Historical Rates of Saphenous Vein Graft Failure

Definition of SVG Failure
Saphenous vein graft occlusion is defined as a complete, 100% occlusion of a saphenous vein graft.

Saphenous vein failure is defined as an occlusion of the vein graft or a 75% or greater stenosis.

Per Patient and Per Lesion Analyses of SVG Failure
The rate of occlusion or failure of saphenous vein grafts is calculated on a per graft basis and a per patient basis. The per patient basis is higher, because only one vein graft out of several must fail for the  patient to be characterized as a failure. Analyses should be presented on both a per patient basis (the unit of  randomization) and a per SVG  basis (the unit that is associated with  clinical events). Because the behavior of multiple SVGs may be  correlated, and this within patient  correlation may reduce the estimate  of the variance in the population,  an adjustment for the within patient  correlation must be provided when  presenting the results on a per SVG  basis. The within patient conocrdance can be adjusted for using a General Linear Model of Intraclass Correlation (GLIMIC).

Historical Rates of SVG Failure and Occlusion
Current rates of graft occlusion and failure are as follows: The rate of per patient vein graft occlusion at 12-18 months is about 42%

The rate of per patient vein graft failure at 12-18 months is about 46%

The rate of per graft vein graft occlusion at 12-18 months is about 26%

The rate of per graft vein graft failure at 12-18 months is about 29%

As a comparison, the rate of internal mammary artery failure at 12-18 months was only 8%.

Underestimation of SVG Failure in Earlier Studies
These carefully ascertained current rates of occlusion are higher than what are often quoted in the literature which were :
 * 15% rate of SVG occlusion at 1 year
 * 25% rate of SVG occlusion at 6 years
 * 40% rate of SVG occlusion at 10 years

Potential for Pre-Operative SVG Failure
It should be noted that studies of SVGs that are not implanted show that about 1% of veins are already stenosed by > 50% before implantation.