Double outlet right ventricle: experimental morphogenesis in the chick embryo heart.

Double outlet right ventricle (DORV) was produced experimentally in the chick embryo by preventing the incorporation of the posteromedial conus into the left ventricle. This was accomplished by placing a ligature around the caudal end of the conus at a stage in which it is exclusively continuous with the right ventricle. The embryos were divided into two groups according to the stage of development of the conal ridge. In one group, the conal ridges had not appeared (stages 17-18); in the other they had begun to develop (stage 22). Both groups were divided into two subgroups; in one the ligature was left in place up to the mature heart stage and in the other it remained for only 24 hours. In all the embryos where the ligature remained until the mature heart stage a DORV was obtained, while in the embryos where the ligature remained in place for only 24 hours a DORV was obtained in only two-thirds of the cases. Two different types of DORV were produced: 1) with anterior and posterior infundibula in which the subpulmonary infundibulum was anterior to the subaortic infundibulum and there was a subaortic infracristal ventricular septal defect (VSD); 2) with side-by-side infundibula in which the subpulmonary infundibulum was on the left side and the subaortic infundibulum on the right side; the VSD was far from both infundibula. Our experiments show that DORV is an essentially infundibular malformation. In DORV there are two types of infundibular relationships: a) with anterior and posterior infundibula, and b) with side-by-side infundibula. The crista supraventricularis in the normal heart and the infundibular septum in DORV are two different anatomic and embryologic structures.