Post-implantation histology of composite autografts used as conduits in the systemic circulation

Abstract

Aortic allografts, which are often used as conduits in reconstructive surgery for congenital cardiac malformations, usually become continuously calcified and so lose their ability to increase in diameter in response to the needs of the growing child. We examined the growth potential of an alternative conduit composed of a longitudinal strip of autologous aortic wall incorporated into an autologous pericardial tube. Ten such composite autografts were implanted in the descending thoracic aortas of lambs for 12 months. Sequential radiological examinations demonstrated appropriate growth, with an increase of more than 200% in the area of the aortic strip. Histological examination of the explanted grafts showed proliferation of a deep band of aortic intima over the surface of the adjacent pericardium, invasion of the intimallpericardial tissue by aortic smooth muscle cells, and the formation of new elastic fibres where smooth muscle replication was most advanced. Thus, the model demonstrated true growth potential. Such composite autografts may well be superior to other types of conduit for clinical reconstructive procedures in young, growing patients.