【作者】 李蕾；

【导师】 谢明星；

【作者基本信息】 华中科技大学 ， 影像医学与核医学， 2016， 硕士

【摘要】 右室常作为左室的从属结构在很长一段时间被研究者所忽略,使得对正常及各种病理状态下的右室功能理解匮乏。临床多种心肺疾病可以引起右室功能障碍,近些年来许多研究已经证实右室功能在疾病预后评估中有重要作用[1-6],右心功能是各种病理类型的肺高压患者的最强预后指标[5],是预测心衰患者预后的独立危险因素[6、7],许多先心病患者术后生存时间及生活质量依赖于右室功能是否正常。右室由于其心肌肌壁薄、顺应性好但收缩力差等特点,对压力负荷升高代偿较差,临床上多种心血管疾病可导致右室压力负荷升高。在右室压力负荷升高过程中,右室心肌发生重构,右室形态及心肌力学等随即发生改变,右室压力持续升高而不加干预可导致右心功能障碍直至右心衰竭等严重后果[8]。所以,在临床中早期、准确的评估右室功能具有重要意义。由于右室心腔内肌小梁丰富、几何结构复杂并且室壁运动与左室相互依赖,准确评估右室功能存在很大困难。通过右心导管检查可以测得右室腔内压力变化速度、心输出量等指标来反映右室功能,但因此检查的有创性而应用受限。心脏核磁共振(CMRI)具有较高的空间分辨率,是目前定量评估右室容积及右室射血分数的金标准[9],但CMRI扫描及分析时间长,时间分辨率低,并需要病人反复做深吸气、深呼气、憋气动作,需患者密切配合,且存在对支架、起搏器等金属植入的患者的应用禁忌,这些限制了CMRI在临床的广泛应用。超声心动图具有便捷、实时和无辐射等特点而广泛应用于临床和科研。由于传统超声有角度依赖性,且右室位于胸骨后方并受肺叶遮挡等原因使传统心动图在评估右室功能较具有较规则椭圆形的左室存在更大的困难[10]。二维超声斑点追踪成像技术(2D-STI)无角度依赖性,是在二维平面上通过追踪心肌斑点的运动轨迹计算出心肌应变和扭转等心肌力学指标来评估心肌的局部和整体功能。现今2D-STI技术已被用于定量的评估右室功能,但其仅局限于二维平面,不能评价心肌的出平面运动,且由于右室复杂的几何形态和收缩方式[10-12]只能评估右室纵向应变,而不能提供环向及径向应变信息。三维超声斑点追踪显像(3D-STI)技术是近年来在三维超声和斑点追踪技术基础上发展起来的一项评估心肌应变的新技术,其在三维空间上追踪心肌斑点运动,从心肌应变层面评估心功能,不仅突破了角度依赖性,且不局限于二维平面从而可以更真实的、更准确的评估心肌功能[13-14]。基于右室形态学角度考虑,三维方法将比二维方法更适合右室功能的研究,已有研究将分析左室功能的3D-STI技术用于评估右室功能且被证实是有效的[6]。持续右室压力升高而不干预会引起右室肥厚而最终导致右心衰竭。在科技和医疗技术飞速发达的当今社会右心衰仍有着较高的病死率,怎样推迟心肌肥厚到发生心衰的时间是迫在眉睫的问题。因此,探讨心肌肥厚发生、发展及其机制具有深远的重要性和现实意义。心肌力学改变与早期组织学、细胞分子机制变化关系尚不清楚,深入研究其组织学、分子生物学基础对于临床在早期诊断、治疗右室功能不全患者方面具有重要意义。本研究旨在进一步明确3D-STI技术在评估右室压力负荷升高时右室局部及整体心肌力学改变,为早期发现右室功能异常、评估治疗效果及预后、随访提供一种新方法,并就右室心肌力学改变的组织学及分子生物学的简单机制做初步探究,研究分为两个部分:第一部分3D-STI技术评价右室压力负荷升高犬右室心肌力学改变本部分研究对象为10只健康雄性比格犬,动物模型为环束比格犬肺动脉主干(PAB)后人为造成右室压力负荷升高,分别采集比格犬术前、术后三个月二维及三维超声图像及数据,运用3D-STI技术评估术前及术后三个月比格犬右室三维应变超声指标变化。此外,10只比格犬在PAB术前及术后三个月均用右心导管测量右室+dp/dt max(最大上升速率)和-dp/dtmin(最大下降变化速率)。一只动物在术后三个月采集超声图像后因麻醉过深死亡。本研究应用3D-STI技术评估PAB后比格犬右室心肌整体与局部心肌应变改变,并探索右室心肌应变改变与右室腔内压力变化的关系。结果:(1)PAB术后PV(肺动脉瓣口收缩期峰速)、RVFWT(右室游离壁厚度)、Tei指数较术前升高(P<0.05),PAB术后PAAT(肺动脉加速时间)、RVFAC(右室面积变化率)低于术前(P<0.05);(2)PAB术后RVGLS(右室整体纵向应变)减低,而RVGRS(右室整体径向应变)及RVGCS(右室整体环向应变)代偿性升高(P<0.05);PAB术后RVFWLSb(右室游离壁基底段纵向应变)减低(P<0.05),PAB术后SEPCSb、a(间隔基底段、中间段环向应变)、及SEPRSmid(间隔中间段径向应变)升高(P<0.05);(3)PAB术后三个月+dp/dtmax、-dp/dtmin均升高(P<0.05),且PAB术后右室+dp/dtmax与RVFWCSmean(右室游离壁平均环向应变)有较好的相关性(P=0.011,r=-0.758)。第二部分右室压力负荷升高犬右室心肌力学改变发生机制初探PAB术后饲养三个月并获得超声及心导管数据后,处死动物,取右室肺动脉瓣下心肌备用为banding组,同时用相同的方法处死3只体重性别与banding组匹配的正常比格犬作为normal组。HE染色测两组右室心肌细胞横径,Masson’s染色测两组右室心肌细胞胶原纤维面积百分比,行免疫组化法检测CD31,以比较两组右室心肌中新生血管密度(MVD);western blot及Real-time RT PCR检测两组右室心肌P53、VEGF、HIF-1α、CX43、bcl2及caspase3的蛋白及基因表达情况以探索右室心肌肥厚的分子及组织学机制。结果:(1)banding组右室细胞横径、胶原纤维面积百分比均高于normal组(P<0.05),banding组新生血管密度低于normal组(P<0.05);(2)banding组P53、Caspase3蛋白较normal组表达升高(P<0.05),banding组HIF1-α、VEGF、CX43蛋白较normal组表达降低(P<0.05);banding组HIF1a、CX43、VEGF、BCL-2基因表达较normal组降低(P<0.05);RVGRS、RVFWRS及RVFWLS与心肌胶原纤维面积有较好的相关性(r=-0.770,P=0.015、r=-0.747,P=0.021、r=0.777,P=0.014),RVFWRSb与VEGF基因含量有较好的相关性(r=0.744,P=0.021)。结论1、肺动脉主干环束诱导的右室压力负荷升高犬右室功能已发生改变,心肌发生肥厚和重建,纵向应变降低,环向及径向应变代偿性升高,同时右室心肌在组织学及分子水平都发生不同改变。2、运用3D-STI技术得出的超声应变参数与血流动力学、分子及细胞指标具有较好相关性表明3D-STI技术为客观评估右室功能提供了一种新方法。更多还原

【Abstract】 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 α, 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.更多还原