Z-scores for fetal atrial volume using real-time three-dimensional echocardiographic Xplane imaging in normal fetuses

Abstract

Objective To establish Z-scores reference ranges for fetal atrial volume in normal fetuses for accurate assessment of fetal cardiac structure and function. Methods Two hundred ninty-three normal fetuses with gestational ages between 18 to 38 weeks were investigated.Biparietal diameter (BPD), femur length (FL) and gestational age (GA) were measured.Left atrial volume (LAV) and right atrial volume (RAV) were obtained using echocardiographic Xplane imaging. Subsequently, the optimal regression equation was established with BPD, FL and GA as the independent variable and LAV and RAV as the dependent variable, and then Z-scores of LAV and RAV were calculated. Results The linear regression equation of LAV and FL was Y=0.056×FL-1.791 (r=0.952); the linear regression equation of RAV and FL was Y=0.057×FL-1.833 (r=0.942); the linear regression equation of LAV and BPD was Y=0.046×BPD-2.289 (r=0.910); the linear regression equation of RAV and BPD was Y=0.047×BPD-2.348 (r=0.903); the linear regression equation of LAV and GA was Y=0.122×GA-2.403 (r=0.952); the linear regression equation of RAV and GA was Y=0.125×GA-2.456 (r=0.942). There was significant heteroscedasticity of standard deviation (SD) with increasing independent variables, then weighted regression of absolute residuals was used in order to minimize the effect of heteroscedasticity, and the linear regression equation was established. The linear regression equation of LAV-SD and FL was Y=0.005×FL-0.119 (r=0.272); the linear regression equation of RAV-SD and FL was Y=0.005×FL-0.104 (r=0.240); the linear regression equation of LAV-SD and BPD was Y=0.00375×BPD-0.125 (r=0.210); the linear regression equation of RAV-SD and BPD was Y=0.00375×BPD-0.10875 (r=0.192); the linear regression equation of LAV-SD and GA is Y=0.0125×GA-0.21125 (r=0.346); the linear regression equation of RAV-SD and GA was Y=0.0125×GA-0.20875 (r=0.308). According to these equations, the Z-score calculation formula for LAV was (measured LAV-predicted LAV from BPD, FL and GA)/SD of predicted LAV; Z-score calculation formula for RAV was (measured RAV-predicted RAV from BPD, FL and GA)/SD of predicted RAV. Conclusions Fetal Z-scores references for the LAV and RAV can be established using common fetal biometrical parameters (including FL, BPD and GA utilizing statistical methods based on a large sample size). This enhances accurate assessment of growth and development of fetal cardiac structures, and provides novel insights for the determination of fetal atrial volume in fetuses with congenital heart disease. Key words: Echocardiography; Left atrial volume; Right atrial volume; Z-score; Xplane