Persistent common atrioventricular canal of the complete form associated with anomalies of the aortic arch system in WKY/NCrj rat fetuses.

Atrioventricular (AV) septal defect with a common AV orifice was found in two near-term rat fetuses, which are descendants of an inbred strain, known to genetically develop tetralogy of Fallot, hypertrophic cardiomyopathy, etc. In one fetus the anterior bridging leaflet was almost entirely committed to the left ventricle but in the other it protruded slightly into the right also, coinciding with type A or type B in humans, respectively. The latter fetus had also a subaortic ventricular septal defect with overriding of the aorta and a double aortic arch. Both fetuses had a narrow pulmonary infundibulum with a muscular band, a dysplastic pulmonary valve, and a markedly hypoplastic ductus arteriosus. Complete AV septal defect and tetralogy of Fallot may be linked genetically, with some common underlying developmental processes.