The size of the aortic arch: a suitable criterion for differentiating between congenital heart diseases with left-to-right shunt?

A retrospective study was carried out to determine whether aortic arch size can be regarded as a reliable criterion for differentiating between congenital left-to-right shunt defects. The PA and AP plain chest films of children of all age groups with ductus arteriosus persistens (DAP) (n = 91), atrial septal defect (ASD) (n = 86), ventricular septal defect (VSD) (n = 87) and a normal control group (n = 387) were used to measure the size of the aortic arch, and an aortic index (AI) was calculated from aortic arch size and the height of the eighth thoracic vertebral body. Three age classes were defined from the AI values of the control group, and the diagnostic groups in each age class were compared with each other. Enlargement of the aortic arch, as reflected in an elevated AI value, was found most frequently in DAP cases. The size of the aortic arch is, however, of varying differential diagnostic value, depending on the age group. No correlation was found between aortic arch size and the size of the left-to-right shunt in cases of DAP.