Small noncoding microRNAs regulate gene expression in cardiac development and disease and have been implicated in the aging process and in the regulation of extracellular matrix proteins.However,their role in age-related cardiac remodeling and atrial fibrillation (AF) was not well understood.The present study was designed to decipher molecular mechanisms underlying age-related atrial structural remodeling and AF.Methods Three groups of dogs were studied:adult and aged dogs in sinus rhythm and with persistent AF induced by rapid atrial pacing.The expressions of microRNAs were measured by quantitative real-time polymerase chain reaction.Pathohistological and ultrastructural changes were tested by light and electron microscopy.Apoptosis index of myocytes was detected by TUNEL.Results Samples of atrial tissue showed the abnormal pathohistological and ultrastructural changes,the accelerated fibrosis,and apoptosis with aging and/or in AF dogs.Compared to the adult group,the expressions of microRNAs-21 and -29 were significantly increased,whereas the expressions of microRNAs-1 and-133 showed obvious downregulation tendency in the aged group.Compared to the aged group,the expressions of microRNAs-1,-21,and-29 was significantly increased in the old group in AF; contrastingly,the expressions of microRNA-133 showed obvious downregulation tendency.Conclusion These multiple aberrantly expressed microRNAs may be responsible for modulating the transition from adaptation to pathological atrial remodeling with aging and/or in AF.