法洛四联症根治术后对左肺动脉狭窄影响机理的数值分析

目的 利用计算流体力学(CFD)方法分析法洛四联症(TOF)根治术后不同的左肺动脉狭窄率（50%,20%,0%）模型的局部血流动力学改变。方法 通过对患者CT数据处理,完成3组左肺肺动脉狭窄几何的全三维数字化重构;结合主肺动脉血流量等临床数据,对3组模型中肺动脉分叉区的血液流动速度场、压力、壁面剪切应力等进行记录。结果 在3组模型的非定常模拟中,左肺动脉起始端均存在与狭窄率相关的反流和血流分布,右肺动脉血流分布规则。3组模型的静态压力、压力损失、壁面剪切力等也不同。结论 肺动脉分支的合理扩大在TOF根治术中有重要意义;术后左肺动脉狭窄是造成肺动脉反流的早期和重要因素;通过CFD模拟术后患者的三维模型可以对手术的效果提供早期参考。     

自制可调节肺动脉环缩装置对右心室作用实验研究

目的通过对动物右心室作用实验的研究,验证自制可调节肺动脉环缩装置的有效性。方法 12只健康雄性小尾寒羊,5～6个月龄,体质量26～37kg。随机分为实验组和对照组,每组各6只,体质量分别为（29.00±2.78）kg和（28.36±4.24）kg,差异无统计学意义（P=0.722）,从左侧第二肋间进胸,游离肺动脉主干,置入自制可调节肺动脉环缩装置,向球囊内注入0.9%NaCl溶液,逐渐增加右心室压力,进行心室训练,达到训练标准所需时间为9～18d。观察超声下右心室形态、血流动力学及心肌组织病理学变化。结果超声下右心室形态、室间隔位置、游离壁厚度均较训练前发生明显改变;血流动力学结果表明右心室/左心室收缩压力比值大于0.6,达到临床上心室训练的标准;右心室的收缩功能（P〈0.05）和舒张功能（P〈0.001）均得到了增强;病理检查结果右心室游离壁厚度及质量、右心室肥大指数、心肌细胞横径与对照组比较差异存在显著统计学意义（P〈0.001）。结论该装置能够达到肺动脉环缩、训练心室的目的 ,并且可双向调节,使用方便,效果可靠。     

双侧双向Glenn手术的全三维血液动力学数值分析

采用计算流体动力学方法,探讨双侧、双向Glenn术后腔-肺连接区域的能量损失情况。通过对患者核磁共振成像处理,完成了左、右肺动脉和左、右上腔静脉连接段的全三维数字化重构,结合相关血液流量等MRI测量结果,模拟了左、右肺动脉不同流量条件下连接段内的血液流动细节。结果表明：在肺动脉不同流量的情况下,腔-肺连接段内的能量损失相差2倍左右,血液流场形态对其有重要影响。由此得出结论：患者术后腔-肺连接段内的血流能量损失较小,人体肺动脉阻力大小决定左右肺的血流分配。在Fontan手术之前对Glenn连接结构进行血液流场的数值分析具有临床意义。     

先天性心脏病相关性肺动脉高压血流动力学特异性研究

目的先天性心脏病相关性肺动脉高压(pulmonary arterial hypertension related to congenital heart disease,PAH-CHD)是肺动脉血流动力学异常所致的一种疾病。研究肺循环血流动力学特异性,有助于了解PAH-CHD发生发展的生物力学因素。方法对5例PAH-CHD患儿和5例无PAH(Non-PAH)的先天性心脏病患儿通过临床及影像资料收集,重建三维血管模型,利用计算流体动力学模拟肺动脉血液流动,对比分析肺动脉血流动力学相关速度流线、壁面剪切力(wall shear stress,WSS)及单位体表面积平均能量损失(·E)差异。结果血流动力学相关指标显示,PAH-CHD患儿左右肺动脉分支处流速和WSS明显升高,主肺动脉处WSS明显降低,·E呈显著增加趋势且与肺动脉直径及入口流量呈明显正相关。结论 PAH-CHD患儿较Non-PAH患儿肺动脉分支处流速和WSS明显升高,主肺动脉WSS降低,·E增加,表明这些血流动力学因素与PAH-CHD密切相关,是临床评估PAH-CHD的潜在血流动力学指标。     

全麻下正常犬二尖瓣环舒缩力的测试及其意义的初步探讨

本实验是将一个特制的环形传感器在全麻体外循环下植入７条正常犬的二尖瓣环处，从而测得在不同血流动力学条件下二尖瓣环舒缩力的变化信号，经过信号处理仪按标定系数计算得到实际测量的力值。结果发现：二尖瓣环舒缩力信号为双峰波形，其中前峰较小与心房收缩时程相对应，后峰较大与心室收缩舒张时程相对应。因此我们认为：前峰代表房性环舒缩力，后峰代表室性环舒缩力。在心肌收缩力恢复到术前状态及增加心肌收缩力时，室性环舒缩     

TOF个性化手术规划的血流动力学模拟

目的法洛四联症(tetralogy of Fallot,TOF)是出现在新生儿中一种常见的先天性心脏病,其初期治疗的关键是在主动脉和肺动脉之间建立人工侧支循环,本研究从血流动力学角度探讨升主动脉与右肺动脉吻合的手术方案对TOF治疗的有效性。方法采用计算流体力学的方法对TOF手术模型进行数值模拟,重点考察搭桥管径对手术效果的影响,并根据增流率、分流率、能量损失、压力分布、壁面切应力分布等血流动力学参数对手术方案进行评价。结果实施搭桥手术后,左、右肺动脉出口的血流量有不同程度的增加。结论升主动脉与右肺动脉吻合的搭桥方案,可以在一定程度上缓解肺动脉狭窄造成的血流供给不足。     

肺血减少型先心病幼猪动物模型的构建

目的:探讨肺血减少型先心病幼猪动物模型构建的方法.方法:选用中华小型幼猪30只,随机分为对照组(A组,n=15)和实验组(B组,n=15).均采用右侧前外侧径路开胸.A组部分阻断主肺动脉10 min后放开,造成一过性肺血减少;B组经右心房表面送入球囊扩张器行人工房间隔造口+肺动脉环缩术,构建肺血减少型先心病模型.手术结束、术后1个月、2个月行血气分析、血常规及超声检查,术后1个月行64排CT检查,术后2个月剖胸验证模型构建情况.结果:A组15例,术后切口感染1例,死亡1例.B组15例,术后切口感染2例,死亡3例,12例存活幼猪模型构建成功.A组术后心脏超声、CT检查及剖胸探查均提示心脏无异常.术后B组心脏超声提示,过隔血流束＞0.5 cm,肺动脉环缩处血流速度在184～355 cm/s,收缩期肺动脉环缩处压差(Systolic trans pulmonary artery banding pressure,Trans-PABP)在20～50 mmHg; CT扫描示肺动脉环缩处直径(BD)为(6.5±1.3)mm;剖胸探查房间隔缺损(ASD)均＞0.5 cm,肺动脉环缩处缩窄明显.与A组比较,B组术后动脉氧分压(Pa02)和动脉氧饱和度( Sa02)逐渐降低(P＜0.05),血红蛋白(HB)和红细胞压积(HCT)逐渐升高(P＜0.05).结论:采用人工房间隔造口+肺动脉环缩术可成功构建肺血减少型先心病幼猪动物模型.该模型稳定性较好,更加接近临床病理生理状态.     

甲亢患者肺阻抗血流图及二维彩色环的临床研究

目的探讨肺阻抗图及二维彩色环反映甲亢右心血流动力学状态的价值.方法采用肺阻抗法检测60例甲亢及80例对照组的血流动力学指标,并与FT3、FT4、TSH测定值做相关对比.结果甲亢肺阻抗图中各参数:肺血流灌注波幅(Hs)、快速射血速率(Cdz/dtmax)、快速射血指数[C/(B-C)]、心率(HR)、Ⅰ环和总环均增大,射血期(B-Y)和快速射血期(B-C)均缩短,与健康组对比差异有显著性意义(p<0.01),且HR和(B-C)与FT3存在一定的相关性.结论肺阻抗图各指标参数,特别是HR、(B-C),可客观敏感无创地综合反映甲亢对右心血流动力学状态的影响.     

内皮素与肺动脉高压关系研究进展

在先天性心脏病中，肺循环合成及分泌内皮素（ＥＴ）增加，且与肺动脉压力及肺循环量呈正相关。在心力衰竭、肺源性心脏病、原发性肺动脉高压、新生儿肺动脉高压及高原性肺动脉高压中，均有肺循环内ＥＴ合成及分泌增加，且与肺动脉压力呈正相关，提示肺血流动力学变化是各种肺动脉高压时肺ＥＴ分泌增加的共同机理，抑或两者互为因果。ＥＴ参与了各种原因所致肺动脉高压的形成     

外源性HGF基因转染对肺动脉高压兔肺血流灌注及肺动脉压力的影响

目的: 探讨外源性肝细胞生长因子(HGF)基因转染高动力性肺动脉高压家兔后促进侧支肺血管生成、改善肺血流灌注、降低肺动脉压力的可行性。方法: 将肺动脉高压兔随机分为对照组、空病毒组和HGF基因转染组; HGF 基因转染组经气管内滴入法转染Ad-HGF, 对照组和空病毒组分别气管内滴入同体积PBS液和Adeno-Null; 4周后, 通过MacLab/8s多功能生理仪行血流动力学检测, 通过抗FⅧ+α-SMA抗体免疫荧光双标检测肺小动脉密度、FITC-lectin灌注+抗α-SMA荧光双标记了解肺血管灌注情况。结果: 气管内给药4周后, HGF基因治疗组含平滑肌细胞的小动脉密度较肺动脉高压对照组和空病毒组(12.5±2.7)/mm²明显增多(P<0.05); HGF组肺血流灌注获得有效改善, 而肺动脉高压对照组和空病毒转染组肺血管仍处于狭窄甚至闭塞状态; HGF治疗组肺动脉平均压明显低于肺动脉高压对照组和空病毒转染组(P<0.05)。结论: 肺动脉高压模型动物经气管滴入法转染外源性HGF, 可以促进肺侧支血管生成, 增加肺灌注并有效降低肺动脉压力。     

改良B-T手术不同搭桥方式的血流动力学比较

目的 通过数值模拟的方法对比分析端对边（end-to-side, ETS）与边对边（side-to-side, STS）两种不同搭桥方式的改良B-T手术（modified blalock-taussig shunt, MBTS）对血流动力学的影响,为临床治疗单心室心脏缺陷综合征提供参考。方法 采集单心室心脏缺陷综合征病人的医学图像,重建病人心脏真实的几何模型;基于虚拟手术操作系统模拟手术过程;采集病人的生理数据,建立病人的集中参数模型（lumped parameter model, LPM）;通过LPM计算提供计算流体力学（computational fluid dynamics, CFD）仿真模型的近生理边界条件;利用有限体积法对模型进行数值仿真。结果 分别获取了ETS模型和STS模型的血液流速以及壁面切应力分布。ETS模型和STS模型的吻合口部位振荡剪切系数（oscillatory shear index, OSI）分别为3.058×10-3和13.624×10-3,能量损失分别为116.5 和94.8 mW,右、左肺动脉流量比RRPA/LPA分别为0.8和1.72。结论 两个模型的能量损失相差不大,对手术的影响相对较小。STS搭桥方式左右肺动脉流量分布均匀,吻合口位置OSI值较小,优于ETS搭桥方式,应着重考虑。本研究为临床治疗单心室心脏缺陷综合征提供重要的理论支持和参考。     

Influence of antegrade pulmonary blood flow on the hemodynamic performance of bidirectional cavopulmonary anastomosis: a numerical study

The role and effect of preserved antegrade pulmonary blood flow (APBF) at the time of bidirectional cavopulmonary anastomosis (BCPA) in the management of single-ventricle physiology is controversial. We investigated the influence of APBF on the fluid dynamics of BCPA connection using computational fluid dynamics (CFD). Patient-specific, three-dimensional geometry of a BCPA connection with native pulmonary artery (PA) trunk was reconstructed and transient CFD simulations were done at four predetermined mean flow rates of PA trunk (0.5L/min, 1L/min, 1.5L/min and 2L/min). During a cardiac cycle, the flow ratio of left pulmonary artery (LPA)/right pulmonary artery (RPA) increased from 1.91 to 2.50, and average control volume power loss increased from 0.76 mW to 18.05 mW when the mean flow rate of PA trunk changed from 0.5L/min to 2L/min. The pulsatility of pressures in LPA, RPA and superior vena cava became more prominent as the amount of APBF increased. Local fluid structures in the connection area at four levels of APBF differed from each other.     

Numerical simulation of a realistic total cavo-pulmonary connection: effect of unbalanced pulmonary resistances on hydrodynamic performance

Total cavo pulmonary connection (TCPC) is one of the surgical techniques adopted to compensate the failure of the right heart in pediatric patients. The main goal of this procedure is the realization of a configuration for the caval veins and for the pulmonary arteries that can guarantee as low as possible pressure losses and appropriate lung perfusion. Starting from this point of view, a realistic TCPC with extracardiac conduit (TECPC) is investigated by means of Computational Fluid Dynamics (CFD) to evaluate the pressure loss under different pressure conditions, simulating different vessel resistances, on the pulmonary arteries. A total flow of 3 L/min, with a distribution between the inferior vena cava (IVC) and the superior vena cava (SVC) equal to 6/4, was investigated; three different boundary conditions for the pressure were imposed, resulting in three simulations in steady-state conditions, to the right pulmonary artery (RPA) and to the left pulmonary artery (LPA), simulating a balanced (deltaP(LPA-RPA) = 0 mmHg) and two unbalanced pulmonary resistances to blood flow (a pressure difference deltaP(LPA-RPA) = +/- 2 mmHg, respectively). The geometry for the TECPC was realized according to MRI derived physiological values for the vessels and for the configuration adopted for the anastomosis (the extra-cardiac conduit was inclined 22 degrees towards the left pulmonary artery with respect to the IVC axis). The computed power losses agree with previous in vitro Particle Image Velocimetry investigations. The results show that a higher resistance on the LPA causes the greater pressure loss for the TECPC under study, while the minimum pressure loss can be achieved balancing the pulmonary resistances, subsequently obtaining a balanced flow repartition towards the lungs.     

双向双侧格林手术的数值研究

目的利用数值模拟方法预测左上腔静脉与肺动脉的连接位置改变对双向双侧格林(BBDG)手术的影响。方法首先,根据拥有左上腔静脉的单心室心脏缺陷综合征病人的医学图像重建出三维几何模型。其次,基于力反馈器创建其他数值模拟所需的模型,并利用有限体积法进行流体力学的数值模拟。最后,分析与评估获得的血流动力学参数。结果血液在左、右上腔静脉与肺主动脉中进行再循环。左上腔静脉到右上腔静脉之间的距离由右上腔静脉直径的2倍逐渐变化到右上腔静脉直径的3.5倍,发现当距离为3倍直径时,能量损失最少,而距离为2倍时,能量损失最大。血液分流比(左肺动脉流量/右肺动脉流量)的计算结果范围为0.65～1.11。结论在BBDG手术的治疗中,左、右上腔静脉之间距离太近会导致不适宜的分流比以及消耗更多的能量。本研究结果对于评价伴随有左上腔静脉的单心室心脏缺陷综合征的治疗手术是非常有意义的。     

In vivo hemodynamic responses to thoracic artificial lung attachment

A thoracic artificial lung (TAL) was attached to the pulmonary circulation in a porcine model. Proximal main pulmonary artery (PA) blood flow, in part or whole, was diverted to the TAL, and TAL outlet blood flow was split between the distal main PA and left atrium (LA). The right ventricle (RV) drove blood flow through the combined TAL/natural lung (NL) pulmonary system. Selective banding placed the TAL in parallel with the NLs, in series with the NLs, or in an intermediary hybrid configuration. Parallel TAL attachment lowered pulmonary system impedance, raised cardiac output (CO), and provided the greatest TAL blood flow rate, but reduced the NL blood flow rate which is important for pulmonary embolic clearance and metabolic blood processing. Hybrid or series TAL attachment raised pulmonary system impedance, lowered CO, increased RV oxygen consumption, and reduced RV oxygen supply. Redesign of the PA anastomoses, TAL inlet graft, and TAL entrance and exit would significantly improve hemodynamics and RV function with TAL attachment. Mean LA pressure increased throughout the experiment, which may indicate damage caused by graft attachment to the LA. Pulmonary resistance-flow rate curves may enable clinical prediction of tolerable TAL attachment configurations.     

Acute effects of pulmonary artery banding in sheep on right ventricle pressure-volume relations: relevance to the arterial switch operation.

The first stage of the two-stage arterial switch operation (ASO) for transposition of the great arteries (TGA) is associated with depressed ventricular function and an unstable immediate post-operative course. It is unclear if this is because of the acute increase in afterload of the thin-walled, low-pressure ventricle by pulmonary artery banding (PAB). To determine the acute effects of afterload increase on the contractile function of thin-walled ventricles, we studied the right ventricular pressure-volume relations of seven sheep before and 30 min after PAB using combined pressure-conductance catheters during inflow reduction. Load independent indices of systolic and diastolic performance were derived from these relations. Pulmonary artery banding increased the mean ratio between right and left ventricular systolic pressure from 0.34 +/- 0.05 to 0.64 +/- 0.10, P < 0.05 (mean +/- SD). There were no significant changes in heart rate and end-systolic volume after banding although there was an incremental trend in the end-diastolic volume and stroke volume. Right ventricular output (530 +/- 163-713 +/- 295 mL min (-1), P < 0.05), slope of the end-systolic pressure-volume relation (ESPVR) (3.7 +/- 2.8-10.0 +/- 4.8 mmHg mL (-1), P < 0.05) and slope of the pre-load recruitable stroke work (PRSW) relation (9.6 +/- 1.8-15.0 +/- 3.1 mmHg, P < 0.05) were significantly increased indicating improved contractile state after banding. The diastolic function curve was unchanged after banding although the right ventricle (RV) was operating at a larger end-diastolic volume. Hence, the RV of sheep responded to acute pressure overload by demonstrating enhanced contractility and evidence of the Frank-Starling mechanism without associated change in right ventricular diastolic performance.