Objective To develop Z-score reference ranges for mitral valve-tricuspid valve distance (MTD) in normal fetuses from the measurements of femur length (FL),biparietal diameter (BPD) or gestational age (GA) using fetal echocardiography.Methods A retrospective cross-sectional study of 1216singleton normal fetuses was performed.The gestation age ranged from 20 to 40 weeks.Non-cardiac fetal biometric parameters included FL and BPD and GA based on menstrual age.MTD was measured in a standard apical four-chamber view.Normal Z-score ranges were developed for MTD using GA,BPD and FL as independent variables.These were accomplished by using first standard regression analysis and then weighted regression of absolute residual values for each parameter in order to adjust for inconstant variance.Results Linear regression model was the best description of the data in each case and correlations between MTD and independent variables (FL,BPD,GA) were excellent.The linear regression equations between MTD and FL,BPD,GA were:Y =0.04629 × FL-0.02868 (r =0.827) ; Y =0.04018 × BPD-0.08293(r =0.767) ; Y =0.0098 × GA-0.07075 (r =0.721),respectively.Heteroscedasticity of standard deviation(SD) with increasing independent variables also could be modeled with a simple linear regression.Linear regression equations between SD of MTD and FL,BPD,GA were:Y =0.0149 × FL-0.0095 (r =0.9947),Y =0.0126 × BPD-0.02793 (r =0.9931),Y =0.00305 × GA-0.021 (r =0.991),respectively.According to these equations,MTD Z-score =(the actual measurement of MTD-predicted MTD)/prediction SD.Conclusions Normal reference ranges and Z-scores for MTD have been provided.These normative data may be useful tools for assessment of fetal MTD,especially has potential applications in Ebstein anomaly or other malformations involved atrioventricular valves.%目的 探讨正常胎儿二尖瓣前叶附着点与三尖瓣隔叶附着点之间的距离(MTD)与其生物学生长参数的相互关系,从而定量MTD的Z-评分实际参考范围.方法 采用彩色多普勒超声心动图对1216例孕龄为20～40周的胎儿进行检测,获得胎儿的股骨长径(FL)、双顶径(BPD)和孕周(GA)等正常胎儿的生长参数,通过标准四腔心观测量MTD.以FL、BPD及GA作为自变量,以预测的MTD为应变量建立MTD的Z-评分参考范围.结果 统计分析显示,直线回归方程能够很好的反映胎儿非心血管参数FL、BPD、GA与心脏参数MTD之间的相关性.直线回归方程式分别为:Y=0.04629×FL-0.02868(r=0.827);Y=0.04018×BPD-0.08293(r=0.767);Y=0.0098×GA-0.07075(r =0.721).标准差(SD)随自变量增大而增大,也呈线性关系,运用绝对残差的加权回归消除SD的异方差性,建立直线回归模型,方程式分别为:Y=0.149×FL-0.0095(r=0.9947);Y=0.0126×BPD-0.02793(r=0.9931);Y=0.00305×GA-0.021(r=0.991).根据这些方程,MTD的Z-评分值=(实际测量的MTD-预测的MTD)/预测SD.结论 运用统计学方法,建立了通过胎儿FL、BPD、GA计算MTD的Z-评分正常参考范围,为正常发育的胎儿心脏提供了更加精准的参考标准,在胎儿相关先天性心脏畸形的诊断方面具有潜在的应用价值.
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