Department of Maternal-Fetal Medicine, Institut Clínic de Ginecologia, Obstetrícia i Neonatologia, Barcelona, Spain.
Fetal Diagn Ther. 2012;32(1-2):96-108. doi: 10.1159/000337329. Epub 2012 Jun 19.
Assessment of cardiac function in the fetal heart is challenging because of its small size and high heart rate, restricted physical access to the fetus, and impossibility of fetal ECG recording. We aimed to standardize the acquisition and postprocessing of fetal echocardiography for deformation analysis and to assess its feasibility, reproducibility, and correlation for longitudinal strain and strain rate measurements by tissue Doppler imaging (TDI) and 2D speckle tracking (2D-strain) during pregnancy.
Echocardiography was performed in 56 fetuses. 2D and color TDI in apical or basal four-chamber views were recorded for subsequent analysis. Caution was taken to achieve a frame rate >70 Hz for speckle tracking and >150 Hz for TDI analysis. For each acquisition, 7.5 s of noncompressed data were stored in cine loop format and analyzed offline. Since fetal ECG information is by definition not available, aortic valve closure was marked from aortic flow and the onset of each cardiac cycle was manually indicated in the 2D images. Sample volume length was standardized at the minimum size. Two observers measured the left and right ventricular peak systolic longitudinal strain and strain-rate.
Strain and strain rate measurements were feasible in 93% of the TDI and 2D-strain acquisitions. The mean time spent on analyzing TDI images was 18 min, with an intraclass agreement coefficient of 0.86 (95% CI 0.77-0.92), 0.83 (95% CI 0.72-0.90), 0.96 (95% CI 0.93-0.98), and 0.86 (95% CI 0.76-0.92) for basal left and right free wall peak systolic strain and strain rate, respectively. Agreement between observers using tissue Doppler also showed high reliability. The mean time spent for 2D-strain analysis was 15 min, with an intraclass agreement coefficient of 0.97 (95% CI 0.95-0.98), 0.94 (95% CI 0.89-0.96), 0.96 (95% CI 0.93-0.98), and 0.84 (95% CI 0.73-0.90) for basal left and right free wall peak systolic strain and strain rate, respectively. Agreement between observers also showed a high reliability that was similar for TDI and 2D-strain. There was a weak correlation between TDI and 2D-strain measurements.
A standard protocol with fixed acquisition and processing settings, including manual indication of the timing events of the cardiac cycle to correct for the lack of ECG, was feasible and reproducible for the evaluation of longitudinal ventricular strain and strain rate of the fetal heart by TDI as well as 2D-strain analysis. However, both techniques are not interchangeable as the correlation between them is relatively poor.
由于胎儿心脏体积小、心率快、胎儿获取途径有限以及无法记录胎儿心电图，因此对胎儿心脏功能进行评估具有挑战性。我们旨在对胎儿超声心动图的采集和后处理进行标准化，以评估其可行性、可重复性，以及通过组织多普勒成像（TDI）和二维斑点追踪（2D-strain）在妊娠期间进行纵向应变和应变率测量的相关性。
对 56 例胎儿进行超声心动图检查。在心尖或基底四腔心切面记录二维和彩色 TDI 以备后续分析。为了进行斑点追踪，需要注意达到帧频>70 Hz，为 TDI 分析>150 Hz。对于每次采集，以电影循环格式存储 7.5 秒的非压缩数据，并离线进行分析。由于胎儿心电图信息是定义上不可用的，因此从主动脉瓣关闭处标记主动脉瓣血流，并且手动在二维图像上指示每个心动周期的开始。样本体积长度标准化为最小尺寸。两名观察者测量左、右心室收缩期峰值纵向应变和应变率。
TDI 和 2D-strain 采集的应变和应变率测量均可行，占 93%。分析 TDI 图像的平均时间为 18 分钟，组内一致性系数为 0.86（95%CI 0.77-0.92）、0.83（95%CI 0.72-0.90）、0.96（95%CI 0.93-0.98）和 0.86（95%CI 0.76-0.92），分别为基底左、右游离壁收缩期峰值应变和应变率。观察者之间使用组织多普勒的一致性也显示出高度可靠性。分析 2D-strain 的平均时间为 15 分钟，组内一致性系数为 0.97（95%CI 0.95-0.98）、0.94（95%CI 0.89-0.96）、0.96（95%CI 0.93-0.98）和 0.84（95%CI 0.73-0.90），分别为基底左、右游离壁收缩期峰值应变和应变率。观察者之间的一致性也显示出高度可靠性，与 TDI 和 2D-strain 相似。TDI 和 2D-strain 测量之间存在弱相关性。
使用固定采集和处理设置的标准方案，包括手动指示心动周期的时间事件以纠正心电图缺失，对于通过 TDI 以及 2D-strain 分析评估胎儿心脏的纵向心室应变和应变率是可行且可重复的。然而，由于两者之间的相关性相对较差，因此这两种技术不能互换使用。
