| Objective:1. Using the Omni-directional M-mode echocardiography to study the changes of myocardial function in type 1 diabetic rabbits and provide theoretic and experimental bases on early diagnosis for myocardial dysfunction in diabetic patients.2. Comparing the Omni-directional M-mode echocardiography with other kinds of echocardiographies to explore its application on assessing regional myocardial function.Methods:New Zealand rabbits were randomly divided classified into three groups which were control group, diabetes mellitus group (DM) group and Hyperlipidemia group (HL group), and these three groups were divided separately into four subgroups (2 week(w),4w ,6w and 8w (n=8)). DM group was induced by alloxan (ALX), while HL group was fed with high-fat diet. Each group was detected by transthoracic echocardiography and measured by Doppler imaging, two-dimensional speckle tracking imaging (2D-STI) and Omni-directional M-mode echocardiography (OME) at different time points (2,4,6,8w). Each group was killed after examination, so that myocardial tissues were observed by light microscopy and electronic microscopy. Parameters of Two-dimensional imaging: Interventricular septal thickness (IVST), left atria diameter ( LAD ), left ventricular internal diameter (LVID), end-diastolic volume of the left ventricle(LVEDV), left ventricular ejection fraction (EF), shortening fraction(FS) and cardiac output ( CO ). parameters of Doppler imaging : velocity of LV filling flow propagation(Vp), peak systolic velocity of mitral annulus (Sa) , peak early diastolic velocity(Ea) and peak late diastolic velocity(Aa). parameters of two-dimensional speckle tracking echocardiography: peak radial strain rate. parameters of omni-directional M-mode echocardiography: myocardial velocity gradient (MVG).Results:1.DM group: There was no significant difference with MVG between DM group and control group on diastolic period at the time points of 2w (P<0.05), the MVG of most segments on diastolic period were significantly lower in DM group than those in control group at the time points of 4,6,8w (P<0.05), There was no significant difference with MVG between DM group and control group on systolic period at the time points of 2,4w (P<0.05), the MVG of most segments on systolic period were significantly lower in DM group than those in control group at the time points of 6,8w (P<0.05). The difference was significant. HL group: There was no significant difference with MVG between HL group and control group on diastolic period at the time points of 2,4w (P<0.05), the MVG of most segments on diastolic period were significantly lower in DM group than those in control group at the time points of 6,8w (P<0.05); There was no significant difference with MVG between HL group and control group on systolic period at the time points of 2,4,6w (P<0.05), the MVG of most segments on systolic period were significantly lower in DM group than those in control group at the time points of 8w (P<0.05). The difference was significant.2. Pathological detection: The results of HE staining showed that the left ventricular myocytes from the DM group and HL group at the time points of 4w arranged irregularly and the pericellar membrane was interrupted and unclear,as well as vacuolation in cadiocytes. Masson staining indicated that collagen tissue increased. From the observation by electron microscopy , myocytolysis, intercalated disk was distorted and interrupted, and mitochondria were swollen and clustered, while microvascular endothelial cells were swollen.Conclusions:1. Myocytolysis, many lipid droplets, mitochondria swelling and condensation, collagen deposition and interstitial fibrosis were the main pathological changes in the myocardium of type I diabetic rabbits.2. LEJ-2 omni-directional M-mode echocardiography can accurately, non-invasively and quantitatively be used in assessment of the early changes of myocardial diastolic function in type 1 diabetic rabbits. |
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