Cardiovascular Z ‐scores in fetuses with tetralogy of Fallot

Objective To establish formulae for the calculation of fetal cardiovascular Z ‐scores based on femur length ( FL ), and to compare cardiovascular parameters between fetuses with tetralogy of Fallot ( TOF ) and normal fetuses in order to assess their value for the prenatal diagnosis of TOF . Methods A total of 329 normal fetuses and 43 fetuses with TOF were included in this study. Eleven cardiovascular dimensions were measured offline after cardiac spatiotemporal image correlation volume acquisition. Normal cardiovascular Z ‐score formulae were constructed for these measurements based on FL by performing a standard regression analysis followed by weighted regression of absolute residual values. The following ratios were calculated: right ventricular internal diameter ( RVID ) to left ventricular internal diameter ( LVID ) and pulmonary artery diameter (PA) to aorta diameter (Ao). Subsequently, all parameters were compared between the normal and TOF groups. Results Formulae for calculating Z ‐scores for the 11 cardiovascular dimensions were constructed. FL was significantly correlated with all cardiovascular dimensions assessed ( r  = 0.816–0.944, P  < 0.001 for all). RVID , Ao, PA , aortic arch isthmus, and ductus arteriosus mean Z ‐scores and PA /Ao ratio were statistically significantly different between normal fetuses and those with TOF . In the TOF group, all Ao Z ‐scores (43/43) were > + 2 and all PA /Ao ratios (43/43) were below the normal 95% range. However, only 48.8% (21/43) of the PA Z ‐scores were < −2. Conclusions The cardiovascular Z ‐score formulae developed can provide a quantitative basis for the prenatal diagnosis of TOF . Aortic dilatation and abnormal PA /Ao ratio may be markers for the antenatal diagnosis of TOF . Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.