Evaluation of normal fetal pulmonary veins from the early second trimester by enhanced-flow (e-flow) echocardiography

To explore the feasibility of using enhanced-flow (e-flow) imaging technology to identify fetal pulmonary veins and establish gestational age-specific reference values at 12-40 weeks' gestation.

The pulmonary venous internal diameter, peak systolic and diastolic flow velocities and visualization rate were analyzed in 332 normal fetuses at 12-40 weeks of gestation. Two-dimensional gray-scale (2D) ultrasound, color Doppler and e-flow imaging were used to detect the pulmonary veins in the four-chamber view by taking the lung as the penetration window.

The pulmonary veins could be visualized as early as 12 weeks' gestational age by e-flow imaging. The right and left pulmonary venous internal diameters and peak systolic and diastolic flow velocities increased with increasing gestational age. Between 12 and 40 gestational weeks, the internal diameter and both the systolic and diastolic flow velocities of the fetal right pulmonary vein were significantly larger than were those of the left vein (P < 0.05). Of 118 fetuses at 12-22 gestational weeks, the visualization rate of the four pulmonary veins (left superior and inferior, right superior and inferior) was 5.9% (7/118) by 2D ultrasound, 41.5% (49/118) by color Doppler and 61.9% (73/118) by e-flow imaging. The visualization rate by e-flow imaging was significantly higher than that using the other two techniques (P < 0.001).

e-flow imaging is apparently a feasible and promising technology with which to identify the fetal pulmonary veins in the early stages of the second trimester.