Relation of early hemodynamic changes to final cardiac phenotype and survival after neural crest ablation in chick embryos.

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Abstract
BACKGROUND Microcinephotography was used to study a model of persistent truncus arteriosus created in chick embryos by ablation of premigratory neural crest destined for the third and fourth aortic arch arteries as well as the septum of the cardiac outflow tract. METHODS AND RESULTS Twenty-five control embryos and 105 of 202 experimental embryos were filmed on day 3 of incubation and then reincubated. The remaining 97 experimental embryos were not filmed because of twisting of the embryos, but they were reincubated. There was no difference in either the survival rate (p greater than 0.23) from day 3 to day 11 of incubation or the incidence of persistent truncus arteriosus (p greater than 0.08) between the filmed and the nonfilmed embryos. Incomplete looping of the cardiac tube observed in experimental embryos during early cardiogenesis correlated with a right ventricular origin of the outflow vessels in the definitive heart. Hemodynamic measurements indicated that there was no difference in heart rate, ejection fraction, systolic and diastolic areas, stroke volume, and cardiac output between controls and the experimental group as a whole. However, embryos that did not survive to day 11 had decreased stroke volume (p less than 0.001) and cardiac output (p less than 0.001), whereas embryos that survived to day 11 with cardiac malformations had increased stroke volume and cardiac output in early embryogenesis. CONCLUSIONS Increased stroke volume and cardiac output may be necessary factors for survival in embryos with cardiac dysmorphogenesis and probably are associated with dilation of the ventricular portion of the cardiac tube, which leads to malalignment of the outflow vessel or vessels.