Risk factor subgroups

Patient-level risk factors

Demographic, comorbidity, and disease severity variables from the individual trial databases were examined and variables mapped by common definitions or groupings. Variables selected for analysis were age , gender , race , diabetes , hypertension , hypercholesterolemia , smoking (ever/never) , and CLI criterion (rest pain vs tissue loss) . Additionally, chronic renal disease (CKD class) and coronary artery disease were examined though results for these are not currently available on this website.

Results demonstrated that the two most potent patient-level predictors at one year were age>80 and presence of tissue loss (TL) at study entry. The combination of these two variables was assessed in a number of ways, in a univariate fashion, as a four-level categorical variable and in a multivariate proportional hazards model. This resulted in the designation of patients with both age>80 and TL as a “ Clinical High Risk ” subgroup (N= 136).

Anatomic level of disease

Outcomes of lower extremity bypass with autogenous vein have not demonstrated a clear relationship to arterial anatomy although various studies have suggested that graft length and outflow may have influence. Bypass grafts were categorized based on the level of the distal anastomosis into one of two groups- infrapopliteal (anastomosis to a tibial or pedal vessel) or above (anastomosis to popliteal or superficial femoral artery at any level). Infrapopliteal anatomy was designated as an “ Anatomic High Risk ” subgroup (N=505).

  • A note about coding of this variable: for our purposes the infrapopliteal group (anatomic highrisk) has a popout value of 0.

Conduit quality/availability

The most potent factor influencing the long term outcomes of autogenous vein bypass is conduit (vein) quality. Specifically, the ability to complete a graft procedure using a single segment of great saphenous vein (SSGSV) results in superior expected outcomes in comparison to grafts comprised of ectopic veins either as single-segment or spliced constructs. We rationalized that conduit availability may be categorized prior to surgery based on clinical evaluation and ultrasound vein mapping studies in a significant proportion of patients. Therefore we segregated the surgical bypass data based on graft composition between those composed of a single GSV segment versus other venous conduits. The latter group was designated as a “ Conduit High Risk ” subgroup (N=163).

  • A note about this variable: for our purposes the conduit highrisk group has a HIGHRISK value of 2, rather than 1.
  • Additionally, these values were only available from the PREVENT III dataset.