ATHEROSCLEROSIS OF AORTOCORONARY ARTERY SAPHENOUS VEIN BYPASS GRAFTS.

Among a series of 109 patients who underwent aortocoronary artery bypass reoperation and received a total of 168 grafts, atherosclerosis was found in 29 saphenous vein grafts. Specimens were obtained at reoperation in 25 patients and at postmortem examination in four. Plaques were found from 3 months to 6 years after operation. The plaques often were combined with old or recent mural thrombi, intimal fibroses, or thickened intima associated with intramural hematomas. Clinical findings did not correlate with risk factors such as hypercholesterolemia, hypertension, or diabetes mellitus. In a well-functioning graft with adequate flow, cellular proliferation generally reflects an adjustment of the venous wall to a higher pressure. Such a vessel retains elastic properties of pulsating structures. In the specimens studied, intimal fibrosis associated with plaques was always poorly cellular, causing the grafts to become rigid. This resulted in irregular flow and, in some patients, dissection. The possible pathogenesis of atheromatosis in vein grafts may include the usual mechanisms of atherogenesis and atheromatous transformation of thrombi. It appears that hemodynamically significant stenosis of vein grafts caused by atherosclerosis is an infrequent complication.