The Limb-chest Lead Synchronous Electrocardiogram Changes During Preparation Of Myocardial Infarction Rat Model With Ligation Lad

Objective:To study the electrocardiogram (ECG) changes during theprocess of anesthesia, open chest, tear pericardium, closed chest and the earlyshort period after ligation of the LAD.In order to provide the theoretical basisfor correctly analysis ECG changes happens on the process of preparation of ratmyocardial infarction model with ligation rat left anterior descending branch(LAD) through open thoracic.Methods：60healthy SD rats, male and female half respectively, weight200-220g,were divided into non-ligation group, LAD ligation with unclosechest group and LAD ligation with chest closed group,20rats in each grouprespectively.After anesthesia,the rat of non-ligation group was fixed on thebedstand with the fur shaving, skin prepping,and then chest opened,pericardiumteared, chest closed in turn to the steps of ligation rat LAD (excludeligation).Recording the ECG before opening chest and after opening chest,aftertearing pericardium and closing chest;In addition to above steps,in LAD ligationwith close chest group,LAD ligation and recording the ECG after the ligationwere done. The difference with the LAD ligation with chest closed group wasthat,there was no chest closed step in LAD ligation with unclose chest group, but ECG was still recorded according to the time when ECG was recorded afterclosed chest in LAD ligation with chest closed group.Recording each ECG inboth limb leads and chest leads.Execution rat with intravenous injection of10%KCl after24h from ligation. Then the rat heart was taken out, washed theresidual blood quickly within normal saline, fixed in10%formaldehydesolution, embedded, sectioned, HE stained and viewed its pathological changesunder the microscope.The indexes of HR, PR interval period, PR segmentdisplacement amplitude,QRS starting point offset value,QRS complexamplitude, QTc, QRS electrical axis, R wave amplitude and ST segmentdisplacement amplitude, T wave amplitude in each ECG were measured.Result: Comparison the parameters within groups,HR began loweringdown since the chest opened in three groups.R wave amplitude shown loweringdown changes after thoracotomy in leads of Ⅱ, V2and V5,T wave also lowereddown in lead of V2and V5in the no-ligation group,the differences arestatistically significant (P＜0.05);For the LAD ligation group,after thoracotomy,R wave amplitude in lead of Ⅰ、Ⅱ、V2、V5shown lowering downchanges.Among them,R wave amplitude in leadⅠ、V5of LAD ligation withunclose chest group，leadⅡ、V5of LAD ligation with close chest grouprecovered partly respectively according to the time after the chest was closed inLAD ligation with close group. Inversely,R wave amplitude in lead aVL ofLAD ligation with unclose chest group arise in the same time.After closed thechest, R wave amplitude in lead of Ⅰ、aVL of close chest group was higher thanthe ones in any other time points.According to the time after the chest wasclosed in LAD ligation with close group,ST segment amplitude in lead of I、aVL、V5in both ligation group was higher than any other times while Ⅲ,aVFlead shifted down. After chest closed the ST segment amplitude of lead V2in close chest group arise, lead aVR’s shown depressed.The differences arestatistically significant (P＜0.05);For the ligation with chest unclosed group,after thoracotomy,T wave inV2,V5lead was lower than the ones before thoracotomy.T wave amplitude ofⅠ,aVL lead in ligation with chest closed group at the time of closed chest washigher than any time before it.The contrary phenomenon happened in lead ofaVF、V1(P＜0.05).T wave amplitude of V5depressed after thoracotomy andrecovered when the chest was closed (P＜0.05).Comparison among groups:the ST segment in V5lead of the LAD ligationwith chest unclosed group at second time after LAD ligation was higher thanno-ligation group at the time after chest closed. Differences are statisticallysignificant（P＜0.05）.Comparison no-ligation group and LAD ligation withchest closed, RV5、STV5、TI、TaVL、TV5in the later one was higher than the formerones according to the time after chest closed. Comparison between LADligation with chest unclosed group and LAD ligation with chest closed group atthe corresponding time point after chest closed，TI、TaVL、TV2and TV5in the laterone was relative higher while TШwas lower. Differences are statisticallysignificant（P＜0.05）.There was no differences for the rest parameters (P＞0.05).Comparison of arrhythmia condition before and after operation,there wasno statistically significant difference for the occurrence rate of arrhythmiabetween non-ligation group and ligation group before ligation.Atrioventricularblock was their main performance.Arrhythmia occurrence rate of ligation groupwas higher than non-ligation group after ligation.The lethal arrhythmia, Ⅲdegree atrioventricular block,ventricular tachycardia,ventricular fibrillation,occurred during this period. Conclusion: opening chest,tearing pericardium will significantly affect theelectrocardiogram (ecg) performance of rats, mainly embody in arrhythmia,heartrate decreased, R wave amplitude reduced, lower T wave amplitude down.Which chest lead V2and V5have the most significant lower amplitude for the Rand T wave; Within the first minute of LAD ligation, open the chest will affectparts of the lead to show the appearance of myocardial ischemia, including theST segment elevation in V2lead and depression in lead aVR lead,T waveamplitude elevation in I,aVL,V5lead and depression in Ш,aVF lead. All thesephenomenon are hidden during thoracotomy and arise after chest closed.AfterLAD ligation,ST segment show the elevation changes in lead of I,avl,V5firstwhich is the sign of myocardial damage. And Ш,aVF lead show the depressionchanges which is the sign of ischemia.I,avl,V5leads are better than II lead as themonitoring lead of MI.Chloral hydrate would lead to arrhythmia in rats,mainlyembody as atrial premature beats, part as ventricular premature beat.Most ofthem are united law;Open chest operation and ligation LAD will lead toarrhythmia,it give priority to with atrioventricular block,part of ventriculartachycardia and ventricular fibrillation.Most severe atrioventricular block,ventricular tachycardia and ventricular fibrillation arrhythmias occurs afterligation LAD;...