Multivariate Cox Regression Analysis of Covariates for Patency Rates After Femorodistal Vein Bypass Grafting

Abstract

Multivariate Cox regression analysis of patency rates for 750 consecutive femorodistal autogenous vein graftings for chronic lower limb ischemia showed that significant independent prognostic covariates were the type of graft (long saphenous or arm vein), presence of diabetes, and absence of a past history of myocardial ischemia. Analysis assumes that patients withdrawn with patent grafts due to death or loss to follow-up would have followed the same course as those who remain, and the degree to which this could distort results was studied. Patients who died with patent grafts were more likely to have had past myocardial ischemia and critical lower limb ischemia. Cox regression analysis for 600 operations after excluding patients who died with patent grafts then showed that significant independent covariates were the type of graft (long saphenous or arm vein) and indication (claudication or critical ischemia); then age, sex, hypertension, diabetes, myocardial ischemia, date of operation, surgeon, site of distal anastomosis, or first compared to repeat operations had no significant influence. Cox regression analysis helps determine which covariates influence graft patency rates, but results are affected by censored data, particularly from patients who die with patent grafts.