Development and regression of intimal thickening of arterially transplanted autologous vein grafts in dogs.

To investigate the influence of hemodynamic conditions on intimal thickening of arterially transplanted autologous vein grafts, two experimental models of canine femoral arteries were prepared. In group I, in which an autologous vein graft was transplanted under abnormal flow conditions (distal poor runoff), intimal thickening gradually developed and reached 358 +/- 33 microns at 8 months, whereas no thickening was observed under normal flow conditions at any time throughout the observation period. In group II the thickened intima, which developed under abnormal flow conditions for 1 month, was reimplanted into the contralateral leg under normal flow conditions. The thickness of the intima markedly regressed to about 66% at 1 month, 50% at 3 months, and 25% at 8 months, respectively, whereas no regression of the thickened intima was observed under continued abnormal flow conditions. Electron microscopic studies revealed that the thickened intima in group I was composed of proliferation of transformed smooth muscle cells with a marked increase in the mitochondria, the rough endoplasmic reticulum, and an abundant fibrous matrix, whereas with the regressed thickness of the intima of group II, the smooth muscle cells were spindle-shaped with distinct myofibrillae. These results provide pertinent data on the process involved in the intimal thickening in cases of graft placement.