Figure 11b. Atrioventricular septal defect in a 2-year-old girl. Axial ECG-gated spin-echo MR images show an atrial septal defect (arrow in a) in the septum primum and an inlet ventricular septal defect (arrow in b), which together produce communication among all four chambers. The right atrium (RA) is markedly enlarged and the right ventricle (*) is hypoplastic. LA = left atrium, LV = left ventricle.