Straddling and displaced atrioventricular orifices and valves.

This is an anatomic study of 96 hearts with straddling or displaced atrioventricular (AV) valves and orifices. In the complete form, both the annulus and the peripheral connections of either AV valve straddle a ventricular septal defect (VSD) and connect to both ventricles. In the annular form, only the annulus, and in the peripheral type only the peripheral connections of the valve are found in both ventricles. In displaced AV valve, the entire annulus and periphery of one AV valve are displaced into the opposite chamber. These anomalies are commonly seen in complete transposition with or without ventricular inversion, and in double outlet right or left ventricle. Straddling mitral valve is frequently seen in the Taussig-Bing heart. Any type of VSD may be associated with straddling tricuspid valve; however, they usually are of the AV canal type. Straddling and displaced AV valves should be differentiated from criss-cross hearts in which both AV valves are completely connected to oppositely placed ventricles.