Response of the Patent Ductus Arteriosus to Indomethacin Treatment

Identification of the presence or absence of a patent ductus arteriosus has created a significant challenge for those who treat premature infants. This challenge is one that has been met by the development of technology. Historically, it was established that an enlarged left atrium in a premature infant was associated with a significant left-to-right shunt from a patent ductus arteriosus. Since left atrial size bore a general relationship to aortic size, a ratio of the two was developed for assessment of shunt magnitude.¹Unfortunately, alterations of left atrial size or the ratio of the two could occur in infants with hypovolemia, congestive cardiac failure, and a host of other conditions. In 1977, a contrast injection technique was reported that provided positive identification of a ductal left-to-right shunt.²This technique, which was specific for ductus arteriosus, required injection through a catheter placed into the thoracic aorta, usually via an