Division of Cardiology, Department of Pediatrics, University of California, San Francisco, San Francisco, California.
Division of Cardiology, Department of Pediatrics, University of Utah, Salt Lake City, Utah.
J Am Soc Echocardiogr. 2023 Sep;36(9):978-997. doi: 10.1016/j.echo.2023.05.010. Epub 2023 Jun 9.
Fetal echocardiography is widely available, but normative data are not robust. In this pilot study, the authors evaluated (1) the feasibility of prespecified measurements in a normal fetal echocardiogram to inform study design and (2) measurement variability to assign thresholds of clinical significance and guide analyses in larger fetal echocardiographic Z score initiatives.
Images from predefined gestational age groups (16-20, >20-24, >24-28, and >28-32 weeks) were retrospectively analyzed. Fetal echocardiography expert raters attended online group training and then independently analyzed 73 fetal studies (18 per age group) in a fully crossed design of 53 variables; each observer repeated measures for 12 fetuses. Kruskal-Wallis tests were used to compare measurements across centers and age groups. Coefficients of variation (CoVs) were calculated at the subject level for each measurement as the ratio of SD to mean. Intraclass correlation coefficients were used to show inter- and intrarater reliabilities. Cohen's d > 0.8 was used to define clinically important differences. Measurements were plotted against gestational age, biparietal diameter, and femur length.
Expert raters completed each set of measurements in a mean of 23 ± 9 min/fetus. Missingness ranged from 0% to 29%. CoVs were similar across age groups for all variables (P < .05) except ductus arteriosus mean velocity and left ventricular ejection time, which were both higher at older gestational age. CoVs were >15% for right ventricular systolic and diastolic widths despite fair to good repeatability (intraclass correlation coefficient > 0.5); ductal velocities and two-dimensional measures, left ventricular short-axis dimensions, and isovolumic times all had high CoVs and high interobserver variability despite good to excellent intraobserver agreement (intraclass correlation coefficient > 0.6). CoVs did not improve when ratios (e.g., tricuspid/mitral annulus) were used instead of linear measurements. Overall, 27 variables had acceptable inter- and intraobserver repeatability, while 14 had excessive variability between readers despite good intraobserver agreement.
There is considerable variability in fetal echocardiographic quantification in clinical practice that may affect the design of multicenter fetal echocardiographic Z score studies, and not all measurements may be feasible for standard normalization. As missingness was substantial, a prospective design will be needed. Data from this pilot study may aid in the calculation of sample sizes and inform thresholds for distinguishing clinically significant from statistically significant effects.
胎儿超声心动图应用广泛，但参考标准数据并不完善。在这项初步研究中，作者评估了（1）在正常胎儿超声心动图中预先指定的测量方法的可行性，以指导研究设计；（2）测量的变异性，以确定临床意义的阈值，并指导在更大的胎儿超声心动图 Z 评分研究中进行分析。
回顾性分析了来自预定胎龄组（16-20 周、＞20-24 周、＞24-28 周和＞28-32 周）的图像。胎儿超声心动图专家评分员参加了在线小组培训，然后独立分析了 73 例胎儿研究（每组 18 例），采用 53 个变量的完全交叉设计，每位观察者对 12 例胎儿重复测量。Kruskal-Wallis 检验用于比较不同中心和年龄组之间的测量值。每个测量值的变异系数（CoV）为标准差与平均值的比值，在个体水平上计算。组内相关系数用于显示组内和组间的可靠性。Cohen's d＞0.8 用于定义具有临床意义的差异。测量值与胎龄、双顶径和股骨长作图。
专家评分员平均每个胎儿完成测量需要 23±9 分钟。缺失率为 0%至 29%。除动脉导管平均速度和左心室射血时间外，所有变量在不同年龄组之间的 CoV 均相似（P＜0.05），而这两个变量的 CoV 在胎龄较大时更高。尽管重复性良好（组内相关系数＞0.5），但右心室收缩和舒张宽度的 CoV 仍大于 15%；尽管观察者间一致性良好（组内相关系数＞0.6），但导管速度和二维测量、左心室短轴尺寸和等容时间的 CoV 均较高，观察者间变异性较大。使用比值（例如三尖瓣/二尖瓣环）代替线性测量时，CoV 并没有改善。总体而言，27 个变量具有良好的组内和组间可重复性，而 14 个变量尽管观察者间一致性良好，但变异性过大。
在临床实践中，胎儿超声心动图的定量存在很大差异，这可能会影响多中心胎儿超声心动图 Z 评分研究的设计，并非所有测量值都可用于标准归一化。由于缺失率较高，需要前瞻性设计。本初步研究的数据可能有助于计算样本量，并为区分具有临床意义和统计学意义的效果提供阈值。
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