The Senescence Process of Internal Thoracic Artery

Objective: The internal thoracic artery (ITA) is the most widely used arterial conduit for coronary artery bypass , because it is very rarely affected by atherosclerosis. However, the state of its wall at the time of grafting procedure could influence the long-term outcome of coronary artery bypass. Methods: We have investigated 20 specimens of distal human ITA, derived from 14 male patients and 6 female patients, aged between 68 and 77 years, operated for atherosclerotic coronary artery disease. The specimens, collected after surgical skeletonization during coronary artery bypass procedures, were fixed in 10% neutral buffered formalin and then paraffin embedded. In addition to haematoxylin & eosin, histochemistry (Weigert's staining, Van Gieson's staining, Verhoeff's staining) for elastic fibers, and immunohistochemistry for muscle cells (smooth muscle actin, caldesmon, desmin), nerve fibers (S-100 protein), and endothelial cells (CD34) were performed. Results: A degenerative pathology, most likely due to aging, characterized by the fragmentation of the internal and external elastic membranes and by the consumption of the elastic network of the tunica media has been microscopically observed in a quarter of our patients, without the achievement of classical signs of overt atherosclerosis (cholesterol deposition, fatty infiltration, endothelial ulceration, intimal calcification), which could compromise the long-term patency of the graft. Conclusions: The degenerative change is followed by a remodelling process, based on the proliferation of unspecialized muscle like cells, able to preserve the architecture and the stability of the arterial wall and consequently its functional long-term behaviour.