Long-term degenerative changes in aortic segment homografts, with particular reference to calcification

The object of this article is to present observations derived from a long-term follow-up (over a period of 8-17 years) of a personal series of aortic segment homografts from which certain important information arises. It will be shown that in those grafts prepared and preserved in a `fresh' state, calcification has not occurred or has been trivial, whereas in 20 cases in which the graft has been prepared by freeze-drying, calcification is absent in only four, i.e., 21%. Nineteen of these 20 have been traced up to date; only one is so far missing. In spite of calcification the functional result has remained excellent; in all, the graft was used to replace a segment of aorta resected for aneurysm or for coarctation. The high incidence of aortic wall calcification must assume clinical significance in relation to aortic valve homografting. This procedure is now well established and it is important to consider the future of the valve homograft, especially as most grafts are being prepared by freeze-drying. By analogy from observations on the rate of homografting of aortic segments, calcification is likely to occur at least in that portion of the aortic wall which carries the valve cusps. Impairment of function of the cusps or their involvement in the calcific process seems likely.