Morphologic features of the normal aortic arch in neonates, infants, and children pertinent to growth

Background. The aorta in newborns rapidly adapts by growth to postnatal circulatory conditions. The question arises what structural features are associated with growth and whether differences occur between the various segments. Methods. Nineteen specimens have been studied: seven from babies less than 1 month, seven from 1 month to 1 year, and five from 1 to 4 years. In each baby the diameter of the aortic segments and its branches were measured. Histologically the number of elastin lamellae was counted, and furthermore, collagen density was quantified at several measurement sites. Results. The diameter of each segment increases rapidly after birth and more so than that of the descending aorta, except for the brachiocephalic artery and its branches and the left common carotid artery, albeit not at the same rate. The ascending aorta is the only segment that shows a decrease in the ratio of elastin lamellae to diameter. Collagen density was always highest in the descending aorta. Conclusions. These observations show that postnatal growth of the thoracic aorta is associated with distinct structural remodeling soon after birth; these observations are of clinical relevance in case of aortic arch abnormalities.