Abstract
To evaluate the behavior of the free internal mammary artery (IMA) graft in coronary bypass surgery an experiment was carried out in canine arteriovenous shunt position. From 6 dogs the IMA was dissected free from the right side as a naked artery and from the left side with the 2-cm-wide surrounding tissue. Three-cm-long free IMA grafts were anastomosed between the carotid artery and the contralateral external jugular vein as arteriovenous fistulas. After six months the grafts were harvested and studied by light microscopy and scan ning electron microscopy (SEM). Of 12 grafts, 10 were patent. In 1 dog both free IMA grafts were throm bosed. By light microscopy intimal thickening was seen in 2 IMA grafts with the surrounding tissue, and me dial fibrosis was seen in 1 naked IMA
graft. In the SEM study in 4 samples of naked IMA grafts and in 2 samples of the IMA grafts with the surround ing tissue, the endothelium covered the luminal surface, although it had degenerated. In other samples the basement membrane was almost de nuded of endothelial cells. This study showed that free IMA grafts main tain their patency well in arterioven ous shunt, although the endothelium was severely degenerated in all grafts.
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