| Objective: To investigate the regularity of early cardiofunctional disorders in dogs with severe myocardial contusion, and to investigate the sensitivity and specificity of DSE and DTE in the diagnosis of MC.Methods: 20 mongrel dogs weighing averagely 11.36±1.50kg. They were divided into twogroups as group A and group B. Twelve dogs were used for the study of myocardial contusion and the study of echocardiography (among these dogs, there were two dogs were not statistically includeddue to early deaths after wounding). 8 were used for the detection by SPECT. The anterior chest wall of dogs were impacted by BIM-II type impact machine, the central impact part was located by ultrasound machine, it was in accord with the superficial area where left ventricular long axis view was. Parameters of impacting: driving pressure 800 kPa, impact area 16.61cm2, inside depressing of the chest wall was 5cm. Time phases of observation were divided as before MC, instantly after MC, and 2h, 4h and 8h after MC. Catheters were placed at the right common carotid artery and the left femoral artery, they were then connected to cardiofunctional analysis instrument combined with extremities electrical connections. Left intraventricular pressure, left ventricular systolic and diastolic functions, mean arterial pressure and ECG were therefore analyzed. Central venous pressure was determined through right femoral veins catheterization. Blood sample of 4 ml was taken and then centrifuged to obtain serum, then samples were stored at -76℃. Electro-chemical luminescence was used to detect cardiac troponins. Color Doppler systems were used to determine the left ventricular functions. DTE (Doppler tissue energy) and DSE (dobutamine stressed echocardiography) were used to detect the changes of different myocardial segments. And the coronary blood reserve (CFR) were also determined at 4 and 8 hours after MC. 8 dogs were selected to be intralabled by 99mTc-RBC, for determination of left ventricular systolic and diastolic functions.Results: 1) Animal model. After MC, various types of arythmia were observed such as ventricular tachycardia, artrioventricular heart block, ventricular vibration, ventricularproiosystole, ventricular intermission and so on. Pathological examinations showed that there were widely-spreaded haemorrhagia of the epicardium, endocardium and the myocardial tissues. There were also congestion or swelling, and even broken of the myocardial fibers. Staining by TTC method showed that there were pieces of necrotic myocardial fibers. Synthesized traumatic scoring on MC of these dogs may concluded as 4 points, which were in agreement with severe injuries. 2)The changes of myocardial markers. After severe MC, no changes of serum phosphocreatinase isoenzymes (CK-MB), myoglobin (Mb) and C-reaction protein were observed. Both the concentrations of troponin T (cTn-T) and troponin I was lower than O.Olng/ml, and they were increased instantly after MC. At 8h after MC, the concentration of cTn-T reached to 0.13 ± 0.052 ng/ml and cTn-I reached to 1.615 ± 0.371 ng/m, while cTn-T was as high as 8 times and cTn-I as 6 times of that of their instant concentration. It is suggested that cTn-T and cTn-I might proberbly be a better marker in the diagnosis of MC. 3) Cardialfunctional changes of dogs with severe MC. Both the left ventricular systolic function and diastolic function of dogs with severe MC were remarkably decreased, LVESP, +dp/dtmax and Vmax decreased continuously and they were not recovered until 8h after MC. And that, LVEDP, -dp/dtmax and T increased continuously and they were not recovered until 8 hours after MC. Cardiofunctional analysis by echocardiography revealed that EF and FS decreased at 2-8 hours after MC. Another analysis by SPECT showed that EF, 1/3ER, PER decreased continuously after MC, and they recovered slightly at 8 hours after MC. While 1/3FF, 1/3FR decreased and TPF delayed continuously without any recover until 8 hours after MC. All these results suggested that left ventricular systolic and diastolic function decreased markedly after severe MC. 4)AppIication of latest techniques of echocardiography on the diagnosis of MC. Detection by Doppler tissue energy (DTE) showed that myocardial motion was obviously weakened or contradicted after MC, there was defect of color filtration showed as black and remarkably outlined from normal myocardial color. At 2 and 4 hours after MC, the necrotic areas and the percentage of necrotic areas to the total areas increased markedly than that of the instant phase. At 8 hours after MC, the necrotic areas and the percentage of necrotic areas to the total areas were 2 times of the instant ones. If we set the left ventricular short axis view as the standard view of myocardial wall segmentation, there were 60 segments in total. Among these segments, there were 39 necrotic segments. The same view were alsobiopsied and stained by TTC. There were 39 necrotic segments observed by pathology. When comparing with the results of pathological TTC staining, both the sensitivity and specificity of DTE was 100%.Altogether 160 segments of ten dogs were examined by dobutamine stressed echocardiography (DSE). Before DSE: Echocardiography revealed 122 segments with wall motion abnormalities instantly after severe MC, at 2 hours after MC there were 133 segments, at 4 hours after MC there were 142 segments while at 8 hours after MC there were 142 segments and 3 cases of ventricular aneurysm. The wall motion scoring and WMSI increased obviously after MC. After DSE: There were 110 segments with motion abnormalities instantly after MC, at 2 hours after MC there were 133 segments, at 4 hours after MC there were 138 segments, and at 8 hours after MC there were 133 segments. Comparing with before DSE, segments with wall motion abnormalities decreased, however, wall motion scoring and WMSI increased. When comparing with TTC staining, there were 54 segments with wall motion abnormalities before DSE, and 52 segments with wall motion abnormalities after DSE. If we consider the segments with wall motion abnormalities as contused myocardium, the sensitivity and specificity of conventional echocardiography was respectively as 100% and 66.67%. While the sensitivity and specificity of DSE was respectively as 100% and 88.89%. When examination of these segments combined DTE and DSE, altogether 47 segments were showed as black, and if we consider this as contused myocardium, its sensitivity and specificity was respectively as 92.2% and 100%.Detection of coronary blood flow reservation (CFR) revealed that PDV and CFR decreased markedly after MC than that of pre-wound value. It was suggested that there existed a decrease of coronary blood flow and insufficient perfusion of the myocardium.Conclusion:1. In this experiment, we successfully established an animal model of dogs with severe MC, this model is stable and well reproducible, and that it could simulate the clinical manifestation of MC more accurately, it is also an ideal experimental model to study myocardial contusion.2. Our experiment revealed that left ventricular systolic and diastolic functions decreased remarkably after severe MC, and that the systolic function decreased moreobviously than diastolic functions.3. Disturbance of the coronary blood flow might be an important reason through inducing secondary myocardial ischaemia and necrosis after MC, and then aggravate the cardiaofunctional disorders.4. Stressed echocardiography may increased the detectable rate and the specificity of abnormal segments after MC, and decrease the false positive rate.5. DTE was able to detect out the criteria and degree of MC at the early phase and with high specificity, and both its sensitivity and specificity was 100%. It might probably be a effective and reliable tool in the early specific diagnosis of the clinical patients who was suspected with MC.
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