Published online by Cambridge University Press: 19 August 2008
We studied 28 fetal rats with atrioventricular septal defect with a common orifice produced from 300 fetuses treated with bis-diamine (200mg) on the ninth and tenth day of pregnancy. After undergoing rapid whole- body freezing on the 21st day, they were studied by means of serial cross-sectional photographs of the frozen thorax. Forty-one fetuses with normal hearts subsequent to treatment with bis-diamine served as controls. Atrioventricular septal defect was isolated in three, or was associated with either tetralogy of Fallot (n=14) or common arterial trunk (n=11). Fetal hydrops was associated with evidence of regurgitation of the atrioventricular valves. In a subgroup with larger right atrial volumes (increased by more than two standard deviation over the mean in the controls), the following parameters were significantly increased: subcutaneous edema, pericardial effusion, thickening of the left atrioventricular valve, cardiac chamber volumes and masses. The superior and inferior caval veins, and the descending aorta were significantly smaller in fetuses with atrioventricular septal defect than in controls. Fetal atrioventricular septal defect, therefore, was associated frequently with hydrops and increased volumes of the right atrium and both ventricles. Hydropic changes included cutaneous edema and increased pericardial, pleural, and peritoneal fluid.