Hydraulic and morphologic study of fibrous intimal hyperplasia in autogenous saphenous vein bypass grafts.

In certain patients who have had aorto-coronary bypass, the grafts are found to have concentric stenosis at the time of reinvestigation. Subsequent morphologic examination of the excised vein has shown marked intimal fibrous hyperplasia. A simplified aorto-coronary bypass system was simulated by a mathematical computer model, through which the entrance effect of various angles by the anastomosis on the flow in the side branch was studied. By matching the coronary impedance to the aortic pressure wave over a cardiac cycle, the model predicted that the optimal angle to obtain the maximum efficiency is 90 degrees. The pathological findings in a group of 108 patients who underwent aorto-coronary bypass grafting with the saphenous vein were correlated with the clinical course, angiographic findings, and hydraulic features. All four categories of data were available in 8. In all but 1 of the 8 patients who underwent reoperation, there was clinical recurrence of angina an average of 10.6 months after the first operation. Repeat angiography revealed severe narrowing of the vein graft in 6 patients and complete occlusion in 2. The angle 0*** subtended by the vein graft with the aorta was estimated at an average of 45.8 degrees.