Effect of external stenting and systemic hypertension on intimal hyperplasia in rat vein grafts.

Abstract

Overdistention of vein grafts in arterial circulation and systemic hypertension are thought to be influential risk factors contributing to vein graft failures. This study tested the effects of external stenting in preventing systemic hypertension and overdistention of the rat vein graft in the long term. Jugular vein grafts were interposed into the carotid artery of normotensive (n = 39) and two-kidney, one-clip hypertensive (n = 30) rats. Jugular vein grafts wrapped with 1.5-mm-diameter polyester stents were used in normotensive (n = 26) and hypertensive (n = 25) rats. The vein grafts were harvested at 1, 2, 4, 8, 12, and 24 weeks after the grafting procedure. The neointimal area and wall thickness were measured by computerized planimetry, and Ki-67 immunohistochemistry was used to detect replicative smooth muscle cells in the graft wall. In each group, intimal hyperplasia was apparent at 1 week and increased gradually to 24 weeks. The number of Ki-67-positive cells was most increased at 2 weeks after the grafting procedure and gradually decreased thereafter. The numbers of Ki-67-positive cells and the extent of intimal hyperplasia were not significantly different between normotensive and hypertensive rats. Both neointima formation and cell proliferation in the graft wall were significantly reduced by external stenting as compared with the results with unstented grafts. Systemic hypertension by itself is not a risk factor for intimal hyperplasia and experimental vein graft failure in the long term. External stenting is effective against intimal hyperplasia, and it is possible to reduce the subsequent atherosclerotic change of the vein graft wall and improve the long-term patency of the vein graft with external stenting.