Membranous subaortic stenosis and patent ductus arteriosus.

Six children (five of them girls) each initially had a large patent ductus arteriosus with auscultatory, radiologic, and electrocardiographic findings typical of that lesion. After surgery for the lesion, an ejection-type basal systolic murmur led to detection of discrete membranous subaortic stenosis, which became worse in late childhood. The murmur became louder, the systolic pressure gradient increased from slight to significant, and hypertrophic subaortic stenosis or aortic insufficiency (or both) developed in the older children. Surgical excision of the membrane afforded improvement, except in one patient with the most severe involvement. Because of the unexpected finding of discrete membranous subaortic stenosis in these infants and young children who had undergone surgery for a large patent ductus arteriosus and because of the treacherous worsening of the effects of the discrete membranous subaortic stenosis as childhood progressed, it is important that those patients with a persistent systolic murmur after ductal ligation not be discharged from cardiac follow-up as cured. Serial cardiac catheterization during the growing years appears to be the most accurate way of detecting worsening discrete membranous subaortic stenosis, so that the membrane can be excised before severe complications occur.