应用经胸超声心动图评估快速左心耳起搏心房颤动模型心脏结构及功能的变化

Transthoracic echocardiography in evaluating the changes of cardiac structure and function in animal models of atrial fibrillation induced by rapid left atrial appendage pacing

目的:应用经胸超声心动图观察高频率左心耳起搏致猪慢性心房颤动模型心脏结构和功能的变化。方法:实验于2005-09/2006-08在南京医科大学第一附属医院江苏省实验动物中心完成。①12只苏钟种猪随机分为实验组及对照组各6只,所有动物均开胸,将起搏电极固定在左心耳根部,高频率脉冲发生器植入左侧胸部囊袋。实验组术后恢复1周后起搏器以500次/min的频率快速起搏左心耳8周;对照组始终不起搏。②术后心电图定期监测起搏、心房颤动的发生情况;于术前、起搏后1周、起搏后4,8周超声心动图观察实验动物左房内径、心室收缩及舒张末左房面积、左房和左室射血分数、左室舒张及收缩末内径、左心室短轴缩短率等变化。结果:①实验组5只完成了实验,术后2周复查心电图,1只动物发生房颤,起搏8周3只发生阵发性房颤,1只未发生房颤;对照组则未发生任何心律失常情况。②左心房相关指标:起搏后1周,实验组左房内径、收缩末期左心房面积和舒张末期左房容积均较起搏前增加[(2.70±0.12),(2.50±0.12)cm;(6.78±0.81),(6.21±0.93)cm2;(4.66±0.53),(3.78±0.57)mL;P均<0.05],左房射血分数较起搏前下降[(55.6±6.0)%,(63.8±4.0)%,P<0.01],至起搏4,8周,左房射血分数进一步降低,左房内径等指标则继续增大。③左心室相关指标:起搏后1周,实验组左室舒张、收缩末期内径较起搏前增加[(3.64±0.13),(3.46±0.15)cm;(2.48±0.08),(2.14±0.09)cm;P均<0.01],左心室短轴缩短率和左室射血分数较起搏前下降[(31.6±2.0)%,(37.8±3.0)%;(60.8±2.0)%,(69.2±4.0)%;P均<0.01];至起搏4,8周,左心室短轴缩短率和射血分数进一步降低,左室舒张、收缩末期内径则继续增大,与对照组比较也差异显著(P<0.05,0.001)。结论:①超声心动图是监测房颤模型建立过程中心房、心室结构和功能变化的有效手段。②高频起搏左心耳是建立猪心房颤动模型的有效方法,快速心房起搏可导致左心房左心室增大及心功能减退。

AIM： To evaluate the heart structure and function changes of the pig models of chronic atrial fibrillation induced by rapid left atrial appendage pacing with the echocardiography. METHODS： The experiment was carried out in the experimental animal center of the First Affiliated Hospital of Nanjing Medical University between September 2005 and August 2006. ①Twelve pigs were randomly divided into experiment group and control group with 6 animals in each group. All the pigs were subjected to thoracotomy and the pacing electrode was fixed on the root of the left atria appendage. The high frequency pulse generator was implanted subcutaneously in the cyst of left chest. Rapid atrial pacing at the rate of 500 beats per minute was initiated one week after operation in the experiment group for 8 weeks, while no pacing was performed in the control group. ②Electrocardiogram was used to monitor the pacing and atrial fibrillation after operation; Echocardiographic study was performed at baseline （before operation）, one, four and eight weeks after pacing to measure the changes in left atrial dimension （LAD）, left atrial area systolic and diastolic diameters of left ventricle （LVDs, LVDd, LADs-A）, eject fraction （LVEF）, fractional shortening （FS） and so on. RESULTS： ①Five pigs in the experiment group finished the experiment. Atrial fibrillation was developed in 1 pig in the electrocardiogram examination two weeks after operation and 3 pigs paroxysmal auricular fibrillation eight weeks after pacing in experimental group. There was no atrial fibrillation in the control group.②Related indexes of the left atrium： One week after pacing, LAD, LADs-A and LADd-A were increased compared with those before pacing [（2.70±0.12）, （2.50±0.12） cm; （6.78±0.81）, （6.21 ±0.93） cm^2; （4.66±0.53）, （3.78±0.57） mL; all P 〈 0.05], while LAEF was decreased [（55.6±6.0）%, （63.8±4.0）%, P 〈 0.01]; After four and eight months of left atrial appendage pacing, LAEF was further decreased, while LAD and other indexes were continuously increased. ③Related indexes of left ventricle： One week after pacing, LVDs and LVDd were significantly increased [（3.64±0.13）, （3.46±0.15） cm; （2.48±0.08）, （2.14±0.09） cm; all P 〈 0.01], and FS and LVEF were decreased significantly [（31.6±2.0）%, （37.8±3.0）%; （60.8±2.0）%, （69.2±4.0）%; all P 〈 0.01]; After four and eight months of pacing, FS and LVEF was further decreased, while LVDs and LVDd were continuously increased, which had significant differences compared with the control group （P 〈 0.05, 0.001）. CONCLUSION： ①Echocardiography could effectively monitor the changes in atrial and ventricular structure and function during the establishment of atrial fibrillation model. ②Rapid left atria appendage stimulating is an effective method to establish the pig models of chronic atrial fibrillation. Rapid atrial pacing could result in the increase of left atrium and ventricle and the decrease of left ventricle function.