【作者】 白晨；

【导师】 张薇；

【作者基本信息】 山东大学 ， 内科学， 2007， 博士

【摘要】 研究背景：心房颤动（房颤）一直被认为是左心房疾病，随着对房颤机制的深入研究和射频消融治疗房颤的进展，学者们开始关注右心房在房颤发生和维持中的作用，但由于方法学的限制，相对左心房而言，在各种病理生理状态下右心房结构、功能和血流动力学改变研究较少。因此，有必要探讨评价右心房的新方法。右心房与左心房类似，主要有三个功能：右室收缩期收集并储存上、下腔静脉回流血的储存器功能；右室舒张早期将腔静脉血流输送至右室的管道功能；右室舒张晚期主动收缩以增强心室充盈的助力泵功能。右心房功能在各种生理及病理状态下发挥其调节右室充盈和维持整体心搏量的重要作用。右心房内的特殊结构和右心房基质改变与心律失常的发生和发展密切相关。心房压力--容积（面积）关系被认为是最精确最具代表性的反映心房功能和血流动力学改变的指标，但心房压力的获取需采用心导管方法，因此，多数应用心房压力--容积环评价心房功能的资料来源于动物实验。在无创性的检测技术中，超声心动图为评价心房结构、功能和血流动力学提供了无创性方法，使有关心房的研究从基础走向临床。特别是声学定量技术（AQ），利用自动边缘检测原理能实时显示心腔面积-时间曲线、容量-时间曲线及及其微分曲线，为左心房功能的评价提供了无创性新方法，但应用AQ技术，能否评价右心房结构、功能和血流动力学改变尚未见报道。肺动脉高压是导致右心室功能障碍的疾病，右心房功能在右心室功能障碍时对维持右心室充盈起重要作用。高血压病是导致左心室功能障碍的疾病，也是非瓣膜性房颤的主要基础心脏病，高血压病对右心系统的影响尚不清楚。应用脉冲波多普勒测量三尖瓣血流频谱，Dernellis等研究发现原发性高血压患者右心房功能减低，但迄今为止，利用AQ技术评价肺动脉高压和高血压患者右心房结构、功能变化的研究尚未见报道。目的：（1）探讨AQ技术对右心房功能评价的可行性；（2）肺动脉高压患者右心房结构和功能的变化；（3）高血压患者右心房结构和功能的变化。方法：研究对象：（1）正常组：20例，男性9例，女性11例，年龄21～60岁，平均（35.21±14.60）岁，均无心血管病史，实验室检查、心电图和超声心动图检查均正常。（2）肺动脉高压组：17例，男性6例，女性11例，年龄15～51岁，平均（38.82±13.43）岁，其中原发性肺动脉高压或肺血管疾病7例，先天性心脏病10例，均为窦性心率，由超声心动图、手术、CT等方法证实诊断，排除高血压、冠心病、糖尿病等其他心脏病。（3）高血压组：50例，男性35例，女性15例，年龄38～65岁，平均（52.24±6.86）岁，均符合WHO/ISH关于高血压诊断标准，即舒张压≥90mmHg（1mmHg=0.133Kpa）和（或）收缩压≥140mmHg。病史0.5～32年，平均12.81±10.3年，经体检和相应实验室检查排除继发性高血压，均为1、2级高血压患者。研究方法：受试者取左侧卧位，平静呼吸，按常规方法进行超声心动图检查，同步记录Ⅱ导联心电图，测量参数取3～5个心动周期的均值。（1）M型超声及二维超声心动图检查：取胸骨旁左室长轴切面，记录二尖瓣腱索水平的左室M-型图像；取心尖四腔心切面，记录舒张末期右心房二维图像；（2）三尖瓣血流频谱：取心尖四腔心切面，在彩色多普勒引导下，将脉冲波多普勒（PW）的取样容积置于三尖瓣瓣尖水平，记录三尖瓣血流频谱；将连续波多普勒的取样线尽量垂直通过三尖瓣瓣尖记录三尖瓣返流频谱，估测肺动脉收缩压；（3）上腔静脉血流频谱：取心尖四腔心切面，在彩色多普勒引导下，将PW取样容积置于上腔静脉入口内约1cm处，仔细调整探头角度直至获得满意的上腔静脉血流频谱；（4）右心房容量曲线：取心尖四腔切面，启动二次谐波显像、自动平均和AQ系统，调节总增益、时间增益补偿和侧向增益补偿等控制键，使AQ曲线与右心房心内膜密切贴合，划定整个右心房的感兴趣区，AQ技术可实时显示右心房容积-时间变化曲线及其微分曲线。测量指标：M型超声及二维超声心动图测量指标：（1）右室前壁厚度（RVAW，mm）；（2）室间隔厚度（IVS，mm）；（3）右室舒张末期内径（RVED，mm）；（4）右心房上下径（RAL，mm）和横径（RAT，mm）；（5）右室射血分数（RVEF）。多普勒超声心动图测量指标：（1）E/A比值；（2）上腔静脉血流频谱逆向A波峰值流速（Ar，cm/s）；（3）肺动脉收缩压（mmHg）。右心房容量曲线测量指标：（1）右室舒张末期右心房容积（EDV，ml）；（2）右室收缩末期右心房容积（ESV，ml）；（3）右心房快速排空期末容积（EREV，ml）；（4）右心房快速排空容积（RE，ml）：据下式计算：RE=ESV-EREV；（5）右心房主动收缩排空容积（AE，ml）：据下式计算：AE=EREV-EDV；（6）右心房储存器容积（RV，ml）：据下式计算：RV=ESV-EDV，RV也为右心房排空总量；（7）右心房快速排空分数（REF，％）：据下式计算：REF=RE/RV×100％；（8）右心房主动收缩排空分数（AEF，％）：据下式计算：AEF=AE/RV×100％；（9）峰值充盈率（PFR，ml/s）；（10）峰值快速排空率（PRER，ml/s）；（11）峰值心房排空率（PAER，ml/s）；（12）PRER/PAER。结果：肺动脉高压患者右心房功能改变的结果：（1）二维和多普勒超声心动图结果：与正常组比较，肺动脉高压组患者RVAW、IVS、RVED和右心房内径均显著增大（P＜0.05～0.001），右室收缩功能减低（P＜0.001）；上腔静脉血流频谱A波峰值流速显著增高（P＜0.01）。肺动脉高压组患者肺动脉收缩压93.81±22.88mmHg。（2）AQ检测检测结果：与正常组比较，肺动脉高压组反映容量的指标ESV、EDV、EREV、AE显著增高（P＜0.001）；右心房储存器容积（RV）、峰值充盈率（PFR）明显增加（P＜0.05～0.01）；心房快速排空分数（REF）明显减低（P＜0.05），峰值快速排空率（PRER）无显著性差异（P＞0.05）；心房主动收缩排空分数（AEF）、峰值心房排空率（PAER）显著增加（P＜0.05～0.01）。高血压患者右心房功能改变的结果：（1）二维和多普勒超声心动图结果：与正常组比较，高血压组RVAW，IVS均显著增大（P＜0.01）；三尖瓣血流频谱E/A＜1。（2）AQ检测结果：与正常组比较，高血压组反映容量的指标ESV、EDV、EREV、RE、AE均显著增高（P＜0.05～0.01）；右心房储存器容积（RV）、峰值充盈率（PFR）明显增加（P＜0.01）；右心房快速排空分数（REF）、右心房主动收缩排空分数（AEF）、峰值快速排空率（PRER）无显著性差异（P＞0.05），峰值快速排空率与峰值心房排空率的比值（PRER/PAER）显著减低（P＜0.01）；峰值心房排空率（PAER）显著增加（P＜0.01）。结论：（1）声学定量技术为评价病理生理状态下右心房结构和功能的变化提供了无创性新方法；（2）肺动脉高压患者右心房结构和功能发生了显著的变化，表现为右心房扩大，管道功能受损，助力泵功能和储存器功能代偿性增强；（3）高血压患者右心房结构和功能发生了显著的变化，表现为右心房扩大，管道功能减低，右心房助力泵功能和储存器功能代偿性增强。背景：心房颤动（房颤）的非药物治疗--射频消融术是近年来电生理领域中的研究热点。目前经导管射频消融房颤的两大术式，阶段性肺静脉电隔离术和环肺静脉口消融术的操作都局限于左心房，而右心房在房颤的发生和发展的作用被忽视。电生理标测已证实，局灶性房颤的部分异位兴奋点位于右心房；右心房内存在一些特殊结构如右心房峡部、冠状静脉窦、界嵴和上下腔静脉开口等，均与心律失常的发生和维持密切相关。新近Yamane等报道了一例起源于上腔静脉的房颤，并成功的进行了射频消融治疗。界嵴是部分房颤发生的重要基础，有研究显示在界嵴后缘和界嵴—梳状肌分界处存在两个单向阻滞区，右心房内的电传导不能跨越阻滞区而形成折返环，导致心房扑动形成，如果传到阻滞的范围缩小，折返环也缩小且不稳定，向周边弥散，即导致房颤发生，因此，右心房在房颤的发生中具有一定的地位。基础和临床研究均已证实，房颤时左心房结构重构在房颤的维持中扮演重要角色，针对肺静脉及其周围的左心房后壁（肺静脉前庭）进行消融，显著提高伴有器质性心脏病房颤患者的射频消融成功率，进一步证实了结构重构是房颤维持的重要基质。房颤能否导致右心房出现结构重构尚不清楚，如果右心房结构重构严重到一定程度，右心房的基质足以使房颤得以维持，此时，单纯消融左心房不能消除房颤，这可能是目前慢性房颤消融成功率较低的原因之一。对房颤左心房结构重构的研究证实，心房肌细胞外基质纤维化和心房扩大是心房结构重构的主要组成部分。基质金属蛋白酶（MMPs）及其内源性组织抑制因子（TIMPs）是调节细胞外基质胶原合成和降解的重要蛋白酶系，晚近在房颤患者的研究中发现，MMPs/TIMPs表达改变与心房肌细胞外基质重构和心房扩大有关。但是，MMPs/TIMPs表达改变是否为右心房结构重构的分子机制尚不清楚。目前对房颤时MMPs/TIMPs的调控和影响因素所知甚少。以往的研究证实，肾素—血管紧张素系统（RAS）激活和细胞内Ca²⁺超载是房颤电重构和结构重构的基本病理生理机制。因此，推测RAS激活、细胞内Ca²⁺超载可能是房颤时MMPs/TIMPs的重要激活途径。近年来的一系列临床研究显示，血管紧张素转换酶抑制剂（ACEI）和血管紧张素Ⅱ受体阻断剂（ARB）通过抑制RAS对房颤有一定的预防作用，但其机制尚未阐明。本研究应用ACEI——卡托普利对房颤动物模型进行干预，探讨其对MMPs/TIMPs表达的影响和对心房结构重构的作用，为应用非传统抗心律失常药物防治房颤提供理论依据。本课题的第一部分已证实了应用声学定量（AQ）技术评价右心房结构和功能改变的可行性，但应用AQ技术评价房颤动物模型右心房改变尚未见报道。目的：（1）应用超声心动图AQ技术评价房颤动物模型建立过程中右心房结构和功能的动态改变；（2）观察右心房组织超微结构、细胞外基质改变；（3）探讨RAS激活在右心房结构重构中的作用；（4）研究MMP-9/TIMP-1在右心房结构重构中的作用；（5）探讨RAS激活和细胞内Ca²⁺超载对MMP-9/TIMP-1的调控作用；（6）分析分子生物学改变与右心房结构和功能变化之间有无平行关系；（7）ACEI对右心房MMP-9 TIMP-1的影响；（8）ACEI对右心房结构改变的保护作用。方法：（1）采用快速心房起搏建立慢性房颤犬动物模型；（2）于快速心房起搏前，起搏后1周、4周、8周采用超声心动图监测右心房面积的变化，二尖瓣、三尖瓣反流及反流程度；（3）于快速心房起搏前，起搏后监测右心房压的变化；（4）采用放射免疫法测定右心房组织中血管紧张素Ⅱ浓度；（5）采用三电极直流等离子体光电光谱法测定右心房心肌细胞内Ca²⁺离子浓度；（6）右心房心肌组织常规HE染色和Masson染色，观察右心房心肌细胞结构和定量胶原含量；（7）采用透射电镜观察右心房心肌组织超微结构；（8）采用RT-PCR定量右心房心肌组织ACE、MMP-9和TIMP-1的转录水平；（9）采用western blot测定右心房心肌组织MMP-9和TIMP-1蛋白质表达水平；（10）采用免疫组织化学方法确定MMP-9和TIMP-1的空间分布情况。结果：（1）房颤动物模型的建立：快速心房房颤组1只犬术后12h猝死，尸检发现右心耳电极脱入右室，推测死亡原因为快速起搏导致室颤；1只犬术后4周出现腹胀，腹水征阳性，进食、活动明显减少，超声检查右心房电极顶端可见一26mm×21mm的低密度光团，并探及大量胸腔积液和腹水，处死后尸检证实电极顶端血栓形成；另一只犬8周ECG检查时起搏器已停止发放脉冲。治疗组亦有1只犬因起搏电极脱入心室造成室颤而死亡。上述4只犬予以剔除。最终房颤组及治疗组各有8只犬完成整个实验。快速心房起搏前，所有犬程序刺激和/或burst刺激均未诱发出房颤。对照组6只犬实验后程序刺激和burst刺激均未诱发出房颤。房颤组2只犬分别在快速心房起搏1周、4周后停起搏复查ECG时出现阵发性房颤；快速心房起搏8周后电生理检查时，2只犬（25％）停止起搏后出现自发性房颤，4只犬（50％）程序刺激诱发出房颤，2只犬（25％）burst刺激诱发出房颤，房颤诱发率100％，表明已成功建立了慢性房颤模型。治疗组1只犬在术后4周停起搏复查心电图时出现阵发性房颤；起搏8周后2只犬程序刺激诱发出房颤，余6只犬程序刺激和burst刺激均未诱发出房颤。（2）超声心动图资料的比较：①快速心房起搏对心房内径的影响：起搏1周后，房颤组右心房面积较起搏前极显著增大（P＜0.001）；随起搏时间延长进一步增加，在起搏8周后，较起搏1周时显著增大（P＜0.05），与起搏4周时无差别（P＞0.05）；房颤组右心房面积在起搏1、4、8周时均较对照组同一时间极显著增加（P均＜0.001）；起搏1周和4周时，治疗组右心房面积与起搏前和对照组相比，有增大趋势，但差异均无统计学意义（P＞0.05）；与房颤组相比，治疗组右心房面积明显减少（P＜0.01～0.001）。起搏8周时，与房颤组相比，治疗组右心房面积明显减少（P＜0.001），但仍高于对照组（P＜0.05）。②快速心房起搏对二尖瓣，三尖瓣血流频谱的影响：彩色多普勒显示起搏犬在起搏过程中发生了不同程度的二尖瓣、三尖瓣反流，随起搏时间的延长反流程度加重。对照组仅有1例在实验过程中发生了轻度二尖瓣反流；起搏8周时，房颤组有8只犬出现了中～重度二尖瓣反流，8只犬出现了轻～中度三尖瓣反流，治疗组可见部分犬出现二尖瓣反流（4只，轻～中度）和三尖瓣反流（3只，轻度），其程度较房颤组轻。③快速心房起搏对右心房容积的影响：与对照组相比，起搏4周后，房颤组ESV，EDV，EREV开始增加，EF，CV降低（P均＜0.05）；起搏8周后，ESV，EDV，EREV极显著增加（P均＜0.001），而EF，PAER极显著降低（P均＜0.001），CV亦明显降低（P＜0.05），余指标在起搏过程中无明显改变。与起搏前相比，房颤组起搏1周后右心房AQ各项指标均无明显改变（P＞0.05）；起搏4周后ESV，EREV，EDV增加（P＜0.05），EF降低（P＜0.05）；起搏8周后ESV，EREV，EDV显著增大（P＜0.001），EF和PAER降低（P＜0.001）。与起搏1周相比，起搏8周后ESV，EREV，EDV增大（P＜0.01），EF和PAER减低（P＜0.01）。余指标在起搏过程中无统计意义改变。但起搏8周后，治疗组ESA、ESV、EDV、EREV增加及EF缩小程度远小于同期房颤组（均P＜0.05）。提示卡托普利对心房快速起搏所致的心房扩大、容量增加、收缩力减弱等结构及功能改变有明显保护作用。（3）快速心房起搏对右心房压的影响：快速心房起搏前，房颤组和对照组右心房压差异无统计学意义（3.17±2.52mmHg VS 4.95±3.24mmHg，P＞0.05）；起搏8周后房颤组右心房压较对照组显著升高（7.09±1.13 VS 4.50±1.51mmHg，P＜0.01），与房颤组相比，治疗组右心房压明显减低（5.28±1.96mmHg VS 7.09±1.13mmHg，P＜0.05），但仍高于对照组（5.28±1.96mmHg VS 4.95±3.24mmHg，P＞0.05）。（4）右心房心肌细胞内Ca²⁺含量的变化：与对照组比较，房颤组右心房心肌细胞内Ca²⁺含量升高36.18％（37.68±10.45ug/mg VS 27.67±4.46ug/mg，P＜0.05）；与房颤组相比，治疗组Ca²⁺含量明显减低（29.88±1.47ug/mg VS 37.68±10.45ug/mg，P＜0.05），但仍高于对照组（29.88±1.47ug/mg VS 27.67±4.46ug/mg，P＞0.05）。（5）右心房心肌血管紧张素Ⅱ含量的变化：与对照组比较，房颤组右心房心肌Ang Ⅱ浓度升高51.94％（11.38±3.77pg/mg VS 7.49±1.65pg/mg，P＜0.05）；与房颤组相比，治疗组右心房心肌Ang Ⅱ明显减低（7.12±1.01pg/mg VS 11.38+3.77pg/mg，P＜0.05），略低于对照组（7.12±1.01pg/mg VS 7.49±1.65pg/mg，P＞0.05）。（6）右心房心肌病理结构的变化：HE染色切片上，对照组心肌细胞结构完整，排列整齐，被少量的间质组织包绕；细胞核大而清晰，规则的纤维网充填于整个心肌细胞；间质内成纤维细胞形状规则，数量适中。房颤组切片上，增大的心肌细胞排列紊乱；细胞核大小不甚规则，核异型性明显，细胞内可见肌纤维断裂；心肌纤维之间连接组织积聚，使心肌细胞之间的间隔增宽；间质内心肌成纤维细胞数量增加。治疗组心肌细胞结构完整，排列轻度不整，胞核清晰，无明显核异型，间质内成纤维细胞形状规则，数量适中，肌纤维细胞数量较对照组稍有增加。Masson染色显示，对照组胶原组织均匀，相邻细胞的胶原纤维网完好；房颤组心肌内胶原组织明显增多，排列紊乱，围绕单个心肌细胞的胶原纤维网减少或断裂。治疗组心肌内胶原组织略显增多，排列轻度不规则，相邻细胞的胶质纤维网清晰可辨。定量分析显示，与对照组相比，房颤组右心房心肌组织胶原含量显著升高（27.75±7.83 VS 19.23±3.67，P＜0.05）；与房颤组相比，治疗组右心房心肌组织胶原含量显著减低（20.47±3.99 VS 27.75±7.83，P＜0.05），但仍高于对照组（20.47±3.99 VS 19.23±3.67，P＞0.05）。（7）心房肌超微结构的改变：对照组心房肌超微结构表现：①肌小节结构高度规整，其间有大小均一的线粒体分布；②心肌内肌原纤维排列整齐，无断裂；③线粒体体积大、数量多，嵴排列紧密呈Z字型；④肌浆网体积大，数量多；⑤胞浆丰富；⑥核膜光滑完整，核仁清晰，异染质成簇聚集在核周部；⑦闰盘结构完整；⑧心房颗粒限制在核周部位；房颤组心房肌超微结构表现：①肌原纤维排列紊乱，肌节结构模糊，断裂；②线粒体数量明显增多，丛状聚集，肌原纤维之间线粒体少见，线粒体变长，大小不一，大部分线粒体呈双层膜结构，线粒体嵴沿长轴排列；③肌浆网肿胀，破裂，数目减少；④核膜凹凸明显，有时可见分叶核，异染质均匀分布在胞浆中；⑤闰盘结构不连续，模糊；⑥糖原在肌溶解区积聚，偶可形成“糖原湖”；⑦心房颗粒增多，分散；治疗组心房肌超微结构表现：①肌小节结构规整，肌节以Z线为界具有明确的周期结构，其间有大小均一的线粒体分布；②心肌内肌原纤维排列整齐，无断裂；③肌节间有成排的线粒体，体积大，数量多；④肌浆网体积大、数量多，未见明显破裂；⑤胞浆丰富；⑥核膜有浅凹陷，胞核清晰，一端富有细胞器；⑦闰盘结构完整，但扭曲增多；⑧未见肌溶解现象及糖原湖，心房颗粒限制在核周部位，未见明显增多。（8）心房肌mRNA转录水平：①与对照组相比，房颤组右心房心肌组织ACE mRNA水平升高45.00％（0.29±0.08 VS 0.20±0.01，P＜0.05）；与房颤组相比，治疗组右心房心肌组织ACE mRNA水平有减低趋势，但差异无统计学意义（0.27±0.07 VS 0.29±0.08，P＞0.05）；②与对照组相比，房颤组右心房心肌组织MMP-9mRNA升高109.09％，TIMP-1mRNA转录水平升高71.43％（MMP-9：0.23±0.04 VS 0.11±0.009；TIMP-1：0.12±0.02 VS 0.07±0.01，P＜0.01）；MMP-9/TIMP-1之比有减低趋势，但差异无统计学意义（1.99±0.68 VS 1.53±0.26，P＞0.05）；与房颤组相比，治疗组MMP-9 mRNA水平明显减低（0.19±0.03 VS 0.23±0.04，P＜0.05），TIMP-1mRNA水平无明显变化（0.12±0.03 VS 0.12±0.02，P＞0.05），但仍高于对照组（0.12±0.03 VS 0.07±0.01，P＜0.01）。（9）MMP-9和TIMP-1 western blot和免疫组织化学染色结果：与对照组相比，房颤组右心房心肌MMP-9蛋白质表达水平明显升高（115.38±22.07 VS 84.75±20.32，P＜0.05），与房颤组相比，治疗组右心房心肌MMP-9蛋白质表达水平明显减低（90.37±18.50 VS 115.38±22.07，P＜0.05）；与对照组相比，房颤组右心房心肌TIMP-1蛋白质表达水平呈减低趋势，但差异未达统计学意义（99.38±17.10 VS 105.63±21.07，P＞0.05），与房颤组相比，治疗组右心房心肌TIMP-1蛋白质表达水平亦无统计学意义（103.94±15.02 VS 99.38+17.10，P＞0.05）。为进一步确定MMP-9和TIMP-1在细胞内的表达状况和组织学定位特征，本研究利用MMP-9和TIMP-1单克隆抗体以免疫组织化学的方法检测其表达水平及细胞定位。结果显示MMP-9在对照组心肌细胞胞浆内呈分布均匀，不规则网状的稀疏的棕色颗粒；在房颤组心肌细胞胞浆内呈分布浓密，不规则网状的棕色颗粒；TIMP-1在对照组心肌细胞浆内分布均匀，呈不规则网状的棕色颗粒，在房颤组呈不规则网状的相对稀疏的棕色颗粒；治疗组MMP-9在心肌细胞胞浆内呈分布均匀，不规则网状的稀疏的棕色颗粒，治疗组TIMP-1在胞浆内的分布与对照组相似。（10）分子生物学指标与超声、血流动力学指标之间的相关分析：直线相关分析显示，右心房心肌组织MMP-9蛋白质水平与右心房面积呈正相关（r=0.73，P＜0.05）；右心房心肌组织TIMP-1蛋白质水平与右心房压呈正相关（r=0.81，P＜0.05）；右心房心肌组织AngⅡ与右心房心肌组织胶原含量、MMP-9蛋白质表达水平呈正相关（r=0.86，P＜0.01；r=0.82，P＜0.05）；右心房心肌组织Ca²⁺浓度与右心房心肌组织MMP-9蛋白质表达水平呈正相关（r=0.72，P＜0.05）。结论：（1）右心房快速起搏房颤模型存在右心房结构重构，表现为右心房心肌细胞超微结构改变，右心房心肌间质纤维化，右心房扩大和右心房功能的改变，右心房结构重构在房颤的维持中可能具有重要地位；（2）右心房细胞内Ca²⁺超载可能是右心房心肌细胞超微结构改变的原因之一；（3）肾素-血管紧张素系统激活是右心房细胞外基质纤维化的重要机制；（4）MMP-9/TIMP-1系统平衡失调是右心房扩大的重要分子机制；（5）局部血管紧张素Ⅱ升高和Ca²⁺是MMP-9的重要激活途径；（6）血管紧张素转换酶抑制剂卡托普利对房颤犬右心房结构重构具有全面抑制作用，表现为右心房超微结构的改善，右心房心肌肌间质纤维化的减轻，扩大右心房的缩小和右心房功能的改善；（7）卡托普利对房颤犬右心房结构重构的保护作用是通过阻断肾素-血管紧张素系统抑制MMP-9的激活实现的；（8）超声心动图声学定量技术是监测房颤动物模型建立过程中右心房结构和功能动态改变的重要方法。更多还原

【Abstract】 Backgroud: Atrial fibrillation （AF） is always considered to be a left atrium associated disease. With the development of the research on the mechanism of AF and the advancement of radio-frequency ablation, attention was paid to the role of right atrium in the occurrence and maintenance of AF. Due to the methodology, however, the research on the structure, function and hemodynamics of right atrium remained relatively less than left atrium in any pathophysiologic state. Thus, it was necessary to approach new methods to study right atrium.Right atrium, similar to left atrium, has three main functions. First, it is just like a conservator that can collect and store the blood from superior and inferior vena cava during the systolic stage. Second, it works as a conduit that can transport the blood from vena cava to right ventricle during the early diastolic stage. Third, it is like a pump that can enhance ventricular filling at the late diastolic stage .In short, right atrium plays an important role in regulating right ventricular filling and maintaining global cardiac output at all pathologic and physiological stages. Right atrial special structures and the changes of matrix are closely related with the occurrence and development of arrhythmias.Atrial pressure-volume （area） relationship was considered the most exact and representative index that could reflect the changes of atrial functions and hemodynamics. Furthermore, acquirements of atrial pressure by catheterization being invasive, most data were obtained from animal experiments. Yet, echocardiography served as a non-invasive method to evaluate atrial structure, function and hemodynamics. So the research about atrium transits from experiment to clinic. According to automatic edge detection principle, acoustic quantification echnique could real-time display cavity area-time curve, capacity-time curve and differential curve .So AQ technique could non-invasively evaluate left atrial function. Nevertheless, whether AQ technique could evaluate right atrial structure, function and hemodynamics has not been reported.Primary pulmonary artery hypertension results in right ventricular dysfunction. While right atrium played an important role in maintaining right ventricular filling when right ventricle was in dysfunction. Hypertension could cause dysfunction of left ventricle and non-valvular atrial fibrillation, and the influence of hypertension on right heart system was unknown yet. Dernellis et al. found that patients with primary hypertension had impaired right atrial function by measuring tricuspid blood flow with pulsed wave Doppler. Yet, AQ technique evaluating right atrial structure, function in patients with primary pulmonary hypertension or primary hypertension has not been reported so far.Objectives: （1）To investigate the feasibility of AQ technique to evaluate right atrial function; （2）To observe the changing of right atrial structure and function in patients with pulmonary artery hypertension; （3）To determine the changing of right atrial structure and function in patients with primary hypertension.Methods: Subjects: Eighty-seven patients were included in this study. （l）Twenty of them were in control group including nine males and eleven females （average 35.21±14.60 years old）, and they had no history of cardiovascular diseases and their examination results of laboratory examination, EKG and echocardiography were normal.（2） Seventeen patients with pulmonary hypertension, including six males and eleven females （average 38.82±13.43 years old）, were enrolled in this experiment. Seven of them had primary pulmonary hypertension or pulmonary vascular diseases, ten with congenital heart diseases. And their diagnoses were made by echocardiography, surgery or CT examination. Also, they had no other heart associated diseases such as hypertension, coronary heart disease and diabetes.（3） The rest were fifty hypertensive patients that were excluded with secondary hypertension, graded I or II class, including thirty-five males and fifteen females （average 52.24±6.86 years old）. Their blood pressure met the criteria of WHO/ISH hypertension diagnosis, which was diastolic pressure≥90mmHg （ 1mmHg =0.133Kpa） and systolic pressure≥140 mmHg .And the history of diseases was 0.5-32 years （average 12.81±10.3 years）.Experimental approach: The patients, quietly breathing, underwent echocardiographic evaluation in the left recumbent position, including M mode, 2-D, Doppler, and AQ curves, which were simultaneously accompanied with II lead electrocardiogram recorded. The averages were obtained by calculating them in all patients over 3-5 cardiac cycles. （1） M-mode and two-dimensional echocardiography: Parasternal long axis view and apical four-chamber view were taken. （2）Tricuspid flow frequency spectrum: Transtricuspid flow profile was assessed by 2-D guided continuouswave Doppler from the apical 4-chamber view by positioning a 3-mm-sized sample volume between the tips of the tricuspid leaflets in diastole and recording at a sweep velocity of 100 mm/s. Then pulmonary systolic pressure was estimated. （3）Superior vena flow spectrum: After the apical four-chamber view being taken, PW sampling volume, guided by color Doppler, was positioned at about 1cm inside superior vena entrance level to get superior vena cava best flow spectrum. （4）Right atrial volume curve: When apical four-chamber view being well displayed, second harmonic imaging, automatically average and AQ system were started, then the control button of total gain, time gain compensation （TGC） and lateral gain compensation （LGC） were regulated to make AQ curve closely aligning with right atrial endocardium and draw total right atrial interested region. AQ technique could real-time display right atrial volume-time curve and its differential curve.Parameters: Parameters of M-mode and two-dimensional echocardiography:（1）right ventricular anterior wall thickness （RVAM, mm）; （2）interventricular septal thickness （IVS, mm）; （3）right ventricular end diastolic diameter （RVED, mm）; （4）right atrial length （RAL, mm） and transverse diameter （RAT, mm）; （5）right ventricular ejection fraction （RVEF）. Parameters of Doppler echocardiography: （1） transtricuspid E/A ratio; （2） Reverse A wave peak velocity of superior vena frequency spectrum （Ar, cm/s）;（3） pulmonary arterial systolic pressure （mmHg）. Parameters of right atrial volume curve: （1）right atrial volume at right ventricular end-diastolic stage （EDV, ml）; （2）right atrial volume at right ventricular end-systolic stage （ESV, ml）; （3）right atrial end-rapid emptying volume （EREV, ml）;（4）right atrial rapid emptying volume （RE, ml）: RE=ESV-EREV; （5）right atrial active contraction emptying volume （AE, ml）: AE=EREV-EDV; （6）right atrial reservoir volume （RV, ml）: RV=ESV-EDV, also RV is right atrial total emptying volume; （7）right atrial rapid emptying fraction （REF, %）: REF=RE/RV×100%; （8）right atrial active contraction emptying fraction （AEF, %）: AEF=AE/RV×100%; （9）peak filling rate （PFR, ml/s）; （10）peak rapid emptying rate （PRER, ml/s）; （11） peak atrial emptying rate （PAER, ml/s）; （12）PRER/PAER.Results: The changes of right atrial functions in patients with pulmonary hypertension: （1） Results of two dimensional and Doppler echocardiography: Compared with control subjects, RVAW, IVS, RVED and right atrial inner diameter were increased significantly （P<0.05～0.01） and right ventricular systolic function was significantly decreased （P<0.001） in patients with pulmonary hypertension. And A wave peak flow velocity of superior vena cava flow spectrum was significantly increased （P<0.001）. The pulmonary arterial systolic pressure was 93.81±22.88 mmHg in patients with pulmonary hypertension. （2）The results detected by AQ technique: Compared with control subjects, the parameters which could reflect the changes of volume, such as ESV, EDV, EREV and AE, were significantly increased （P<0.05～0.01） in patients with pulmonary hypertension, and right atrial RV and PFR were increased significantly （P<0.05-0.01）. And REF of right atrium was significantly decreased （P<0.05）. Yet PRER had no significant difference （P>0.05）. AEF and PAER of right atrium were significantly increased （P<0.05～0.01） in patients with pulmonary hypertension.The changes of right atrial functions in patients with primary hypertension: （1） Results of two dimensional and Doppler echocardiography: Compared with control subjects, RVAW and IVS were significantly increased （P<0.01） and tricuspid flow frequency spectrum showed E/A<1 in patients with primary hypertension. （2） The results detected by AQ technique: Compared with control subjects, the parameters which could reflect the changes of volume, such as ESV, EDV, EREV, RE and AE, were significantly increased （P<0.05-0.01） in patients with primary hypertension. And right atrial RV and PFR were increased significantly （P<0.01）. Yet PEF, AEF and PRER of right atrium had no significant difference （P>0.05）. PRER/PAER was decreased significantly （P<0.01） and PAER was increased significantly （P<0.01）.Conclusions: （1） Acoustic quantification technique can non-invasively evaluate right atrial structural and functional changing under the conditions of pathophysiology. （2） In patients with pulmonary hypertension atrial structure and functions altered significantly, including dilated right atrium, impaired right atrial conduit function and compensatory enhancement of right atrial booster pump and reservoir functions, to facilitate right ventricular filling. （3） In hypertensive patients significant alterations of atrial structure and functions consist of dilated right atrium, decreased right atrial conduit function and compensatory enhancement of right atrial booster pump and reservoir functions. Background: Non-drug therapy to atrial fibrillation （AF） has been a hot spot in electrophysiological fields recently. With the development of pulmonary vein electric isolation aiming at triggering foci and atrial linear ablation around pulmonary vein aiming at the matrix maintaining AF, the success rate of treating AF with radiofrequency catheter ablation has been greatly increased since 1998 especially 2002. At present, the achievement rate of treating paroxysmal AF with radiofrequency ablation stays from 80% to 90%, but the achievement rates of treating persistent AF and permanent AF are still lower and a certain recurrent rate is also existent, as well as a low long-term achievement rate, yet the morbidity of chronic persistent AF is significantly higher than paroxysmal AF. Therefore, how to improve the achievement rate of treating chronic persistent AF with radiofrequency ablation is widely concerned and then the mechanism of AF becomes a hot spot. Recently Yamane etc. has reported a case of AF which originated from superior vena cava and was successfully cured with radiofrequency ablation. Crista terminalis is an important source of some AF. Some study showed that there were two regions of unidirectional block on the posterior border of crista terminalis and demarcation between crista terminalis and pectinate muscles, so reentrant cycle formed to cause atrial flutter as the electricity conduction of right atrium couldn’t track the block regions. If the range of blocking region became smaller, the reentrant cycle would then become smaller and instable, and diffuse around to result in atrial fibrillation. Consequently, right atrium played an important role in the occurrence of AF.The experimental and clinical research confirmed that the structure remodeling of left atrium played an important role in maintaining AF. Further study revealed that isolating pulmonary vein and the left atrial posterior wall around that （pulmonary vein vestibulum） by radiofrequency ablation would dramatically improve the success rate of curing AF patients with anatomical heart diseases. However, whether AF could cause right atrial structural remodeling was unknown yet. And if right atrial structural remodeling was serious to some extent, right atrial matrix remodeling itself could maintain AF. So AF couldn’t be eliminated by treating left atrium alone with radiofrequency ablation, which might be one of the reasons for so low success rate of treating chronic AF at present.The research on left atrial structural remodeling in patients with AF confirmed that the main components of atrial remodeling were the fibrosis of atrial myocardial extracellular matrix and atrial enlargement. Matrix metalloproteinase-9 （MMP-9） and its endogenous tissue inhibitor of metalloproteinase-1 （TIMP-1） were important protease systems that regulate the synthesis and degradation of extracellular matrix collagen. Lately the research on patients with AF showed that the alterations of MMPs/ TIMPs expression were associated with atrial myocardial extracellullar matrix remodeling and atrial enlargement. However, whether the alterations of MMPs/ TIMPs expression were the mechanism of right atrial structural remodeling remained unclear. At present, little is known about the factors regulating and influencing MMPs/TIMPs in AF patients. Previous studies confirmed that the activation of renin-angiotensin system （RAS） and intracellular calcium (Ca²⁺ ) overload were the basic pathophysiological mechanisms of electrical and structural remodelings in AF. As a result, it suggested that the activation of RAS and intracellular Ca²⁺ overload might be important pathways of activating MMPs/ TIMPs during AF.In recent years, a series of clinical studies showed that angiotensin-converting enzyme inhibitor （ACEI） and angiotensin II receptor blocker （ARB） could prevent AF to a certain extent by inhibiting RAS, but its mechanism has not been elucidated yet. This study investigated the effects of ACEI on the expression of MMPs/TIMPs and its effects on atrial structural remodeling through administration of ACEI on the animal models with AF. Also, it provided a theoretical basis for preventing and treating AF with non-traditional anti-arrhythmic drugs. The first part of this topic has confirmed the feasibility of evaluating right atrial structural and functional changes by AQ technique, but the application of AQ technique to evaluate the changes of right atrium in animals with AF has not been reported.Objectives: （1）To evaluate the dynamic changes of right atrial structure and functions using echocardiography and AQ technique in the process of establishing animal models with AF; （2）To observe the changes of right atrial ultrastructure and extracellular matrix; （3）To detect the effects of RAS activation on right atrial structural remodeling; （4）To determine the effects of MMP-9/TIMP-1 on right atrial structural remodeling; （5）To investigate the regulating effects of RAS activation and intracellular Ca²⁺ overload on MMP-9/TIMP-1; （6）To explore the parallel relationship between molecular biological changes and right atrial structural and functional changes; （7）To observe the influence of ACEI on MMP-9/ TIMP-1 of right atrium; （8）To assess the protective effect of ACEI on right atrial structure.Methods: （1） First, dog models with chronic atrial fibrillation were estabalished by rapid atrial pacing. （2） The changes of right atrial area and mitral, tricuspid refluxing and refluxing degree were monitored by echocardiography before pacing and after rapid atrial pacing for 1 week, 4 weeks and 8 weeks. （3） Right atrial pressure was monitored before and after rapid atrial pacing. （4） Right atrial myocardium AngII was determined by radioimmunoassay. （5） Intracellular Ca²⁺ concentration in right atrial myocardium was detected by three-electrode DC plasma photoelectric spectrometry. （6） The structure and collagen content of right atrial myocardium were observed and quantified by conventional HE and Masson staining. （7） The ultrastructure of right atrial myocardium was observed using transmission electron microscopy （TEM）. （8） The mRNA expressions of ACE, MMP-9 and TIMP-1 were determinded by reverse transcription polymerase chain reaction （RT-PCR） in right atrial myocardium. （9） The protein levels of MMP-9 and TIMP-1 were analyzed by western blot. （10） The spatial distributions of MMP-9 and TIMP-1 were determined by immunohistochemistry.Results:（1） The establishment of animal models with AF: One dog of rapid atrial pacing group was dead after 12 hours, and the autopsy found that the electrode in right atrial appendage entered into right ventricle, suggesting that the cause of its death was ventricular fibrillation by rapid pacing. Four weeks after surgery, another dog manifested abdominal distension and sign of ascites was positive. And its food intake and action were decreased obviously. Ultrasonic examination found that one 26mm×21mm low density echogenic mass at the top of atrial electrode and there were a lot of pleural effusion and ascites. The autospy confirmed that the cause was thrombogenesis at the top of electrode. Eight weeks after surgery, another dog’s pacemaker stopped releasing pulse when ECG examination was taken. One dog in treating group was dead because the pacing electrode entered ventricle causing ventricular fibrillation. So the four dogs mentioned above were not included in this experiment. Eventually, pacing group and treatment group each had 8 dogs completed the entire experiment. Before rapid atrial pacing, AF could not been provoked among all dogs by programming stimulation and/or burst stimulation. After this experiment AF was not provoked among 6 dogs in control group by programming stimulation and /or burst stimulation. Two dogs of pacing group respectively emerged paroxysmal AF at 1 week and 4 weeks after rapid atrial pacing. Electrophysiologic examination was carried out at 8 weeks after rapid atrial pacing, two dogs （25%） emerged spontaneous AF; AF were provoked among 4 dogs （50%）by programming stimulation, among 2 dogs （25%） by burst stimulation. It suggested that we had successfully established chronic AF models. One dog of treatment group emerged paroxysmal AF at 1 week after operation, two dogs emerged AF by programming stimulation at 8 weeks after pacing, and the other 6 dogs did not emerged AF by programming and burst stimulation. （2）Echocardiographic data comparison: ①The influence of rapid atrial pacing on atrial diameter: One week after pacing, right atrial areas were extremely significantly increased （P<0.001） compared with that before pacing in pacing group and the inner diameter was further increased with time going on. Eight weeks after pacing, the inner diameter was significantly increased （P<0.05） compared with that of 1 week after pacing, and there was no difference compared with that of 4 weeks after pacing （P>0.05）. And right atrial areas of pacing group were extremely significantly increased after pacing 1, 4, 8 weeks compared with those of control group at the same time respectively （P<0.001）. One and four weeks after pacing, right atrial areas of treatment group trended to enlarge compared with those of control group before pacing, but the difference had no significance（P>0.05）, and compared with pacing group, right atrial areas of treatment group were significantly decreased （P<0.01～0.001）. Eight weeks after pacing, right atrial areas of treatment were significantly decreased （P<0.001） compared with pacing group, but significantly increased compared with control group （P<0.05）.② The influence of rapid atrial pacing on mitral and tricuspid flow frequency spectrum: Color Doppler showed that mitral and tricuspid regurgitations took place in pacing groups in the process of pacing and it was more serious with the pacing time increased. And only one dog in control group had light mitral regurgitation in the experiment. Eight weeks after pacing, eight dogs in AF group had moderate-heavy mitral regurgitations and 8 dogs had light-moderate tricuspid regurgitations. And 4 dogs in treatment group had mitral regurgitations （light～moderate） and tricuspid regurgitations （3 dogs, light）, the degree was lighter than that of AF group.③ The influence of rapid atrial pacing on right atrial volume: Compared with control group, ESV, EDV and EREV of AF group began to increase and EF and CV were decreased （P<0.05） 4 weeks after pacing, and ESV, EDV and EREV were significantly increased （P<0.001）, while EF and PAER decreased significantly （P<0.001） and also CV was decreased significantly （P<0.05） 8 weeks after pacing, the other parameters had no significant changes in pacing progress. In atrial fibrillation group, compared with before pacing, right atrial AQ parameters each had no significant changes 1 week after pacing （P>0.05）; ESV, EREV and EDV were significantly increased （P<0.05） and EF was significantly decreased （P<0.05） 4 weeks after pacing, and ESV, EREV and EDV were significantly increased （P<0.001） while EF and PAER were significantly decreased （P<0.001） 8 weeks after pacing. Compared with 1 week after pacing, ESV, EREV and EDV were significantly increased （P<0.01） and EF and PAER was significantly decreased （P<0.01） 8 weeks after pacing. And other parameters had no statistical significance. However, eight weeks after pacing, the increase of ESA, ESV, EDV and EREV and the decrease of EF in treatment group were less than those in pacing group （P<0.05）. It suggested that captopril had significant protection on atrial structural and functional changes such as atrial enlargement, increased volume and decreased contraction caused by atrial rapid pacing. （3）The influence of rapid atrial pacing on right atrial pressure: Before rapid atrial pacing, there was no statistical significance between right atrial pressure in AF group and that in control group（3.17±2.52 mmHg VS 4.95±3.24 mmHg, P>0.05）. Eight weeks after pacing, right atrial pressure in AF group was significantly increased compared with control group （7.09±1.13 VS 4.50±1.51 mmHg, P<0.01） , and right atrial pressure in treatment group was significantly decreased compared with that in AF group （5.28±1.96 mmHg VS 7.09±1.13 mmHg, P <0.05） , but was still higher than that in control group （5.28±1.96 mmHg VS 4.95±3.24 mmHg, P>0.05 ） . （4）The changes of intracellular calcium concentration in right atrial myocardium: Compared with control group, intracellular calcium concentration in right atrial myocardium was significantly increased by 36.18% in AF group （37.68±10.45 ug/mg VS 27.67±4.46 ug/mg, P<0.05）. And compared with pacing group, calcium concentration was significantly decreased in treatment group （29.88±1.47 ug/mg VS 37.68±10.45 ug/mg, P<0.05）, and it was still higher than that in control group（29.88± 1.47 ug/mg VS 27.67±4.46 ug/mg, P>0.05） . （5）Angiotensin II content of right atrial myocardium: Compared with control group, the concentration of AngII in right atrial myocardium was significantly increased by 51.94% （11.38±3.77 pg/mg VS 7.49±1.65 pg/mg, P<0.05） in AF group. And compared with AF group, the concentration of Angll in right atrial myocardium was significantly decreased in treatment group （7.12±1.01 pg/mg VS 11.38±3.77 pg/mg, P<0.05） ,and it was a little lower than that in control group （7.12±1.01 pg/mg VS 7.49±1.65 pg/mg, P>0.05 ） . （6） Structural changes of right atrial myocardium: Atrial myocardium sections from controls showed normally structured cardiomyocytes, which were surrounded by a small amount of connective tissue. The nuclei were big and legible. Connective tissue network was in the myocardia. Yet fibroblasts in the interstice were regular-sized and moderate-numbered. Sections from AF dogs showed enlarged myocardia were disarranged, the nuclei were in irregular size and obvious heteromorphism. Some myofilaments were disrupted and collagen tissues were accumulated among the myofilaments to broaden the gaps between cardiomyocytes. The amount of myofibroblasts in interstitium was increased. In treating dogs the structure of atrial myocardium was almost the same as that in control except for a slight rise in the amount of connective tissue. Masson stain showed that collagen tissue was appropriate arranged among cardiomyocytes in controls. The appearance of the connective tissue framework of the myocardium was unchanged. Samples from AF dogs showed, however, that collagen tissue disarranged and disrupted in some area increased markedly. While in treating dogs collagenous fibers were slightly increased and disarranged, but exhibited an intact collagen network. The quantitative analysis showed that the content of collagen in right atrial myocardium was significantly increased in AF group compared with control group （27.75±7.83 VS 19.23±3.67, P<0.05）. Compared with AF group, the content of collagen in right atrial myocardium was significantly decreased in treating group （20.47±3.99 VS 27.75±7.83, P<0.05）, but it was still higher than that of control group （20.47±3.99 VS 19.23±3.67,P>0.05）. （7） Ultrastructural changes of atrial myocardium: ①At the ultrastructural level, atrial myocytes from controls showed a highly organized sarcomeric structure with rows of uniform-sized mitochondria between them.②The myofibrillae in myocardium were arranged regularly with no ruptur.③ The mitochondria were enlarged and considerable, and the cristae were tightly arranged like ’Z’ shape. ④ The sarcoplasmic reticulum were in large size and a large number. ⑤ The endochylema was enriched.⑥A typical distribution of heterochromatin in the form of clusters at the nuclear memrane was present in all cardiomyocyte nuclei. The nucleoli can be easily observed.⑦Intercalated disc were normally structured.⑧ Atrial granules were mainly confined to the perinuclear area. Atrial myocytes from AF dogs showed characteristic changes as below: ①Contractile material was depleted （myolysis）. The myofibrillae in myocardium were arranged irregularly with ruptures. The disapperance of sarcomeres was often limited to the vicinity of the nuclei but also frequently involved the entire cytosol, in which only fragments of sarcomeres were present.②Typical changes in size and shape of mitochondria were seen in area depleted of sarcomeres. Many mitochondria had become elongated and in different sizes. The cristae were arranged along the long axis. ③The sarcoplasmic reticulum became swelling, disrupted, and decreased in number. ④The nuclear membrane was not smooth and the segmented nucleus could be seen. And the heterochromatins were dispersed uniformly throughout the nucleoplasm. ⑤ Intercalated discs were discontinued and indistinct.⑥Huge amount of glycogen accumulated the myolytic space in almost all cells that underwent myolysis, even formed "glycogen lake" . ⑦ Atrial granules were increased and scattered widely. Similar atrial myocytic structures were observed in treating dogs with alterations intermediate between the two groups above. （8）The mRNA transcription level of atrial myocardium: ① Compared with control group, the level of ACE mRNA of right atrial myocardium increased by 45.00% in AF group （0.29±0.08 VS 0.20±0.01, P<0.05）, and compared with AF group, the level of ACE mRNA of right atrial myocardium trended to decrease in treatment group, but the difference had no statistical significance （0.27±0.07 VS 0.29±0.08, P>0.05） .②Compared with control group, MMP-9 mRNA of right atrial myocardium increased by 109.09% and the transcription level of TIMP-1 mRNA increased by 71.43% in AF group（MMP-9: 0.23±0.04 VS 0.11±0.009; TIMP-1: 0.12±0.02 VS 0.07±0.01, P<0.01）, and MMP-9/TIMP-1 trended to decrease but had no statistical significance（1.99±0.68 VS 1.53±0.26, P>0.05） . Compared with AF group, MMP-9 mRNA in treatment group was significantly decreased （0.19±0.03 VS 0.23±0.04, P<0.05） , but the level of TIMP-1 mRNA had no significant changes （0.12±0.03 VS 0.12±0.02, P>0.05） , still it was higher than that of control group （0.12±0.03 VS 0.07±0.01, P<0.01） . （9）The western blot and immunohistochemical staining results of MMP-9 and TIMP-1: Compared with control group, the protein expression level of MMP-9 in right atrial myocardia was significantly increased in AF group （115.38±22.07 VS 84.75±20.32, P<0.05） . Compared with AF group, the protein expression level of MMP-9 in right atrial myocardia was significantly decreased in treatment group （90.37±18.50 VS 115.38±22.07. P<0.05）. Compared with control group, the protein expression level of TIMP-1 trended to decrease in right atrial myocardia, but there was no statistical significance （99.38±17.10 VS 105.63±21.07,P>0.05） .And compared with AF group, the protein expression level of TIMP-1 in right atrial myocardia also had no statistical significance （103.94±15.02 VS 99.38±17.10, P>0.05） .To further determine the intracellular expression and histological locating characters of MMP-9 and TIMP-1, MMP-9 and TIMP-1 monoclonal antibodies were used to detect their expressions and cellular localization by immunohistochemical method. The result revealed that MMP-9, irregular reticular sparse brown granules, which were evenly-distributed in myocardial cytoplasm in control group and that MMP-9, irregular reticular brown granules, which were densely-distributed in myocardial cytoplasm in AF group. And TIMP-1, irregular reticular brown granules, which were evenly-distributed in myocardial cytoplasm in control group, but irregular reticular relative-sparse brown granules in AF group. MMP-9, irregular reticular sparse brown granules which were evenly-distributed in myocardial cytoplasm in treatment group and the distribution of TIMP-1 in myocardial cytoplasm in treatment group was the same as that in control group. （10）The relationships between molecular biological parameters and ultrasonic, hemodynamic parameters: Linear correlation analysis showed that the protein level of MMP-9 in right atrial myocardia was positively correlated with right atrial area （r =0.73, P<0.05） and the protein level of TIMP-1 had a positive correlation with right atrial pressure （r =0.81, P<0.05） . Ang II in right atrial myocardia was positively correlated with the content of collagen and the protein expression level of MMP-9 （r=0.86, P<0.01; r =0.82, P<0.05, respectively）, and the calcium concentration of right atrial myocardia was positively correlated with the protein expression level of MMP-9 0=0.72, P<0.05) .Conclusions: （1） Atrial fibrillation models of right atrial rapid pacing caused right atrial structural remodeling, which referred to right atrial myocardial ultrastructural changes, right atrial interstitial fibrosis, enlargement of right atrium and alterations of right atrial functions. （2） Intracelluler calcium overload might result in the changes of the ultrastrutures in right atrial myocardial cells. （3） The activation of renin-angiotensin system was an crucial mechanism responsible for the extracellular matrix fibrosis of right atrium. （4） The imbalance of MMP-9/TIMP-1 system was an important molecular mechanism of the enlargement of right atrium. （5） Local angiotensin II elevation and calcium overload played important roles in the activations of MMP-9. （6） Angiotensin-converting enzyme inhibitor （ACEI）-captopril could generally inhibit structural remodeling of right atrium in dogs with AF, which included the improvement of right atrial ultrastructures, the alleviation of interstitial fibrosis of right atrium, the reduction of dilated right atrium and the renewal of right atrial functions. （7） The protective effect of captopril on the right atrium in AF dogs was that it could prevent the structural remodeling via inhibiting the activation of MMP-9 by blocking the renin-angiotensin system. （8） Acoustic quantification （AQ） technique supplied a significant method to monitor the dynamic changes of right atrial structures and functions in the process of establishing animal models with AF.更多还原