Ann Thorac Surg 1995;59:1428
© 1995 The Society of Thoracic Surgeons
DISCUSSION
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Introduction
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 Introduction
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See also page 1423.
DR JOHN M. KRATZ (Charleston, SC): I enjoyed your paper. This issue brings to mind a more prevalent question, and that is regarding the ITA placed to a coronary artery that is maybe only 40% or 50% obstructed, thinking that we will put it in now to prepare for when future problems develop. Have you studied the internal mammary artery in a similar model going to an unobstructed coronary artery and what it does over time?
DR OTAKI: In previous studies, when the ITA graft was anastomosed to nonstenotic coronary arteries (circumflex), the ITA graft was widely patent in competition with native coronary arteries. This study was designed to observe acute and chronic competitive flow from vein graft in the ITA graft when the ITA graft was located proximally to the vein graft.
DR HENDRICK B. BARNER (St. Louis, MO): I will make a comment without a question. The ITA of a 9- to 13.5-kg dog is about the size of the ITA of a 70-kg man. When the ITA is competing with a fully patent coronary artery in the dog, this represents a different situation than in a human, and your previous studies have reflected that ITA patency is fully maintained when competing with a fully patent coronary. Thus, your present data are not surprising, because a vein graft is significantly larger than the ITA with which it is competing. The clinical correlate of this is provided by Kitamura. Kitamura has studied more than 100 individuals late after bypass grafting with the ITA, and he has correlated late ITA diameter with the degree of coronary stenosis and shown a very nice continuum, whereby as the coronary stenosis increases, the late ITA diameter is greater, and vice versa.
DR OTAKI: Doctor Barner, thank you so much for your comments. Current studies from Japan and Europe regarding ITA and vein dual grafting have demonstrated that almost 50% of ITA grafts were patent. In our opinion, based on the present study, when ITA contribution to distal perfusion is less than 20% or 25% of total distal perfusion, the ITA graft will be occluded totally; when its contribution to distal perfusion is 20% to 50%, ITA shows a string sign and is open; and when ITA contribution to distal perfusion is more than 50% of total distal perfusion, ITA can preserve long-term patency.
