心肌长轴运动位移参数对心梗患者左室局域功能的影响

目的 :探讨心梗病人左心室不同节段心肌沿长轴运动的位移特征及其临床意义 ,寻求评价局域心肌功能的合理量化指标。方法 :利用定量组织速度成像中的速度时间积分曲线对 15例心肌梗死病人 (MI组 )和 16例正常人 (正常对照组 )左室各相关节段长轴方向的位移进行测量分析。结果 :MI组病人收缩期位移峰值明显降低 ,收缩期位移上升速率减低 ,等容收缩期位移峰值减低 ,部分节段出现位移方向的改变 ,等容舒张期梗死节段及对侧壁出现第二次位移峰值。结论 :( 1)心肌缺血导致局域心肌沿长轴方向的位移异常 ;( 2 )心肌沿长轴方向的位移特征可直接反映心肌的运动特征 ,可作为反映左室心肌长轴功能的量化指标。     

应用二维斑点追踪技术评价中老年高钾血症患者左心室应变变化

目的通过二维斑点追踪技术对中老年高钾血症患者左心室心肌应变能力的检测,评价临床治疗效果。方法选择内蒙古自治区人民医院慢性肾衰竭致高钾血症中老年患者24例,其中男性16例,女性8例;年龄55~79岁,平均年龄68.6岁。超声诊断心肌损害性改变。临床对症治疗前后,应用二维斑点追踪技术定量分析在治疗前后的左心室长轴纵向应变(LS)、径向应变(RS)、圆周应变(CS),并与血钾、血肌酐进行相关性分析。结果超声表现为左心室壁弥漫性增厚17例(70.83%),左心室壁回声增强22例(91.67%),二尖瓣瓣器回声增强或见粗大光点11例(45.83%),左心室内径增大1例(4.17%),心包积液21例(87.50%)。入院治愈后,22例恢复正常,1例死亡,1例进展为扩张型心肌病。左心室长轴RS、LS、CS在治疗前后有显著提高(RS:8.97±1.27 vs 11.92±1.41;LS:14.96±2.41 vs 19.47±2.74;CS:9.68±1.59 vs 13.52±1.43),差异有统计学意义(P0.05)。患者血钾、血肌酐的血样标本水平变化与心肌应变改善程度呈正相关(r=0.887,P0.01)。结论二维斑点追踪技术在中老年高钾血症患者心肌应变的诊断及治疗随访中具有一定的应用价值。     

斑点追踪成像技术评价心脏淀粉样变性患者左心室整体及局部纵向收缩功能

目的应用二维斑点追踪成像技术(2D-STI)检测心脏淀粉样变性(CA)患者左心室长轴收缩功能的变化,探讨其临床应用价值。方法选择确诊的CA患者20例为CA组,其中男性13例,女性7例,平均年龄54.80岁。选取年龄和性别匹配的健康志愿者30例为正常对照组,其中男性18例,女性12例,平均年龄54.85岁。分别采集心尖四腔心切面、心尖两腔心切面和心尖左心室长轴切面的二维动态图像,应用2D-STI获取左心室18个心肌节段收缩期纵向峰值应变,计算左心室基底段、中间段、心尖段的平均纵向峰值应变及左心室整体纵向峰值应变。结果所有受检者左心室心尖段到基底段纵向峰值应变逐渐减低。CA组左心室各节段收缩期纵向应变峰值均显著低于正常对照组,差异均有显著统计学意义(P0.001)。CA组左心室基底段、中间段、心尖段平均纵向峰值应变及左心室整体纵向峰值应变均显著低于正常对照组,差异均有显著统计学意义(P0.001)。结论 CA患者左心室整体及局部纵向收缩功能均减低,2D-STI能够从长轴纵向应变的角度更敏感、准确评估CA患者收缩功能的变化,适合临床广泛开展。     

辛伐他汀对慢性心力衰竭大鼠左室重构的影响

目的:探讨辛伐他汀对慢性心力衰竭大鼠心肌纤维化及心肌超微结构的影响.方法:利用腹主动脉缩窄法建立雄性Wistar大鼠心衰模型,随机分为心衰假手术组、模型组和辛伐他汀组.观察各组大鼠左心室肌质量指数(LVMI),H-E和Massion染色观察左心室心肌形态结构变化,电镜下观察左心室心肌的超微结构,SP免疫组织化学检测左心室心肌中结缔组织生长因子(CTGF)表达情况,RT-PCR测定各组大鼠左心室心肌CTGF mRNA水平.结果:与假手术组相比,模型组LVIM、心肌胶原容积分数(CVF)、CTGF蛋白及mRNA表达明显上升.与模型组相比,辛伐他汀组LVMI、CVF、CTGF蛋白及mRNA表达均明显下降.光镜和电镜结果显示,辛伐他汀组心肌损害程度较模型组明显减轻.结论:辛伐他汀能显著改善慢性心力衰竭大鼠心肌肥厚,逆转心肌纤维化和超微结构的异常方面,其机制可能与下调CTGF的表达有关.     

基于核素心肌影像数据心室模型的研究

介绍了一种单光子发射型计算机断层显像(SPECT)、正电子发射计算机断层显像(PET)心肌核素断层显像左心室提取及优化算法研究,选用"半球加圆柱"模型,提出应用左心室心肌最大放射性计数值采样。采用多参数Powell最优化方法进行模型参数的拟合,并将拟合结果同医师诊断结果进行对比,高度相关评分的一致率为83.2%。     

基于BP神经网络的左心室心肌组织参数反演方法的研究

因为蕴含着心肌组织特性变化等病理特征,人体左心室的变形和动力学特性已成为心脏疾病临床诊断的重要依据.本研究基于BP神经网络方法,通过对左心室临床诊断数据的反演,开展左心室心肌组织参数识别研究.首先,使用Matlab语言编写图像识别程序提取人体左心室CT影像中内外膜位置点,在SolidWorks软件中建立左心室的真实几何...     

磁共振T2-Mapping成像对呼吸衰竭患者心肌损害的临床应用价值

目的　探讨磁共振T2-Mapping成像对呼吸衰竭患者心肌损害的临床应用价值。 方法　选择2016年8月到2018年12月本院内科诊治的呼吸衰竭患者122例作为研究组，同期无呼吸衰竭病史的78例内科患者作为对照组。所有患者给予超声心动图与磁共振T2-Mapping成像，记录成像参数并进行相关性分析。 结果　衰竭组的DT值高于对照组（P<0.05）；两组E/A与Pulmonary S/D ratio值对比无统计学差异（P>0.05）；两组心磁共振图像质量Ⅲ级与Ⅳ级分别占比80.3%、9.8%和76.9%和12.8%，对比均无统计学差异（P>0.05）；衰竭组短轴位与长轴位的左心室前壁、后壁T2值均大于对照组（P<0.05）；衰竭组患者中，Pearson相关性分析显示短轴位、长轴位的左室前壁、后壁T2值与DT值均呈正相关性（P<0.05）。 结论　磁共振T2-Mapping成像能反映呼吸衰竭患者心肌损害情况，通过定量评估心肌T2值可有效评估左心室心肌功能，对指导临床治疗方案的抉择和预后判断具有重要作用。     

磁共振T2-Mapping成像对呼吸衰竭患者心肌损害的临床应用价值

目的　探讨磁共振T2-Mapping成像对呼吸衰竭患者心肌损害的临床应用价值。 方法　选择2016年8月到2018年12月本院内科诊治的呼吸衰竭患者122例作为研究组,同期无呼吸衰竭病史的78例内科患者作为对照组。所有患者给予超声心动图与磁共振T2-Mapping成像,记录成像参数并进行相关性分析。 结果　衰竭组的DT值高于对照组（P<0.05）;两组E/A与Pulmonary S/D ratio值对比无统计学差异（P>0.05）;两组心磁共振图像质量Ⅲ级与Ⅳ级分别占比80.3%、9.8%和76.9%和12.8%,对比均无统计学差异（P>0.05）;衰竭组短轴位与长轴位的左心室前壁、后壁T2值均大于对照组（P<0.05）;衰竭组患者中,Pearson相关性分析显示短轴位、长轴位的左室前壁、后壁T2值与DT值均呈正相关性（P<0.05）。 结论　磁共振T2-Mapping成像能反映呼吸衰竭患者心肌损害情况,通过定量评估心肌T2值可有效评估左心室心肌功能,对指导临床治疗方案的抉择和预后判断具有重要作用。     

左心室三维应力与左心室收缩功能的相关性研究

目的研究左心室三维应力与反映左心室收缩功能的生物力学指标——最大心肌劲度(maxEav)的相关性,以获得反映左心室收缩功能的简单且实用的生物力学指标。方法选取34例健康人为研究对象,其中男性19例,女性15例;年龄34～75岁,平均年龄49.2岁。应用超声心动图测定心脏左心室收缩末期内径和后壁厚度及射血分数;左心室收缩末期中壁长短径、室壁厚度;联合袖带肱动脉血压值计算左心室收缩末期压力。应用上述各测值计算maxEav及左心室收缩末期径线、圆周、长轴应力(σr、σθ、σm),进行相关性统计学分析。结果σr=(-62.55±0.53)N/cm2;σθ=(27.81±1.36)N/cm2;σm=(62.58±2.88)N/cm2;maxEav=(226.52±9.36)N/cm2;LVEF=(63.13±1.01)%。maxEav与σr无相关性(r=0.067,P>0.05);maxEav与σθ有极显著负相关性(r=-0.510,P<0.01);maxEav与σm有极显著正相关性(r=0.563,P<0.01)。LVEF与三向应力无相关性(P>0.05)。结论应用左心室收缩末期圆周及长轴应力两项生物力学指标评价左心室收缩功能较为简便实用且准确。     

施行人工辅助心脏时心肌耗氧量的研究

近年来许多人进行了各种循环辅助装置对于心肌耗氧量影响的研究,以此推断心肌的能量代谢。Dennis等在施行滚轮式泵左心房一主动脉傍路时,心肌耗氧量减少33％;Pierce等报告左心房傍路,心肌耗氧量减少22％。左心室傍路减少47％;Miller报告左心房傍路减少36％,左心室傍路减少59.8％,从而得出左心室傍路效果最好的结论。Pennock等报告,左心室傍路率在90-99％时,心肌耗氧量减少29.6％,而施行完全傍路时则减少49.3％。Watanabe等报告,施行左心室傍路,心肌耗氧量减少67％;而Wakabayashi应用搏动性泵,施行左心房和左心室的同时傍路,正常心脏的心肌耗氧量并未减少,他认为此乃傍路使心脏损伤所致。佐     

A simulation of three-dimensional systolic flow dynamics in a spherical ventricle: Effects of abnormal wall motion

Alterations in left ventricle (LV) wall motion induced by ischemia will affect flow dynamics, and these altered flow fields can be used to evaluate LV pumping efficiency. LV chamber flow fields were obtained in this study by solving the discretized three-dimensional Navier-Stokes equations for viscous, incompressible unsteady flow by using the finite analytic method. Several cases of abnormal wall motion (AWM) were simulated by a manipulation of the boundary conditions to produce regions of hypokinesis, akinesis, and dyskinesis. These solutions were used to determine the central ejection region (CER), defined as the region of flow domain in which the obtained velocity field vectors are aligned ±3° from the LV long axis. A CER coefficient was computed from information on the location and orientation of the CER within the LV cavity. Contraction of the spherical ventricle produced a vector field that was symmetric with respect to the long axis. For the simulations of AWM, an asymmetrical flow pattern developed, became more pronounced with increasing severity of AWM, and resulted in a shorter CER that shifted toward the ischemic region. The CER coefficients decreased monotonically with increased severity in AWM from 0.948 in the normal case to a low of 0.164 for the most severe case of AWM. The CER coefficient quantitatively displayed the sensitivity of the flow patterns to even moderate degrees of hypokinesis. In addition, visualization of the three-dimensional flow field reinforced the necessity of three-dimensional simulations to capture aspects of the flow that existing methods of two-dimensional flow imaging that use ultrasound may miss.     

Right ventricular volume measurement using the conductance catheter method: validation in excised porcine hearts

The conductance catheter method for measuring right ventricular (RV) volume changes was assessed in seven excised porcine hearts. A 5-FG conductance catheter was placed within a latex balloon and positioned in the RV cavity of seven freshly excised porcine hearts. Conductance was recorded while saline was withdrawn from the intraventricular balloon in 2 ml decrements. Linear regression analysis of measured conductance versus reference volumes was computed. The effect of left ventricular (LV) filling and catheter length on conductance derived RV volume was also determined. Conductance derived volumes were highly correlated with reference volumes [R2 0.976, standard deviation (SD) 0.035]. The mean gradient of regression was 0.97 (SD 0.10), and it was not significantly affected by LV volume alterations. However, when we analyzed LV filling, a small but significant increase in the y-intercept was observed (LV empty 3.11 ml, SD 1.71; LV full 4.58, SD 2.39; p = 0.008). Introduction of the catheter through either the tricuspid or pulmonary orifices were both effective in ventricular volume measurement. The effect of mismatch between the catheter length and the RV long axis dimension was evaluated by changing the position of the active sensing electrodes along the catheter body. Conductance measurements, obtained from catheters shorter than the long axis of the RV, still maintained a highly linear correlation with real volume, but regression gradients were significantly reduced (long 0.975, SD 0.087; medium 0.787, SD 0.094; small 0.589, SD 0.091; p < 0.001). These results show that a conductance catheter of appropriate length can accurately measure RV volume, despite the complex shape and geometric changes associated with ventricular filling.     

Topology of Blood Transport in the Human Left Ventricle by Novel Processing of Doppler Echocardiography

Novel processing of Doppler-echocardiography data was used to study blood transport in the left ventricle (LV) of six patients with dilated cardiomyopathy and six healthy volunteers. Bi-directional velocity field maps in the apical long axis of the LV were reconstructed from color-Doppler echocardiography. Resulting velocity field data were used to perform trajectory-based computation of Lagrangian coherent structures (LCS). LCS were shown to reveal the boundaries of blood injected and ejected from the heart over multiple beats. This enabled qualitative and quantitative assessments of blood transport patterns and residence times in the LV. Quantitative assessments of stasis in the LV are reported, as well as characterization of LV vortex formations from E-wave and A-wave filling.     

Longitudinal systolic shortening of the left ventricle: an echocardiographic study in subjects with and without preserved global function.

The atrioventricular (AV) plane displacement was studied by echocardiography in 79 subjects (45 healthy subjects and 34 patients with acute myocardial infarction or chronic congestive heart failure). From apical 4- and 2-chamber views the displacement of the AV plane towards the apex in systole was recorded at 4 sites in the left ventricle (LV) corresponding to the septal, anterior, lateral, and posterior walls and the mean value from the above 4 sites (AV-mean) was calculated. In addition, in healthy subjects, the AV plane displacement at right ventricular free wall was also recorded. The AV-mean correlated well with the echocardiographic ejection fraction determined by biplane area-length method (r = 0.96, P less than 0.001). The correlation was also high when the percentage of the left ventricular shortening along the long axis was used (r = 0.97, P less than 0.001). The correlation between ejection fraction and AV-mean was also good when separate analysis was made for the subjects with preserved ejection fraction (r = 0.86, P less than 0.001) and decreased ejection fraction (r = 0.82, P less than 0.001). The right ventricle had a significantly higher AV plane displacement (P less than 0.001) than the LV. The study also includes determination of the muscular excursions of the septal and posterior walls along the short axis of the left ventricle from the parasternal long axis view. The AV plane displacement of the respective walls was relatively greater (P less than 0.001) compared to concentric contractions. The septal and posterior wall excursions along the short axis correlated poorly with the AV plane displacement of the respective walls (r = 0.55, P less than 0.01 and r = 42, P less than 0.05).     

Novel device to change left ventricular shape for heart failure treatment: device design and implantation procedure

The Myocor Myosplint is designed to decrease left ventricular (LV) wall stress by changing LV shape, thus improving contractile function in dilated hearts. This shape change is accomplished by surgically placing three Myosplints perpendicular to the LV long axis, drawing the LV walls inward, and creating a symmetric, bilobular LV. Specially designed instruments aid in the precise delivery of these devices. The purpose of this study was to test the safety and feasibility of the procedure in dogs. Dilated cardiomyopathy was induced in 40 healthy dogs (26.3+/-1.7 kg) by ventricular pacing at 230 beats per minute for an average of 25+/-4 days. Using epicardial echocardiography, we placed the Myosplints across the LV chamber, avoiding the major coronary arteries, papillary muscles, and mitral valve. Once placed, the Myosplints were used to draw the LV walls inward to a prescribed distance. In all cases, we successfully implanted three Myosplints without using cardiopulmonary bypass. There were no complications related to the device or procedure. Myosplint implantation to change LV shape is safe and repeatable on a beating cardiomyopathic canine heart. Further study of the procedure will be needed in humans.     

Left ventricular diastolic relaxation and pressure-diameter relations during ischaemic left ventricular failure in the dog

The significance of severe ischaemic left ventricular (LV) failure on the LV isovolumic relaxation process and diastolic chamber stiffness has been investigated in nine open-chest pentobarbital-anaesthetized dogs. LV failure was induced by bolus injections of 50 micron microspheres into left coronary vascular bed until LV minor axis diameter had increased about 25% and end-diastolic pressure about 20 mmHg. Such ischaemic LV failure did not shift the relation between diastolic LV pressure and minor axis diameter compared with pressure-diameter curves obtained before induction of failure. Neither inotropic nor chronotropic stimulation evoked such shifts. Assuming exponential pressure decline, LV relaxation was significantly slower during failure, but proceeded in all experimental conditions at rates which indicated complete relaxation in late diastole. Analysis of the pressure decline during LV relaxation demonstrated that this process proceeded faster than assumed by an exponential function both before and during LV failure.     

A 3D Hermite-based multiscale local active contour method with elliptical shape constraints for segmentation of cardiac MR and CT volumes

Analysis of cardiac images is a fundamental task to diagnose heart problems. Left ventricle (LV) is one of the most important heart structures used for cardiac evaluation. In this work, we propose a novel 3D hierarchical multiscale segmentation method based on a local active contour (AC) model and the Hermite transform (HT) for LV analysis in cardiac magnetic resonance (MR) and computed tomography (CT) volumes in short axis view. Features such as directional edges, texture, and intensities are analyzed using the multiscale HT space. A local AC model is configured using the HT coefficients and geometrical constraints. The endocardial and epicardial boundaries are used for evaluation. Segmentation of the endocardium is controlled using elliptical shape constraints. The final endocardial shape is used to define the geometrical constraints for segmentation of the epicardium. We follow the assumption that epicardial and endocardial shapes are similar in volumes with short axis view. An initialization scheme based on a fuzzy C-means algorithm and mathematical morphology was designed. The algorithm performance was evaluated using cardiac MR and CT volumes in short axis view demonstrating the feasibility of the proposed method.     

A model of the mechanics of the left ventricle

The relation between cardiac muscle mechanics and left ventricular (LV) pump function is simulated by a mathematical model. In the following article special attention is paid to the relation between LV pressure and LV volume on the one hand and the transmural distribution of sarcomere length and fiber stress on the other. The LV is simulated by a thick-walled cylinder composed of 8 concentric shells. The myocardial material is assumed to be anisotropic. The orientation and sequential activation of the muscle fibers across the LV wall are considered per shell. Twisting of the base with respect to the apex around the axis of the LV is simulated by rotation of the upper cross-sectional surface of the cylinder with respect to the lower one aroud the axis of the cylinder. The model reveals that twisting of the LV is an important means to equalize transmural differences in sarcomere shortening and end-systolic fiber stress. When torsion is allowed, transmural differences in sarcomere shortening and end-systolic fiber stress are less than 18% and 16%, respectively. When torsion is prevented as in most of the models of LV-mechanics described in literature, these transmural differences increase up to 32% and 42%, respectively. Supported by the Foundation for Medical Research FUNGO, which is subsidized by the Netherlands organization for the Advancement of Pure Research.     

Dynamic cardiomyoplasty decreases myocardial workload as assessed by tissue tagged MRI

The effects of dynamic cardiomyoplasty (CMP) on global and regional left ventricular (LV) function in end-stage heart failure still remain unclear. MRI with tissue-tagging is a novel tool for studying intramyocardial motion and mechanics. To date, no studies have attempted to use MRI to simultaneously study global and regional cardiac function in a model of CMP. In this study, we used MRI with tissue-tagging and a custom designed MR compatible muscle stimulating/pressure monitoring system to assess long axis regional strain and displacement variations, as well as changes in global LV function in a model of dynamic cardiomyoplasty. Three dogs underwent rapid ventricular pacing (RVP; 215 BPM) for 10 weeks; after 4 weeks of RVP, a left posterior CMP was performed. After 1 year of dynamic muscle stimulation, the dogs were imaged in a 1.5 T clinical MR scanner. Unstimulated and muscle stimulated tagged long axis images were acquired. Quantitative 2-D regional image analysis was performed by dividing the hearts into three regions: apical, septal, and lateral. Maximum and minimum principal strains (lambda, and lambda2) and displacement (D) were determined and pooled for each region. MR LV pressure-volume (PV) loops were also generated. Muscle stimulation produced a leftward shift of the PV loops in two of the three dogs, and an increase in the peak LV pressure, while stroke volume remained unchanged. With stimulation, lambda1 decreased significantly (p<0.05) in the lateral region, whereas lambda2 increased significantly (p<0.05) in both the lateral and apical regions, indicating a decrease in strain resulting from stimulation. D only increased significantly (p<0.05) in the apical region. The decrease in strain between unassisted and assisted states indicates the heart is performing less work, while maintaining stroke volume and increasing peak LV pressure. These findings demonstrate that the muscle wrap functions as an active assist, decreasing the workload of the heart, while preserving total pump performance.     

Effect of flow disturbances remaining at the beginning of diastole on intraventricular diastolic flow and colour M-mode Doppler echocardiograms

A computational model of the fluid dynamics of intraventricular flow was used to investigate the importance of the effects of flow disturbances existing within the left ventricle (LV) at the onset of diastole on a diastolic flow field. The simulation started with a quiescent flow state; it continued for a number of cardiac cycles to obtain a cyclically repeatable flow. After the flow became periodic, the initial diastolic flow was not quiescent: flow disturbances, remnants of a systolic flow, were present within the LV. Nevertheless, they faded away during an acceleration phase of diastole and almost ceased by the end of this phase. Consequently, a flow field during a deceleration phase of diastole, characterised by the formation of a vortex ring, was hardly affected by the initial flow disturbances. The propagation velocity of a colour M-mode Doppler echocardiogram obtained by scanning velocity along the LV long axis was 0.58ms⁻¹ in the case where diastolic flow was initially quiescent and 0.56ms⁻¹ in the case where flow disturbances existed at the beginning of diastole. These results indicated that the colour M-mode Doppler echocardiographic technique captures flow dynamics produced purely by ventricular expansion, with little influence from initial diastolic flow disturbances.