The watershed: a factor in coronary vein graft occlusion

In 50 patients with one or more aortocoronary saphenous vein grafts investigated by angiography the patency rate of grafts inserted into arteries with a total proximal occlusion was significantly higher than of those inserted into arteries with a proximal stenosis. The interval between operation and investigation in the two groups was similar. In 10 patients with double grafts, one to an occluded and one to a non-occluded artery, there were 7 with one blocked graft, in each case to the non-occluded artery. In the other 3 both grafts were patent. A watershed was shown at angiography in one patient with a graft inserted into a stenosed artery; the distal run-off appeared good, but reflux of the contrast up the coronary artery into the aorta occurred when injecting into the graft, and vice versa. This watershed may operate to a minor degree in all grafts inserted into non-occluded arteries, and by causing stasis at the anastomosis, could explain the higher incidence of graft occlusion in this group. Ligation of the coronary artery proximal to the anastomosis may therefore be necessary to achieve the highest patency rate.