心内组织多普勒超声显像标测心脏传导系统心肌兴奋(摘要)

目的 应用具有高分辨率心内超声组织多普勒显像技术标测心脏传导系统电兴奋诱导的心肌收缩,探讨其临床应用可行性和范围。 方法 5条狗开胸模型。通过11F血管鞘从右颈内静脉或股静脉插入10F心内超声导管分别置留于上腔静脉、右心房和右心室腔内。刺激电极随机置入心室壁内(心外膜下心肌和心内膜下心肌)。首先,采用二维灰阶超声观察窦房结、右心房壁、房室交界区、室间隔和左心室游离壁的解剖结构。其次,采用心内超声组织多普勒显像技术获取窦性心律上述各点的心肌速度和加速度二维、M型和脉冲频谱图像。再次,在心室起搏时记录心肌速度和加速度起始和分布,其心肌机械兴奋的空间部位和时相分别与刺激电极的部位与电刺激时相比较。     

组织多普勒显像定量分析窦房结功能

目的 评价心动周期中窦房结内机械运动参数（如：加速度）的时空变化规律及其与心脏电兴奋之间的相关性。方法 制作5只犬开胸动物模型,用心内超声探头采集时间顺序窦房结组织多普勒图像,利用计算机图像处理与分析方法获取时间顺序窦房结内组织的加速度定量数据。结果 得到了窦房结兴奋过程中窦房结内心肌运动的加速度－时间曲线,其舒张末期初始加速度的起始时相与同步心电图特定时机（如：P波起始点）对照,二者具有很好的时相相关性。结论 由窦房结内组织多普勒顺序图像中得到的心肌兴奋的加速度－时间曲线及其与心电图时相之间的相关性,提示心内组织多普勒显像技术可用于定量评价窦房结内心肌机械兴奋及其与心肌电兴奋之间的关系。     

心腔内组织速度图模式对心肌异位兴奋显像的实验研究

目的：评价心腔内组织多普勒速度图（TVI）模式对心肌异常激动及传导的显像功能。方法：10只开胸犬心室起搏，采用心腔内TVI模式，观察室性心律时室壁的速度分布变化。结果：对照心电图，心腔内TVI模式可检测到心室起搏时室壁最早出现的收缩运动，该区域与起搏电极放置部位相一致；并可在随后的心室起搏波过程内观察到该处收缩运动的扩散。结论：心腔内TVI技术能够实时显示与心肌电活动密切相关的机械运动，从而使观察心肌兴奋的发生和传导成为可能。     

心腔内组织多普勒对心肌兴奋的发生及传导显像的实验研究

目的初步评价心腔内组织多普勒成像（TDI）对心肌激动及传导的显像功能。方法10只开胸犬心室起搏前后，采用心腔内TDI加速度图模式，分别观察窦性心律和室性心律时房、室间隔与室壁的加速度分布变化。结果心腔内TDI加速度图模式可检测到窦性心律时房、室间隔的加速度增高区域的分布与下移过程；心室起搏时检测到的最早的高加速度区与起搏电极放置部位相一致。结论心腔内TDI技术能够实时显示与心肌电活动密切相关的机械运动，从而使观察心肌兴奋的发生和传导成为可能。     

心脏起搏动态三维心室超声组织多普勒速度与灰阶解剖融合成像的初步研究

目的建立动态三维组织多普勒超声显像及其与动态三维灰阶解剖超声图像融合成像的方法,并揭示窦性心律和心脏起搏状态下心室壁心肌电机械兴奋起始点及其传播类型的准确时空变化过程.方法采用经胸和经食道超声对13例心脏起搏患者和2例窦性心律患者进行检查,通过旋转扫描以3°间隔分别获取窦性心律、DDD起搏和VVI起搏状态下时间顺序的心室二维灰阶、组织多普勒速度图像;采用Four sightTM技术对所采集的超声灰阶和多普勒频移信号三维数据行匹配、储存、传输和插值滤波,并最终完成可视化的心室动态三维组织多普勒速度显像、动态三维灰阶解剖结构显像及其融合成像.结果建立的可视化动态三维组织多普勒和灰阶解剖融合成像方式能准确显示窦性心律、DDD起搏和VVI起搏状态下心室壁心肌整体和局部心肌电机械兴奋所导致的较高速度起始点,及其传播的时空变化过程;动态三维组织多普勒和灰阶解剖融合显像图像可以任意角度旋转和切割以显示心室壁不同层面的由心肌电机械兴奋导致的心肌运动速度变化及其分布;同时动态三维灰阶解剖成像清晰显示了作为起搏位置参考点的起搏电极位置、形态和走行方向,该起搏电极位置与动态三维组织多普勒和灰阶解剖融合成像的速度起始点位置一致;窦性心律和心脏起搏状态下心室壁心肌电机械兴奋起始点及其传播类型的时空变化类型和过程完全不同;该技术同时能够实现图像的在线距离、面积和容积测量.结论建立了稳定可靠的动态三维心脏组织多普勒显像、动态三维灰阶解剖显像及其融合成像方法;所建立的动态三维图像具有较高的时空分辨率,能够应用于准确显示窦性心律和心脏起搏状态下心室壁心肌电机械兴奋起始点及其传播类型的时空变化过程,将有助于更为精确的心脏电生理介入诊断和治疗.     

识别普通心律失常——心电图简介

心脏传导周期心脏的固有的规律性收缩的能力似乎是由起源于窦房结的电刺激所引起的,窦房结位于右心房后壁。这是心脏的正常起搏点,它由自律神经系统的兴奋所支配。激动沿着穿过左、右心房的传导通道到达房室结引起心房收缩将血液排到心室。激动继续经心房通过希氏束,分别由左、右束支到达左、右心室,位于每侧束支末端的浦倾野氏纤维,将激动传遍左、右心室使之收缩并将血排到体内。     

多普勒组织显像定位心室除极起始点的准确性

为了确定多普勒组织显像（ＤＴＩ）评价心室除极起始点的准确性，使用了两种起搏方法。２例有阵发性室上性心动过速的患者和２０例安置ＶＶＩ永久起搏器的患者，分别被施以食道调搏和心室起搏术。在左心室和右心室各切面显示清楚时，重叠多普勒组织显像加速度模式两维图像。当食道调搏电极或心室起搏电极释放刺激脉冲电流时，观察心室壁加速度改变的起始位置。结果发现：心室壁加速度改变起始点位置与食道调搏和心室起搏电极位置的吻合率在左右心室分别均为１００％。说明多普勒组织显像加速度模式能准确显示心室壁加速度改变的起始位置，从而间接反映心室壁的除极起始点和传导顺序。     

超声心动图对心脏同步化运动的评价及在CRT中的作用

正常心脏具有起搏、兴奋和传导功能,心肌的兴奋通过电一机械偶联引起心肌收缩。心肌是功能性合胞体,又由于其特殊传导系统的快速传导,兴奋一经引起,可使心房或心室肌细胞在近于同步的情况下兴奋和收缩。心脏有节律、协调地同步收缩和舒张是实现其泵血功能的必要条件。当心肌存在病变时会出现电活动和,或机械活动不同步,使心室泵血功能减低。心肌的兴奋和传导性是电活动,电活动不同步,如心房纤颤、房室不同步、宽的QRS波致心室不同步,主要通过心电图检出。     

心肌酶、超声心动图、心肌核素显像在评价胸部放疗患者心脏损害中的应用

目的探讨心肌酶、超声心动图、心肌核素显像在胸部放疗心肌损伤检测中的价值。方法选择30例放疗治疗肿瘤患者,分别于放疗前和放疗后行心电图、心肌酶、超声心动图、99mTc-MIBI核素心肌显像检查。结果治疗前后血清乳酸脱氢酶(LDH)、谷草转氨酶(AST)变化不明显,P>0.05,磷酸激酶(CK)磷酸激酶同工酶(CK-MB)变化相对敏感P<0.05;治疗前后心电图变化表明,以窦性心动过速、ST-T改变、心房颤动居多,又以ST-T改变最为明显。放疗前后左心室射血分数,短轴缩短率、室间隔室壁增厚率、左心室后壁室壁增厚率差异无统计意义(P>0.05),左心室舒张功能指标比率有统计学意义(P<0.05)。心肌核素显像(MPI)和心肌酶、心电图阳性例数和敏感性接近,均高于心脏超声的敏感性,但差异无统计学意义。结论评价放射线引起或诱发的心肌损伤,早期以心肌酶谱改变,心电图、核素心肌显像较有价值,晚期心脏超声较有价值。     

彩色多普勒组织成像评价心壁运动和激动顺序的实验研究

本文采用超声心动图彩色多普勒组织成像（ＤＴＩ）新技术对６条开胸犬正常心脏运动进行研究。通过用速度、加速度显示方式分析心脏各标准切面的室壁运动发现：（１）ＤＴＩ能对心脏各室壁节段的运动作出正确的彩色编码，心脏各节段及心肌各层运动速度并非一致，左室后壁的运动速度高于前壁及前间隔的运动速度，室间隔左室面高于右室面，以左室后壁心内膜面运动速度最高，反映了心肌各节段的收缩能力的不一致性，这种不一致性也可能与心肌纤维特殊的排列方式有关；而且认为在分析室壁运动时，尤其是定量分析时，应考虑到室壁运动的这种差异；（２）从加速度显示方式分析，能够直视心肌传导上的差异，再现心肌激动的顺序，与心肌传导的电生理研究结果基本相符，为今后评价心脏传导系统的疾病提供客观的依据。     

Subendocardial motion in hypertrophic cardiomyopathy: assessment from long- and short-axis views by pulsed tissue Doppler imaging.

BACKGROUND: Tissue Doppler imaging (TDI) is a recently developed technique that allows the instantaneous measurement of intrinsic regional myocardial motion velocity. Pulsed TDI is capable of separately assessing left ventricular (LV) regional motion velocity caused by circumferential and longitudinal fiber contraction. This particular feature of function is still controversial in patients with hypertrophic cardiomyopathy (HC). METHODS: To better characterize intrinsic circumferential and longitudinal LV systolic myocardial function in HC, we used pulsed TDI to measure short- and long-axis LV motion velocities, respectively. The subendocardial motion velocity patterns at the middle of the LV posterior wall (PW) and ventricular septum (IVS) in LV parasternal and apical long-axis views were recorded by pulsed TDI in 19 patients with nonobstructive HC and in 21 normal controls (NC). RESULTS: Peak short- and long-axis systolic subendocardial velocities in both the LV PW and IVS were significantly smaller in the HC group than in the NC group, and the time to peak velocity was significantly delayed. Furthermore, peak PW systolic velocity was significantly greater along the long axis than along the short axis in the NC group (8.8 +/- 1.5 cm/s vs 8.2 +/- 1.4 cm/s, P <.05), whereas the opposite was observed in the HC group (6.1 +/- 1.2 cm/s vs 7.5 +/- 1.0 cm/s, P <.0001). No significant differences were found in either group between the long- and short-axis IVS velocities (HC: 5.9 +/- 1.4 cm/s vs 5.5 +/- 1.3 cm/s; NC: 7.8 +/- 1.3 cm/s vs 7.9 +/- 1.6 cm/s). CONCLUSIONS: By using the capability of pulsed TDI for the evaluation of intrinsic myocardial velocity instantaneously in a specific region and direction, we found impairment of LV myocardial systolic function in patients with HC not only in the hypertrophied IVS but also in the nonhypertrophied LV PW. We also found a greater decrease in LV PW velocities along the long axis than the short axis, suggesting greater impairment of long-axis contraction in patients with HC. Because our HC patients did not appear to have excessive intracavitary pressure, these results suggest that the relatively normal-appearing PW is directly affected by the HC pathologic process.     

Imaging techniques in cardiac electrophysiology

Modern cardiac electrophysiology procedures include catheter-based arrhythmia ablation and transvenous device implantation, which are highly dependent on accurate, real-time cardiac imaging. With the realization that anatomic structures are critical to successful electrophysiologic procedures, accurately defining a patient's cardiac anatomy has become more important. Fluoroscopy allows for 2D imaging of cardiac structures in real-time, and is used to guide catheter and lead placement, but does not allow for visualization of soft tissues. Intracardiac echocardiography allows for both direct visualization of anatomic structures within the heart and real-time imaging during catheter placement. Despite advances in intracardiac echocardiography catheters that allow for larger windows, the ability to accurately delineate anatomic structures depends on the patient's anatomy and operator experience. Neither of these techniques allows for electrical mapping of the heart; however, both anatomic and electrical intracardiac mapping can be achieved with advanced mapping systems. These systems allow for real-time catheter localization, help elucidate cardiac anatomy, evaluate electrical activation during arrhythmias and guide catheter placement for deliverance of radiofrequency current. More recently, 3D cardiac computed tomography has been used to accurately define intracardiac anatomy; however, catheter tracking and electrical mapping cannot be performed by computed tomography. Mapping systems are now being merged with computed tomography images to produce an accurate anatomic and electrical map of the heart to guide catheter ablations. The objective of this paper is to describe the current imaging and mapping techniques used in electrophysiologic procedures.     

Tissue Doppler imaging of the fetal heart.

OBJECTIVES: The objectives of this study were: (i) to assess the feasibility of a tissue Doppler imaging (TDI) evaluation in the fetus, (ii) to identify color-TDI patterns consistent with the various phases of the cardiac cycle; and (iii) to assess myocardial velocities and the myocardial velocity gradient. METHODS: Eighty-nine normal fetuses between the 17th and the 37th week of gestation were studied. Color-TDI was superimposed on an apical four-chamber view of the fetal heart and three cardiac cycles captured in cine-loop format. By reviewing the cine-loop strip, color patterns consistent with the various phases of the cardiac cycle were identified. The procedure was then repeated with a transverse four-chamber view. On each frame corresponding to mid-systole, early and late diastole, myocardial velocities were calculated at the subepicardial and subendocardial layer and regressed against gestational age. Statistics included correlation and regression analysis, calculation of the 95% confidence intervals and of the Cronbach's alpha reliability coefficient for repeated observations. RESULTS: TDI examination is acceptably reproducible in the fetus. We were able to identify color-TDI patterns depicting the systolic contraction wave, ventricular relaxation and atrial contraction. Statistical evaluation demonstrated that: all variables (systolic right and left subendocardial and subepicardial velocities, early diastolic right and left subendocardial and subepicardial velocities, end diastolic right and left subendocardial velocities, right subepicardial velocities) except end-diastolic right and left subepicardial velocities, showed a positive correlation with advancing gestational age; subendocardial velocities were higher than subepicardial ones throughout the cardiac cycle in both ventricles; systolic myocardial velocities were higher in the left ventricle whereas early diastolic velocities were higher in the right ventricle; and the ratio between early and late diastolic subendocardial velocities (EM/AM) was constantly < 1 and did not change with advancing gestational age. CONCLUSIONS: TDI evaluation of the fetal heart is feasible and reproducible. Color-TDI is able to identify the various phases of the cardiac cycle. Quantitative evaluation of myocardial velocities has shown also in the fetus the existence of the myocardial velocity gradient found in postnatal life.     

Imaging techniques in cardiac electrophysiology

Modern cardiac electrophysiology procedures include catheter-based arrhythmia ablation and transvenous device implantation, which are highly dependent on accurate, real-time cardiac imaging. With the realization that anatomic structures are critical to successful electrophysiologic procedures, accurately defining a patient’s cardiac anatomy has become more important. Fluoroscopy allows for 2D imaging of cardiac structures in real-time, and is used to guide catheter and lead placement, but does not allow for visualization of soft tissues. Intracardiac echocardiography allows for both direct visualization of anatomic structures within the heart and real-time imaging during catheter placement. Despite advances in intracardiac echocardiography catheters that allow for larger windows, the ability to accurately delineate anatomic structures depends on the patient’s anatomy and operator experience. Neither of these techniques allows for electrical mapping of the heart; however, both anatomic and electrical intracardiac mapping can be achieved with advanced mapping systems. These systems allow for real-time catheter localization, help elucidate cardiac anatomy, evaluate electrical activation during arrhythmias and guide catheter placement for deliverance of radiofrequency current. More recently, 3D cardiac computed tomography has been used to accurately define intracardiac anatomy; however, catheter tracking and electrical mapping cannot be performed by computed tomography. Mapping systems are now being merged with computed tomography images to produce an accurate anatomic and electrical map of the heart to guide catheter ablations. The objective of this paper is to describe the current imaging and mapping techniques used in electrophysiologic procedures.     

Myocardial Stretch Post-atrial Contraction in Healthy Volunteers and Hypertrophic Cardiomyopathy Patients

In cardiac high-frame-rate color tissue Doppler imaging (TDI), a wave-like pattern travels over the interventricular septum (IVS) after atrial contraction. The propagation velocity of this myocardial stretch post-atrial contraction (MSPa) was proposed as a measure of left ventricular stiffness. The aim of our study was to investigate the MSPa in patients with hypertrophic cardiomyopathy (HCM) compared with healthy volunteers. Forty-two healthy volunteers and 33 HCM patients underwent high-frame-rate (>500 Hz) TDI apical echocardiography. MSPa was visible in TDI, M-mode and speckle tracking. When assuming a wave propagating with constant velocity, MSPa in healthy volunteers (1.6 ± 0.3 m/s) did not differ from that in HCM patients (1.8 ± 0.8 m/s, p = 0.14). Yet, in 42% of patients with HCM, the MSPa had a non-constant velocity over the wall: in the basal IVS, the velocity was lower (1.4 ± 0.5 m/s), and in the mid-IVS, much higher (6.1 ± 3.4 m/s, p < 0.0001), and this effect was related to the septal thickness. The reason is hypothesized to be the reaching of maximal longitudinal myocardial distension in HCM patients.     

心腔内超声评价希氏束起搏心脏血流动力学和解剖结构重构

目的采用单一的心腔内超声心动图和组织多普勒显像技术检测和评价直接希氏束起搏诱导的心室激动顺序、心脏解剖结构和血流动力学重构.方法六只急性闭胸直接希氏束起搏狗模型.采用美国Medtronic导向引导鞘管和主动螺旋电极,在心腔内超声心动图和组织多普勒显像技术引导下将起搏电极分别置放于希氏束(n=6)和右室心尖(n=6).所有部位的起搏频率均控制为120次/min.采用二维灰阶、血流频谱多普勒和组织多普勒技术,分别测量和计算心脏不同部位起搏时心室各房室和相连大血管解剖结构内径和容量、心肌的激动顺序和相关血流动力学参数,并进行不同起搏状态上述测量参数的配对统计比较.结果希氏束起搏状态下,左心室壁内心肌的激动顺序、心脏主要解剖结构和血流动力学参数与窦性心律状态下相同参数比较无显著性差异;与右心室心尖起搏状态下相同参数比较有显著性差异.结论单一的心腔内超声和组织多普勒技术能够有效地量化评价心脏起搏状态下的心脏解剖结构和血流动力学改变.与右心室心尖部起搏相比较,希氏束起搏能够明显地改善心脏解剖和血流动力学重构.     

定量组织多普勒速度图评价不同孕周正常胎儿心脏室壁运动

目的探讨超声定量组织多普勒速度成像技术(QTVI)评价正常胎儿心室壁运动的临床价值。方法运用彩色组织多普勒速度成像图对100例孕18~40周正常胎儿心脏进行检测,在心尖四腔图切面,对左右心室壁及室间隔的9个观察点的速度曲线进行分析,测量收缩期运动速度Vs,舒张早期运动速度Ve,舒张晚期运动速度Va,并进行分析和统计学处理。结果正常胎儿心室壁运动速度的变化趋势为基底部>中部>心尖部,左心室、间隔收缩期运动速度相近,右心室收缩期运动速度略高于左心室及间隔,在舒张晚期间隔与左心室的速度相近,但低于右心室。室壁运动速度随孕周增加亦增加。结论组织多普勒速度成像技术用于评价胎儿室壁运动是可行的,它安全、准确、可靠。