CYBB and familial atrioventricular septal defect: Histological analysis of Nox2−/− hearts at P0 shows that 34% of Nox2−/− mice were born with various CHDs including atrial septal defects (ASD, 18%), ventricular septal defects (VSD, 18%), and severe cases of septal malformation in the form of atrioventricular canal defects (AVCD, 3.3%), which are septation defects (Table 2, Figure 2(a)).