The relationship between single ventricle and small outlet chamber and straddling and displaced tricuspid orifice and valve.

This paper deals with the anatomic differences between single ventricle and small outlet chamber, straddling tricuspid orifice and valve, and displaced tricuspid orifice and valve. In single ventricle, both atrioventricular orifices enter a chamber which contains the sinuses of both definitive ventricles, while a small outlet chamber represents the definitive infundibulum of the right ventricle. In straddling tricuspid orifice and valve, the primitive left ventricle contains the sinus of the definitive infundibulum of the right ventricle. In straddling tricuspid orifice and valve, the primitive left ventricle contains the sinus of the definitive left ventricle and also a portion of the sinus of the definitive right ventricle. The primitive right ventricle contains the infundibulum and part of the sinus of the definitive right ventricle. In displaced tricuspid orifice, the primitive left ventricle contains the sinus of the definitive left and almost all of the sinus of the definitive right ventricle. However, a posterior ventricular septum is formed, so that a portion of sinus or apical recess of the definitive right ventricle is included in the primitive right ventricle together with its infundibulum. Possible embryologic speculations are offered to account for these entities. The differences in the anatomy of these entities may be important to the surgeon.