Nature of coarctation in hypoplastic left heart syndrome

The study was designed to establish the underlying pathology of aortic coarctation in hypoplastic left heart syndrome. Aortic coarctation in patients with hypoplastic left heart syndrome is a significant problem when a Norwood procedure or heart transplantation is performed. Previous reports have claimed that the obstruction was merely a branch-point phenomenon and that ductal tissue was absent. Five heart specimens with hypoplastic left heart syndrome and aortic coarctation were examined histologically. The distal segment of the aortic arch, together with the arterial duct, were dissected and processed en bloc. The blocks were sectioned parallel to the longitudinal axis of the aortic arch. In 4 hearts the coarctation was in the preductal position. Ductal tissue encircled the aortic lumen and extended into the aorta both proximally and distally from the ductal orifice. The fifth case showed medial thickening of the aortic wall in the paraductal position, but without ductal tissue. The arterial duct showed histologic characteristics of persistent patency. Our observations suggest that aortic coarctation in the preductal position in hypoplastic left heart syndrome is caused by the extension of ductal tissue. The findings may have an impact on clinical strategies for hypoplastic left heart syndrome.