Intra-utero diagnosis of anomalous right ventricular muscle bundles in association with a ventricular septal defect: a case report.

The morphology and natural history of anomalous right ventricular muscle bundles (ARVMB) have been described in a number of postnatal studies. Whether this is a congenital or acquired cardiac lesion remains obscure. A fetal echocardiogram performed in a 32-week gestation mother showed a large ventricular septal defect and anomalous right ventricular muscle bundles, which were easily appreciated at the ostium-infundibular level. The diagnosis was confirmed postnatally and at 6 months of age the child underwent surgical repair. This report documents the presence of ARVMB in a fetus, at a time when hemodynamics cannot explain the development of right ventricular muscle bundles. It suggests that at least, the morphologic substrate for this disease is congenital.