Spiral autogenous venous graft in the replacement of large vessels. An experimental study with special reference to replacement of the inferior vena cava.

The replacement of large veins poses a difficult problem. Autogenous venous grafts have turned out to be the best replacements for veins. There is, however, no vein available for direct substitution of large veins. The purpose of the present work was to develop a method for replacing a large vein or artery with a vein of smaller caliber, using the dog as the experimental animal. The following conclusions can be drawn on the basis of the present findings: 1. When a small-caliber vein is cut open and then sutured in spiral form over a Haegar stent to obtain the desired caliber, the graft can be used to replace a large vein. The method is sufficiently simple and rapid for clinical application. 2. In the vein that is most difficult to replace, i.e. the infrarenal vena cava, the spiral autogenous venous graft remained patent without medication or concurrent peripheral A-V fistula in 88 per cent (15/17) of cases over a long follow-up. No late occlusions occurred. The spiral grafts that remained patent showed no essential morphologic changes, and the grafts retained soft, vein-like walls throughout the study. 3. The spiral venous grafts implanted into the canine abdominal aorta also functioned well. All nine grafts remained patent, and none showed aneurysmal dilatation over a one-year follow-up. The spiral aortic grafts were regularly "arterialized", i.e. developed distinct thickening of the graft wall. The new layer that grew on the inner surface of the graft, the neointima, gradually thickened, but its growth ceased after six months postoperatively. 4. In the infrarenal vena cava of the dog the spiral venous graft and synthetic PTFE graft behaved in completely different ways. The patent spiral grafts showed no essential changes during the follow-up: no caliber variation, no signs of thrombosis, and no late occlusions. All the PTFE grafts, on the other hand, showed various signs of thrombosis. This resulted in an occlusion rate of 50 per cent (5/10) of the grafts within three months. In the PTFE grafts that remained patent the neointima seemed to have developed through organization of the thrombotic layer on the inner surface of the graft. In the dogs followed up for more than six months, the middle part of the PTFE graft was coated by a loosely attached, hard thrombus, which might cause occlusion if it later detaches.