Echocardiographic Assessment of Ductus Arteriosus Shunt in Premature Infants

Echocardiograms were performed on premature infants with a patent ductus arteriosus (PDA) in order to assess the magnitude of the left-to-right shunt. Ten of 14 infants with a hemodynamically significant PDA required ligation because of intractable cardiac failure. Twenty infants served as controls. These consisted of seven infants without heart disease, ten infants who were examined echocardiographically after surgical ligation of a PDA, and three infants who were considered to have closed the PDA spontaneously prior to echocardiographic examination. We measured the left atrial (LA) and aortic root (Ao) diameters and an LA/Ao ratio was used to assess left atrial size. The LA/Ao ratio was 1.28 ± 0.23 ( sd ) in the group with PDA and 0.86 ± 0.10 in the control group. Infants who required surgical ligation all had an LA/Ao ratio above 1.15 (mean 1.38 ± 0.19). After ligation of the PDA the ratio returned to normal levels (0.87 ± 0.12). Sequential studies performed on seven infants demonstrated the usefulness of the LA/Ao ratio in following the changes in left-to-right ductus shunting and left ventricular failure as well as the effects of medical and surgical therapy. The LA/Ao ratio is helpful in differentiating infants with respiratory distress due to ductus shunting and left ventricular failure from intrinsic pulmonary disease.