Postoperative changes in angiographically normal saphenous vein coronary bypass grafts using intravascular ultrasound

We examined the process of vessel wall thickening in angiographically normal saphenous vein grafts (SVGs) using intravascular ultrasound. Fifteen SVGs were studied in the early stage (within 1 month postoperatively) and 14 SVGs in the late stage (over 6 months postoperatively). Lumen cross-sectional area (CSA) and vessel CSA were measured. Vessel wall area (VWA) was calculated and %VWA was defined as VWA / vessel CSA. Vessel CSA, VWA, and %VWA were significantly larger in the late stage than in the early stage (28.8 vs 21.6 mm(2), 15.8 vs 5.3 mm(2), 55.7% vs 24.9%, respectively) and lumen CSA was smaller in the late stage (12.8 vs 16.2 mm(2)). VWA correlated with vessel CSA, but not with lumen CSA. The time course of %VWA showed that %VWA in the late stage was a plateau state. From these findings, we concluded that the wall thickening process in SVGs begins within 6 months postoperatively and is accompanied by compensatory vessel enlargement.