Fetal ventricular interactions and wall mechanics during ductus arteriosus occlusion in a sheep model

We investigated the effect of fetal sheep ductus arteriosus occlusion (DO) on the distribution of cardiac output and left and right ventricular function by tissue and pulsed Doppler at baseline; after 15 and 60min of DO induced with a vascular occluder; and 15min after release of DO. Ductal occlusion decreased fetal pO₂. Mean left ventricular output increased (p<0.001) from 725 to 1013mL/min, and right ventricular (1185mL/min vs. 552mL/min) and systemic (1757mL/min vs. 1013mL/min) cardiac outputs fell (p<0.001) after 15min of DO, compared with baseline. Pulmonary vascular impedance decreased and volume blood flow increased more than threefold during DO, whereas foramen ovale volume blood flow remained unchanged. Left ventricular systolic function was unaffected, whereas isovolumic relaxation velocity deceleration decreased. Right ventricular functional indices remained unchanged. We conclude that DO increased pulmonary volume blood flow, not foramen ovale volume blood flow. Left ventricular output increased, although not as much as right ventricular output fell, resulting in decreased systemic cardiac output. During DO, left ventricular function exhibited diminished relaxation.