Doppler flow velocity waveforms in the embryonic chicken heart at developmental stages corresponding to 5–8 weeks of human gestation

Abstract

To obtain Doppler velocity waveforms from the early embryonic chicken heart by means of ultrasound biomicroscopy and to compare these waveforms at different stages of embryonic development. We collected cardiac waveforms using high-frequency Doppler ultrasound with a 55-MHz transducer at Hamburger-Hamilton (HH) stages 18, 21 and 23, which are comparable to humans at 5 to 8 weeks of gestation. Waveforms were obtained at the inflow tract, the primitive left ventricle, the primitive right ventricle and at the outflow tract in 10 different embryos per stage. M-mode recordings were collected to study opening and closure of the cushions. By exploring the temporal relationship between the waveforms, using a secondary Doppler device, cardiac cycle events were outlined. Our results demonstrate that stage- and location-dependent intracardiac blood flow velocity waveforms can be obtained in the chicken embryo. The blood flow profiles assessed at the four locations in the embryonic heart demonstrated an increase in peak velocity with advancing developmental stage. In the primitive ventricle the 'passive' (P) filling peak decreased whereas the 'active' (A) filling peak increased, resulting in a decrease in P to A ratio with advancing developmental stage. M-mode recordings demonstrated that the fractional closure time of the atrioventricular cushions increased from 20% at stage HH 18 to 60% at stage HH 23. High-frequency ultrasound biomicroscopy can be used to define flow velocity waveforms in the embryonic chicken heart. This may contribute to an understanding of Doppler signals derived from valveless embryonic human hearts at 5 to 8 weeks of gestation, prior to septation.