[Anatomic study of early failures of aortocoronary venous bypass].

A post-mortem study of 10 patients who died soon after an aorto-coronary by-pass procedure (16 grafts) showed that 5 grafts were blocked by recent thrombus (31%) in 5 patients, 3 of whom had infarcts as a result. It seems that the two main causative factors of early thrombosis were: -the wider calibre of the saphenous graft; the ratio of the circumference of the graft to the circumference of the coronary artery at the site of anastomosis is greater when there is a graft thrombosis (5.6/1 +/- 2.2) than when the graft is permeable (2.3/1 +/- 1.1) (p less than 0.01); -stenosing atherosclerosis of the artieal tree beyond the anastamosis. Changes in the endothelium of the vein, especially those caused by suturing, could equally well play a part in thrombus formation. Certain other factors, such as an insufficiently large graft ostium into the aorta, and poor outflow in the distal arterial bed, or an insufficiently large territory of supply belonging to the artery which has been bypassed, may also influence the degree of myocardial revascularisation brought about by the operation. A by-pass procedure requires a vein graft with a reasonably small diameter which matches, if at all possible, that of the coronary artery, and a good flow in the distal arterial bed, which must be confirmed at operation.