| Part 1 MRI evaluation of postoperative pericardial adhesions in rabbit models of myocardial infarctionObjective:The aim of the present study was to investigate the role of MRI in evaluating postoperative pericardial adhesions in rabbit models of myocardial infarction.Methods:Twenty-five Japanese white rabbits were randomly divided into conventional operation group (n=11) and anti-adhesion membrane placed group (n=14), both underwent chest-opening coronary artery ligation surgery. After 8 weeks, in vivo MRI and exploratory thoracotomy were performed respectively to observe the degree of adhesions according to respective criteria. Data were analyzed by Wilcoxon's rank test. The consistence between MRI and exploratory thoracotomy were detected using consistency check.Results:The number of none adhesion, mild adhesions and severe adhesions observed by MRI were 3,3,5 cases respectively in conventional operation group and 4,9,1 cases respectively in anti-adhesion membrane placed group; the number observed by exploratory thoracotomy were 2,4,5 cases in conventional operation group and 5,7,2 cases in anti-adhesion membrane placed group. The difference between the two groups was statistically significant. (P=0.021 from MRI, and P=0.025 from reoperation). The cases of none adhesions, mild adhesions and severe adhesions from MRI consistent with exploratory thoracotomy were 5,9,6 cases. MRI results were consistent with exploratory thoracotomy results (Kappa=0.69, p<0.001).Conclusions:Magnetic resonance imaging assessment of pericardial adhesions is in good agreement with exploratory thoracotomy, MRI would be a good means of adhesions evaluation after cardiac surgery. Part 2 Effect of postoperative pericardial adhesions on cardiac function in rabbit models by using MRIObjective:To elucidate the effect of the degree of postoperative pericardial adhesions on cardiac function in rabbit models of myocardial infarction.Methods:Thirty Japanese white rabbits underwent chest-opening coronary artery ligation surgery to obtain rabbit models of myocardial infarction. Rule out 5 animals with serious infection or death, and the remaining 25 rabbits were enrolled in this study. After 8 weeks, in vivo MRI was performed to calculate the left ventricular function; the parameters are EDV, ESV, SV and EF values. Then, exploratory thoracotomy was performed to observe the degree of adhesions according to clinical criteria:no adhesion, mild adhesions, moderate adhesions and severe adhesions. Measured data of four groups were compared with One-way ANOVA analysis.Results:The number of no adhesion, mild adhesions, moderate adhesions and severe adhesions observed by exploratory thoracotomy were 7,5,6,7 cases. EDV and ESV values from MRI showed no significant difference between four groups (P=0.33 and 0.95, respectively). But the value of ESV in severe adhesions showed significantly statistical differences from the other 3 groups (P<0.001, respectively). SV and EF values from MRI showed significantly statistical differences between four groups (P=0.001 and<0.001, respectively), and in a linear relation with the adherent degree. Conclusions:In the preparation of myocardial infarction model, Severe postoperative pericardial adhesions affect cardiac function significantly, particularly in the systolic function. Such models should be rejected in the studies of cardiac function. Part 3 Ventricular remodeling after myocardial infarction in MRI studyPurpose:To observe the change of cardiac function after acute myocardial infarction in rabbit models, and to study MRI imaging characteristics of ventricular remodeling.Methods:Forty-five Japanese white rabbits underwent chest-opening coronary artery ligation surgery to obtain rabbit models of myocardial infarction. The animals were performed in vivo MRI at totla six time-point with before surgery,1 week,2 weeks,4 weeks,6 weeks,8 weeks. Cardiac function parameters were measured, including:left ventricular end diastolic volume (EDV), stroke volume (SV), ejection fraction (EF), peak ejection rate (PER) and peak filling rate (PFR). Comparison of heart function is variation with time after myocardial infarction. At each time point,5 animals randomly selected and were performed re-thoracotomy for gaining specimens of the heart. Each heart speciment was examined by MRI with the sequence of diffusion tensor imaging (DTI). The value of apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were collected; meanwhile, three-dimensional reconstruction of cardiac fiber structure of colored orientationmap and the regional main eigenvector map were performed.Results:Left ventricular diastolic and systolic slope of the curve reduced, the change was in the most obvious between the first 2 weeks and 4 weeks. Left ventricular EDV increase in progress according to the time extending, EF was significantly decreased (F=12.713, P <0.001), and EDV showed an increasing trend (F=1.71, P=0.148). EF show a downward trend with the increase of EDV, linear regression analysis, an equation was set up with y=-5.58x+57.7, (F=8.855, R=1.30, P=0.0049). On the other hand, PER decreased progressively before 4-weeks post-infarction (P=0.034). PFR also decreased, but with no significant difference (P=0.065). Myocardial first pass perfusion rising slope of the curve decreased with time in each group showed no significant difference (P> 0.05). FA value decreased, but ADC value showed upward trend according to the post-infarction time. FA value and ADC value were significantly different between the infarct region and adjacent region (P<0.05), but there was no significantly different between adjacent region and remote region (P> 0.05).Conclusions:MRI measurement of parameters of cardiac function and arranged orderly of myocardial fiber bundles are consistent with the evolution of pathological changes. MRI can be used to predict ventricular remodeling after myocardial infarction.Part 4 The role of function parameters on prediction of ventricular remodeling postinfarction by using MRIPurpose:To observe the change of cardiac function of old myocardial infarction (OMI) and to investigate the role of cardiac function parameters in prediction of ventricular remodelingMethods:Collection of 33 patients with old myocardial infarction, including 28 males and 6 females,60.2 years±9.5(from 45 to 79 years old). Healthy volunteers as the control group with 12 patients, aged from 40 to 62 years old, mean age wae (52.2±5.8) years. All patients and healthy controls underwent MRI examination. MRI measurement of heart function parameters including:DIR, TIR, EDV, ESV, EF, PER, PFR, and measure the percentage of the area ratio of myocardial infarction. As a dividing line of 24%, patients were divided into two groups with no remodeling group and remodeling group. Parameters were nalysised of the groups of heart function. The ROC analysis was used to evaluate the preidiction of cardiac funtion patameters for ventricular remodeling. All statistics using SPSS 17.0, and P<0.05 was significant difference. Results:Thinning wall were observed after infarction, with an average 5.64 mm±1.21mm. The ventricual morphology after infarction was irregular, and bulging like on local wall.3 of them were accompanied with vntricular aneurysm. Compared with normal myocardium signal,12 cases showed low signal on the sequence of DIR, and 6 cases showed slightly higher signal on the sequence of TIR.15 cases showed relatively hyerintensity on the sequence FIESTA. On delayed enhancement, the regions of myocardial infarction were showed obviously hyperintensity. The ventricular function parameters EDV and ESV of old myocardial infarction were increase than control group, otherwise, the values of EF, PER and PFR were decreased. The increase of ESV has a linear relationship with EDV, but the change of PER, PFR and EF showed a negative linear relationship with EDV. The change of SV was no significantly with other paprameters. PFR, EDV, ESV can be used as independent factors for predicting ventricular remodeling, with the areas under the curve (AUC) were 0.725,0.741 and 0.764, respectivly, using ROC analysis. The cut-off values were 2.27 EDV/sec,140.23ml and 79.12ml, respectivly.Conclusion:MRI can evaluate the morphological changes of myocardial infarction. Systolic and diastolic function can be used to assessment of cardiac function parameters, and these parameters act important roles on predicting ventricular remodeling,... |
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