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OP18.04: Flow velocity waveforms in the chicken embryonic heart at developmental stages comparable with the first trimester of human pregnancy

Objectives: Assessment of inflow, ventricular and outflow velocity waveforms in the chicken embryonic heart at 3, 3.5 and 4 days incubation time, using ultrasound biomicroscopy. Background: Due to limited resolution, first-trimester human derived flow velocity waveforms are a mixture of inflow, ventricular velocity and outflow waveforms and are therefore difficult to interpret. The chicken embryo is a widely accepted and appropriate model for studying cardiac morphology and function during embryogenesis. The early development of avian and mammalian hearts is largely similar. Knowledge of the velocity waveforms in the embryonic heart might be for importance for discriminating between normal and disturbed development. Methods: Ultrasound imaging measurements were performed with a 55-Mhz probe (VisualSonics, Vevo 770). With 2D imaging the embryonic heart was visualized and the Doppler sample volume positioned at the inflow tract, the ventricle and the outflow tract. The ultrasonic examination was performed at days 3, 3.5 and 4 of incubation, which corresponds to 5 to 8 weeks of human pregnancy. Measurements were repeated ten times in different embryos. Results: Reproducible stageand location-dependent waveforms were found. At incubation day 3 the inflow could be characterized by three, and the ventricular waveforms by four peaks per heartbeat, most likely including one reflection peak. The number of peaks gradually reduced to two and three at 4 days incubation, respectively. The outflow tract showed only one dominant peak throughout the developmental stages studied. Conclusions: These data strongly suggest that in early developing phases a reflection peak is present in the ventricle. The biomechanics of the developing embryonic heart seem to be different from that previously assumed, as also suggested in the embryonic zebra fish model (Science, 2006 Vol.312: 751–3). The limited resolution obtained with human ultrasound might be the reason why this has not been observed in humans.