40 MHz Doppler characterization of umbilical and dorsal aortic blood flow in the early mouse embryo

Physiological study of the developing mouse circulation has lagged behind a dvances in molecular cardiology. Using an innovative high-frequency Doppler system, we noninvasively characterized circulatory hemodynamics in early m ouse embryos. We used image-guided 43 MHz pulsed-wave (PW) Doppler ultrasou nd to study the umbilical artery and vein, or dorsal aorta in 109 embryos. Studies were conducted on embryonic days (E) 9.5-14.5. Heart rate, peak blo od flow velocities, and velocity time integrals in all vessels increased fr om E9.5-14.5, indicating increasing stroke volume and cardiac output. Heart rate, ranging from 192 bpm (E9.5) to 261 bpm (E14.5), was higher than prev iously reported. Placental impedance, assessed by the time delay between th e peaks of the umbilical arterial and venous waveforms and by venous pulsat ility, decreased with gestation. Acceleration time, a load-independent Dopp ler index of cardiac contractility, remained constant but seemed sensitive to heart rate. High-frequency PW Doppler is a powerful tool for the quantit ative, noninvasive investigation of early mouse circulatory development. (C ) 2000 World Federation for Ultrasound in Medicine & Biology.