Spectrum of Congenital Cardiac Anomalies Produced in Chick Embryos by Mechanical Interference with Cardiogenesis

Abstract

Stage 19 to 20 white leghorn chick embryos were subjected to an operative manipulation in which a wire device was passed under the outflow tract of the cardiac tube, and allowed to remain in place from 24 to 60 hours. The embryos were then permitted to develop until hatching. Twenty-eight embryos, including eight sham operated controls, all of whom were normal, survived to at least the 18th embryonic day, and are included in this report. A spectrum of cardiac anomalies was produced as follows: group 1, widening of the left ventricular outflow tract unassociated with other defects; group 2, widening of the left ventricular outflow tract with a subaortic ventricular septal defect, 0.8 mm or less in its greatest dimension; group 3, a large ventricular septal defect, 1.5 mm or more in its greatest dimension, with varying degrees of abnormal position of the aorta, including "overriding" of the aorta, but with maintenance of continuity between the aortic and mitral valve annuli; group 4, the double outlet syndrome, in which both great vessels arise from the anatomic right ventricle with complete muscular separation between the aortic and mitral valves. In the time period studied, the double outlet syndrome represents the extreme of the continuum. However, it is possible that other forms of this spectrum exist, some perhaps incompatible with embryonic life, and that these may be produced by changing the experimental technique.