| Part I The Establishment of the Swine Myocardial Infarction ModelObjectives:Discussion of the feasibility, effectiveness, stability and repeatability of using the pig myocardial infarction model in open chest ligation experiment of the first diagonal branch of the anterior descending coronary artery and conduct analysis on the modeling method.Method:Prior to the operation, collect venous blood from 8 healthy and same-age adult female Tibetan pigs, each weighing 30-40 kg, and test the collected blood for myocardial damage factors and myocardial enzymes. Keep the pigs constantly under dynamic ECG monitoring and maintain their breath with artificial assistance after anesthesia, and conduct open-chest ligation of the first diagonal branch of the anterior descending coronary artery at the spot approximately 1.0cm away from the left trunk,6h after the operation collect venous blood and test it for myocardial damage factors and myocardial enzymes, and with the dynamic variation of the cardiogram assess the modeling status of the myocardial infarction model. Based on the electrocardiogram variation and the increase of myocardial damage factors and myocardial enzymes before and after the coronary artery, decide whether the modeling of myocardial infarction is successful.Result:1. Conducted thoracotomy on all the 8 pigs and succeeded in 6 pigs, the overall survival rate was 75%. One pig died due to overdosed muscle relaxant, and one pig died due to incorrect intubation and untimely rescue.2. After ligation of the first diagonal branch of the anterior descending coronary artery at the spot approximately 1.0cm away from the left trunk, all the six pigs showed arched elevation at the ST segment and obvious increased levels of myocardial damage factors and changes in myocardial enzymes including hsTnl, MYO, LDH, CK, CK-MB, which indicates successful establishment of the myocardial infarction model on the six pigs, which allows for the next step of the experiment.Conclusion:1. In building the myocardial infarction model, taking the near-end segment of the first diagonal branch of the left anterior descending branch of the coronary artery for ligation can effectively achieve the objective for preparation. This method of model preparation is high in success rate and low in mortality rate, and highly repeatable, which is an ideal method for preparing animal models of myocardial infarction.2. Intra-operative anesthesia (including muscle relaxants), assisted breath are important conditions for the successful making of the model, so are post-operation infection prevention and provision of suitable external environment.Part Ⅱ Value of Ultrasonic Strain Image in Diagnosis and Treatment of Myocardial InfarctionObjectives:Adopting the traditional ultra-sonic cardiogram and Speckle Tracking Image (STI), combined with analysis of the pattern and features of the myocardial form and function changes of the left ventricle after ligation of the anterior descending branch of the coronary artery, discuss the value of traditional ultra-sonic cardiogram and SIT techniques in assessment of the myocardial form and function changes in myocardial infarction.Method:1. Take same-age healthy adult Tibetan Pigs, conduct ligation at the spot of the near-side first diagonal branch of the anterior descending branch 1.0cm away from the left trunk to make the myocardial infarction model.2. Conduct ultra-sonic cardiogram on the myocardial infracted pigs which survived and in which models were successfully made after the coronary ligation operation 6h,24h,48h,72h and 96h after the operation.3. Use traditional ultra-sonic cardiography to measure respectively the size of heart cavity, left ventricular end diastolic volume (LVEDV), left ventricular end systolic volume (LVESV), and heart function parameters, i.e., the left ventricular ejection fraction (LVEF).4. Collect ultra-sonic section graph, applying off-line speckling tracking technique to analyze ultra-sonic papillary muscle short-axis horizontal radial strain (SR) peak value and circumferential strain (SC) peak value and local myocardial rotation angle (Rot) of different segments of the left ventricle.Result:Successful making of models on 6 pigs.1. Before the coronary artery ligation the healthy pig’s heart is close to or within the normal range of adult human measures in form, heart cavity size and the ultra-sonic measurement of the blood at the valve orifice, which can well simulate human heart activity and blood dynamics variation.2. Prior to and 6h,24h,48h,72h and 96h after the coronary artery ligation, the conventional measured ultra-sonic values showed changes after repeated measurement analysis of variance. LVEDV,LVESV and LVEF measurements showed significant difference, the corresponding P-values were all 0.000.3. Prior to and at different time points after the coronary artery ligation, the peak strain values of infarction segments SR, SC and Rot showed changes. With repeated measurement analysis of variance these SR, SC and Rot at different time spots prior to and after the ligation showed statistically significant difference at the changes at the anterior septal apical segment, the anterior wall of apical segment and the side wall of apical segment. For SR, SC and Rot at the anterior septal apical segment, P=0.001,0.001,0.000; for SR, SC and Rot at the anterior wall of apical segment, P=000; for SR, SC and Rot at the lateral wail of apical segment, P=0.000,0.008,0.001.Conclusion:1. With ultra-sonic measurement of the heart cavity inside diameter, it has been proven that pig heart is similar in size to human heart, and the myocardial infarction modeling is stable after ligation at the anterior descending branch of the coronary artery. Pig is suitable for animal modeling of myocardial infarction.2. STI can sensitively detect variation in local myocardial contraction function in animal models of myocardial infarction; after myocardial infarction the strain at each side of the defected segments decreases, so that it is possible to conduct quantitatively assessment of the deformation features in myocardial damage.Part III The Application Value of Gated Myocardial Perfusion Imaging in Diagnosis and Treatment of Myocardial InfarctionObjectives:Adopt 99Tc-methoxyisobutylisonitrile (99mTc-MIBI) gated myocardial perfusion imaging (GMPI) to analyze the patterns and features of the myocardial perfusion and functional change of the left ventricle after ligation at the anterior descending branch of the coronary artery of the myocardial infarction model pigs, and attempt to discuss the value of assessment of the myocardial perfusion and function of myocardial infarction with GMPI and ultra-sonic cardiography.Method:1. Choose same-aged healthy adult Tibetan pigs, conduct ligation at the first diagonal branch of the anterior descending branch to make myocardial infarction models.2. On the surviving myocardial infarction pigs on which modeling was successful, conduct GMPI once respectively prior to and 6h,24h,48h,72h, 96h after the ligation.3. Apply SPECT/CT and post-processing software to analyze the blood perfusion condition and heart function parameters of each segment of left ventricular wall.4. Conduct comparison analysis with the results of ultra-sonic cardiography.Result:Successful modeling on 6 pigs.1.6h after the coronary artery ligation, the GMPI showed no positive or only extremely tiny perfusion defection areas; 24h after the ligation, GMPI showed sparseness and defect at the anterior septal apical segment, the anterior wall of apical segment and the lateral wall of apical segment.2.48h,72h and 96h after the coronary artery, the GMPI still showed the above perfusion detection areas and the defection area showed no obvious change or a bit smaller as time passed.3. Measured values of LVEDV, LVESV and LVEF taken before the coronary artery ligation and 6h,24h,48h,72h and 96h after it showed variation with significant difference (all P=0.000) after repeated measurement analysis of variance.4. For healthy pigs, the LVEF values measured with GMPI and STI showed good correlation (r=0.84, P=0.03), and this correlation decreases after myocardial infarction. However, before and 6h,24h,48h,72h and 96h after the coronary artery ligation, LVEF, LVEDV and LVESV measurements given by these two methods showed variation trends with good consistency as time goes by after the ligation.Conclusion:1.99mTc-MIBI rest gated myocardial perfusion imaging can be used for assessing diagnosis of myocardial perfusion 24h after the coronary artery ligation. However, this must be cautious for early-phased infarction diagnosis within 6 hours.2. Diagnosis using 99mTc-MIBI GMPI and ultra-sonic STI 24h after the myocardial infarction show consistent judgment of the infarction segments 24h after the myocardial infarction happened.3. LVEF showed good correlation between the two methods, which decreases after the myocardial infarction; and between the two methods LVEF, LVEDV and LVESV showed variation trends with good consistency as time passed after the coronary artery ligation.4. Joint application of GMPI and ultra-sonic STI is highly valued, which can be used for comprehensive assessment of myocardial damage and heart function. |
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