Hypoplastic aortic arch morphology pertinent to growth after surgical correction of aortic coarctation

Background. Whether a hypoplastic transverse arch will grow after successful coarctectomy remains controversial. Methods. We studied 15 coarctation specimens with hypoplastic transverse arch. Eight patients were less than 1 month old and 7 were between 1 and 3 months. The diameter and length of the various segments of the aortic arch were measured. The number of elastin lamellae was determined histologically. Collagen density was quantified with a microdensitophotometer. Using immunohistochemistry, we determined α-actin-positive smooth muscle cells in the media of the ascending aorta and the hypoplastic transverse arch. Results. Despite a hypoplastic transverse arch, the ascending and descending aorta grew. The absolute number of elastin lamellae in the hypoplastic transverse arch was low, but when expressed as a ratio versus its diameter, this number was high (p < 0.05). Collagen density showed high absolute values in the descending aorta. In the older group, 4 of 7 showed no staining for α-actin in the hypoplastic transverse arch, whereas under 1 month of age, only 2 of 8 cases were negative. Conclusions. The hypoplastic transverse arch is characterized by a relatively high number of elastin lamellae. Fewer α-actin-positive cells in the hypoplastic transverse arch occur in older specimens, which could indicate a diminished potential growth.