Closure of the ductus arteriosus in normal and malformed human heart.

Histopathological studies were made on 9 necropsy specimens of ductus arteriosus with hypoplastic left heart syndrome and I with rubella syndrome. A control group of 40 normal specimens were also studied. In the 17th week of gestation, ductus arteriosus was composed of few elastic fibers, a thick continuous internal elastic lamina and a wide hypocellular area. In the 8th month of gestation, there was a disruption of the internal elastic laminas, partially degeneration on inner layer of the media and circular fashion arrangement of smooth muscle fibers. In the 40th week of gestation, there was a thickening of the intima, a regular arrangement of muscle :fi~ers in the outer layer of the media, cell degeneration between the intima and the outer layer of the media, presence of cleft tissue in the inner and outer layer of the media, an irregular arrangement and a whorl-like muscle nodles in the intermediate layer of the media. In the term fetuses, there was prominent mounds and disruption of the internal elastic lamina, and disintegretion of medial structure. In a case with rubella syndrome there was an absence of disruption of the internal elastic lamina and of mounds or intimal thickening and presence of abundant elastic fibers in the media as in the aorta. In a case with hypoplastic left heart syndrome the internal lamina was thick and continuous, and no mounds were observed. There was aboundant elastic fibers in the media, while in 5 hearts there was a lower mounds, disruption of internal elastic lamina and relatively well developed elastic fibers in the media. Two hearts with hypoplastic left heart syndrome showed normal ductus arteriosus. Based on the data from this observation it was suggested that congenital structural anomalies of the ducutus arteriosus play an important role in the formation of patent ductus arteriosus. 35