| As often considered to be the affiliated part of left ventricular in a long time,people lack understanding about normal and various kinds of pathological state of right ventricular function. A variety of clinical cardiopulmonary diseases can cause right ventricular dysfunction, many studies have confirmed that the right ventricular function play an important role in the disease prognosis assessment in recent years.[1-4]Right ventricular function is the strongest prognostic indicators in patients with various pathological types of pulmonary hypertension[5],which is also an independent risk factor to predict the prognosis of patients with heart failure[6?7]. Postoperative survival time and the quality of life of many congenital heart disease patients depends on whether right ventricular function is normal. Due to its thin wall and good ventricular compliance but poor contraction, right ventricular is unable to well compensate for pressure overload,while a variety of cardiovascular diseases can lead right ventricular pressure overload increasing. In the process of right ventricular pressure load increasing, the myocardium remodeling, during this process morphologic and myocardial mechanics change immediately, continuous high pressure overload can result in right ventricular dysfunction even right heart failure[8]. Therefore, early accurate evaluation of right ventricular function in clinical is particularly important.Because of complex geometry?rich trabecular and relying on the movement of left ventricular, it is difficult to accurate assess right ventricular function. Right cardiac catheterization can evaluate right ventricular function by testing the speed of changing in right ventricular pressure and cardiac output, but its invasiveness limits clinical wide application. Cardiac magnetic resonance imaging(CMRI)which with high spatial resolution is the gold standard of quantitative assessment of right ventricular volume and right ventricular ejection fraction[9]. But CMRI has a long scanning and analyzing time, low temporal resolution, and requires the patient repeatedly to do deep inspiration, deep expiration, holding breath which demand high corporation of patients, furthermore the high price and the patients with metal in the body are not allowed this inspection, all these restrict the CMRI widely used in clinical.Echocardiography is widely used in clinic because of its low price?free of radiation and stable repeatability. There is angle dependency with traditional echocardiography,and the location of right ventricular is behind the breastbone which beside the lungs that make it more difficult to estimate right ventricular function than left ventricle whose shape is relatively regular oval[10]. Two-dimensional speckle tracking imaging(2 D- STI) can real-time tracking myocardial spots on two-dimensional plane trajectory which can overcome angle dependence, through strain and torsion index to assess segment and global myocardial formation. 2 D- STI has been used to quantitative assessment of right ventricular function, but only limited to the two-dimensional plane, and can't evaluate myocardial out of plane movement? Because of the complicated geometry and contraction way in right ventricular [10-12],2D-STI only can assess the right ventricular longitudinal strain, the radial strain and circumferential strain information are not available. Three-dimensional speckle tracking imaging(3 D- STI) is a new technology developed on the basis of three-dimensional echocardiography and spot tracking imaging technology,it is tracking myocardial spot movement in 3 D space, from the change of myocardial deformation to assess myocardial function, which overcome angle dependency and the limitations of two-dimensional plane, could evaluate myocardial function more reliable and accurate[13?14]. Based on right ventricular morphology, the three dimensional method will be more suitable for right ventricular function research than 2 D methods, 3 D- STI technique which specialized for left ventricular research has been used to evaluate right ventricular function and proved to be effective [6].Right ventricular pressure overload can cause myocardium hypertrophy, which could result in heart failure if without medicine care. Right heart failure's fatality rate is still high in today's society, so the problem how to delay the progress of myocardial hypertrophy to heart failure is that we need solve. Therefore, it's necessary and full of reality to discuss mechanism of myocardial hypertrophy. The relationship between the changes of myocardial mechanics and the early change of histology and cell and molecular mechanism is unclear, further study of its function of histology, molecular biology basis will benefit for early diagnosis and treatment of right ventricular dysfunction.This study aims to further clarify the 3 D- STI technology in assessment of right ventricular function with pressure overload in segment and global myocardial formation, providing a new method in early detection of changes in right ventricular function and evaluation for clinical treatment effect and prognosis, and make preliminary research on the myocardium of the mechanical changes of histology and molecular biology mechanism. The research included two parts:Part1 Evaluation of myocardial mechanics change of right ventricular in beagles with right ventricular pressure overload by 3D-STIThe research object of part I was 10 healthy male beagles, pulmonary artery banding(PAB) was used to induce RV pressure overload. Preoperative and postoperative 3 months 2 d and 3 d ultrasound images and data were gathered in beagles. The 3D-STI technology was used to assess preoperative and postoperative 3 months' beagles with the conventional and three dimensional strain parameters. In addition, 10 animals were calculated rate of right ventricular pressure maximum + dp /dt max and minimum-dp /dtmin preoperative and postoperative 3 months. An animal was dead because of anesthesia deeply after collection of 3D ultrasound images three months later. We evaluated the right ventricular segment and global myocardium strain changes in beagles which after surgery with 3 D- STI technique, and to investigate the relationship between the myocardium strain and the changes of right ventricular pressure. Results:(1)The beagles after surgery's parameter PV(pulmonary valve peak systolic velocity), RVFWT(right ventricular free wall thickness), Tei index were valuable higher than before the surgery(P < 0.05), parameter PAAT(pulmonary acceleration time), RVFAC(right ventricular area change rate) were valuable lower than before the surgery(P < 0.05);(2) The parameter RVGLS(right ventricular global longitudinal strain) was valuable lower than before the surgery, the RVGRS(right ventricular global radial strain) and RVGCS(right ventricular global circumferential to strain)were valuable higher than before the surgery(P < 0.05); The parameter RVFWLSb(right ventricular free wall basal segment longitudinal strain) were valuable lower than before the surgery(P <0.05), the SEPCSb(septum basal segment circumferential strain), SEPCSmid(septum middle segment circumferential strain) and SEPRSmid(septum middle segment radial strain) were valuable higher than before the surgery(P < 0.05);(3) The parameter+ dp/dtmax,-dp/dtmin were valuable higher than before the surgery(P < 0.05), and parameter + dp/dtmax was related to RVFWCSmean after surgery(right ventricular free wall average circumferential to strain)(P = 0.011, r = 0.011).PART 2 The pilot study of right ventricular myocardial mechanics change mechanism in beagles with right ventricular pressure overloadBeagles were put to death after ultrasound and postoperative cardiac catheterization data were taken, taking right ventricular myocardial behind pulmonary valve standby, using the same method to death three gender and weight matched as banding group at the same time which set of normal group.(1)Transverse diameter of myocardium were acquired between two groups with HE staining,Myocardial cell collagen fiber area percentage compared between two groups with Masson's staining. Use the immunohistochemical method to test CD31 to compare microvascular density(MVD) between two gtoups.(2)Western blot and Real-time RT PCR were used to test protein and gene expression about P53 and VEGF, alpha, CX43 HIF- 1, bcl2 and caspase3 to explore the histology and molecular biology mechanism of myocardium hypertrophy in right ventricle. Results(1)The transverse diameter cell diameter and the collagen fiber area percentage in banding group were valuable higher than those in normal group(P < 0.05), microvascular density in banding group was lower than normal group(P < 0.05);(2)Protein P53, Caspase3 expression increased in the banding group compared with normal group(P < 0.05), protein HIF1 ?, VEGF and CX43 expression reduced in the banding group compared with normal group(P < 0.05); Gene HIF1 a, CX43, VEGF, BCL- 2 expression were reduced in the banding group compared with normal group(P < 0.05);(3)RVGRS, RVFWRS and RVFWLS were associated with myocardial collagen fiber area(r = 0.770, P = 0.770 and r = 0.747, P = 0.021, r = 0.777, P = 0.014), RVFWRSb related to the content of VEGF gene(r = 0.744, P =0.744).Conclusions1. PAB caused pressure overload–induced beagles had been damaged in right ventricular systolic and diastolic function by different degree, and myocardial hypertrophy and remodeling, the longitudinal strain was reduced, radial strain and circumferential strain were increasing compensatory, right ventricular myocardium changed in histology and molecular levels at the same time.2.The significant correlations of RV 3D-STE parameters with hemodynamic, molecular and cellular parameters indicate that 3D-STE may be very useful in the objective assessment of RV function. |
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