| Objective: The research aims to invistgate the changes and evolution of morphologyby real time three dimensional echocardiography (RT-3DE)and myocardial mechanicsusing the two dimensional speckle tracking imaging technology(2D-STI) during leftventricular aneurysm (LVA) formation after acute myocardial infarction (AMI) in rabbits.And explore the effect of matrix metalloproteinase-9(MMP-9) on LVA formation afterAMI from the serology and molecular biology, which provide the theoretical basis forclinical early diagnosis, early treatment LVA and evaluating cardiac function. Methods:Part one:This part is about the evaluating animal livability and the formation rate of LVAafter AMI.80New Zealand rabbits were divide into four group according to the differentway of thoracotomy and ligating the different coronary artery. Group A: A rabbit model ofLVA was prepared in20New Zealand rabbits by ligating the middle segment of the leftanterior descending artery and thoracotomy by cuting the middle sternum. Group B: Arabbit model of LVA was prepared in20New Zealand rabbits by ligating the middlesegment of the left anterior descending artery and the left circumflex artery andthoracotomy by cuting the middle sternum. Group C: A rabbit model of LVA was preparedin20New Zealand rabbits by ligating the middle segment of the left anterior descendingartery and thoracotomy was performed through the left fourth intercostal space. Group D:A rabbit model of LVA was prepared in20New Zealand rabbits by ligating the middlesegment of the left anterior descending artery and the left circumflex artery andthoracotomy was performed through the left fourth intercostal space. At4weeks after theprocedure,the LVA characteristics, animal livability and the formation rate of LVA were compared with four group. Part two: A rabbit of LVA was established in20New Zealandrabbits by ligating the middle segment of the left anterior descending artery and the leftcircumflex artery and thoracotomy was performed through the left fourth intercostal space.RT-3DE and2D-STI were performed at preoperative and postoperative1d,2d,3d,1w,2w,3w,4w. At4weeks later, the survived animals which haved formed LVA wereenrolled into this study. RT-3DE was uses to observe the LVA volume, shape, formatingtime and the changes of heart function at different time.2D-STI was performed tomeasure the changes of radial strain rate (SrR) and circumferential strain rate (SrC) atsystolic and diastolic at different time. Part three: A rabbit of LVA was established in20New Zealand rabbits by ligating the middle segment of the left anterior descending arteryand the left circumflex artery and thoracotomy was performed through the left fourthintercostal space. RT-3DE was performed at preoperative and postoperative1d,2d,3d,1w,2w,3w and4w. At4weeks later, the survived animals which had formed LVA wereenrolled into this study. The MMP-9serum concentration was measured by the doubleantibody sandwich ABC-ELISA method and expression of MMP-9was detected byimmunohistochemistry,while mRNA and protein were detected by RT-PCR and WesternBlot at different time phase, respectively. Results: Part one:(1) The animal livability ingroup A, B, C, D was90%,65%,95%and70%respectively. Compared with group B andD, there were significantly higher in group A and C (P<0.05).(2) The formation rate ofLVA after AMI in group A, B, C and D was50%,84%,53%and86%, respectively.Compared with group B and D, there were significantly higher in group A and C (P<0.05).(3) Compared with group A and C, LVEDV, LVESV, and LVAV were significantlyenlarged in group B and D, while LVEF was significantly decreased, there were statisticsdifference(P<0.05). Part two:(1) In the survived animals, the LVA come into being atpostoperative2d. There was an increase trend in the amount of LVA formation frompostoperative2d to postoperative3w. While the LVEDV, LVESV and LVAV showed anincrease trend from postoperative2d to postoperative3w (P<0.05), however there was adecreasing trend in LVEF from postoperative2d to postoperative3w (P<0.05). Therewere no statistics difference between postoperative3w and postoperative4w (P>0.05).Moreover, there were high correlations between LVEF and LVAV, LVA volume/LVEDV(r=0.778,0.911, respectively, all p<0.05). Of note, had the tightest inverse relationshipwith LVEF (r=-0.911, p <0.01). Specifically, LVAV/LVEDV>16%corresponded to LVEF<50%, and LVEF decreased1.1%while LVAA/LVEDV increased1%.(2) Compared withpreoperative, there were significant decrease in the SrR-S, SrR-E, SrR-A,SrC-S, SrC-E and SrC-A at postoperative1d,2d,3d,1w,2w,3w and4w(P<0.05). Compared withpostoperative1d, there were significant decrease in the SrR-S, SrR-E, SrR-A,SrC-S,SrC-E and SrC-A at postoperative2d,3d,1w,2w,3w and4w(P<0.05), while Therewere no statistics difference between postoperative3w and postoperative4w (P>0.05).SrC-Santerior wall, SrR-Santerior wall, SrC-Slateral wall, and SrR-S lateral wall weresignificant decrease than other segment at the same time postoperative (P<0.05), andSrC-Santerior wall, SrR-Santerior wall, SrC-Slateral wall, and SrR-S lateral wall hadhigh correlations with LVEF((r=0.895,n0.887,0.890,0.891, respectively, all p <0.05).(4)Compared with the each segment in the strain rate decrease percentage at systole, therewere significant decrease at anterior and lateral wall (P<0.05). while There were nostatistics difference at each segment at diastole (P>0.05).The ROC curve analysis showedthat when the strain rate decrease percentage was60%as the critical point, the strain ratedecrease percentage of SrR-Santeriorwall, SrR-Slateralwall, SrC-Santeriorwall andSrC-Slateralwall had a sensitivity of83.30%,84.40%,83.30%and67.70%and aspecificity was73.60%,78.20%,69.70%and83.30%for prognosis ventricularneurysm,repectively. Part three: Compared with preoperative, there were an significantincrease in the serum concentration of MMP-9, expression of MMP-9positive cell,mRNA CT value of MMP-9and Protein quantitative value of MMP-9at postoperative1d2d,3d (P<0.05), and arrived at the peak at postoperative3d, decreased frompostoperative3d to postoperative4w, respectively, and till postoperative4w,there weremore high level than preoperative (all p <0.05). In AMI group, there was the same changetrend with LVA group, however the mangitute of decrease was larger than the mandututein LVA group(p <0.05).(2)There were good correlations between MMP-9and LVAvolumenand LVEF (r=0.65,0.78, respectively, all p<0.05)..Conclusion: The conclusionof the research can be drawn from the following four aspects,(1) It maybe can play theimportant role in establishment of animal model of LVA after AMI that differentcoronary artery is ligated. Real-time three-dimensional echocardiography can be as a newmethods to accurately measure the LVA volume and evaluate the LVA morphology.(2)LVA comes to being at postoperative2d and completely forms at postoperative3w. TheLVA volume increasingly enlarges from postoperative2d to postoperative3w. Theparameter of LVA volume/LVEDV can be as a new indictor for evaluating the cardiacfunction.(3) The myocardial SrR and SrC significantly reduce after VA formation,especially in the anterior and lateral segments.The strain rate decrease percentage in theanterior and lateral segments at systole could be as an important indicator to predict the formation of VA after myocardial infarction.(4) MMP-9all along play a key role in theLVR after AMI from postoperative1d to postoperative4w, and has a close influence onLVA formation after AMI, and has a high correlation with LVA volume and LVEF, whichmaybe as a new indictor to predict the LVA volume and LVEF. |
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