DUCTUS VENOSUS INDEX - A METHOD FOR EVALUATING RIGHT-VENTRICULAR PRELOAD IN THE 2ND-TRIMESTER FETUS

This study was designed to examine ventricular preload by measuring th e ductus venosus index during the second trimester of pregnancy. A tot al of 137 women were entered into the study. Each fetus was examined w ith real-time, color and pulsed Doppler ultrasound. The color Doppler maximal velocity setting was adjusted so that the umbilical vein was h omogeneous in color, did not demonstrate aliasing, and filled the veno us lumen. The pulsed Doppler gate was placed within the ductus venosus in all subjects. Color Doppler identified a turbulent flow velocity w ithin the ductus venosus which was not present in the umbilical vein, hepatic vein or inferior vena cava. The ductus venosus pulsed Doppler waveform demonstrated flow velocity from the umbilical vein to the hea rt during ventricular systole, the rapid filling phase of ventricular diastole, and atrial systole. However, flow velocity was decreased dur ing atrial systole compared to ventricular systole and the rapid filli ng phase of diastole. The ductus venosus index was computed from the D oppler waveform of the ductus venosus at points consistent with ventri cular and atrial systole ((ventricular systole-atrial systole)/ventric ular systole). Regression analysis demonstrated a significant (p = 0.0 01) relationship between the ductus venosus index and gestational age (ductus venosus index = 75.5757 - 7.25484 x weeks gestation); standard error of the estimate = 7.21959, R = -0.451. One fetus with a hypopla stic left atrium and ventricle demonstrated a normal ductus venosus in dex. Two fetuses, one with pulmonary atresia and the second with sever e cardiovascular dysfunction, demonstrated an abnormal ductus venosus index associated with absent flow velocity during atrial systole. This was associated with notching in the umbilical vein. The ductus venosu s index is an angle-independent measurement from which right ventricul ar preload may be evaluated.