Parametric imaging of the chick embryonic cardiovascular system: a novel functional measure

Morphogenesis of the cardiovascular system is likely linked to its functional development. This report presents an approach to functional assessment of early cardiovascular development using parametric imaging based on videodensitometry. Trypan blue was injected into the sinus venosus of chick embryos at stage 20 (3.5 d of incubation). Images were recorded on videotape, digitized, and analyzed by a microcomputer. A sampling window was placed over the entire image, and a densogram (time-density curve) for each pixel in the window was obtained. Parameters extracted from the densogram and its derivative were plotted in form of: 1) maximal image, 2) peak derivative image, and 3) time to peak derivative image. This approach revealed isochronal lines that divide the aortic arch and dorsal aorta into several segments. Regional flow velocity at these segments was estimated by dividing the distance between isochronal lines by the time interval. Flow velocity at the mid-systolic phase at the dorsal aorta and at the fourth aortic arch was 35.9 and 45.0 mm/s, respectively. Shear rate at the vessel wall was estimated to be 2.7 times larger at the fourth aortic arch than at the dorsal aorta. The extensive remodeling experienced by the aortic arch system compared with the dorsal aorta could be related to increased shear rate on the walls of the aortic arches.