Predictors of major amputation despite patent bypass grafts.

Objective: Despite patent vein bypass grafts, some patients with critical limb ischemia (CLI) receive major amputations. We analyzed the predictive factors leading to major amputation in the presence of patent lower extremity bypass (LEB) grafts.

Methods: Data from the Project of Ex-Vivo vein graft Engineering via Transfection III (PREVENT III), a large prospective randomized trial of 1404 patients who underwent LEB with vein graft for CLI, were queried for outcomes. The primary outcome was major amputation with patent (PMA) LEB compared with patients with patent LEB who achieved limb salvage (PLS). The population excluded those who received amputation for occluded grafts. A Cox proportional hazard model identified independent predictors.

Results: Of 1404 LEB patients, 162 (11.5%) had major amputation: 89 (6.3%) with patent and 73 (5.2%) with occluded LEB. For PMA, 21 of 89 (23.6%) developed critical stenosis and 11 of 21 (52.4%) were revised. For PLS, 460 of 1242 (37.0%) developed critical stenosis and 351 of 460 (76.3%) were revised. Predictive patient factors included having preoperative gangrene (vs rest pain; hazard ratio [HR], 3.504; 95% confidence interval [CI], 1.533-8.007; P = .0029), diabetes (HR, 1.800; 95% CI, 1.006-3.219; P = .0477), black (vs white) race (HR, 1.779; 95% CI, 1.051-3.011; P = .0321), baseline creatinine clearance <25 mL/min (vs >65 mL/min; HR, 1.759; 95% CI, 1.016-3.048; P = .0439), prior history of coronary artery bypass grafting (HR, 1.702; 95% CI, 1.080-2.683; P = .0221), and lower baseline activity quality of life score (HR, 1.401; 95% CI, 1.105-1.778; P = .0054). Postoperative wound factors included gangrenous changes (HR, 5.830; 95% CI, 1.647-20.635; P = .0063), surgical wound necrosis (HR, 5.319; 95% CI, 1.478-19.146; P = .0105), deep (vs superficial) wound infection (HR, 3.815; 95% CI, 1.220-11.927; P = .0213), and wound healing abnormally (HR, 3.754; 95% CI, 1.061-13.278; P = .0402). Associated postoperative consequences leading to PMA included having recurrent CLI symptoms (HR, 2.915; 95% CI, 1.816-4.681; P < .0001), a severe (vs mild) adverse event (HR, 2.751; 95% CI, 1.391-5.443; P = .0036), fewer percutaneous revisions (HR, 2.425; 95% CI, 1.573-3.740; P < .0001), discharge on low-molecular-weight heparin (HR, 2.087; 95% CI, 1.309-3.326; P = .0020), and decreasing days to critical stenosis/occlusion/revision/amputation (HR, 1.010; 95% CI, 1.007-1.012; P < .0001).

Conclusions: Whereas a patent vein graft is important to all vascular surgeons, additional factors should be considered in trying to attain limb salvage for patients with CLI. These factors include intervening surgically before CLI has progressed to a state of gangrene or limited activity and optimizing nutrition, diabetes control, cardiac conditions, and activity level. Revision offers hope for clinical improvement but may be delayed when there is no graft lesion identified. The absence of a graft lesion to revise may also portend amputation despite a patent graft because of nongraft-related factors such as infection. Finally, the experience of a severe (vs mild) adverse event may also result in limb loss despite a patent graft. Systematic efforts to reduce severe adverse events among patients may also lead to increased limb salvage.