The Change Of Right Ventricular Function With Different Left Ventricular Geometry And The Study Of Relationship Between Fluid Shear Stress And Vascular Endothelial Function In Rabbits With Hyperthyroid Cardiomyopathy

Objective:1.To evaluate the change of right ventricular function with different left ventricular geometry in rabbits with hyperthyroid cardiomyopathy by quantitative tissue velocity imaging(QTVI). 2.To study the relationship between fluid shear stress and vascular endothelial function in rabbits with hyperthyroid cardiomyopathy by high-frequency ultrasonography.Methods: Part one: Divided thirty purebred New Zealand rabbits which were provided by the exprimental animal center of Dalian medical university into two groups randomly, sexuality is not concerned, the body mass ranging from 2.10±0.15 kg. These rabbits were randomly divided into two groups: experimental group(n=20) and control group(n=10). Rabbit with hyperthyroid cardiomyopathy model was established by intraperitoneal injection of levothyroxine for 28 days in experimental group. 5 ml physiological saline was intraperitoneal injected in control group for 28 days. The parameters of conventional echocardiography and quantitative tissue velocity imaging(QTVI) were obtained at the end of 28 th day in two groups. The relevant parameters included: left ventricular end diastolic diameter(LVDd), interventricular septal thickness at end diastole(IVSTd), left ventricular posterior wall thickness end diastole(PWTd), the early diastolic blood flow velocity(E), peak velocity during systole(Vs), systolic acceleration(a), peak velocity during diastole(Ve), and E/Ve. Use the formula to calculate the left ventricular mass(LVM), left ventricular mass index(LVMI), relative wall thickness(RWT). According to the parameters of conventional echocardiography and Ganau in experimental group were divided into two types: concentric hypertrophy subgroup(CH subgroup) and eccentric hypertrophy subgroup(EH subgroup). Part two: Animal grouping and rabbit with hyperthyroid cardiomyopathy model were the same as the part one. Measured the level of FT3 and FT4 in every rabbits’ serum with electrochemical luminescence. Obtained the parameters of abdominal aorta by using high-frequency ultrasonography, as follows: the diameter of abdominal aorta(D), peak velocity and mean velocity of abdominal aorta. Fluid shear stress and endothelial dependent dilation(EDD) and non-endothelial dependent dilation(NEDD) of abdominal aorta were calculated according to formula.Results: Part one:1. The parameters of conventional echocardiography: IVSTd、PWTd、RWT and LVMI in CH subgroup all increased obviously when compared with control group(all P<0.01), there was no significant difference in LVDd between CH subgroup and control group(P>0.05). LVDd、IVSTd、PWTd and LVMI in EH subgroup all increased obviously when compared with control group(all P<0.01), but there was no significant difference in RWT between EH subgroup and control group(P>0.05). LVDd and LVMI in EH subgroup were increased obviously when compared with CH subgroup(both P<0.05), RWT in EH subgroup decreased obviously(P<0.01). 2.QTVI parameters of tricuspid valve of right ventricular: Ve was decreased obviously in CH subgroup when compared with control group, whereas E/Ve increased obviously(both P<0.05), there were no significant differences in Vs、a、E between CH subgroup and control group(all P>0.05). Ve, Vs and a in EH subgroup all decreased obviously when compared with control group and CH subgroup(all P<0.01), E/Ve increased obviously(P<0.05), there was no difference in E among three groups(all P>0.05).Part two:1.The level of serum FT3 and FT4: The level of serum FT3 and FT4 in experimental group were increased obviously when compared with control group(both P<0.01). 2.The hemodynamics parameters of abdominal aorta: The diameter of abdominal aorta, peak velocity and mean velocity of abdominal aorta all increased obviously in experimental group when compared with control group(all P<0.05). Mean fluid shear stress of abdominal aorta increased obviously in experimental group than that of control group(P<0.01). 3.Both EDD and NEDD of abdominal aorta: Both EDD and NEDD of abdominal aorta decreased obviously in experimental group when ompared with control group(both P<0.01). 4.Correlation analysis:The increasing fluid shear stress of abdominal aorta was negatively related to EDD and NEDD of abdominal aorta in rabbits with hyperthyroid cardiomyopathy.(r=-0.67, r=-0.52, both p<0.05).Conclusion:1.QTVI can effectively assess the change of right ventricular systolic and diastolic function with different left ventricular geometry in rabbits with hyperthyroid cardiomyopathy. 2.High-frequency ultrasonography can accurately evaluate the change of fluid shear stress and its effects on vascular endothelia in experimental rabbits with hyperthyroid cardiomyopathy.