Noninvasive Assessment of Fetal Pulmonary Blood Flow in Experimental Pulmonary Hypertension in the Fetal Lamb

The aim of this study was to assess pulmonary arterial blood flow changes induced by the creation of a systemic arteriovenous fistula (120 d gestation) in the fetal lamb using Doppler technique. Doppler echocardiographic assessment of the pulmonary artery blood flow performed 1, 6, and 14 d after surgery showed that mean pulmonary arterial blood flow in the left or right pulmonary artery was 224 ± 58 mL/min at day 1 in the fistula group, significantly higher than in the control group (113 ± 22 mL/min; p < 0.01, ANOVA test) whether no difference was found at days 6 and 14. The mean inner diameter of the left pulmonary artery measured on postmortem lung arteriograms compared favorably to the one measured on day 14 at the same level on ultrasound. The mean left pulmonary arterial blood flow, measured at birth on day 14 after surgery, using ultrasonic flow transducer, was not statistically different from the one measured by Doppler on day 14. Our data demonstrate that echocardiography allows accurate assessment of pulmonary arterial blood flow in utero, providing evidence suggesting transient high pulmonary blood flow that did not last >6 d after the creation of a systemic fistula.