Time-dependent thickening of the intima in aortocoronary saphenous vein grafts: clinicopathological analysis of 24 patients.

The present study was undertaken to investigate histological changes in aortocoronary saphenous vein grafts (SVGs) and the relationship between intimal thickening of the SVGs and the interval after grafting. The SVGs were divided into five groups according to the degree of intimal thickening and associated luminal narrowing: minimal thickening (0%-10% stenosis), slight thickening (11%-25% stenosis), slight-to-moderate thickening (26%-50% stenosis), moderate thickening (51%-75% stenosis), and severe thickening (76%-100% stenosis). SVGs showing minimal thickening had been implanted for 0-3 weeks, those with slight thickening for 2-13 weeks, those with slight-to-moderate thickening for 5-13 weeks, those with moderate thickening for 30-52 weeks, and those with severe thickening for 30-83 weeks. Thickening of the intima in SVGs (intimal hyperplasia) was time-dependent, and began as early as 2 weeks after the graft surgery. The change was diffuse and concentric, and observed from an aortic root to a coronary site. The major cell type involved in the intimal hyperplasia was the smooth muscle cell.