Morphological characterization of ventricular septal defect with posterior deviation of the outlet septum.

Ventricular septal defect (VSD) with posterior deviation of the outlet septum is frequently associated with left ventricular outflow obstruction and aortic arch anomalies. In this study, 17 patients with large VSD and posterior deviation of the outlet septum were evaluated. The VSD was further classified into 'high' and 'low' types according to the extension of the VSD; the high-type VSD (8 patients) extended mainly to the outlet or infundibular portion and the low-type VSD (9 patients) extended mainly to the trabecular or inlet portion. Related morphological features, such as outlet septum hypoplasia, muscle bundle between aortic-mitral valve junction, pulmonary artery overriding and aortic arch anomalies, were found more frequently in patients with high-type VSD, while tricuspid valve straddling and outlet septum hypertrophy were found more often in patients with low-type VSD. This classification for VSD with posterior deviation of the outlet septum helps to predict the morphological features of left ventricular outflow tract and aortic arch anomalies.