Chondroid metaplasia in the tunica media of the aorta in dogs submitted to saphenous vein aorto-cava by-pass.

We submitted twelve dogs to aorto-superior vena cava by-pass with saphenous vein. Six months later, all dogs had developed areas of chondroid metaplasia in the tunica media of the aorta, near the area of anastomosis. Three dogs also had bony metaplasia. The Foci of metaplasia had no relation to sutures. This lesion begins with a build-up store of glycosaminoglycans in the tunica media. Later, elastic fibers show a fenestration and dissolution, while chondrocytes replace smooth muscle fibres. We suggest that the rupture of the vasa vasorum during operation and the traction and pulsation of the by-pass over the area of suture could be the cause of this direct metaplasia.