Experimental studies on the long term fate of the vein and artery grafts and its choice in aortocoronary bypass surgery.

Experimental studies of aorto-coronary bypass were performed using the technique of distal coronary artery perfusion in 47 dogs to ellucidate the flow characteristics at various grafts and long term fate of grafts up to 440 days after operation. On short term results, early graft occlusion seems to occur within 2 weeks with 6.5 days of mean in Group I and II (free grafts) when inflammatory reaction is most prominent. After 2 weeks patency rate was 65% in Group I and II, more than 80% of patency rate were obtained in Group III. In Group IV (prosthetic grafts), all but few (3 cases) could survive for more than 24 hours. In flow characteristic, artery and vein graft of which diameter is larger than that of the coronary artery can maintain enough the basal flow after ligation of the proximal coronary artery. In Group III (IMA-Circumflex anastomosis group), the internal mammary artery must be large enough to carry the blood to coronary artery lest the graft flow becomes below the basal flow. In Group IV, grafts can carry full flow but long term studies were not done because of early graft occlusion. There are much differences between free artery and vein grafts. In artery graft except IMA proper arterial structure is being kept until 440 days but has arteriosclerotic wall changes similar to human being. On the contrary, almost all free vein grafts have subintimal hyperplasia with collagen deposit and fibrous tissue and still progress after one year. These findings demonstrate that ischemia and hydrauiic effect in the graft must be important factor for the irreversible graft wall changes.