Altered hemodynamics in chick embryos after extraembryonic venous obstruction

Objective To obtain insight into hemodynamics during abnormal cardiac devel opment, a chick model was developed recently in which a spectrum of conotru ncal anomalies, in combination with abnormal semilunar valves and/or pharyn geal arch artery malformations, was induced through extraembryonic venous o bstruction (venous clip) at stage 27 (70-h incubation). Methods In chick embryos of stage 24 and stage 34 control (n = 8; n = 21) a nd with venous clip (n = 11; n = 18), we simultaneously measured dorsal flo w velocities with a 20-MHz pulsed Doppler velocity meter and dorsal aortic (stage 24) and vitelline artery (stage 34) blood pressures with a servo-nul l system. After the hemodynamic recordings were collected, all 58 embryos w ere subjected to morphological examination. The hemodynamic data were corre lated with the morphology. Statistical comparison was performed between con trol and experimental values. Results At stage 24, venous clip embryos showed impaired looping. Physiolog ically, only a decrease in peak acceleration was found in these embryos (p < 0.05). At stage 34, a spectrum of conotruncal malformations was seen, tha t consisted of a ventricular septal defect in combination with abnormal sem ilunar valves and/or pharyngeal arch malformations. A dextroposed aorta in combination with a ventricular septal defect was diagnosed as double-outlet right ventricle. Hemodynamically peak systolic and mean velocities, peak s ystolic and mean blood Flows and stroke volume were increased while the hea rt rate was reduced after placement of the venous clip (p < 0.05). In both stages, pressure readings showed no statistically significant differences b etween control and experimental embryos. Conclusion Our findings suggest that the hemodynamic changes seen in venous clip embryos reflect the presence of a compensatory mechanism.