Aneurysmal dilatation of the ductus arteriosus (ADA) has beeN considered a rare condition. We present 3 neonates seen during the last 2 years (1993-1995) with ADA, with prenatal diagnosis in one patient, and postulate a new theory for its pathogenesis. All 3 infants were delivered after term pregnancy and were admitted to NICU due to cardiopulmonary distress. Fetal echocardiogram was obtained in one case due to fetal distress and showed normal cardiac anatomy, right atrial and right ventricular dilatation with dilated ductus arteriosus, which was restricted at its pulmonary artery end, with turbulent right to left ductal flow. Chest X ray showed a mediastinal mass in 2 patients. All 3 were diagnosed during the first 12 hours of life by echocardiography. Echocardiograms showed structurally normal heart with ADA shunting left to right through a restricted segment at its pulmonary artery end. ADA was confirmed by aotography in all 3. In two infants the aneurysms became progressively small as was demonstrated by serial echocardiography after the ductal closure and chest x-ray showed resolution of mediastinal mass by 5-7 days of life. One infant underwent surgical resection of the ADA after observation for 5 days with no change in the size of ADA.
CONCLUSIONS: Increasing reports of ADA in newborn infants reflect availability of high resolution echocardiography. Theories of pathogenesis include 1) delayed closure at its aortic end with exposure of ductal diverticulum to systemic pressure, 2) abnormal differentiation of periductal aortic wall, 3) prolonged exposure to prostaglandin E1, 4) bacterial or mycotic infection of the ductus, and 5) increased ductal flow in utero as in arteriovenous fistulas. We postulate, however, that in at least some cases, ADA is a congenital lesion that may represent post stenotic dilatation of ductus due to turbulent flow through a stenotic segment at its pulmonary artery end during fetal life. Thus, presence of ADA as a cause of fetal distress should be excluded, in selected cases, by fetal echocardiography.
