Observations on detailed histology of the internal thoracic artery and their relevance to its comparatively low incidence of atheroma

The internal thoracic artery (ita) is of value as a coronary artery bypass graft. It is much less prone to develop atheroma than coronary arteries and much less prone to develop graft occlusive disease than the alternative saphenous vein graft, but the reasons for its comparative resistance to atheroma are unclear. We have sought to define the detailed structure of the artery along its length and have shown that the media of the artery changes from an elastic structure in its proximal part to a muscular one in its distal part. The internal elastic lamina has a well-defined structure at all levels, in contrast to the external elastic lamina which becomes well defined only in its distal part. The significant difference in the structure of the media of the ita, compared to that described for the coronary arteries, may be relevant to the observed difference in atheroma between this artery and the similarly sized epicardial coronary arteries. © 1994 Wiley-Liss, Inc.