腹主动脉部分缩窄大鼠模型体外心脏的电生理特点

Electrophysiological characteristics of the isolated heart of rats with partial coarctation abdominal aorta

目的:观察腹主动脉部分缩窄模型大鼠体外心脏的电生理特点。方法:实验于2005-04/08在北京中医药大学东直门医院重点实验室完成。①取雄性SD大鼠30只,单纯随机分为3组,正常组6只,假手术组和模型组各12只,后2组又分为造模后4,8周2个时间点,每个时间点6只。②造模后4周、8周采用飞利浦HDI5000超声诊断仪、15MHz高频线阵探头,经胸骨旁左室长轴切面检测大鼠心脏左室室壁厚度及左室腔内径。③超声检测完毕后剪取大鼠心脏,称量左室质量,计算左室心肌质量指数(实测左室质量/体表面积)。④造模后第8周时取下心脏进行体外灌流,吸附电极记录单相动作电位,测量动作电位复极20%,50%,90%的时间(APD20,APD50,APD90),有效不应期,动作电位最大幅度,零相上升的最大速度。结果:经补充后29只大鼠进入结果分析。①心脏超声指标比较:造模后第4周模型组室间隔舒张末期厚度大于假手术组[(2.57±0.35),(1.86±0.15)mm,P<0.01];造模后第8周模型组室间隔舒张末期厚度、左室后壁舒张末期厚度和左室舒张末期内径均大于假手术组[(2.52±0.32),(1.94±0.07)mm,P<0.01;(2.54±0.30),(2.06±0.11)mm,P<0.01;(6.27±0.54),(5.65±0.34)mm,P<0.05];模型组左室舒张末期内径第8周较第4周显著增加(P<0.01)。②左室心肌质量指数:造模后第4,8周,模型组均高于假手术组[(28.88±2.57),(15.10±1.49)g/m2;(31.09±2.85),(28.88±2.57)g/m2;P均<0.01]。③体外心脏电生理参数:模型组左心房APD90长于假手术组(P<0.05),有效不应期/APD90比值小于假手术组(P<0.05);左心室APD20,APD50,APD90和有效不应期长于假手术组(P<0.01,0.05),有效不应期/APD90比值小于假手术组(P<0.05);右心室各参数比较无差异;模型组APD90离散度(左心室-右心室)显著高于假手术组[(56.8±4.7),(18.7±4.0)ms,P<0.01];模型组有效不应期离散度(左心室-右心室)也显著高于假手术组[(25.4±1.1),(5.2±0.8)ms,P<0.01]。结论:部分缩窄大鼠腹主动脉模型的早期(4周)是由压力负荷致心脏左室向心性肥厚的模型,随着压力负荷的持续和容量负荷的增加,左室逐渐演变为向心性肥厚和离心性肥厚的混和型肥厚(8周)。混合型肥厚心脏左心室、左心房单相动作电位的复极时间均显著延长,心脏不同部位离散度增加,这些电生理特点是促进折返形成,造成心律失常的主要原因。

AIM： To study the electrophysiological characteristics of the isolated heart of rats with partial coarctation abdominal aorta. METHODS： The experiment was conducted jn the Key Laboratory of Dongzhimen Hospital, Beijing University of Traditional Chinese Medicine from April to August 2005. ①Thirty male Sprague Dawley rats ware selected and randomly assigned to three groups： normal group （n =6）, sham operation group （n =12） and model group （n =12）. The latter two groups were subdivided into two time points groups： 4 and 8 weeks after modeling groups with 6 rats in each group. ② Four and eight weeks after modeling, the thickness of left ventricular wall and the inside diameter of left cavity in rats were detected by Philips HDI5000 ultrasonograph with 15 MHz high frequency linear array detecting head from the long axis view of left ventricle near the breast bone. ③Than the hearts of rats ware taken to weigh the weight of left ventricle and calculate the left ventricular mass index （LVMI, actual left ventricular mass/surface area）. ④At the eighth week after modeling, the monophesio action potential （MAP） including 20%, 50% and 90% duration of action potentials （APD20, APD50, APD90）, effective refractory period （ERP）, action potential maximal amplitude and the maximal velocity of phase zero increase were recorded by adsorption electrode in ex vivo perfusion rat hearts. RESULTS： Twenty-nine rats ware involved in the result analysis after supplement.①Comparison of ultrasound indexes of heart： Four weeks after modeling, the interventricular septum thickness （IVST） of the model groups was increased compared with the sham operation groups [（2.57±0.35）, （1.86±0.15） mm, P 〈 0.01]; eight weeks later, IVST, left ventricular posterior wall thickness （LVPWT） and left ventricle diameter （LVD） were higher than the sham operation groups [（2.52±0.32）, （1.94±0.07）mm, P 〈 0.01; （2.54±0.30）, （2.06±0.11）mm, P 〈 0.01; （6.27±0.54）, （5.65±0.34）mm, P 〈 0.05]; Moreover, LVD of the model groups at the eighth week was increased markedly compared with that at the fourth week （P 〈 0.01）. ②LVMI： At weeks 4 and 8, LVMI of the model groups was higher than the sham operation groups [（28.88±2.57）, （15.10±1.49） g/m^2; （31.09±2.85）, （28.88±2.57） g/m^2; P 〈 0.01]. ③Electrophysiological indexes of ex v/vo heart： Compared with the sham operation groups, APD90 of left atrium was longer （P 〈 0.05）, and the ratio of ERP and APD90 was smaller （P 〈 0.05）; APD20 APD50 APD90 and ERP in the left ventricle was longer than the sham operation groups （P 〈 0.01, 0.05）, but the ratio of ERP and APD90 was smaller （P 〈 0.05）; no significant differences were found among the indexes in the right ventricle. The dispersions of APD90 （LVAPD90-RVAPD90） and ERP （LVERP-RVERP） in the model groups were higher than the sham operation significantly [（56.8±4.7）, （18.7±4.0） ms, P 〈 0.01; （25.4±1.1）, （5.2±0.8） ms, P 〈 0.01]. CONCLUSION： The left ventricle of rat with partial coarctation abdominal aorta rat is concentric hypertrophy induced by pressure overload in eady state （four weeks）. With the pressure load continuing and volume load increasing, the left ventricle gradually develops into mixed myocardial hypertrophy including concentric hypertrophy and eccentric hypertrophy （eight weeks）. MAP repolarization duration of left ventricle and left atrium in heart with mixed myocardial hypertrophy is prolonged significantly and the dispersion in different sections of heart is increased. These electrophysiological characteristics, which lead to reentry, may be the main reasons for arrhythmia in myocardial hypertrophy heart.