Use of Intravascular Ultrasound to Evaluate Restenosis of the Saphenous Vein Graft Following Stent Placement
Bypass vein grafts have a tendency to narrow or "stenose" in the months and years following bypass surgery. This stenosis seen is most likely caused by intimal hyperplasia which causes luminal narrowing and eventually late graft occlusion if the graft is not treated with some sort of intervention such as balloon angioplasty or intravascular stent implantation. Intravascular stents were placed in saphenous vein bypass grafts done in pig carotid arteries. The stents were evaluated at three and six week time intervals with intravascular ultrasound to determine the degree of restenosis after stent implantation. Average percent stenosis for all grafts at three and six weeks were 16.2 +- 7.21 and 31.9 +- 9.24 respectively. The average percent stenosis at the narrowest portion of the grafts was 14.4 +- 11.6 after three weeks and 45.5 +- 8.03% after six weeks. A regression analysis was done to examine the association between ultrasound and angiographic measurements of lumen size. Results showed a correlation coefficient of r=0.82 and p<0.00l. The current study showed the development of an animal model that mimics the disease process as it occurs in humans with significant amounts of restenosis in the vein grafts following stent implantation. The implantation of stents proved to lessen the severity of the effects intimal hyperplasia but did not provide a cure for the disease process.