392: Relating abnormal ductus venosus (DV) flow to fetal cardiac dysfunction

DV flow velocity waveform reflects atrial changes in 4 phases: ventricular systole (S), ventricular relaxation (v), diastole (D), and atrial contraction (a). It is assumed that an abnormal DV signifies cardiac dysfunction, but this has never been proven. Our study examines the relationship between an abnormal DV waveform and more direct measurement of fetal cardiac function. 129 referred patients (fetal growth restriction 22, twin-transfusion 80, cardiac defect 7, other 20) had abnormal DV Doppler (PIV z-score > 2.0). We calculated velocity ratios of the 4 phases: S/v, S/D, S/a, v/D, V/a, D/a. All then had direct cardiac function tests: myocardial performance index (MPI), derived from isovolumetric contraction, ejection and isovolumetric relaxation times of both ventricles. Diastolic function was depicted by the ratio of early flow velocity (E) and late peak flow (A) through the a/v valves (E/A). Reference ranges from pregnancies with normal outcome allowed calculation of Z-scores for all variables. We compared multiple parameters from both DV and direct assessment, so an adjusted statistical significance of p<0.005 was used. In 472 exams at 17 - 34 weeks, abnormal DV PIV alone bore no consistent relationship to cardiac function, but individual velocity ratios derived from the DV did. End-systolic relaxation (S/v) and subsequent passive and active ventricular filling (v/D; v/a) correlated with MPI (S/v vs left MPI, v/D vs left MPI and v/a vs. both MPI, all p<0.005 (Spearman). S/v and v/D correlated with both E/A (p<0.0001). DV S/D ratio reflecting passive diastolic filling correlated with both E/A (p=<0.0001). Active diastolic filling (S/a and D/a) also correlated with MPI of both ventricles (all p<0.002). Phasic DV velocity indices show relationships with cardiac function that are not reflected in the pulsatility index alone. In patients with an abnormal DV PIV, the components of venous flow need to be analyzed, or direct ventricular assessment performed, to define the underlying deficits.