Two dimensional alignment of valves in the cardiac skeleton is studied using 49 fetal hearts. They are standardized with fixed length between the centers of mitral and tricuspid valves. The relations among the parameters and of wall thichness ratio are studied, especially by the change of gestational age, mitral aortic distance and pulmonary-aortic distance, the angles between the two lines and mitral-tricuspid line. Anterior shift of great vessels was seen in heart with gestational age less than 20 weeks. Long mitral-aortic distance showed anterior shift of the great arteries and left ventricle was relatively thicker than right ventricle. Narrow aortomitral-tricuspid angle denoted posterior shift of great vessels and thich right ventricle.
Short pulmonary-aortic distance denoted antero-posterior alignment and posterior shift of the vessels and thick left ventricle. Left-right alignment of vessels was not associated with right-ward shift but only with pulmonic displacement to the left. By these observation abnormal alignment of valves in cardiac skeleton would be a basic defect in bulboventricular malformation and we could find basic difference of cardiac skeleton, between normal variation and abnormal heart.
Normal embryonic development of human heart is studied with special emphasis to the formation of atrioventricular and ventriculoarterial connections and their significance in congenital heart disease. Twenty nine human embryos and 8 chick embryos are used in this study. Human embryos are analyzed by reconstruction of serial section slides and chick embryos are microdissected and examined by scanning electron microscopy. In the early cardiac development (Streeter horizon 12), bulbo-ventricular fold divided two ventricles first. The atrioventricular canal is incompletely divided and the canal was in contact neither with septum primum nor with ventricular septal crest. Infundibular and truncal septa were not seen. The division of A-V canal was observed during the stages 14-15. Septation of truncus arteriosus (Streeter horizon 15-17) was followed by septation of bulbus cordis (Streeter horizon 16-17). The shortening of mitral-aortic distance and downward left shift of aortic valve occured after the trunco-infundibular septation and finally the secondary interventricular formen closed at the end of seventh week (Streeter horizon 20-21).