The silent ductus arteriosus.

Preterm infants at risk of developing a patent ductus arteriosus were followed sequentially by physical examination, echocardiographic determinations of the LA/AO ratio, and chest roentgenograms. The results show that a significant number of infants who have no clinical signs or symptoms of a PDA have large left-to-right shunts. The presence of this shunt was suggested by acute increase in left atrial size by ECHO determination and confirmed by retrograde single-film aortography. Clinical signs and symptoms often developed several days after documentation of the left-to-right shunt.