The Experimental Study Of The Development Of Early Myocardial Function And Perfusion In Diabetic Rats

Part one: The Development of Early Myocardial Function and Perfusion in Diabetic Rats: the Velocity Vector Imaging and Myocardial Contrast Echocardiography StudyObjective: The aim of the study was to investigate the development of early myocardial function and perfusion with velocity vector imaging (VVI) and myocardial contrast echocardiography (MCE) in diabetic rats. The mechanism of diabetic cardiomyopathy (DCM) will be approached, in order to provide theoretic and experimental bases on early diagnosis and treatment for DCM. Methods: The diabetes mellitus (DM) group comprised 40 male diabetic rats, induced with streptozotocin. The control group comprised 40 normal male rats, comparable body weights with the DM group. The DM group was divided into four subgroups (0 week (w), 2w, 4 w and 8w after diabetic model established) and the control group was also divided into four subgroups matched with the DM group. Each rat was performed with cardiac catheterization, conventional echocardiography, VVI and MCE. Myocardial function and perfusion were measured from parasternal short axis view at mid level of left ventricle by VVI and MCE. When all the operations were finished, the myocardium was collected for pathological examination. The parameters were compared between the control group and the DM group. In addition, the differences among four subgroups in the control group and the DM group were compared, respectively. Results: Excepted for the non-established and dead diabetic rats, the numbers of the DM subgroups were eight rats in the 0w, seven rats in the 2w, eight rats in the 4w and six rats in the 8w subgroup, respectively. There were ten rats in each control subgroups. The diastolic circumferential strain rate in the 4w DM subgroup was reduced compared with that in the controls. It was the earliest signal of impairment in myocardial function at baseline with VVI in the DM rats. Diastolic and systolic circumferential strain rate, circumferential strain, systolic velocity and diastolic velocity in the 8w DM subgroup were reduced significantly. The tendency of the VVI parameters in the DM group were decreased associated with the diabetic course, earlier than the conventional echocardiographic parameters. The myocardial blood volume and myocardial blood flow of the 8w DM subgroup with MCE were decreased than those in the control subgroup. The results of cardiac catheterization and pathological examination were consistent with the results of VVI and MCE. Conclusion: The early impairment of myocardial function and perfusion in the DM rats can be detected with the VVI and MCE. It is earlier in the impairment of myocardial function than that in the abnormality of myocardial perfusion. The phenomenon demonstrates that diabetic cardiomyopathy play an important role during the early stage of DCM. Part two: The Development of Early Myocardial Function and Perfusion in Diabetic Rats: the Stress Echocardiography StudyObjective: The aim of this study was to investigate the development of early myocardial function and perfusion with velocity vector imaging (VVI) and myocardial contrast echocardiography (MCE) combined with dipyridamole stress echocardiography in diabetic rats. Methods: Each rat was performed with cardiac catheterization, conventional echocardiography, VVI and MCE at baseline and after dipyridamole stress. The reserve parameters were compared between the control group and the DM group. In addition, the differences among four subgroups in the control group and the DM group were compared, respectively. The other methods were similar to the part one. Results: No significant differences were found in the heart rate after dipyridamole stress in each group. The earliest reduced sign of impaired myocardial function was the diastolic circumferential strain rate reserve in the 2w DM subgroup. The diastolic and systolic circumferential strain rate, circumferential strain, systolic velocity and diastolic velocity and their reserves in the 4w and 8w DM subgroup were lower significantly than the controls. The tendency of the VVI parameters in the DM group were decreased associated with the DM course. MCE demonstrated that the 4w and 8w DM subgroup had lower myocardial blood velocity reserve and myocardial blood flow reserve than the control subgroup. The myocardial blood volume reserve was reduced in the 8w DM subgroup, too. The results of cardiac catheterization and pathological examination were consistent with the results of VVI and MCE combined with the dipyridamole stress. Conclusion: The impairment of myocardial function and perfusion in the DM rats are detected earlier with the VVI and MCE combined with dipyridamole stress. In addition, the impairments of myocardial function play an important role during the early stage of DCM.Part there: The Effect of Myocardial Function and Perfusion in Diabetic Rats with Early Insulin TreatmentObjective: To assess the myocardial function and perfusion with early insulin treatment by velocity vector imaging (VVI) and myocardial contrast echocardiography (MCE) combined with dipyridamole stress in diabetic rats. Results: The 20 rats in the 8w subgroups of the control and the DM groups in the Part two became the control group and the DM group in this study. The treatment group was including 10 new diabetic rats. Every rat in the treatment group was hypodermic injected with protamime biosynthetic human insulin after the diabetic model established. Each rat was performed with cardiac catheterization, conventional echocardiography, VVI and MCE at baseline and after dipyridamole stress. The other methods were similar to the part one. Results: There were significant differences of VVI parameters among three groups. The VVI parameters in the DM and the treatment groups were reduced compared with those in the control group. The systolic velocity, circumferential strain, systolic and diastolic circumferential strain rate in the treatment group were increased, indicating myocardial function improvement with insulin. The VVI reserve parameters in the treatment group were higher than the DM group. At baseline MCE, myocardial blood flow was increased significantly in the treatment group compared with that in the DM group. After stress, myocardial blood flow reserve in the treatment group was still higher than that in the DM group. Other parameters were similar to those in the DM group, though they all were lower in the two groups than those in the controls. The results of cardiac catheterization and pathological examination were consistent with the results of VVI and MCE at baseline and at dipyridamole stress. Conclusion: The myocardial function and perfusion are improved with early insulin treatment in the diabetic rats. In addition, the improvement of myocardial function is dominant during the early stage of DCM.