Prediction of fluid responsiveness using respiratory variations in left ventricular stroke area by transoesophageal echocardiographic automated border detection in mechanically ventilated patients

Background  

Left ventricular stroke area by transoesophageal echocardiographic automated border detection has been shown to be strongly correlated to left ventricular stroke volume. Respiratory variations in left ventricular stroke volume or its surrogates are good predictors of fluid responsiveness in mechanically ventilated patients. We hypothesised that respiratory variations in left ventricular stroke area (ΔSA) can predict fluid responsiveness.     

Single-beat real-time three-dimensional echocardiographic automated contour detection for quantification of left ventricular volumes and systolic function

To assess the feasibility and accuracy in measuring left ventricular (LV) end-diastolic volume (EDV), end-systolic volume (ESV) and ejection fraction (EF) with Siemens single-beat real-time 3D transthoracic echocardiography. The LV volumes and EF were measured in 3D datasets acquired by six imaging modes (time-1-harmonic (T1H), time-1-fundamental, time-2-harmonic, time-2-fundamental, space-1-harmonic (S1H), and space-1-fundamental) in 41 patients using the automated contouring algorithm and compared with manually corrected 3DE QLAB measurements. The main determinates of the temporal and spatial resolutions of 3D datasets acquired were the fundamental and harmonic modes. Consequently, the S1H mode had the lowest volume rate and highest spatial resolution. Compared with the 3DE QLAB analysis, the S1H mode resulted in the best LV volumes and EF estimates in all patients (0 ± 10 % for EF, ?7 ± 44 ml for EDV, ?7 ± 39 ml for ESV) and in the 10 patients with correct LV contour tracking according to a visual assessment from the multiplanar reconstruction views in all six modes (0 ± 9 % for EF, ?3 ± 23 ml for EDV, ?2 ± 14 ml for ESV). The T1H mode was the best alternative. Overall 28 patients (68 %) could be analysed automatically and satisfyingly with the S1H and T1H modes: 0 ± 8 % (EF), 0 ± 27 ml (EDV) and ?1 ± 16 ml (ESV). The accuracy of the Siemens automated RT-3D algorithm in measuring LV volumes and EF is significantly influenced by the different imaging modes. The S1H mode may be the preferred 3D acquisition mode, supplemented by the T1H mode in enlarged LVs that do not fit in the S1H acquisition sector.     

Improved two-dimensional echocardiographic technique for left ventricular aneurysm detection

In order to determine the sensitivity and reproducibility of a new two-dimensional echocardiographic technique for detecting left ventricular aneurysms, 16 patients suspected of having aneurysms were evaluated prospectively. Left ventricular angiography demonstrated aneurysms in 15 of the 16 patients. All 15 were detected by two-dimensional echocardiography but three were identified only in a view rotated 45 degrees clockwise from the apical four-chamber view. The analysis of 16 wall segments for each patient showed excellent agreement between two observers. Therefore, two-dimensional echocardiography, utilizing four apical views 45 degrees apart, is reliable and reproducible for the detection of left ventricular aneurysms.     

Determination of left ventricular ejection fraction using intravenous contrast and a semiautomated border detection algorithm.

Manual endocardial tracing using Simpson's method (MANUAL SIMP) provides an accurate assessment of left-ventricular ejection fraction (LVEF). We have previously demonstrated in patients who are difficult to image: (1) the incremental accuracy of contrast-enhanced power harmonic imaging and MANUAL SIMP in the calculation of LVEF; and (2) the use of intravenous contrast-combined MANUAL SIMP was the most accurate method of LVEF determination. However, MANUAL SIMP is time-consuming, requires accurate planimetry of the endocardial borders, and is difficult to apply routinely in the clinical situation. The current study prospectively studied the accuracy of intravenous contrast and a semiautomated endocardial border detection algorithm in the determination of LVEF in 51 patients with suboptimal images. LVEF was also calculated using contrast-enhanced power harmonic imaging and MANUAL SIMP. We demonstrated that there was good agreement between LVEF determined using both MANUAL SIMP and semiautomated endocardial border detection, and radionuclide angiography (standard of comparison).     

Impact of on-line endocardial border detection on determination of left ventricular volume and ejection fraction by transthoracic 3-dimensional echocardiography.

This study was performed to determine whether use of on-line automated border detection (ABD) could reduce data analysis time for 3-dimensional echocardiography (3DE) while maintaining accuracy of 3DE in measures of left ventricular (LV) volumes and ejection fraction (EF). The study proceeded in 2 phases. In the validation phase, 20 subjects were examined with the use of 3DE and of monoplane 2-dimensional (2D) ABD. Results were compared with the reference standard of magnetic resonance imaging (MRI). In the test phase, 20 subjects underwent two 3DE studies (once with images optimized for visual border definition and once with images optimized for ABD border tracking) and a conventionally used 2D ABD study. For 3DE, volumes and EF were determined with the use of manually traced borders and ABD. Analysis times were recorded with a digital stopwatch. In the validation phase, 3DE and MRI results correlated very well (r = 0.99) without systematic differences. Comparison of 2D ABD with MRI showed good correlation for LV volumes (r >/= 0.90) and EF (r = 0.85) despite significant underestimation. For the test phase, Acoustic Quantification-optimized 3-dimensional datasets underestimated end-diastolic volume and EF relative to visually optimized 3-dimensional datasets regardless of whether borders were hand-traced or ABD was used. However, correlations ranged from r = 0.96 to r = 0.98 for LV volumes and 0.88 to 0.91 for LV EF and were superior to those for 2D ABD. Data analysis times decreased moderately with the use of ABD, but scan times increased; total study times were unchanged. Use of on-line ABD with 3DE reduces data analysis time and is more accurate than conventional monoplane 2D ABD but results in underestimation of LV volumes and EF. Additional automated postprocessing techniques may be required to obtain accurate measures, consistently using 3DE in conjunction with on-line ABD.     

多普勒超声心动图评价兔左心室舒张功能与充盈压

目的 探讨舒张早期二尖瓣口血流速度(E)、瓣环运动速度(Ea)及E/Ea比值等多普勒指标在评价左心室舒张功能和充盈压方面的价值.方法 采用缩窄腹主动脉法建立18只左心室压力超负荷兔舒张功能不全模型(模型组),应用多普勒超声心动图观察左心大小、室壁厚度、射血分数(EF)及舒张功能指标,心导管测量左心室舒张末压(LVEDP).8只健康兔作为LVEDP对照(对照组).结果 模型组左心房增大、左心室肥厚、LVEDP明显增高(P＜0.01);多普勒指标Ea降低、E/Ea增高(P均＜0.01),而E/A无明显变化;LVEDP与E/Ea呈正相关(r=0.54,P<0.05).结论 在左心室肥厚所致的舒张功能不全动物模型中,Ea降低反映心肌主动松弛功能减退,E/Ea与LVEDP结合,可综合评价左心室舒张功能及充盈压.     

Impact of presence of abnormal wall motion on echocardiographic determination of left ventricular function with automated boundary detection technique: re-evaluation

It is still unclear whether echocardiography with an automated boundary detection technique (ABD) can accurately determine the left ventricular (LV) volume and function particularly in the presence of LV wall asynergy. We intended to re-evaluate the reliability and application of the ABD, which was based on the acoustic quantification technique (Sonos 2500, Hewlett Packard) for the LV volume measurement in patients without or with LV wall asynergy. A total of 80 patients (mean age 56 years) who underwent left ventriculography (LVG) were divided into two groups. The group A consisted of 29 patients with normal LV wall motion and the group B consisted of 51 patients with generalized or regional LV wall motion abnormality. In group A patients, the LV end-diastolic volume (LVEDV) was 96 ± 25 ml by ABD and 112 ± 33 ml by LVG and those of LV end-systolic volume (LVESV) were 44 ± 14 ml by ABD and 48 ± 17 ml by LVG, thus resulting in the underestimation of LV volume by 12% in average. Under these conditions, the LV ejection fraction (LVEF) by ABD, 54 ± 8%, correlated well with that by LVG, 58 ± 7%. Although underestimation of LV volume by 17% in average also occurred in groups B (N.S.), LVEF was found to correlate well with that by LVG; 27 ± 8% vs 30 ± 11% (r=0.87, SEE=3.1%) for 21 patients with the generalized LV asynergy; 39 ± 10% vs 39 ± 12% (r=0.86. SEE=3.3%) for 30 patients with the regional LV asynergy. These results demonstrate the feasibility of the ABD in determining the LVEF, although underestimation can occur in measuring the absolute LV volume in patients with or without LV asynergy.     

Automated endocardial border detection and evaluation of left ventricular function from contrast-enhanced images using modified acoustic quantification.

Automated border detection (ABD) techniques have been used for the quantitative assessment of left ventricular (LV) performance but require adequate visualization of the endocardial border to accurately track the blood-tissue interface. We sought to evaluate whether ABD could be used in conjunction with an infusion of echocardiographic contrast to objectively quantify LV systolic performance. Twenty-one subjects had LV volume and ejection fraction (EF) assessed by hand-tracing and prototype ABD software during contrast infusion. The mean hand-traced EF was 45% +/- 16%. Automatic tracking of contrast-enhanced endocardial borders with prototype ABD software was possible in all subjects. This allowed generation of signal averaged LV volume waveforms, from which quantitative LV ejection fraction was obtained. There were no significant differences in LV volumes or EF between contrast-enhanced acoustic quantification and manually traced borders. This technique has the potential of providing objective quantitation of LV volume and function in patients with technically limited echocardiograms.     

超声心动图二尖瓣环自动追踪技术评价正常人左心室舒张功能

目的探讨超声心动图二尖瓣环自动追踪技术(AMAT)评价正常人左心室舒张功能的临床应用价值。方法健康成人志愿者54例,按年龄分为青年组(19~45岁)和中老年组(45~75岁)。超声AMAT成像模式检查,分别测量二尖瓣环间隔侧和侧壁侧舒张早期及舒张晚期运动速度(MAVe、MAVa),同时应用频谱多普勒测量二尖瓣口舒张期血流频谱E、A峰。对两组间及组内测值进行比较,分析MAVe、MAVe/MAVa与二尖瓣口血流E峰的相关性。结果①与青年组比较,中老年组MAVe、MAVe/MAVa显著降低;且二尖瓣口舒张期血流E峰与两组MAVe、MAVe/MAVa显著相关;②两组组内比较:二尖瓣环间隔侧速度普遍较侧壁侧低,中老年组二尖瓣环间隔侧和侧壁侧MAVa差异有统计学意义。结论AMAT技术可准确反映左心室早期舒张功能降低。     

左室声学造影有效性和安全性研究

目的应用国产声学造影剂全氟丙烷人血白蛋白微球注射液,经静脉注射后观察左室内膜边界识别效果,并对其安全性进行评价。方法对81例至少有一个以上节段内膜边界显示不清的患者,经静脉注射造影剂0.01mgkg,观察心内膜节段显像、室壁运动及左室充盈状态。观察造影前后患者生命体征、心电图,血、尿常规,肝肾功能。采用改良Simpson法分别测量造影前后射血分数。结果造影前左心室内膜显影评分为5.27±1.74,造影后为11.44±0.88。应用造影剂可更准确测量射血分数,清晰显示96%的心内膜节段的室壁运动,并使81例患者左心室均可完全显影达3级。造影后患者的生命体征、心电图及肝肾功能未见明显异常。结论国产声学造影剂可明显改善左室内膜边界的识别,且安全性和患者的耐受性较好。     

实时三维超声心动图结合半自动边界探测技术评价左室容积和收缩功能的可行性研究

目的探讨实时三维超声心动图(RT-3DE)结合半自动边界探测技术测量正常和异常左室容积及收缩功能的可行性、准确性及可重复性。方法健康自愿者20例,冠心病患者25例纳入统计,应用Philips iE33成像系统采集三维数据,使用Tomtec4D LV-Analysis CAP2.5软件脱机测量左室容积参数,包括舒张末期容积(EDV)、收缩末期容积(ESV)、每搏量(SV)和射血分数(EF),并与二维超声心动图(2DE)的双平面Si mpson's法测值比较。结果①正常组和冠心病组中,RT-3DE与Si mpson's法所测EDV、ESV、SV和EF差异均无统计学意义且一致性好(P>0.05)。②两组中,两法所测EDV、ESV、SV和EF高度相关,但冠心病组相关系数均较正常组相应测值有所降低。③两法的观察者间变异在正常组中均小,冠心病组较正常组有所增加,且冠心病组中Si mpson's法的观察者间变异增加更为明显,大于RT-3DE法的观察者间变异。结论RT-3DE结合半自动边界探测技术测量左室容积及收缩功能的方法简便、可行、准确、重复性高,在临床上具有推广应用的价值。     

Model-based determination of cut-off values for left ventricular hypertrophy from echocardiographic myocardial mass data.

1. The left ventricular myocardial mass is a measurement that is easy to obtain by echocardiography. It is currently used for the definition of left ventricular hypertrophy, but cut-off values are often critical, since they depend on covariates of left ventricular myocardial mass such as sex, age, body surface area, physical training, blood pressure, etc. As it is very difficult in any laboratory to obtain a sufficient number of normal subjects for the establishment of left ventricular myocardial mass experimental distributions, we propose a non-linear model for the calculation of echocardiographic left ventricular myocardial mass distribution in normal subjects, from personal and literature data. left ventricular myocardial mass probability density function was computed from the following two assumptions: the joint distribution of the internal and external left ventricular diameters is assumed to be bivariate normal, and the relation between left ventricular myocardial mass and ventricular diameters is given by the formula of Devereux & Reicheck (Devereux, R. B. & Reicheck, N. Circulation 1977; 55, 613-8). 2. The Gaussian assumption was tested by using skewness tests. The model was further developed for the myocardial mass index distribution. The calculated probability density functions were compared with experimental data and showed very good agreement. Furthermore, they were used to define cut-off values of left ventricular hypertrophy at selected false-positive ratios. Finally, since left ventricular myocardial mass may vary under normal conditions with co-variates, the model may provide co-variate-matched cut-off values for any, even small, series of non-diseased control subjects.     

Left ventricular endocardial surface detection based on real-time 3D echocardiographic data.

OBJECTIVE: A new computerized semi-automatic method for left ventricular (LV) chamber segmentation is presented. METHODS: The LV is imaged by real-time three-dimensional echocardiography (RT3DE). The surface detection model, based on level set techniques, is applied to RT3DE data for image analysis. The modified level set partial differential equation we use is solved by applying numerical methods for conservation laws. The initial conditions are manually established on some slices of the entire volume. The solution obtained for each slice is a contour line corresponding with the boundary between LV cavity and LV endocardium. RESULTS: The mathematical model has been applied to sequences of frames of human hearts (volume range: 34-109 ml) imaged by 2D and reconstructed off-line and RT3DE data. Volume estimation obtained by this new semi-automatic method shows an excellent correlation with those obtained by manual tracing (r = 0.992). Dynamic change of LV volume during the cardiac cycle is also obtained. CONCLUSION: The volume estimation method is accurate; edge based segmentation, image completion and volume reconstruction can be accomplished. The visualization technique also allows to navigate into the reconstructed volume and to display any section of the volume.