Ventricular Septal Defects and Pulmonic Stenosis with and without Dextroposition

Anatomic Features and Embryologic Implications

¹ Department of Surgery, the New York Hospital-Cornell Medical Center, New York, New York; Departments of Pathology, the Charles T. Miller Hospital, St. Paul; University of Minnesota, Minneapolis

While overriding of the aorta over the right ventricle is a normal anatomic feature, dextroposition indicates a pathologic condition. It is characterized by deviation of the conus septum, partial presence of a subaortic infundibulum, counterclockwise rotation of the aortic root, and prolongation of the combined cardiac infundibulum. The septal defect which is present in dextroposition represents a malalignment gap between the ventricular and the distal cones septum. Dextroposition with obstruction to the pulmonary flow is considered as representative of tetralogy of Fallot, and without obstruction as the Eisenmenger complex. Infundibular isolated VSDs are deficiency defects in the infundibular septum without dextroposition. The normal overriding aorta may often simulate a dextroposition. Recognition, however, of the specific anatomic features of the VSD as well as absence of anatomic features of dextroposition may avoid errors in the anatomic diagnosis.