0564: Can systolic Doppler velocimetry of fetal aortic isthmus help predicting post-natal clinical impact of ventricular septal defects?

Objectives Left ventricular ejection causes a forward flow in the fetal aortic isthmus while right ventricle (RV) has a retrograde influence. The objective of this study was to test the hypothesis that non restrictive ventricular septal defects (VSD) could cancel out the normal fetal RV preponderance and its retrograde systolic effect on the isthmic flow pattern. Methods Doppler recordings of 24 fetuses with isolated VSD from 18 to 38 weeks were reviewed. Nine VSD’s were found large in post-natal life (symptoms, medical or surgical treatment) and 15 were restrictive (no symptom, no therapy). A control group was constituted of 104 normal fetuses. In all cases, an isthmic systolic index (ISI) was calculated as follows: (Nadir of end-systolic velocity / Peak systolic velocity) x 10. The gestational evolution of the ISI’s of the 3 groups was compared. Results In the control group, before 27 weeks of gestation, reference values of ISI were stable at +2±2 SD. After 28 weeks, a brief end-systolic retrograde flow was observed, increasing steadily with gestation and causing a fall of ISI whose mean value reached - 3± 2 SD at 38 weeks. From 18 to 27 weeks there was no statistical difference between groups. Beyond 28 weeks, ISI of restrictive VSD fetuses followed the same fall observed in normal fetuses, whereas ISI’s of large VSD’s remained stable and statistically higher than values of both normal fetuses (p Conclusions ISI provides a simple way to assess the relative performance of both ventricles throughout fetal life. Following the identification of a VSD, this index offers, for the first time, to fetal echocardiographers, an objective and easily accessible tool to predict the posnatal impact of the malformation.